UMBC GESTAR II

Permanent URI for this collectionhttp://hdl.handle.net/11603/24116

n December 2021, GESTAR II partnered with NASA Goddard Space Flight Center’s Earth Science Division to advance Earth science and Goddard’s leadership by providing a competitive environment to hire and retain high-quality scientists who are on track to be leaders at NASA, in academia and in industry. GESTAR II exemplifies the power of mentorship, embracing a career development strategy that only a university research center can provide. In GESTAR II, early-career researchers and students can build outstanding resumes, launching them to become the Earth science leaders of tomorrow.

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Dynamical Mechanisms Underlying the 2022/23 California Flooding: Analysis With A Stationary Wave Model
(2024) DeAngelis, Anthony M.; Schubert, Siegfried D.; Chang, Yehui; Lim, Young-Kwon; Thomas, Natalie; Koster, Randal D.; Bosilovich, Michael G.; Molod, Andrea M.; Collow, Allison; Dezfuli, Amin
In late December 2022 and the first half of January 2023, much of California experienced an unprecedented series of atmospheric rivers that produced heavy rains and near-record flooding. Previous work shows that a chain of dynamical events contributed to the extreme precipitation, including the development of a Rossby wave (as a result of forcing linked to the MJO) that emerged from the Indian Ocean in mid-December, and the subsequent development of a persistent positive Pacific North American (PNA) pattern that ultimately directed moisture onto the US West Coast starting in late December. Here, we use a stationary wave model (SWM) to further elucidate the dynamical and thermodynamical processes that drove the aforementioned chain of events. The results reveal the following: 1) The mid-December Rossby wave was likely induced by vorticity stretching and advection in the middle East linked indirectly to the MJO, 2) The initial development of the PNA in late December was triggered by transient and stretching sources of vorticity in the Pacific that were themselves induced by the aforementioned Rossby wave, and 3) The PNA was maintained through mid-January in part by diabatic heating west of Hawaii that was associated with anomalous precipitation influenced by the PNA circulation anomalies, thus representing a feedback on the PNA. One key finding from the SWM analysis is the limited direct role of tropical heating for inducing any of the dynamical mechanisms related to the California extreme event.
A comparison of the meridional meandering of extratropical precipitation during boreal winter: eddy momentum flux versus Eulerian storm tracks
(Springer Nature, 2025-03-13) Yoo, Changhyun; Jin, Daeho; Lee, Sukyoung; Kim, Daehyun
The latitudinal distribution of winter extratropical precipitation is often regarded as being determined by the location and intensity of the storm track. Here, we compare the precipitation variability associated with the meridional eddy momentum flux (EMF) with that associated with an Eulerian storm track measure. Observations show that when the midlatitude EMF is anomalously poleward, the occurrence of moderate-to-heavy precipitation (1–33 mm day-1) increases between 45°N and 70°N, while decreasing between 25°N and 45°N. This shift occurs mostly downstream of the climatological storm track maximum, with generally greater precipitation anomalies compared to those associated with storm track changes. The shift is tied to changes in horizontal moisture transport primarily by planetary scale waves. These results suggest that, in addition to the storm track intensity, dynamics of the horizontal wave tilts which affect the EMF intensity need to be considered when projecting future changes in precipitation variability.
Applied Uses of MERRA Reanalyses: Current and Future Prospects
(2024) Bosilovich, Michael; Stackhouse, Paul; Uz, Stephanie Schollaert; Dezfuli, Amin; Thomas, Natalie; Collow, Allison
During the initial planning of the Modern Era Retrospective-analysis for Research and Applications (MERRA), the project was envisioned to become a tool for applied sciences and decision makers, as well as weather and climate research. MERRA was the first reanalysis to provide data at 1 hourly frequencies. After discussions with wind energy users, 50m above the surface winds were included in the data collection to begin to represent the environment at the turbine height. MERRA-2 was the first reanalysis to include interactive and assimilated aerosols. From these, PM 1, 2.5 and 10 records have been computed and contribute to the climate and health sector. The US Center for Disease Control is accessing MERRA-2 data for comparison along with their health data. MERRA-2 Extreme Indices have been computed from the high frequency data (e.g. precipitation maxima, heat waves and fire weather). These have been used to characterize the changing extremes in the United States and around the globe as well as the weather associated with the extremes.The next-generation, MERRA-21C, includes increased resolution (25km) and continues to provide innovative Earth system data. For example, a boundary layer collection will provide constant height level data starting at 100m, continuing up to 4000m. This will provide detailed information about the boundary layer processes that greatly affect the biosphere. Chemical tracers for constituents are included in the system. The ensemble data assimilation is run with 32 members, and the variance for critical variables are stored. We will explore the use of this variance as one measure of uncertainty relevant for applied uses, which has not been included in any MERRA reanalysis. We will discuss use case scenarios developed to engage with the energy and financial sectors, to better understand their needs for climate data. Prospects for further downscaling of reanalyses will also be explored.
Analyses of Virtual Ship-Tracks Systematically Underestimate Aerosol-Cloud Interactions Signals
(AGU, 2025) Yuan, Tianle; Song, Hua; Oreopoulos, Lazaros; Wood, Robert; Meyer, Kerry; Crawford, Alice; Smith, William; Eastman, Ryan
Ship-tracks are important natural/opportunistic experiments to study aerosol-cloud interactions (ACIs). However, detectable ship-tracks are not produced in many instances. Virtual ship-tracks have been conceived to expand the scale of ACIs analyses. Cloud responses in virtual ship-tracks differ strongly from those of detected ones. Here we show that the current approach of virtual ship-tracks can lead to systematic biases and errors and suggest necessary improvements. Errors in trajectory modeling introduce mismatches between areas actually affected by ship-emissions and virtual ship-track locations, that is, positional errors. Positional errors systematically underestimate ACI signals and the underestimate is severe as indicated by analysis of cloud droplet number concentration changes. The assumption of fixed ship-track width also systematically diminishes resulting aerosol effects by more than 10%, which leads to a forcing difference of around 0.1 Wm⁻². We make suggestions to improve the simulation of virtual ship-tracks so that their full potential for studying ACIs can be unleashed.
Trophic amplification of Southern Ocean plankton emerges from changing seasonality
(2025-03-27) Xue, Tianfei; Arteaga Quintero, Lionel Alejandro | Pahlow, Markus; Frenger, Ivy
Southern Ocean plankton dynamics are climate-sensitive. Using CMIP6 multi-model ensemble projections, we find that the seemingly stable Southern Ocean plankton biomass under climate change masks opposing trends across different geographic zones. Plankton in the subpolar zone is projected to remain relatively stable due to compensatory changes in bottom-up and top-down processes. Plankton in the subtropical and seasonal ice zones are projected to experience negative and positive trophic amplification, respectively, with zooplankton decreasing and increasing proportionally more than phytoplankton. The predicted trophic amplification arises from uneven seasonal changes in zooplankton grazing, driven by changes in phytoplankton. The negative trophic amplification in the subtropical zone primarily originates during the shallow mixed-layer period, where further shoaling of the mixed layer in the changing climate accentuates nutrient limitation. The consequent reduction in phytoplankton growth and concentration leads to a disproportionate decline in zooplankton grazing and biomass. The positive trophic amplification in the seasonal ice zone also occurs mainly during the shallow mixed-layer season. Improved light availability due to shoaling of the relatively deep mixed layer, sea ice retreat, and warmer temperatures boost phytoplankton growth, together with further suppressing surface phytoplankton, resulting in a disproportionate increase in zooplankton grazing and biomass. Our results underscore the importance of assessing seasonal and regional variations in plankton dynamics to unveil the nuanced effects of climate change on marine plankton ecosystems.
Transboundary sky waters in the Middle East: Definition, challenges, and opportunities
(PLOS, 2024-12-02) Dezfuli, Amin; Zaitchik, Benjamin F.
Transboundary water disputes in the Middle East have increased in recent years due to growing constraints on water resources. Efforts to harvest more water from the atmosphere through weather intervention projects have exacerbated existing conflicts. Here, we propose that atmospheric water vapor should be recognized as a transboundary resource that involves substantial uncertainty. As such, this note serves as a starting point for characterizing various components of this concept, the knowledge gaps, and a roadmap to address those gaps. These efforts would reduce uncertainties and help integrate the sky water into transboundary water negotiations and collaborative understanding.
The Great Plains Low-Level Jet in MERRA-2
(2024-12) DeAngelis, Anthony M.; Bosilovich, Michael G.; Collow, Allison; Schubert, Siegfried D.; Koster, Randal D.; Dezfuli, Amin; Akkraoui, Amal EL; Thomas, Natalie; Lim, Young-Kwon
The Great Plains low-level jet (GPLLJ), characterized by its diurnally varying southerly winds in the lower troposphere, is a critical component of the hydroclimate in the central US. Here, we evaluate the representation of the GPLLJ in the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) developed by NASA’s Global Modeling and Assimilation Office (GMAO). Based on a preliminary analysis of several strong GPLLJ events, MERRA-2 is shown to be a valuable dataset for studying the horizontal, vertical, and diurnal characteristics of the LLJ. A comparison with rawinsonde and radar wind profiles suggests that the strength and height of the LLJ is overall realistic in MERRA-2.
Substantial Diel Changes of Cloud Adjustments to Aerosols in Ship-tracks
(2025-04-09) Yuan, Tianle; Song, Hua; Wood, Robert; Oreopoulos, Lazaros; Meyer, Kerry; Smith, William; Eastman, Ryan
Human induced changes in atmospheric aerosols have introduced a climate forcing by modifying cloud droplet number concentration, liquid water, and cloud fraction. This forcing is subject to large uncertainties as cloud adjustments have not only complex dependence on background conditions, but also temporal fluctuations, especially those driven by diel variations in solar heating. However, direct observations of such diel changes are still limited. Here, we present observational evidence of substantial diel changes in the cloud adjustments to aerosols within ship tracks, linear lines of polluted clouds captured in satellite images. We developed a novel method to automatically determine the age of each ship-track segment and analyze cloud adjustments to aerosols. We show that more aged polluted clouds with extended nighttime exposure exhibit higher increases in cloud fraction. By contrast, liquid water path adjustments follow a non-monotonic pattern: they generally decrease with time before reversing trend in clouds formed at nighttime. Most of these diel contrasts are statistically significant and likely stem from differences in solar heating and cloud precipitation. The increase in cloud fraction adjustment suggests a larger aerosol effective radiative forcing, -0.1 to -0.4 W per meter squared, than the estimate without considering temporal variations, while the temporal changes in liquid water path adjustments may partially offset it. These findings underscore the importance of diel variations in aerosol cloud interactions. Our approach demonstrates that ship tracks, despite appearing as instantaneous observations, yield valuable insights into the temporal evolution of cloud adjustments.
Spatiotemporal Patterns of Subsidence and Sea Level Rise in the Samoan Islands 15 Years After the 2009 Samoa-Tonga Earthquake
(AGU, 2025-04-05) Huang, Stacey; Sauber, Jeanne M.; Han, Shin-Chan; Ray, Richard; Fielding, Eric
Fifteen years after the 2009 Samoa-Tonga earthquake, rates of subsidence on the Samoan Islands remain elevated compared with pre-earthquake levels. Coastal flooding has become a regular occurrence, increasing coastal erosion, risk of saltwater intrusion in freshwater aquifers, and threats to critical infrastructure. There is an urgent need to characterize ongoing trends in local and regional subsidence and constrain future behavior to inform the development of effective coastal resilience measures. Here, we have leveraged a multi-sensor, multi-frequency remote sensing suite to track changes in subsidence rates on the islands of Upolu (Samoa) and Tutuila (American Samoa). Our updated GPS/GNSS and tide gauge/altimetry records elucidate subsidence relaxation trends since the earthquake, and our analysis of high-resolution InSAR data from the Sentinel-1 mission—overcoming difficulties presented by vegetated terrain and small landmass sizes—reveal an unprecedented view of local subsidence in the Samoan Islands. These local signals need to be accounted for in coastal planning, including for the development of updated flooding thresholds that are relevant to the Samoan Islands and that account for spatial heterogeneities in subsidence. Overall, we find that subsidence on Upolu has nearly returned to pre-earthquake levels; meanwhile, subsidence on Tutuila will likely continue for a few more decades but ease more quickly than previously predicted. Both of these trends should alleviate previously anticipated pressures associated with high subsidence coupled with sea level rise.
Scattering properties and Lidar Characteristics of Asian Dust Particles Based on Realistic Shape Models
(2025-03-26) La Luna, Anthony; Zhang, Zhibo; Zheng, Jianyu; Song, Qianqian; Yu, Hongbin; Ding, Jiachen; Yang, Ping; Saito, Masanori
The lidar backscattering properties of Asian dust particles, namely the lidar ratio (𝑆) and backscattering depolarization ratio (δ), were studied using a discrete dipole approximation (DDA) model. The three-dimensional morphology of the dust particles was reconstructed in fine detail using the focused ion-beam (FIB) tomography technique. An index based on the symmetry of the scattering phase matrix was developed to assess the convergence of random orientation computation using DDA. Both the 𝑆 and δ exhibit an asymptotic trend with dust particle size: the 𝑆 initially decreases while the δ increases with size, before both approach their asymptotic values. The lidar properties were found to have statistically insignificant dependence on effective sphericity. The presence of strongly absorbing minerals, such as magnetite, can greatly reduce the dust's single-scattering albedo and δ. Utilizing the robust asymptotic trend behavior, two parameterization schemes were developed: one to estimate the δ of a single dust particle given its size, and the other to estimate the δ of dust particles with a lognormal particle size distribution given the effective radius. The parameterization scheme was compared with results based on the TAMUdust2020 database, showing hexahedrals to reasonably represent realistic geometries with similar physical properties.
A systematic comparison of ACE-FTS δD retrievals with airborne in situ sampling
(2025-04-04) Clouser, Benjamin Wade; KleinStern, Carly Cyd; Desmoulin, Adrien; Singer, Clare E.; St. Clair, Jason; Hanisco, Thomas F.; Sayres, David S.; Moyer, Elisabeth J.
The isotopic composition of water vapor in the upper troposphere and lower stratosphere (UTLS) can be used to understand and constrain the budget and pathways of water transport into that region of the atmosphere. Measurements of the water isotopic composition help further understanding of the region's chemistry, radiative budget, and the sublimation and growth of polar stratospheric clouds and high-altitude cirrus, both of which are also important to stratospheric chemistry and Earth's radiation budget. Here we present the first intercomparison of water isotopic composition δD using in situ measurements from the ChiWIS, Harvard ICOS, and Hoxotope instruments and satellite retrievals from ACE-FTS. The in situ data comes from the AVE-WIIF, TC4, CR-AVE, StratoClim, and ACCLIP field campaigns, and satellite retrievals of isotopic composition are derived from the ACE-FTS v5.2 data set. We find that in all campaign intervals, the satellite retrievals above about 14 km altitude are depleted by up to 150 ‰ with respect to in situ measurements. We also use in situ measurements from the ChiWIS instrument, which has flown in both the Asian Summer Monsoon (AM) and the North American Monsoon (NAM), to confirm the isotopic enhancement in δD observed in satellite retrievals above the NAM.
Multispectral Land Surface Reflectance Reconstruction Based on Non-Negative Matrix Factorization: Bridging Spectral Resolution Gaps for GRASP TROPOMI BRDF Product in Visible
(MDPI, 2025-03-17) Hou, Weizhen; Liu, Xiong; Wang, Jun; Chen, Cheng; Xu, Xiaoguang
In satellite remote sensing, mixed pixels commonly arise in medium- and low-resolution imagery, where surface reflectance is a combination of various land cover types. The widely adopted linear mixing model enables the decomposition of mixed pixels into constituent endmembers, effectively bridging spectral resolution gaps by retrieving the spectral properties of individual land cover types. This study introduces a method to enhance multispectral surface reflectance data by reconstructing additional spectral information, particularly in the visible spectral range, using the TROPOMI BRDF product generated by the Generalized Retrieval of Atmosphere and Surface Properties (GRASP) algorithm. Employing non-negative matrix factorization (NMF), the approach extracts spectral basis vectors from reference spectral libraries and reconstructs key spectral features using a limited number of wavelength bands. The comprehensive test results show that this method is particularly effective in supplementing surface reflectance information for specific wavelengths where gas absorption is strong or atmospheric correction errors are significant, demonstrating its applicability not only within the 400–800 nm range but also across the broader spectral range of 400–2400 nm. While not a substitute for hyperspectral observations, this approach provides a cost-effective means to address spectral resolution gaps in multispectral datasets, facilitating improved surface characterization and environmental monitoring. Future research will focus on refining spectral libraries, improving reconstruction accuracy, and expanding the spectral range to enhance the applicability and robustness of the method for diverse remote sensing applications.
Multi-GNSS Airborne Radio Occultation Observations as a Complement to Dropsondes in Atmospheric River Reconnaissance
(AGU, 2021-11-22) Haase, J. S.; Murphy, Michael; Cao, B.; Ralph, F. M.; Zheng, M.; Delle Monache, L.
Variations in the water vapor that atmospheric rivers (ARs) carry toward North America within Pacific storms strongly modulates the spatiotemporal distribution of west-coast precipitation. The “AR Recon” program was established to improve forecasts of landfalling Pacific-coast ARs and their associated precipitation. Dropsondes are deployed from weather reconnaissance aircraft and pressure sensors have been added to drifting ocean buoys to fill a major gap in standard weather observations, while research is being conducted on the potential for airborne Global Navigation Satellite System (GNSS) radio occultation (ARO) to also contribute to forecast improvement. ARO further expands the spatial coverage of the data collected during AR Recon flights. This study provides the first description of these data, which provide water vapor and temperature information typically as far as 300 km to the side of the aircraft. The first refractivity profiles from European Galileo satellites are provided and their accuracy is evaluated using the dropsondes. It is shown that spatial variations in the refractivity anomaly (difference from the climatological background) are modulated by AR features, including the low-level jet and tropopause fold, illustrating the potential for RO measurements to represent key AR characteristics. It is demonstrated that assimilation of ARO refractivity profiles can influence the moisture used as initial conditions in a high-resolution model. While the dropsonde measurements provide precise, in situ wind, temperature and water vapor vertical profiles beneath the aircraft, and the buoys provide surface pressure, ARO provides complementary thermodynamic information aloft in broad areas not otherwise sampled at no additional expendable cost.
Integrating Frequency-Domain Representations with Low-Rank Adaptation in Vision-Language Models
(2025-03-08) Khan, Md Azim; Gangopadhyay, Aryya; Wang, Jianwu; Erbacher, Robert F.
Situational awareness applications rely heavily on real-time processing of visual and textual data to provide actionable insights. Vision language models (VLMs) have become essential tools for interpreting complex environments by connecting visual inputs with natural language descriptions. However, these models often face computational challenges, especially when required to perform efficiently in real environments. This research presents a novel vision language model (VLM) framework that leverages frequency domain transformations and low-rank adaptation (LoRA) to enhance feature extraction, scalability, and efficiency. Unlike traditional VLMs, which rely solely on spatial-domain representations, our approach incorporates Discrete Fourier Transform (DFT) based low-rank features while retaining pretrained spatial weights, enabling robust performance in noisy or low visibility scenarios. We evaluated the proposed model on caption generation and Visual Question Answering (VQA) tasks using benchmark datasets with varying levels of Gaussian noise. Quantitative results demonstrate that our model achieves evaluation metrics comparable to state-of-the-art VLMs, such as CLIP ViT-L/14 and SigLIP. Qualitative analysis further reveals that our model provides more detailed and contextually relevant responses, particularly for real-world images captured by a RealSense camera mounted on an Unmanned Ground Vehicle (UGV).
Impact of electric and clean-fuel vehicles on future PM2.5 and ozone pollution over Delhi
(IOP, 2024-07-09) Mogno, Caterina; Wallington, Timothy J.; Palmer, Paul I.; Hakkim, Haseeb; Sinha, Baerbel; Sinha, Vinayak; Steiner, Allison L.; Sharma, Sumit
We investigate the impact of adoption of electric vehicles and cleaner fuels on future surface levels of PM2.5 and ozone over Delhi for two contrasting seasons, pre-monsoon and post-monsoon. We run the WRF-Chem atmospheric transport model at high resolution (4 km) with two transport emission scenarios for year 2030: (1) a scenario with electrification of two- and three-wheelers and light commercial vehicles, and (2) a scenario which also includes conversion of diesel vehicles to compressed natural gas (CNG). Compared to the baseline values in 2019, the scenario with both electrification and conversion of diesel vehicles to CNG has a greater reduction in PM2.5 concentrations (up to 5%) than the electrification of two- and three-wheelers and light commercial vehicles alone (within 1%), mainly due to the the greater reduction in primary emissions of PM2.5 and black carbon from diesel conversion to CNG. Vehicles electrification could result in an increase in the daily maximum 8-hours ozone concentrations, which are partially offset by additionally converting to CNG—by ?1.9% and +2.4% during pre-monsoon and post-monsoon seasons. This reflects higher NOx emissions from the CNG vehicle scenario compared to electrification-alone scenario, which limits the increase of surface ozone in the VOC-limited chemical environment over Delhi. Our findings highlight the importance of a coordinated strategy for PM2.5 and ozone when considering traffic emission controls, and highlight that the transition to electric vehicles should be accompanied by the conversion of diesel vehicles to CNG to limit surface ozone increase and achieve greater reduction in PM2.5 concentrations over Delhi. However, the small changes in PM2.5 and in ozone compared to the baseline scenario highlight the importance of joint emissions reduction from other sectors to achieve substantial progress in PM2.5 and ozone air quality in Delhi.
Impact of increased anthropogenic Amazon wildfires on Antarctic Sea ice melt via albedo reduction
(Cambridge University Press, 2025-03-10) Chakraborty, Sudip; Devnath, Maloy Kumar; Jabeli, Atefeh; Kulkarni, Chhaya; Boteju, Gehan; Wang, Jianwu; Janeja, Vandana
This study shows the impact of black carbon (BC) aerosol atmospheric rivers (AAR) on the Antarctic Sea ice retreat. We detect that a higher number of BC AARs arrived in the Antarctic region due to increased anthropogenic wildfire activities in 2019 in the Amazon compared to 2018. Our analyses suggest that the BC AARs led to a reduction in the sea ice albedo, increased the amount of sunlight absorbed at the surface, and a significant reduction of sea ice over the Weddell, Ross Sea (Ross), and Indian Ocean (IO) regions in 2019. The Weddell region experienced the largest amount of sea ice retreat (~ 33,000 km²) during the presence of BC AARs as compared to ~13,000 km² during non-BC days. We used a suite of data science techniques, including random forest, elastic net regression, matrix profile, canonical correlations, and causal discovery analyses, to discover the effects and validate them. Random forest, elastic net regression, and causal discovery analyses show that the shortwave upward radiative flux or the reflected sunlight, temperature, and longwave upward energy from the earth are the most important features that affect sea ice extent. Canonical correlation analysis confirms that aerosol optical depth is negatively correlated with albedo, positively correlated with shortwave energy absorbed at the surface, and negatively correlated with Sea Ice Extent. The relationship is stronger in 2019 than in 2018. This study also employs the matrix profile and convolution operation of the Convolution Neural Network (CNN) to detect anomalous events in sea ice loss. These methods show that a higher amount of anomalous melting events were detected over the Weddell and Ross regions.
From Column to Surface: Connecting the Performance in Simulating Aerosol Optical Properties and PM₂.₅ Concentrations in the NASA GEOS-CCM Model
(NTRS, 2024-12) Mogno, Caterina; Colarco, Peter R.; Collow, Allison; Strode, Sarah A.; Valenti, Vanessa; Liang, Qing; Oman, Luke; Knowland, K. Emma
Evaluating spectral cloud effective radius retrievals from the Enhanced MODIS Airborne Simulator (eMAS) during ORACLES
(EGU, 2025-02-27) Meyer, Kerry; Platnick, Steven; Arnold, G. Thomas; Amarasinghe, Nandana; Miller, Daniel J.; Small-Griswold, Jennifer; Witte, Mikael; Cairns, Brian; Gupta, Siddhant; McFarquhar, Greg; O'Brien, Joseph
Satellite remote sensing retrievals of cloud effective radius (CER) are widely used for studies of aerosol–cloud interactions. Such retrievals, however, rely on forward radiative transfer (RT) calculations using simplified assumptions that can lead to retrieval errors when the real atmosphere deviates from the forward model. Here, coincident airborne remote sensing and in situ observations obtained during NASA's ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) field campaign are used to evaluate retrievals of CER for marine boundary layer stratocumulus clouds and to explore impacts of forward RT model assumptions and other confounding factors. Specifically, spectral CER retrievals from the Enhanced MODIS Airborne Simulator (eMAS) and the Research Scanning Polarimeter (RSP) are compared with polarimetric retrievals from RSP and with CER derived from droplet size distributions (DSDs) observed by the Phase Doppler Interferometer (PDI) and a combination of the Cloud and Aerosol Spectrometer (CAS) and the Two-Dimensional Stereo Probe (2D-S). The sensitivities of the eMAS and RSP spectral retrievals to assumptions about the DSD effective variance (CEV) and liquid water complex index of refraction are explored. CER and CEV inferred from eMAS spectral reflectance observations of the backscatter glory provide additional context for the spectral CER retrievals. The spectral and polarimetric CER retrieval agreement is case dependent, and updating the retrieval RT assumptions, including using RSP polarimetric CEV retrievals as a constraint, yields mixed results that are tied to differing sensitivities to vertical heterogeneity. Moreover, the in situ cloud probes, often used as the benchmark for remote sensing CER retrieval assessments, themselves do not agree, with PDI DSDs yielding CER values 1.3–1.6 µm larger than CAS and with CEV roughly 50 %–60 % smaller than CAS. Implications for the interpretation of spectral and polarimetric CER retrievals and their agreement are discussed.
A Diagnosis of Oceanic Precipitation in IMERG-GMI
(AMS, 2025-03-06) Watters, Daniel C.; Huffman, George J.; Gatlin, Patrick N.; Kirstetter, Pierre-Emmanuel; Bolvin, David T.; Joyce, Robert; Nelkin, Eric J.; Tan, Jackson; Wolff, David B.
Diagnosing errors in spaceborne oceanic precipitation estimates is difficult due tocomplicated multi-satellite algorithms and limited surface-based measurements. The Global Precipitation Measurement (GPM) mission helps to alleviate these challenges with NASA’s Integrated Multi-satellitE Retrievals for GPM (IMERG) product, which is transparently designed to encourage community validation activities, and the GPM Validation Network, which collects observations across global precipitation regimes from over 100 ground-based weather radars to serve as reference datasets for the GPM precipitation products. This study uses the GPM Validation Network’s oceanic precipitation observations from 32 island and coastal radars to diagnose the performance of IMERG V06B & V07B Final Run products during GPM Microwave Imager (GMI) overpasses (i.e., IMERG-GMI) in the period June 2014 – September 2021. Errors are traced from the input Level-2 (satellite footprint) Goddard Profiling Algorithm climate (GPROF-CLIM) GMI product through the successive gridding, calibration and precipitation distribution restoration steps of IMERG’s Level-3 (gridded) algorithm. Results highlight that IMERG-GMI V07B outperforms V06B in detecting and quantifying oceanic precipitation, with a significant improvement over high-latitude ocean (V06B: +143%; V07B: +50%). Furthermore, there is a clear oceanic latitudinal trend in the mean relative bias of IMERG-GMI V07B (high-latitude: +50%; mid-latitude: +10%; tropical: -41%), which largely traces back to GPROF-CLIM V07 (high-latitude: +22%; mid-latitude: -8%; tropical: -44%), with bias differences driven by IMERG’s passive microwave calibration scheme. This error tracing approach supports future IMERG algorithm developments by disentangling how algorithm steps enhance or mitigate errors.
Dynamic Impact of the Southern Annular Mode on the Antarctic Ozone Hole Area
(MDPI, 2025-02-27) Lee, Jae N.; Wu, Dong L.
This study investigates the impact of dynamic variability of the Southern Hemisphere (SH) polar middle atmosphere on the ozone hole area. We analyze the influence of the southern annular mode (SAM) and planetary waves (PWs) on ozone depletion from 19 years (2005–2023) of aura microwave limb sounder (MLS) geopotential height (GPH) measurements. We employ empirical orthogonal function (EOF) analysis to decompose the GPH variability into distinct spatial patterns. EOF analysis reveals a strong relationship between the first EOF (representing the SAM) and the Antarctic ozone hole area (γ = 0.91). A significant negative lag correlation between the August principal component of the second EOF (PC2) and the September SAM index (γ = -0.76) suggests that lower stratospheric wave activity in August can precondition the polar vortex strength in September. The minor sudden stratospheric warming (SSW) event in 2019 is an example of how strong wave activity can disrupt the polar vortex, leading to significant temperature anomalies and reduced ozone depletion. The coupling of PWs is evident in the lag correlation analysis between different altitudes. A “bottom-up” propagation of PWs from the lower stratosphere to the mesosphere and a potential “top-down” influence from the mesosphere to the lower stratosphere are observed with time lags of 21–30 days. These findings highlight the complex dynamics of PW propagation and their potential impact on the SAM and ozone layer. Further analysis of these correlations could improve one-month lead predictions of the SAM and the ozone hole area.

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