Langley Research Center

Tropospheric Emissions: Monitoring of Pollution (TEMPO) is observing air quality andatmospheric composition over North America from a geostationary orbit since its operationsstarted in August 2023. TEMPO observes the continent every 40 to 60 minutes at a spatialresolution on the order of ~ 2 x 4.5 km 2 . Together with the Geostationary EnvironmentMonitoring Spectrometer (GEMS, launch 2020) monitoring Asia and the Sentinel-4/UVN(launch 2025) monitoring Europe, TEMPO is part of the current global constellation ofgeostationary sensors devoted to the observation of air quality. Like GEMS and Sentinel-4/UVN,TEMPO uses backscattered ultraviolet and visible solar radiation to retrieve atmosphericamounts of key trace gases and aerosols associated with air quality and atmospheric chemistry.Among the species retrieved from TEMPO observations of nitrogen dioxide and formaldehydeare important to understand emissions and atmospheric chemistry, including the formation anddestruction of tropospheric ozone.After multiple version updates over the first two years of the mission, the TEMPO Level 2 NO 2and HCHO products have undergone significant enhancements to improve the performance andaccuracy of the slant column retrievals, air mass factor calculations and post-processingcorrections including destriping for NO 2 and background for HCHO. We illustrate theperformance of both retrievals (version 3 & 4), evaluating their fitting uncertainty and showingcomparisons with independent correlative measurements and other satellite products showcasingsmall noise levels and remarkable accuracy with well quantified biases. We continue byillustrating the capacity of TEMPO products focusing on different case studies showingTEMPO’s high temporal and spatial resolution. We finalize discussing aspects of the retrievalsubject to improvement and our plans to address them.

Climate forcing due to increases in well-mixed greenhouse gases (e.g., CO2 and methane) and the radiative response to the forcing have led to an imbalance between how much solar radiant energy is absorbed by Earth and how much thermal infrared radiation is emitted to space. Presently, Earth is absorbing »1 Wm-2 more energy from the sun than it is emitting to space as infrared radiation. A positive Earth energy imbalance (EEI) is concerning as it leads to increases in global mean temperature, sea level, heat accumulation within the ocean, and melting of snow and sea ice. Satellite and in-situ measurements indicate that EEI has more than doubled since 2000, increasing at a rate of 0.43±0.17 Wm-2 per decade. To put this into context, the cumulative planetary heating since 2000 associated with EEI is a factor of 26 larger than the global direct primary energy consumption for the same period. In this presentation, I will discuss the observations used to track changes in EEI and summarize our current understanding of the factors driving the observed changes. Of particular interest are recent EEI changes: EEI anomalies relative to the long-term average have subsided appreciably owing to an unprecedented and prolonged increase in outgoing longwave radiation. The underlying causes for this will be discussed.

The planetary boundary layer confines moisture, turbulence, and locally emitted air pollutants, thus accurately discerning the height of this layer is important for constraining pollutant transport and distribution and improved regional weather and climate forecasting. Traditional methods of boundary layer height (BLH) determination rely on radiosonde measurements of potential temperature profiles. However, these sounding measurements lack the instrumentation needed to characterize the chemical composition of the boundary layer that can be provided by larger airborne platforms. In 2024, the NASA DC-8 flew over the Philippines, South Korea, Taiwan, and Thailand during the Airborne and Satellite Investigation of Asian Air Quality (ASIA-AQ) campaign. Measurements during this campaign included an extensive array of gas, particulate, and meteorological measurements. We will present results of a turbulence-based method using 3D winds to determine the boundary layer height across DC-8 vertical flight profiles, including missed approaches at urban airports. The results from this method were used to develop a boundary layer flag for the campaign, and the computed DC-8 BLHs were compared to mixed layer heights determined by an airborne-based LIDAR system.

Abstract. NASA's Tropospheric Emissions: Monitoring of Pollution (TEMPO) geostationary satellite sensor provides high temporal and spatial resolution measurements critical for monitoring air quality. During the Synergistic TEMPO Air Quality Science (STAQS) component of the 2023 AGES+ campaign, extensive surface, airborne, and remote-sensing observations were collected over the New York City/Long Island Sound region, enabling comprehensive investigation of ozone and its precursors, including nitrogen dioxide (NO2) and formaldehyde (HCHO). Evaluating TEMPO (version 3) NO2 and HCHO column retrievals against Pandora and GEO-CAPE Airborne Simulator (GCAS) observations shows TEMPO can capture urban-suburban pollution gradients and exhibits biases comparable to previous satellite validation studies with strong agreements for NO2 (R ≈ 0.79–0.81), though sharp transitions between high and low emission regions remain challenging. The high-resolution (1.33 km × 1.33 km) WRF-Chem simulation reproduces the major spatiotemporal patterns of surface ozone and NO2 (R ≈ 0.56–0.73), supporting its use to fill observational gaps. By integrating TEMPO, WRF-Chem, in situ measurements, and Tropospheric Ozone Lidar network and Doppler wind lidar observations, we characterize the spatiotemporal dynamics of ozone under different pollution regimes. High-pollution days involve early urban precursor accumulation, entrainment of pollutant-rich residual-layer air, and sea-breeze-driven recirculation toward coastal regions. Moderate days exhibit localized enhancements driven by transport, such as downwind plume transport, while low-pollution days show efficient dispersion and limited ozone formation. This multi-platform framework highlights the importance of resolving fine-scale variability in coastal and transition zones and demonstrates TEMPO's value for improving ozone forecasting and mitigation in complex environments

Abstract Stratosphere‐troposphere exchange (STE) plays a crucial role in Earth's climate; however, the significance of small‐scale processes such as midlatitude convection to global STE remains understudied. Midlatitude tropopause‐overshooting convection is especially important to climate because it can enhance stratospheric water vapor, which has its greatest radiative forcing sensitivity in the extratropical lower stratosphere. Thus, it is essential to understand what factors influence the strength and prevalence of overshooting storms and associated STE. The U.S. Dynamics and Chemistry of the Summer Stratosphere (DCOTSS) field campaign during 2021 and 2022 was the first large‐scale airborne primarily focused on sampling stratospheric impacts from overshooting convection. Our research utilizes the extensive DCOTSS data set in combination with radar, satellite, and environmental observations to investigate relationships between observed stratosphere composition change and storm and environmental characteristics. Our results demonstrate greater magnitudes of STE for above‐anvil cirrus plume (AACP)‐producing storms and mesoscale convective systems (MCSs). In addition, the most extreme enhancements in water vapor and other tropospheric gases occur where the tropopause height is low and the depth of overshooting is high, especially for AACP‐producing storms. We also investigate the impact of storm and environmental characteristics on pathways for hydration (air mass transport and mixing vs. ice sublimation), finding that they also modulate the frequencies of each process at different altitudes. Namely, mixing is found to be most prevalent in AACP‐producing storms and MCSs, which can help explain transport differences between water vapor and other gases.

Abstract. A variety of chemical and dynamical processes in the troposphere and stratosphere affect tropical total column ozone (TCO), the net effect of which may cause changes in surface UV radiation and impact human and ecosystem health. We use dynamical linear modeling to estimate tropical trends in TCO and partial column ozone (PCO) in the troposphere and three stratospheric layers to assess agreement between satellite observational composites and chemistry–climate model (CCM) simulations from two multi-model experiments (CCMI-1 and CCMI-2022). While both model experiments show tropical TCO increases over 2000–2021, CCMI–2022 trends (+2.5 DU) agree slightly better with observations than CCMI-1 (+1.6 DU). However, this overall agreement obscures multiple systematic differences in PCO trends between the models and observations across atmospheric layers. For example, since 2000 tropical tropospheric PCO increased significantly in CCMI-2022 (+1.5 DU) but not in CCMI–1 (+0.3 DU), largely explaining the difference in TCO trends. Also, despite nearly identical stratospheric PCO trends, CCMI-2022 trends are slightly more negative in the lower stratospheric (by ~0.5 DU), compensated by more positive middle/upper stratosphere trends compared to CCMI-1. Crucially, substantial differences exist across observational PCO trends, particularly in the troposphere and middle/upper stratosphere, and these disagreements limit the ability to evaluate CCM fidelity. Furthermore, while the inter-model correlation between late and early 21st century trends is suggestive of a potential emergent constraint on future ozone trends, the spread in observational trends precludes its observational implementation.

Abstract The Arctic has experienced rapid sea ice loss and a substantial surface albedo decline, altering its radiation budget. CMIP6 (Coupled Model Intercomparison Project Phase 6) models capture these trends but show considerable inter‐model spread in the magnitude, distribution, and seasonality of Arctic surface albedo. Over land, spread in AMIP (Atmospheric Model Intercomparison Project) and CMIP6 is associated with snow cover variations, while over the ocean, where sea ice dominates, the sources are less clear. We compare CMIP6 simulations with observations from the Clouds and the Earth's Radiant Energy System (CERES) and develop a decomposition method to quantify contributions from sea ice albedo, concentration, and extent. Over the Arctic Ocean, all three factors contribute to inter‐model spread in CMIP6. In AMIP, despite prescribed sea ice concentrations, we were surprised to find an inter‐model spread in Arctic Ocean albedo similar to that in CMIP6, driven solely by sea ice albedo. Applying the decomposition to future projections shows that the largest decline occurs in the Central Arctic, driven primarily by reductions in sea ice extent. After 2045, sea ice extent emerges as the dominant driver, highlighting ice edge retreat as key to future albedo decline. These findings pinpoint key sources of inter‐model spread in Arctic surface albedo and offer insights into quantifying shortwave (SW) radiative effect associated with sea ice responses in future projections.

<strong class="journal-contentHeaderColor">Abstract.</strong> Aerosols in the upper troposphere play an important role in Earth&rsquo;s radiative balance and atmospheric composition. Satellite observations have revealed a recurrent enhancement of aerosol extinction coefficient (AEC) in the upper troposphere and near the tropopause over the Asian summer monsoon (ASM) anticyclone (ASMA) region during July&ndash;August. However, substantial uncertainties remain regarding (i) the influence of ASM dynamics and climate variability on these aerosols, (ii) the extent to which the upper-tropospheric aerosol trends reflect changes in surface pollutant emissions, and (iii) the ability of global models to simulate aerosol amounts, variability, and key controlling processes in the upper-tropospheric ASMA region. Here, we present results from an AeroCom-coordinated global multi-model study addressing these issues. Using simulations from nine models for 2000&ndash;2018, we find large inter-model differences in non-volcanic AEC over the upper-tropospheric ASMA region, with coefficients of variation ranging from 64 % to 86 %. Approximately half of this spread is attributable to differences in transport and wet removal processes, as diagnosed using common tracers, with discrepancies in wet removal contributing about eight times more than those associated with transport. The multi-model ensemble indicates an overall increase in non-volcanic AEC over the past two decades, consistent with rising anthropogenic emissions in Asia, while interannual variability is linked to climate variability as represented by the Multivariate ENSO Index. Through comparison with satellite observations, we further identify persistent model deficiencies, particularly in the representation of volcanic aerosols, and highlight priorities for future coordinated model developments and evaluation.

Urban Air Mobility (UAM) is a rapidly emerging industry targeting delivery of air transportation services around metropolitan areas with the potential for aviation to become a practical part of everyday life while leveraging emerging technologies and operational concepts. This whitepaper, a collaboration between NASA’s Air Mobility Pathfinders (AMP) project and Wisk, explores the interoperability between crewed and uncrewed aircraft in UAM operations, leveraging operational concepts put forth in the Federal Aviation Administration (FAA) UAM Concept of Operations (ConOps) for the Midterm UAM phase. Specifically, UAM aircraft are envisioned to takeoff and land from vertiports and primarily operate within Cooperative Areas (CAs). CAs are designated as airspace volumes with specific requirements for performance, communication, and surveillance in which UAM Operators follow cooperative operating practices (COPs). Additionally, Third-Party Service Providers (TSPs) are envisioned to play a crucial role in conflict management, including both strategic and tactical deconfliction within the CAs.

<strong class="journal-contentHeaderColor">Abstract.</strong> We present an updated evaluation of stratospheric ozone profile trends in the 60&deg;S&ndash;60&deg;N latitude range using long-term ground-based and satellite climate data records, as well as simulations by chemistry-climate models. The trends are evaluated using the LOTUS (Long-term Ozone Trends and Uncertainties in the Stratosphere) regression model. Analyses of satellite data confirm statistically significant positive ozone trends in the period 2000&ndash;2024 in the upper stratosphere of ~1&ndash;3% decade^-1, with larger trends at mid-latitudes compared to the tropics. The trends are slightly positive or close to zero in the middle stratosphere, and mostly negative, &minus;1&ndash;2% decade^-1, in the lower stratosphere; but they are not statistically significant. The ozone trends are similar to previous analyses (2000&ndash;2020 trends). Ozone trends in 2000&ndash;2024 predicted by climate model simulations are in good agreement with combined satellite trends. In the upper stratosphere, models predict a slightly stronger ozone recovery than observations. In the lower stratosphere, both models and satellite observations report negative trends of in the tropics, while modelled ozone trends are slightly positive at mid-latitudes. Ozone profile trends over several stations estimated from ground-based records capture the same overall vertical pattern of ozone trends as merged gridded satellite datasets. Analyses of regional ozone trends in 2003&ndash;2024 using merged satellite datasets confirmed the previous observations of a longitudinal structure in ozone trends in the NH mid-latitude stratosphere, with positive trends over Scandinavia and negative trends over Siberia. However, the magnitude of this dipole-like structure is reduced compared to previous analyses.