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Summary of the 2023 Sun – Climate Symposium

Introduction

Observations of the Sun and Earth from space continue to revolutionize our view and understanding of how solar variability and other natural and anthropogenic forcings impact Earth’s atmosphere and climate. For more than four decades (spanning four 11-year solar cycles and now well into a fifth), the total and spectral solar irradiance and global terrestrial atmosphere and surface have been observed continuously, providing an unprecedented, high-quality time series of data for Sun–climate studies, such as the Total Solar Irradiance (TSI) composite record – see Figure 1.

Sun Climate figure 1
Figure 1. The Total Solar Irradiance (TSI) composite record spans almost 5 decades and includes measurements from 13 different instruments (9 NASA and 4 international).
Figure credit: Greg Kopp, Laboratory for Atmospheric and Space Physics (LASP)/University of Colorado (UC).

Sun–Climate Symposia, originally called SOlar Radiation and Climate Experiment (SORCE) Science Team Meetings, have been held at a regular cadence since 1999 – before the launch of SORCE in 2003. These meetings provide an opportunity for experts from across the solar, Earth atmosphere, climate change, stellar, and planetary communities to present and discuss their research results about solar variability, climate influences and the Earth-climate system, solar and stellar variability comparative studies, and stellar impacts on exoplanets.

The latest iteration was the eighteenth in the series and occurred in October 2023. (As an example of a previous symposium, see Summary of the 2022 Sun–Climate Symposium, in the January–February 2023 issue of The Earth Observer [Volume 35, Issue 1, pp. 18–27]). The 2023 Sun–Climate Symposium took place October 17­–20 in Flagstaff, AZ – with a focus topic of “Solar and Stellar Variability and its Impacts on Earth and Exoplanets.” The Sun–Climate Research Center – a joint venture between NASA’s Goddard Space Flight Center (GSFC) and the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado (UC) with the Lowell Observatory hosting the meeting. The in-person meeting had 75 attendees – including 7 international participants – with diverse backgrounds covering a wide range of climate change and solar-stellar variability research topics – see Photo.

Sun Climate Group Photo
Photo. Attendees at the 2023 Sun–Climate Symposium in Flagstaff, AZ.
Photo credit: Kelly Boden/LASP

Update on NASA’s Current and Planned TSIS Missions

The current NASA solar irradiance mission, the Total and Spectral Solar Irradiance Sensor (TSIS-1), marks a significant advance in our ability to measure the Sun’s energy input to Earth across various wavelengths. Following in the footsteps of its predecessors, most notably SORCE, TSIS-1 contributes to the continuous time series of solar energy data dating back to 1978 – see Figure 1. The two instruments on TSIS-1 improve upon those on previous missions, enabling scientists to study the Sun’s natural influence on Earth’s ozone layer, atmospheric circulation, clouds, and ecosystems. These observations are essential for a scientific understanding of the effects of solar variability on the Earth system. 

TSIS-1 launched to the International Space Station (ISS) in December 2017 and is deployed on the Station’s EXpedite the PRocessing of Experiments to Space Station (ExPRESS) Logistics Carrier–3 (ELC-3). Its payload includes the Total Irradiance Monitor (TIM) for observing the TSI and the Spectral Irradiance Monitor (SIM) for measuring the Solar Spectral Irradiance (SSI) – see comparison in Figure 2. The mission completed its five-year prime science mission in March 2023. SIM measures from 200–2400 nm with variable spectral resolution ranging from about 1 nm in the near ultraviolet (NUV) to about 10 nm in the near infrared (NIR). TSIS-1 has been extended by at least three more years as part of the Earth Sciences Senior Review process.

TSIS-2 is intended as the follow-on to TSIS-1. The mission is currently in development at LASP and GSFC with a planned launch around mid 2025. The TSIS-2 payload is nearly identical to that of TSIS-1, except that the payload will ride on a free-flying spacecraft rather than be mounted on a solar pointing platform on the ISS. NASA hopes to achieve 1–2 years of overlap between TSIS-1 and TSIS-2. Achieving such measurement overlap between missions is crucial to the continuity of the long-term records of the TSI and SSI without interruption and improving the solar irradiance composite.

In addition to the current solar irradiance mission and its planned predecessor, NASA is always looking ahead to plan for the inevitable next solar irradiance mission. Two recent LASP CubeSat missions – called Compact SIM (CSIM) and Compact TIM (CTIM) – have tested miniaturized versions of the SIM and TIM instruments, respectively. Both CSIM and CTIM have performed extremely well in space – with measurements that correlate well with the larger instruments – and are being considered as continuity options for the SSI and TSI measurements. Based on the success of CSIM and CTIM, LASP has developed a concept study report about the Compact-TSIS (CTSIS) as a series of small satellites viable for a future TSIS-3 mission.

Sun Climate Figure 2
Figure 2. The Solar Spectral Irradiance (SSI) variability from TSIS-1 Spectral Irradiance Monitor (SIM) is compared to the Total Solar Irradiance (TSI) variability from TSIS-1 Total Irradiance Monitor (TIM). The left panel shows the SIM SSI integrated over its wavelength range of 200–2400 nm, which is in excellent agreement with the TSI variability during the rising phase of solar cycle 25. The right panels show comparison of SSI variability at individual wavelengths to the TSI variability, revealing linear relationships with ultraviolet variability larger than TSI variability, visible variability similar to TSI variability, and near infrared variability smaller than TSI variability.
Figure credit: Erik Richard/LASP

Meeting Overview

After an opening plenary presentation in which Erik Richard [LASP] covered the information on TSIS-1, TSIS-2, CSIM, and CTIM presented in the previous section on “NASA’s Current and Planned Solar Irradiance Missions,” the remainder of the four-day meeting was divided into five science sessions each with oral presentations, and a poster session featuring 23 contributions.

The five session topics were:

  1. Solar and Stellar Activity Cycles
  2. Impacts of Stellar Variability on Planetary Atmospheres
  3. Evidence of Centennial and Longer-term Variability in Climate Change
  4. Evidence of Short-term Variability in Climate Change
  5. Trending of Solar Variability and Climate Change for Solar Cycle 25 (present and future)

There was also a banquet held on the final evening of the meeting (October 19) with special presentations focusing on the water drainage system and archaeology of the nearby Grand Canyon – see Sun-Climate Symposium Banquet Special Presentation on the Grand Canyon National Park.

The remainder of this report summarizes highlights from each of the science sections. To learn more, the reader is referred to the full presentations from the 2023 Sun–Climate Symposium, which can be found on the Symposium website by clicking on individual presentation titles in the Agenda tab.

Session 1: Solar and Stellar Activity Cycles

Sun-like stars (and solar analogs, solar twins) provide a range of estimates for how the Sun’s evolution may affect its solar magnetic cycle variability. Recent astrophysics missions (e.g., NASA’s Kepler mission) have added thousands of Sun-like stars to study, compared to just a few dozen from a couple decades ago when questions remained if the Sun is a normal G star or not.

Tom Ayres [UC Center for Astrophysics and Space Astronomy (CASA)] gave the session’s keynote presentation on Sun-like stars. He pointed out that the new far ultraviolet (FUV) and X-ray stellar observations have been used to clarify that our Sun is a normal G-type dwarf star with low activity relative to most other G-type dwarf stars.

Travis Metcalfe [White Dwarf Research Corporation (WDRC)] discussed the recent progress in modeling of the physical processes that generate a star’s magnetic field – or stellar dynamo. He explained how the presence of stellar wind can slow down a star’s rotation, which in turn lengthens the period of the magnetic cycle. He related those expectations to the Sun and to the thousands of Sun-like stars observed by Kepler.

Continuing on the topic of solar dynamo, Lisa Upton [Space Systems Research Corporation (SSRC)] and Greg Kopp [LASP] discussed their recent findings using a solar surface magnetic flux transport model, which they can use to reconstruct an estimated TSI record back in time to the anomalously low activity during the Maunder Minimum in the 1600s. Dan Lubin [University of California San Diego (UCSD)] described efforts to identify grand-minimum stars – which exhibit characteristics similar to our Sun during the Maunder Minimum. Using Hamilton Echelle Spectrograph observations, they have identified about two dozen candidate grand-minimum stars.

In other presentations and posters offered during this session, Adam Kowalski [LASP]) discussed stellar and solar flare physics and revealed that the most energetic electrons generated during a flare are ten times more than previously thought, while Moira Jardine [University of St. Andrews, Scotland]) discussed the related subject of space weather on the Sun and stars and how the coronal extent was likely much larger for the younger Sun. Three presenters – Debi Choudhary [California State University, Northridge], Garrett Zills [Augusta University], and Serena Criscuoli [National Solar Observatory] –discussed how solar emission line variability from both line intensity and line width are good indicators of magnetic activity on the Sun and thus relevant for studies of Sun-like star variability. Andres Munoz-Jaramillo [Southwest Research Institute (SWRI)] highlighted the importance of archiving large datasets showing the Harvard dataverse as an example. Juan Arjona [LASP] discussed the solar magnetic field observations made using the Max Planck Institute for Solar System Research’s GREGOR solar telescope.

Session 2: Impacts of Stellar Variability on Planetary Atmospheres

Presenters in this session focused on how the stellar variability can impact exoplanet evolution and climate. By analyzing data from NASA’s Kepler mission, scientists have discovered numerous Earth-like planets orbiting other stars – or exoplanets, which has enabled comparative studies between planets in our Solar System and exoplanets.

Aline Vidotto [University of Leiden, Netherlands] gave this session’s keynote presentation in which he discussed the impact of stellar winds on exoplanets. In general, younger stars rotate faster and thus have more stellar variability. The evolution of the exoplanet’s atmosphere is dependent on its star’s variability and also modulated by the exoplanet’s own magnetic field. Robin Ramstad [LASP] further clarified a planetary magnetic field’s influences on atmospheric evolution for planets in our solar system.

Vladimir Airapetian [GSFC] presented an overview of how laboratory measurements used to simulate pre-biosignatures – characteristics that precede those elements, molecules, or substances that would indicate past or present life – could be created in an exoplanet atmosphere by highly energetic particles and X-rays from stars with super flares, very large-scale magnetic eruptions on a star that can be thousands of times brighter than a typical solar flare. While the probability of a super flare event is low for our Sun (perhaps 1 every 400 years), super flares are routinely observed on more active stars.

The stellar flares and the spectral distribution of the flare’s released energy can have large impacts on exoplanet’s atmospheres. Laura Amaral [Arizona State University] presented on the super-flare influences on the habitable zone of exoplanets and explained how the flare’s significantly enhanced X-ray emissions would greatly accelerate water escape from the exoplanet’s atmosphere. Ward Howard [ UC CASA] showed that exoplanet transits can also provide information about starspots (akin to the dark sunspots on the Sun) when a transit event happens to occult a starspot – see Figure 3. Ward also explained the importance of observing the transit events at multiple wavelengths, referred to as transit spectroscopy, to understand the physical characteristics of the starspots. Yuta Notsu [LASP] compared the energetics observed in many different stars using X-ray and far ultraviolet (FUV) observations to estimate stellar magnetic field strengths, which in turn can be used to estimate the stellar extreme ultraviolet (EUV) spectra. Those results provide new information on how the stellar spectra could evolve during the lifetime of Sun-like stars, and how those spectral changes can affect the atmospheric escape rates on their exoplanets.  

Nina-Elisabeth Nemec [University of Göttingen, Germany] described how Kepler observations of exoplanets rely on tracking their transits across its host star’s disk. She explained some of the challenges that arise with analyzing such transits when there are large starspots present. 

Sun Climate figure 3
Figure 3. Illustration of an exoplanet transit that will occult a starspot. The transit light curve can provide information about the size of the starspot, and transit observations at multiple wavelengths can reveal physical parameters, such as temperature, of the starspot.
Figure credit: Ward Howard, CASA/University of Colorado

Session 3: Evidence of Centennial and Longer-term Variability in Climate Change

Venkatachalam “Ram” Ramaswamy [National Oceanic and Atmospheric Administration’s (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL)] gave the keynote for this session in which he discussed Earth’s variable climate change over the past two centuries. He explained in detail Earth’s energy budget and energy imbalance, which leads to less land and sea ice, warmer temperatures at the surface and in the atmosphere and ocean, and more extreme weather. These weather changes have different regional impacts, such as more floods in some regions and more drought in different regions – see Figure 4. 

Sun Climate Figure 4
Figure 4. The rainfall amount has shifted over the past fifty years (red is less and blue is more) with strong regional impacts on droughts and floods.
Figure credit: Ram Ramaswamy/NOAA/GFDL

Bibhuti Kumar Jha [SWRI], Bernhard Hofer [Max Planck Institute for Solar System Research, Germany], and Serena Criscuoli [National Solar Observatory] discussed long-term solar measurements from the Kodaikanal Solar Observatory and showed that the chromospheric plages (Ca K images) have 1.6% faster solar rotation rate than sunspots (white light images). Timothy Jull [University of Arizona (UA)], Fusa Miyake [Nagoya University, Japan], Georg Fueulner [Potsdam Institute for Climate Impact Research, Germany], and Dan Lubin discussed the impact that solar influences (i.e., solar flares, solar energetic particles) have had on Earth’s climate over hundreds of years through their impact on phenomena such as the natural distribution of carbon dioxide in the atmosphere and fluctuations in the North Atlantic Oscillation.  

Hisashi Hayawawa [Nagoya University] and Kalevi Mursula [University of Oulu, Finland] discussed the influence that ever-changing sunspots and magnetic fields on the Sun are having on climate – with a focus on the Maunder Minimum period. Irina Panyushkina [UA] and Timothy Jull presented tree ring radioisotope information as it relates to climate change trends as well as long-term, solar variability trends. According to Lubin, if a reduction in solar input similar to what happened during the Maunder Minimum would happen today, the resulting reduction in temperature would be muted due to the higher concentration of greenhouse gases (GHG) in the atmosphere.

Session 4: Evidence of Short-term Variability in Climate Change

Session 4 focused on discussions that examined shorter-term variations of solar irradiance and climate change. Bill Collins [Lawrence Berkeley National Laboratory (LBNL)] started off the session with a presentation on Earth albedo asymmetry across the hemispheres from Nimbus-7 observations, and then showed some important differences when looking at the Clouds and the Earth’s Radiant Energy System (CERES) record – shown in Figure 5. Lon Hood [UA] discussed the changes in atmospheric circulation patterns which might be the consequence of Arctic sea ice loss increasing the sea level pressure over northern Eurasia. Alexi Lyapustin [GSFC] described how higher temperatures are causing an extension of the wildfire season in the Northern hemisphere by 1–3 months.

Sun Climate Figure 5
Figure 5. The albedo difference between the visible and near-infrared bands are shown for the southern hemisphere (red line) and the northern hemisphere (blue lines) for CERES [left] and Nimbus 7 [right]. The southern hemisphere albedo difference is higher than the northern hemisphere albedo difference, both for the 1980s as measured by Nimbus-7 and for the recent two decades as measured by CERES. These hemispheric differences are related mostly to differences in cloud coverage. The seasonal effect on the albedo difference values is about 2%, but the changes from 1980s to 2010s appear to be about 10%.
Figure credit: Bill Collins/Lawrence Berkeley National Laboratory

Jae Lee [GSFC/University of Maryland, Baltimore County] discussed changes in the occurrence and intensity of the polar mesosphere clouds (PMCs), showing high sensitivity to mesospheric temperature and water, and fewer PMCs for this solar cycle. In addition, some presenters discussed naturally driven climate changes. Luiz Millan [JPL], whose research has found that the water-laden plume from the Hunga-Tonga-Hunga-Ha’apai (HT-HH) volcano eruption in January 2022 has had a warming effect on the atmosphere as well as the more typical cooling effect at the surface from the volcanic aerosols. In another presentation, Jerry Raedar [University of New Hampshire, Space Science Center] showed results from his work indicating about 5% reductions in temperature and pressure following major solar particle storms, but noted differences in dependence between global and regional effects.

Session 5: Trending of Solar Variability and Climate Change for Solar Cycle 25 (present and future)

Session 5 focused on trends during Solar cycle 25 (SC-25), which generated lively discussions about predictions. It appears the SC-25 maximum sunspot number could be about 15% higher than the original SC-25 maximum predictions. Those differences between the sunspot observations and this prediction may be related to the timing of SC-25 ramp up. Lisa Upton started off Session 5 by presenting both the original and latest predictions from the NASA–NOAA SC-25 Prediction Panel. Her assessment of the Sun’s polar magnetic fields and different phasing of magnetic fields over the Sun’s north and south poles suggests that the SC-25 maximum will be larger than the prediction – see Figure 6.

The next several speakers – Matt DeLand [Science Systems and Applicatons Inc. (SSAI)], Sergey Marchenko [SSAI], Dave Harber [LASP], Tom Woods [LASP], and Odele Coddington [LASP] – showed a variety of TSI and SSI (NUV, visible, and NIR) variability observations during SC-25. The group consensus was that the difference between the SC-24 and SC-25 maxima may be due to the slightly higher solar activity during SC-25 as compared to the time of the SC-24 maximum – which was an anomalously low cycle. The presenters all agreed that SC-25 maximum may not have been reached yet (and SC-25 maximum may not have occurred yet in 2024).

Sun Climate Figure 6
Figure 6. The sunspot number progression (black) during solar cycle 25 is higher than predicted (red). The original NASA–NOAA panel prediction was for a peak sunspot number of 115 in 2025. Lisa Upton’s updated prediction is for a sunspot number peak of 134 in late 2024.
Figure credit: NOAA Space Weather Prediction Center

On the climate change side, Don Wuebbles [University of Illinois, Urbana-Champaign] provided a thorough overview of climate change science showing that: the largest impacts result from the activities of humans, land is warming faster than the oceans, the Arctic is warming two times faster than rest of the world, and 2023 was the hottest year on record with an unprecedented number of severe weather events.

There were several presentations about the solar irradiance observations. Leah Ding [American University] presented new analysis techniques using machine learning with Solar Dynamics Observatory (SDO) solar images to study irradiance variability. Steve Penton [LASP] discussed new SIM algorithm improvements for TSIS-1 SIM data product accuracy. Margit Haberreiter [Physikalisch-Meteorologisches Observatorium Davos (PMOD), Switzerland] discussed new TSI observations from the Compact Lightweight Absolute Radiometer (CLARA) on the Norwegian NorSat-1 microsatellite. Marty Snow [South African National Space Agency] discussed a new TSI-proxy from the visible light (green filter) Solar Position Sensor (SPS) flown on the NOAA Geostationary Operational Environmental Satellites (GOES-R). (The first of four satellites in the GOES-R series launched in 2016 (GOES-16) followed by GOES-17 and GOES-18 in 2018 and 2022 respectively. The final satellite in the series – GOES-U – launched June 25, 2024 will become GOES-19 after checkout is complete.)

Peter Pilewskie [LASP] discussed future missions, focusing on the Libera mission for radiative energy budget, on which he is Principal Investigator. Selected as the first Earth Venture Continuity mission (EVC-1), Libera will record how much energy leaves our planet’s atmosphere on a day-by-day basis providing crucial information about how Earth’s climate is evolving. In Roman mythology, Libera was Ceres’ daughter. The mission name is thus fitting as Libera will act as a follow-on mission to maintain the decades long data record of observation from NASA’s suite of CERES instruments. Figure 7 shows the CERES climate data record trends over the past 20 years.

Sun Climate figure 7
Figure 7. The CERES Earth Radiation Budget (ERB) climate data record shows a positive trend for the absorbed solar radiation [left] and the net radiation [right] and a small negative trend for the emitted terrestrial radiation [middle].
Figure credit: Peter Pilewskie/adapted from a 2021 paper in Geophysical Research Letters

Susan Breon [GSFC] discussed the plans for and status of TSIS-2 , and Tom Patton [LASP] discussed CTSIS as an option for TSIS-3 – both of these topics were discussed earlier in this article in the section on “NASA’s Current and Planned Solar Irradiance Missions.”

Angie Cookson [California State University, San Fernando Observatory (SFO)] shared information about the SFO’s 50-year history, and how analyses of solar image observations taken at SFO are used to derive important indicators of solar irradiance variability – see Figure 8.

Sun Climate Figure 8
Figure 8. The San Fernando Observatory (SFO) [left] has been making visible [middle] and near ultraviolet (NUV) [right] solar images from the ground for more than 50 years. Those solar images have been useful for understanding the sources of solar irradiance variability.
Figure credit: Angie Cookson/SFO
Black Separator Line

Sun-Climate Symposium Banquet Special Presentation on the Grand Canyon National Park

At the Thursday evening banquet, two speakers – Mark Nebel and Anne Millar – from the National Park Service (NPS) presented some of their geological research on the nearby Grand Canyon. Nebel discussed the water drainage systems surrounding the Grand Canyon while Millar described the many different fossils that have been found in the surrounding rocks. Nebel explained how  the Grand Canyon’s water drainage system into the Colorado River is complex and has evolved over the past few decades – see map and photo below. Millar brought several samples of the plant and insect fossils found in the Grand Canyon to share with banquet participants. Those fossils ranged in time from the Bright Angel Formation ocean period 500 million years ago to the Hermit Formation period 285 million years ago – when the Grand Canyon was semi-arid land with slow-moving rivers.

Sun Climate Grand Canyon Map
Map and photo credit: Mark Nebel/NPS
Black Separator Line

Conclusion

Altogether, 80 presentations during the 2023 Sun–Climate Symposium spread across 6 sessions about solar analogs, exoplanets, long-term climate change, short-term climate change, and solar/climate recent trending. The multidisciplinary group of scientists attending made for another exciting conference for learning more about the TSIS solar irradiance observations. Sun–Climate recent results have improved perception of our Sun’s variability relative to many other Sun-like stars, solar impact on Earth and other planets and similar type impacts of stellar variability on exoplanets, and better characterization of anthropogenic climate drivers (e.g., increases in GHG) and natural climate drivers (Sun and volcanoes).

The next Sun–Climate Symposium will be held in spring 2025 with a potential focus on polar climate records, including polar ice trends and long-term solar variabilities derived from ice-core samples. Readers who may be interested in participating in the 2025 science organizing committee should contact Tom Woods and/or Dong Wu [GSFC].

separater line

Acknowledgments

The three co-authors were all part of the Science Organizing Committee for this meeting and wish to acknowledge the other members for their work in planning for and participating in another successful Sun–Climate Symposium. They include: Odele Coddington, Greg Kopp, and Ed Thiemann [all at LASP]; Jae Lee, Doug Rabin, and Dong Wu [all at GSFC]; Jeff Hall, Joe Llama, and Tyler Ryburn [all at Lowell Observatory]; Dan Lubin [UCSD’s Scripps Institution of Oceanography (SIO)]; and Tom Stone [U.S. Geological Survey’s Astrogeology Science Center]. The authors and other symposium participants are also deeply grateful to Kelly Boden [LASP] for organizing the logistics and management of the conference, and to the Lowell Observatory, the Drury Inn conference center staff, and the LASP data system engineers for their excellent support in hosting this event.

Tom Woods
University of Colorado, Laboratory for Atmospheric and Space Research
tom.woods@lasp.colorado.edu

Peter Pilewskie
University of Colorado, Laboratory for Atmospheric and Space Research
peter.pilewskie@lasp.colorado.edu

Erik Richard
University of Colorado, Laboratory for Atmospheric and Space Research
erik.richard@lasp.colorado.edu

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Jul 18, 2024

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      OMI and Data Products Update
      Pieternel Levelt [Royal Netherlands Meteorological Institute (KNMI)—OMI Principal Investigator (PI) and NCAR’s Atmospheric Chemistry Observations & Modeling (ACOM) Laboratory—Director] began her presentation by dedicating the meeting to the memory of Johan de Vries, whose untimely death came as a shock to the OMI and TROPOMI teams – see In Memoriam: Johan de Vries for a celebration of his accomplishments and contributions to the OMI-TROPOMI team. She then went on to give a status update on OMI, which is one of two currently operating instruments on EOS Aura [the other being the Microwave Limb Sounder (MLS)]. OMI is the longest operating and stable ultraviolet–visible (UV-VIS) spectrometer. It continues to “age gracefully” thanks to its design, contamination control measures undertaken after the launch, and stable optical bench temperature. Lessons learned during integration of OMI on the Aura spacecraft (e.g., provide additional charged couple device shielding) and operations (i.e., monitor partial Earth-view port blockages) guided the development and operations of the follow-on TROPOMI mission.
      Continued monitoring of OMI performance is crucial for extending science- and trend-quality OMI records to the end of the Aura mission (currently expected in 2026). Antje Ludewig [KNMI] described the new OMI Level-1B (L1B) processor (Collection 4), which is based on TROPOMI data flow and optimized calibrations. The processor has been transferred to the U.S. OMI ST, led by Joanna Joiner [NASA’s Goddard Space Flight Center (GSFC)]. Matthew Bandel [Science Systems and Applications, Inc. (SSAI)] described NASA’s new OMI monitoring tools.
      Sergey Marchenko [SSAI] discussed OMI daily spectral solar irradiance (SSI) data, which are used for monitoring solar activity and can be compared with the dedicated Total and Spectral Solar Irradiance Sensor (TSIS-1) on the International Space Station. Continuation of OMI measurements will allow comparisons with the upcoming NASA TSIS-2 mission. Antje Inness [European Centre for Medium-range Weather Forecasts (ECMWF)] described operational assimilation of OMI and TROPOMI near-real time data into the European Copernicus Atmosphere Monitoring Service (CAMS) daily analysis/forecast and re-analysis – see Figure 1.
      In Memoriam: Johan de Vries
      Johan de Vries
      June 10, 1956 – May 8, 2024 Johan de Vries [Airbus Netherlands—Senior Specialist Remote Sensing] passed away suddenly on May 8, 2024, after a distinguished career. As a member of the Ozone Monitoring Instrument (OMI)–TROPOspheric Monitoring Instrument (TROPOMI) program, Johan conceptualized the idea of using a two-dimensional (2D) charged couple detector (CCD) for the OMI imaging spectrometer. This “push-broom” design led to high-spatial resolution spectra combined with high-spatial resolution and daily global coverage capability. His pioneering design for OMI has now been repeated on several other U.S. and international atmospheric composition measuring instruments – in both low and geostationary orbits – that are either in orbit or planned for launch soon. This achievement ensures that Johan’s legacy will live on for many years to come as these push-broom Earth observing spectrometers result in unprecedented data for environmental research and applications. The OMI and TROPOMI teams express their deepest condolences to de Vries family and colleagues over this loss. 
      Figure 1. An example of TROPOMI pixel nitrogen dioxide (NO2) observations over Europe on September 8, 2018 [top] and the corresponding super observations [bottom] for a model grid of 0.5 x 0.5o. Cloudy locations are colored grey. TROPOMI super observations are tested for use in the European Centre for Medium Range Weather Forecasting (ECMWF) Copernicus Atmosphere Monitoring Service (CAMS) data assimilation framework and will also be used for combined OMI–TROPOMI gridded datasets. Figure credit: reprinted from a 2024 paper posted on EGUSphere. Updates on OMI and TROPOMI Level-2 Data Products
      The U.S. and Netherlands OMI STs continue to collaborate closely on reprocessing and improving OMI and TROPOMI L2 science products. During the meeting, one or more presenters reported on each product, which are described in the paragraphs that follow.
      Serena Di Pede [KNMI] discussed the latest algorithm updates to the Collection 4 OMI Total Column Ozone (O3) product, which is derived using differential absorption spectroscopy (DOAS). She compared results from the new algorithm with the previous Collection 3 and with both the TROPOMI and OMI NASA O3 total column (Collection 3) algorithms. Collection 4 improved on previous versions by reducing the retrieval fit error and the along-track stripes of the product.
      Juseon “Sunny” Bak and Xiong Liu [both from Smithsonian Astrophysical Observatory (SAO)] gave updates on the status of the Collection 4 O3 profile products.
      Lok Lamsal [GSFC/University of Maryland, Baltimore County (UMBC)] and Henk Eskes [KNMI] compared Collection 3 and Collection 4 of the nitrogen dioxide (NO2) products.  
      Zolal Ayzpour [SAO] discussed the status of the OMI Collection 4 formaldehyde (HCHO) product.
      Hyeong-Ahn Kwon [SAO] presented a poster that updated the Glyoxal product.
      Omar Torres [GSFC] and Changwoo Ahn [GSFC/SSAI] presented regional trend analyses using the re-processed OMI Collection 4 absorbing aerosol product – see Figure 2.
      Figure 2. Reprocessed OMI records (from Collection 4) of monthly average aerosol optical depth (AOD) at 388 nm derived from the OMI aerosol algorithm (OMAERUV) over Western North America (WNA): 30°N–50°N, 110°W–128°W) [top] and over Eastern China (EC): 25°N–43°N, 112°E–124°E) [bottom]. A repeatable annual cycle over WNA occurred with autumn minimum at around 0.1 and a spring maximum in the vicinity of 0.4 during the 2005–2016 period. After 2017 much larger AOD maxima in the late summer are associated with wildfire smoke occurrence. Over EC (bottom) the 2005–2014 AOD record depicts a large spring maxima (0.7 and larger) due to long-range transport of dust and secondary pollution aerosols followed by late autumn minima (around 0.3). A significant AOD decrease is observed starting in 2015 with reduced minimum and maximum values to about 0.2 and 0.5 respectively. The drastic change in AOD load over this region is associated with pollution control measures enacted over the last decade. Figure credit: Changwoo Ahn/GSFC/SSAI and Omar Torres/GSFC Updates on EOS Synergy Products
      Several presenters and posters during the meeting gave updates on EOS synergy products, where OMI data are combined with data from another instrument on one of the EOS flagships. These are described below.
      Brad Fisher [SSAI] presented a poster on the Joint OMI–Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products.
      Wenhan Qin [GSFC/SSAI] presented a poster on the MODIS–OMI Geometry Dependent Lambertian Equivalent Surface Reflectivity (GLER) product.
      Jerry Ziemke [GSFC and Morgan State University (MSU)] presented on the OMI–MLS Tropospheric Ozone product that showed post-COVID tropospheric O3 levels measured using this product, which are consistent with similar measurements obtained using other satellite O3 data – see Figure 3.
      Figure 3. Anomaly maps of merged tropospheric column O3 (TCO) satellite data (Dobson Units) for spring–summer 2020–2023. In this context, an anomaly is defined as deseasonalized O3 data. The anomaly maps are derived by first calculating seasonal climatology maps for 2016–2019 (i.e., pre-COVID pandemic) and then subtracting these climatology maps from the entire data record. 
      Note: The sensors used in this analysis include: the Ozone Mapping and Profiler Suite (OMPS)/ Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) and Cross-track Infrared Sounder (CrIS) on the Joint Polar Satellite System (JPSS) missions, which currently include the joint NASA–NOAA Suomi National Polar-orbiting Partnership (Suomi NPP), NOAA-20, and NOAA-21; the Earth Polychromatic Imaging Camera (EPIC)/MERRA-2 on the Deep Space Climate Observatory (DSCOVR); the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS), both on EOS Aura; the Infrared Atmospheric Sounding Interferometer (IASI)/ Fast Optimal Retrievals on Layers (FORLI), IASI/SOftware for Fast Retrievals of IASI Data (SOFRID), and IASI/Global Ozone Monitoring Experiment–2 (GOME2). IASI flies on the European MetOp-A, -B, and -C missions. The OMPS/MERRA-2 and EPIC/MERRA-2 products subtract coincident MERRA-2 stratospheric column O3 from total O3 to derive tropospheric column O3. Figure credit: Jerry Ziemke/GSFC and Morgan State University (MSU)  Updates on Multisatellite Climate Data Records
      The OMI ST also discussed refining and analyzing multisatellite climate data records (CDRs) that have been processed with consistent algorithms. Several presenters reported on this work, who are mentioned below.
      Jenny Stavrakou [Koninklijk Belgisch Instituut voor Ruimte-Aeronomie, Royal Belgian Institute for Space Aeronomy (BIRA–IASB)], reported on work focusing on the OMI and TROPOMI HCHO CDR and Huan Yu [BIRA–IASB)] reported harmonized OMI and TROPOMI cloud height datasets based on improved O2-O2 absorption retrieval algorithm.
      Lok Lamsal [GSFC/UMBC, Goddard Earth Sciences Technology and Research (GESTAR) II], Henk Eskes, and Pepijn Veefkind [KNMI] reported on the OMI and TROPOMI NO2 CDRs – see Figure 4. 
      Si-Wan Kim [Yonsei University, South Korea] reported on OMI and TROPOMI long-term NO2 trends.
      Figure 4. OMI nitrogen dioxide (NO2) time series bridging the first GOME mission (which flew on the European Remote Sensing Satellite–2 (ERS–2) from 1995–2011 with limited coverage after 2003) and measurements from the two currently operating missions – OMI (2004–present) and TROPOMI (2017–present) – offer consistent climate data records that allow for studying long-term changes. This example shows tropospheric NO2 column time series from three instruments over Phoenix, AZ. The overlap between the OMI and TROPOMI missions allows for intercomparison between the two, which is crucial to avoid continuity-gaps in multi-instrument time series. The ERS-2 (GOME) had a morning equator crossing time (10:30 AM), while Aura (OMI) and Metop (TROPOMI) have afternoon equator crossing times of 1:45 PM and 1:30 PM respectively. Figure credit: Lok Lamsal/GSFC/University of Maryland, Baltimore County (UMBC) Update on Aura’s Drifting Orbit
      Bryan Duncan [GSFC—Aura Project Scientist] closed out the first day with a presentation summarizing predictions of Aura’s drifting orbit. Overall, the impact of Aura’s drift is expected to be minor, and the OMI and MLS teams will be able to maintain science quality data for most data products. He thanked the OMI/TROPOMI ST and user community for expressing their strong support for continuing Aura observations until the end of the Aura mission in mid–2026.
      DAY TWO
      The second day of the meeting focused on current and upcoming LEO and GEO Atmospheric Composition (AC) missions.
      TROPOMI Mission and Data Product Updates
      Veefkind presented an update on the TROPOMI mission, which provides continuation and enhancements for all OMI products. Tobias Borssdorf [Stichting Ruimte Onderzoek Nederland (SRON), or Netherlands Institute for Space Research] explained how TROPOMI, with its innovative shortwave infrared (SWIR) spectrometer, measures CH4 and carbon monoxide (CO). This approach continues measurements that began by the Measurements of Pollution in the Troposphere (MOPITT) instrument on Terra.
      Hiren Jethva [NASA Airborne Science Program] and Torres presented new TROPOMI near-UV aerosol products, including a new aerosol layer optical centroid height product, which takes advantage of the TROPOMI extended spectral range – see Figure 5.
      Figure 5. Global gridded (0.10° x 0.10°) composite map of aerosol layer optical centroid height (AH) retrieved from TROPOMI O2-B band observations from May–September 2023. Figure credit: Hiren Jethva/NASA Airborne Science Program GEMS–TEMPO–Sentinel-4 (UVN): A Geostationary Air Quality Constellation
      TROPOMI global observations serve as a de facto calibration standard used to homogenize a new constellation of three missions that will provide AC observations for most of the Northern Hemisphere from GEO. Two of the three constellation members are already in orbit. Jhoon Kim [Yonsei University—PI] discussed the Geostationary Environmental Monitoring Spectrometer (GEMS), launched on February 19, 2020 aboard the Republic of Korea’s GEO-KOMPSAT-2B satellite. It is making GEO AC measurements over Asia. The GEMS team is working on validating measurements of NO2 diurnal variations using ground-based measurements from the PANDORA Global Network over Asia and aircraft measurements from the ASIA–AQ field campaign.
      Liu discussed NASA’s Tropospheric Emission Monitoring of Pollution (TEMPO) spectrometer, launched on April 7, 2023, aboard a commercial INTELSAT 40E satellite. From its GEO vantage point, TEMPO can observe the Continental U.S., Southern Canada, Mexico, and the coastal waters of the Northwestern Atlantic and Northeastern Pacific oceans.
      Gonzales Abad [SAO] presented the first measurements from TEMPO. He explained that TEMPO’s design is similar to GEMS, but GEMS includes an additional visible and near infrared (VNIR) spectral channel (540–740 nm) to measure tropospheric O3, O2, and water vapor (H2Ov). TEMPO can perform optimized morning scans, twilight scans, and scans with high temporal resolution (5–10 minutes) over selected regions. Abad reported that the TEMPO team released L1B spectra and the first provisional public L2 products (Version 3), including NO2, HCHO, and total column O3. Andrew Rollins [National Oceanic and Atmospheric Administration’s (NOAA) Chemical Sciences Laboratory (CSL)] reported that the TEMPO team is working on validation of provisional data using both ground-based data from PANDORA spectrometers and data collected during several different airborne campaigns completed during the summer of 2023 and compiled on the AGES+ website.
      Ben Veihelmann [ESA’s European Space Research and Technology Center—PI] explained that ESA’s Copernicus Sentinel-4 mission will be the final member of the GEO AC constellation. Veefkind summarized the Sentinel-4 mission, which is expected to launch on the Meteosat Third Generation (MTG)-Sounder 1 (MTG-S1) platform in 2025. The mission is dedicated to measuring air quality and O3 over Europe and parts of the Atlantic and North Africa. Sentinel-4 will deploy the first operational UV-Vis-NIR (UVN) imaging spectrometer on a geostationary satellite. (Airbus will build UVN, with ESA providing guidance.) Sentinel-4 includes two instruments launched in sequence on MTG-S1 and MTG-S2 platforms designed to have a combined lifetime of 15 years. The mission by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) will operate Sentinel-4, and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) or German Aerospace Center will be responsible for operational L2 processing.
      These three GEO AC missions, along with the upcoming ESA/EUMETSAT/Copernicus LEO (morning orbit, 9:30 a.m.) Sentinel-5 (S5) mission, will complete a LEO–GEO satellite constellation that will enable monitoring of the most industrialized and polluted regions in the Northern Hemisphere into the 2030s. Sentinel-5 will not continue the OMI–TROPOMI data record in the early afternoon; however, it will be placed in the morning orbit and follow ESA’s Global Ozone Monitoring Experiment (GOME) and EUMETSAT GOME-2 missions. By contrast, GEO AC observations over the Southern Hemisphere are currently not available. Several presenters described ongoing projects for capacity building for LEO satellite air quality data uptake and emission monitoring in Africa and advocated for the new geostationary measurements.
      Synergy with Other Current or Upcoming Missions
      Attendees discussed the synergy between upcoming AC, GHG, and ocean color missions. Current trends in satellite AC measurements are toward increased spatial resolution and combined observations of short-lived reactive trace gases – which are important for air quality (AQ) monitoring – and long-lived GHG – which are important for climate monitoring and carbon cycle assessments. Some trace gases (e.g., O3 and CH4) are both polluters and GHG agents. Others [e.g., NO2 and sulfur dioxide (SO2 )] are aerosol [particulate matter (PM)] and O3 precursors and are used as proxies and spatial indicators for anthropogenic CO2 and CH4 emissions.
      Yasjka Meijer [ESA—Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) Mission Scientist]) reviewed the plans for CO2M, which includes high-resolution measurements [~4 km2 (~1.5 mi2)] of CO2 , CH4 , and NO2.
      Jochen Landgraf [SRON] described ESA’s new Twin Anthropogenic Greenhouse Gas Observers (TANGO) mission, which has the objective to measure CO2 , CH4 , and NO2 at even higher spatial resolution [~300 m (~984 ft)] using two small CubeSat spectrometers flying in formation.
      Hiroshi Tanimoto [National Institute for Environmental Studies, Japan] described the Japan Aerospace Exploration Agency’s (JAXA) Global Observing SATellite for greenhouse gases and water cycle (GOSAT-GW) mission, which includes the Total Anthropogenic and Natural Emission mapping SpectrOmeter (TANSO-3) spectrometer to simultaneously measure CO2 , CH4, and NO2 with ~1–3 km (~0.6–1.8 mi) spatial resolution in focus mode. GOSAT-GW will also fly the Advanced Microwave Scanning Radiometer 3 (AMSR3).
      Joanna Joiner [GSFC—Geostationary Extended Operations (GeoXO) Project Scientist and ACX Instrument Scientist] described the plans for the next-generation U.S. geosynchronous satellite constellation, which will consist of three satellites covering the full Earth disk: GEO-East, GEO-West, and GEO-Central. (By contrast, the current Geostationary Operational Environmental Satellite (GOES) series has two satellites: GOES–East and GOES–West.) GEO-Central will carry an advanced infrared sounder (GXS) for measuring vertical profiles of many trace gases, temperature and humidity, and a new UV-VIS spectrometer (ACX), which is a follow-on to TEMPO for AQ applications. Both GXS and ACX instruments will be built by BAE Systems, which acquired Ball Aerospace and Technology, and will also build the GeoXO ocean color spectrometer (OCX).
      Andrew Sayer [UMBC] described NASA’s Plankton, Aerosols, Clouds, and ocean Ecosystem (PACE), which launched on February 8, 2024. The PACE payload includes a high-spatial resolution [~1 km (~0.6 mi) at nadir] Ocean Color Instrument (OCI), which is a UV-Vis-NIR spectrometer with discrete SWIR bands presenting additional opportunities for synergistic observations with the AC constellation. Sayer presented OCI “first light” aerosol data processed using the unified retrieval algorithm developed by Lorraine Remer [UMBC].
      The second day concluded with a joint crossover session with NASA’s Health and Air Quality Applied Sciences Team (HAQAST) followed by a poster session. Several OMI–TROPOMI STM participants presented on a variety of topics that illustrate how OMI and TROPOMI data are being used to support numerous health and AQ applications. Duncan, who is also a member of HAQAST team, presented “20 years of health and air quality applications enabled by OMI data.” He highlighted OMI contributions to AQ and health applications, including NO2 trend monitoring, inferring trends of co-emitted species [e.g., CO2, CO, some Volatile Organic Compounds (VOCs)], validation of new satellite missions (e.g., TEMPO, PACE), and burden of disease studies.
      DAY THREE
      Discussions on the third day focused on advanced retrieval algorithms, leading to new products and new applications for OMI and TROPOMI data. Several presentations described applications of TROPOMI CH4 data and synergy with small satellites.
      Advanced Retrieval Algorithms and New Data Products
      Ilse Aben [SRON] described TROPOMI global detection of CH4 super-emitters using an automated system based on Machine Learning (ML) techniques – see Figure 6. Berend Schuit [SRON] provided additional detail on these methods. He introduced the TROPOMI CH4 web site to the meeting participants. He explained how TROPOMI global CH4 measurements use “tip-and-cue” dedicated satellites with much higher spatial resolution instruments [e.g., GHGSat with ~25-m (~82-ft) resolution] to scan for individual sources and estimate emission rates. Most CH4 super-emitters are related to urban areas and/or landfills, followed by plumes from gas and oil industries and coal mines.
      Figure 6. Methane plume map produced by SRON shows TROPOMI large CH4 emission plumes for the week of the OMI–TROPOMI meeting (June 3–6, 2024). Figure credit: Itse Aben/Stichting Ruimte Onderzoek Nederland (SRON) Alba Lorente [Environmental Defense Fund—Methane Scientist] introduced a new MethaneSAT satellite launched in March 2024, which aims to fill the gap in understanding CH4 emissions on a regional scale [200 x 200 km2 (~77 x 77 mi2)] from at least 80% of global oil and gas production, agriculture, and urban regions. Alex Bradley [University of Colorado, Boulder] described improvements to TROPOMI CH4 retrievals that were achieved by correcting seasonal effects of changing surface albedo.
      Daniel Jacob [Harvard University] presented several topics, including the highest resolution [~30 m (~98 ft)] NO2 plume retrievals from Landsat-8 – see Figure 7 – and Sentinel-2 imagers. He also discussed using a ML technique trained with TROPOMI data to improve NO2 retrievals from GEMS and modeling NO2 diurnal cycle and emission estimates. He introduced the ratio of ammonia (NH3) to NO2 (NH3/NO2) as an indicator of particulate matter with diameters less than 2.5 µm (PM2.5) nitrate sensitivity regime. Jacob emphasized the challenges related to satellite NO2 retrievals (e.g., accounting for a free-tropospheric NO2 background and aerosols).
      Figure 7. Landsat Optical Land Imager (OLI) image, obtained on October 17, 2021 over Saudi Arabia, shows power plant exhaust, which contains nitrogen dioxide (NO2) drifting downwind from the sources (the two green circles are the stacks). The ultra-blue channel (430–450 nm) on OLI enables quantitative detection of NO2 in plumes from large point sources at 30-m (~98-ft) resolution. This provides a unique ability for monitoring point-source emissions of oxides of nitrogen (NOx). The two stacks in the image are separated by 2 km (~1.2 mi). Figure credit: Daniel Jacob – repurposed from a 2024 publication in Proceedings of the National Academies of Sciences (PNAS) Steffen Beirle [Max Planck Institute for Chemistry, Germany] explained his work to fit TROPOMI NO2 column measurements to investigate nitric oxide (NO) to NO2 processing in power plant plumes. Debra Griffin [Environment and Climate Change Canada (ECCC)] used TROPOMI NO2 observations and ML random forest technique to estimate NO2 surface concentrations. Sara Martinez-Alonso [NCAR] investigated geographical and seasonal variations in NO2 diurnal cycle using GEMS and TEMPO data.  Ziemkecombined satellite O3 data to confirm a persistent low anomaly (~5–15%) in tropospheric O3 after 2020.  Jethva presented advanced OMI and TROPOMI absorbing aerosol products. Yu described improved OMI and TROPOMI cloud datasets using the O2-O2 absorption band at 477 nm. Nicholas Parazoo [Jet Propulsion Laboratory (JPL)] described TROPOMI Fraunhofer line retrievals of red solar-induced chlorophyll fluorescence (SIF) near O2-B band (663–685 nm) to improve mapping of ocean primary productivity. Liyin He [Duke University] described using satellite terrestrial SIF data to study the effect of particulate pollution on ecosystem productivity.
      New Applications
      Zachary Fasnacht [SSAI] used OMI and TROPOMI spectra to train a neural network to gap-fill MODIS and Visible Infrared Imaging Radiometer Suite (VIIRS) ocean color data under aerosol, sun glint, and partly cloudy conditions. This ML method can also be applied to PACE OCI spectra. Anu-Maija Sundström [Finnish Meteorological Institute (FMI)] used OMI and TROPOMI SO2 and O3 data as proxies to study new particle formation events. Lindsey Anderson [University of Colorado, Boulder] described how she used TROPOMI NO2 and CO measurements to estimate the composition of wildfire emissions and their effect on forecasted air quality. Heesung Chong [SAO] applied OMI bromine oxide (BrO) retrievals to the NOAA operational Ozone Mapping and Profiling Suite Nadir Mapper (OMPS-NM) on joint NOAA–NASA Suomi-National Polar-orbiting Partnership (Suomi NPP) satellite with the possibility to continue afternoon measurements using similar OMPS-NM instruments on the four Joint Polar Satellite System missions (JPSS-1,-2,-3,-4) into the 2030s. (JPSS-1 and -2 are now in orbit and known as NOAA-20 and -21 respectively; JPSS-4 is planned for launch in 2027, with JPSS-3 currently targeted for 2032.)
      Kim demonstrated the potential for using satellite NO2 and SO2 emissions as a window into socioeconomic issues that are not apparent by other methods. For example, she showed how OMI and TROPOMI data were widely used to monitor air quality improvements in the aftermath of COVID-19 lockdowns. (Brad Fisher [SSAI] presented a poster on a similar topic.)
      Cathy Clerbaux [Center National d’Études Spatiale (CNES), or French Space Agency] showed how her team used TROPOMI NO2 data to trace the signal emitted by ships and used this information to determine how the shipping lanes through the Suez Canal changed in response to unrest in the Middle East. Iolanda Ialongo [FMI] showed a similar drop of NO2 emissions over Donetsk region due to the war in Ukraine. Levelt showed how OMI and TROPOMI NO2 data are used for capacity-building projects and for air quality reporting in Africa. She also advocated for additional geostationary AQ measurements over Africa.
      DAY FOUR
      Discussions on the final day focused on various methods of assimilating satellite data into air quality models for emission inversions and aircraft TEMPO validation campaigns. The meeting ended with Levelt giving her unique perspective on the OMI mission, as she reflected on more than two decades being involved with the development, launch, operation, and maintenance of OMI.  
      Assimilating Satellite Data into Models for Emissions
      Brian McDonald [CSL] described advance chemical data assimilation of satellite data for emission inversions and the GReenhouse gas And Air Pollutants Emissions System (GRA2PES). He showed examples of assimilations using TROPOMI and TEMPO NO2 observations to adjust a priori emissions. He also showed that when TEMPO data are assimilated, NOx emissions adjust faster and tend to perform better at the urban scale. Adrian Jost [Max Planck Institute for Chemistry] described the ESA-funded World Emission project to improve pollutant and GHG emission inventories using satellite data. He showed examples of TROPOMI SO2 emissions from large-point sources and compared the data with bottom-up and NASA SO2 emissions catalogue.
      Ivar van der Velde [SRON] presented a method to evaluate fire emissions using new satellite imagery of burned area and TROPOMI CO. Helene Peiro [SRON] described her work to combine TROPOMI CO and burned area information to compare the impact of prescribed fires versus wildfires on air quality in the U.S. She concluded that prescribed burning reduces CO pollution. Barbara Dix [University of Colorado, Boulder, Cooperative Institute for Research in Environmental Sciences] derived NOx emissions from U.S. oil and natural gas production using TROPOMI NO2 data and flux divergence method. She estimated TROPOMI CH4 emissions from Denver–Julesburg oil and natural gas production. Dix explained that the remaining challenge is to separate oil and gas emissions from other co-located CH4 sources. Ben Gaubert [NCAR, Atmospheric Chemistry Observations and Modeling] described nonlinear and non-Gaussian ensemble assimilation of MOPITT CO using the data assimilation research testbed (DART).
      Andrew (Drew) Rollings [CSL] presented first TEMPO validation results from airborne field campaigns in 2023 (AGES+ ), including NOAA CSL Atmospheric Emissions and Reactions observed from Megacities to Marine Aeras (AEROMMA) and NASA’s Synergistic TEMPO Air Quality Science (STAQS) campaigns.
      A Reflection on Twenty Years of OMI Observations
      Levelt gave a closing presentation in which she reflected on her first involvement with the OMI mission as a young scientist back in 1998. This led to a collaboration with the international ST to develop the instrument, which was included as part of Aura’s payload when it launched in July 2004. She reminisced about important highlights from 2 decades of OMI, e.g., the 10-year anniversary STM at KNMI in 2014 (see “Celebrating Ten Years of OMI Observations,” The Earth Observer, May–Jun 2014, 26:3, 23–30), and the OMI ST receiving the NASA/U.S. Geological Survey Pecora award in 2018 and the American Meteorological Society’s Special award in 2021.
      Levelt pointed out that in this combined OMI–TROPOMI meeting the movement towards using air pollution and GHG data together became apparent. She ended by saying that the OMI instrument continues to “age gracefully” and its legacy continues with the TROPOMI and LEO–GEO atmospheric composition constellation of satellites that were discussed during the meeting.
      Conclusion
      Overall, the second OMI–TROPOMI STM acknowledged OMI’s pioneering role and TROPOMI’s unique enhancements in measurements of atmospheric composition: 
      Ozone Layer Monitoring: Over the past two decades, OMI has provided invaluable data on the concentration and distribution of O3 in the Earth’s stratosphere. This data has been crucial for understanding and monitoring the recovery of the O3 layer following international agreements, such as the Montreal Protocol. Air Quality Assessment: OMI’s high-resolution measurements of air pollutants, such as NO2, SO2, and HCHO, have significantly advanced our understanding of air quality. This information has been vital for tracking pollution sources, studying their transport and transformation, and assessing their impact on human health and the environment. Climate Research: The data collected by OMI has enhanced our knowledge of the interactions between atmospheric chemistry and climate change. These insights have been instrumental in refining climate models and improving our predictions of future climate scenarios. Global Impact: The OMI instrument has provided near-daily global coverage of atmospheric data, which has been essential for scientists and policymakers worldwide. The comprehensive and reliable data from OMI has supported countless research projects and informed decisions aimed at protecting and improving our environment. OMI remains one of the most stable UV/Vis instruments over its two decades of science and trend quality data collection. The success of the OMI and TROPOMI instruments is a testament to the collaboration, expertise, and dedication of both teams.
      Nickolay Krotkov
      NASA’s Goddard Space Flight Center
      Nickolay.a.krotkov@nasa.gov
      Pieternel Levelt
      National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling
      levelt@ucar.edu
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    • NASA
      Oral History with Stephen G. Jurczyk, 1962 – 2023
      By NASA
      1 Min Read Oral History with Stephen G. Jurczyk, 1962 – 2023
      NASA Acting Administrator Stephen G. Jurczyk Credits: NASA Steve Jurczyk’s NASA career began in 1988 at Langley Research Center as an engineer in the Electronic Systems Branch. During his time at Langley, he served in other roles, including director of engineering and director of research and technology.  Jurczyk was named as director of Langley in 2014, then in 2015 he left Langley to serve as the associate administrator for the Space Technology Mission Directorate at NASA Headquarters.  He quickly rose to the rank of associate administrator in 2018, and in January 2021 was named the agency’s acting administrator
      Read more about Steve Jurczyk
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      Read more about Dr. Mary L. Cleave
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    • European Space Agency
      Proba-3 will constantly measure Sun’s energy output
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      Proba-3 is such an ambitious mission that it needs more than one single spacecraft to succeed. In order for Proba-3’s Coronagraph spacecraft observe the Sun’s faint surrounding atmosphere, the disk-bearing Occulter spacecraft must block out the fiery solar disk. This means Proba-3’s Occulter ends up facing the Sun continuously, making it a valuable platform for science in its own right.
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