Abstract This paper describes improvements to geophysical retrievals from NASA's Advanced Microwave Precipitation Radiometer (AMPR) during the Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex). The retrieved products are validated using independent data sets, and example applications in addressing science questions about the maritime tropics are provided. Multi‐linear regression equations previously developed to retrieve cloud liquid water path (CLW), total precipitable water vapor (WV), and 10‐m wind speed (WS) from AMPR brightness temperatures in the midlatitudes were examined. Initial testing revealed that the CLW methods required modification for the maritime tropics, likely due to the stark environmental differences. Minor WS adjustments were also needed to account for the presence of a new AMPR radome. Compared with numerical simulations, the updated CLW equation performed nearly an order of magnitude better than its predecessor. Validating AMPR CLW with airborne polarimeter‐derived CLW throughout CAMP2Ex yielded a median absolute deviation that is less than the predecessor CLW equation's uncertainty and comparable to CLW precisions observed in past studies. In situ WV and WS validation using dropsondes was promising, with mean deviations that are less than their target uncertainties. Correlating AMPR CLW with polarimeter‐derived cloud‐top height (CTH) indicated an expected CLW ∝ CTH2 relation for CTH < 4 km, but reduced CLW for CTH > 4 km may have been associated with cloud droplet removal via accretion and/or mixed‐phase onset. These results demonstrate the power of airborne radiometer geophysical retrievals as standalone metrics and the insight they provide when used alongside other data sets.

The derivation of geophysical parameters from passive microwave observations over land has always been challenging. Soil conditions, land cover, and the atmosphere affect the measurements to varying degrees, and it is difficult to isolate these individual contributions. In this study, we assess whether multiangle observations provide additional information that can strengthen existing retrieval algorithms. Between October and November 2024, a series of airborne flights carrying the advanced microwave precipitation radiometer (AMPR) were conducted over the United States. Three land-based flights with multiangle observations from 0 degrees to 45 degrees and dual-polarized measurements at 10.7, 19.35, and 37.1 GHz were analyzed. The data showed a strong linear relationship between the microwave polarization ratio and the incidence angles within the 25 degrees-45 degrees range (e.g., $R<^>{2} \gt 0.9$ for 71.2% of all flight scans analyzed at 10.7 GHz). The linear model for the polarization ratio showed a similar performance in terms of root-mean-square error (RMSE) to simulations based on a $\tau $ - $\omega $ radiative transfer model and commonly used assumptions. The observed linearity was further evaluated with satellite observations from the AMSR2. This evaluation confirmed the observed linearity across all three frequencies. The slope of the relationship between the polarization ratio and the incidence angle was calculated for each multiangle flight scan, which was sensitive to both soil moisture (SM) and vegetation. This new parameter, which was derived from multiple observations, appeared to be consistent in time and space, revealing similar patterns along flight lines acquired at different times. The slope was used as input in regression models (RMs) to derive SM. A model solely based on 10.7-GHz data revealed a strong correlation ( $R<^>{2} = 0.81$ ) with Level-3 SM from the SM active passive (SMAP) mission, demonstrating the potential of multiangle retrievals with established SM products.

Aerosol modulation of atmospheric convection remains an important topic in ongoing research. A key challenge in evaluating aerosol impacts on cumulus convection is isolating their effects from environmental influences. This work investigates aerosol effects on maritime tropical convection using airborne observations from NASA's Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex). Eight environmental parameters with known physical connections to cloud and storm formation were identified from dropsonde data, and 92 dropsondes were matched with corresponding CAMP2Ex flight "scenes." To constrain environmental conditions, scenes were binned based on their association with "low," "medium," or "high" values for each dropsonde-derived parameter. In each scene and environmental bin, eight radar- and radiometer-based parameters with physical implications for convective intensity and/or prevalence were correlated with lidar-derived aerosol concentrations to examine trends in convective characteristics under different aerosol conditions. Threshold values used to stratify the environments were varied across four sensitivity tests to examine how the convective-aerosol correlations within each environmental bin responded. The results were generally inconclusive, with relatively weak correlations observed with limited statistical significance in many cases. Some interesting and potentially impactful comparisons identified in the convective-aerosol analyses support the idea of warm-phase convective invigoration trends and suggest that higher aerosol concentrations were correlated with stronger and/or more-prevalent convection in some cases, while other cases saw a "Goldilocks" zone of medium aerosol concentration favoring enhanced convection. Our results also stress the importance of considering environmental conditions when evaluating aerosol impacts.

An internationally collaborative airborne campaign in July 2023-led by the University of Bergen (Norway) and NASA, with contributions from many other institutions-discovered that thunderstorms near Florida and Central America produce gamma rays far more frequently than previously thought. The campaign was called Airborne Lightning Observatory for Fly's Eye Geostationary Lightning Mapper (GLM) Simulator (FEGS) and Terrestrial Gamma-ray Flashes (TGFs), which shortens to ALOFT. The campaign employed a unique sampling strategy with NASA's high-altitude ER-2 aircraft, equipped with gamma-ray and lightning sensors, flying near ground-based lightning sensors. Real-time updates from instruments, downlinked to mission scientists on the ground, enabled immediate return to thunderstorm cells found to be producing gamma rays. This maximized the observations of radiation created by strong electric fields in clouds and showed how gamma-ray production may be physically linked to the thunderstorm life cycle. ALOFT also sampled storms entirely within the stereo-viewing region of the GLM instruments on GOES-16/GOES-18and performed multiple underflights of the International Space Station Lightning Imaging Sensor (ISS LIS), while using an upgraded FEGS instrument that demonstrated the operational value of observing multiple wavelengths (including ultraviolet) with future spaceborne lightning mappers. In addition, a robust complement of airborne active and passive microwave sensors-including X- and W-band Doppler radars, as well as radiometers spanning 10-684 GHz-sampled some of the most intense convection ever overflown by the ER-2. These observations will benefit planned convection-focused NASA spaceborne missions. ALOFT is an exemplar of a high-risk, high-reward field campaign that achieved results far beyond original expectations. SIGNIFICANCE STATEMENT: Though it has been known for years that thunderstorms sometimes produce gamma rays, the Airborne Lightning Observatory for Fly's Eye Geostationary Lightning Mapper (GLM) Simulator (FEGS) and Terrestrial Gamma-ray Flashes (TGFs) (ALOFT) campaign discovered that this high-energy radiation is ubiquitous and highly dynamic in tropical thunderstorms. As these thunderstorms intensify, strong electric fields generate gamma-ray glows, and within those glows, powerful TGFs often occur. When the storms weaken, the gamma-ray production weakens. This means gamma rays can be an indicator of thunderstorm evolution, like lightning flash rate. Thus, thunderstorm radiation is not just a boutique topic for lightning physicists, but also relevant to forecasters, storm scientists, and those impacted by aviation hazards. Moreover, ALOFT gathered important validation data for spaceborne lightning sensors and sampled some of the most intense convection ever overflown by NASA aircraft.

Abstract. While most large-scale smoke advection occurs within the free troposphere, Maritime Continent smoke transport is suspected to be unique in its long-range, near-surface transport. Such a pathway likely creates strong gradients and uncertainties in interpreting satellite and model data on light extinction, air pollution, and cloud condensation nuclei. This paper documents High Spectral Resolution Lidar (HSRL) data from the 2019 ONR PISTON cruise and NASA CAMP2Ex flights that revealed Maritime Continent smoke and pollution transport pathways and heterogeneity around the Marine Atmospheric Boundary Layer (MABL) over thousands of kilometers. Observations showed that 95 % of integrated aerosol backscatter occurred below 2500 m altitude. The R/V Sally Ride observed 50th and 84th percentile aerosol backscatter altitudes at ~600 and ~1500 m respectively, regardless of aerosol loading. Peak backscatter values occurred within or near the MABL top, diminishing as we approached 2–3 km altitude, but with occasional plumes reaching the melting level at 4800 m. At monsoonal scales, aerosol models largely account for the observed directional wind shear that causes altitude-dependent particle transport: near-surface particles remain in the core monsoon flow around the MABL, while at lower latitudes, aerosol layers aloft advect more eastwardly. Around the MABL, however, significant cloud-scale variability exists due to fine-scale flow, halo-entrainment-detrainment, and cold pool phenomena. Backscatter enhancements beneath individual clouds, extending to the ocean surface, likely relate to MABL-free troposphere exchange and air-sea interaction. So while aerosol transport occurs near the surface, particle extinction heterogeneity must still be considered for in situ observations and satellite retrievals.

While most large-scale smoke advection occurs within the free troposphere, Maritime Continent smoke is suspected to be unique in its long-range, near-surface transport. Such a pathway likely creates strong gradients and uncertainties in interpreting satellite and model data on light extinction, air pollution, and cloud condensation nuclei. This paper documents High Spectral Resolution Lidar (HSRL) data from the 2019 ONR PISTON cruise and NASA CAMP2Ex flights that revealed Maritime Continent smoke and pollution transport pathways and heterogeneity around the Marine Atmospheric Boundary Layer (MABL) over thousands of kilometers. Observations showed that 95 % of integrated aerosol backscatter occurred below 2500 m altitude. The R/V Sally Ride observed 50th and 84th percentile aerosol backscatter altitudes at ∼600 and ∼1500 m respectively, regardless of aerosol loading. Peak backscatter values occurred within or near the MABL top, diminishing as we approached 2–3 km altitude, but with occasional plumes reaching the melting level at 4800 m. At monsoonal scales, aerosol models largely account for the observed directional wind shear that causes altitude-dependent particle transport: near-surface particles remain in the core monsoon flow around the MABL, while at lower latitudes, aerosol layers aloft advect more eastwardly. Around the MABL, however, significant cloud-scale variability exists due to fine-scale flow, halo-entrainment-detrainment, and cold pool phenomena. Backscatter enhancements beneath individual clouds, extending to the ocean surface, likely relate to MABL-free troposphere exchange and air-sea interaction. So while aerosol transport occurs near the surface, particle extinction heterogeneity must still be considered for in situ observations and satellite retrievals.

The NASA Cloud, Aerosol, and Monsoon Processes Philippines Experiment (CAMP2Ex) employed the NASA P-3, Stratton Park Engineering Company (SPEC) Learjet 35, and a host of satellites and surface sensors to characterize the coupling of aerosol processes, cloud physics, and atmospheric radiation within the Maritime Continent's complex southwest monsoonal environment. Conducted in the late summer of 2019 from Luzon, Philippines, in conjunction with the Office of Naval Research Propagation of Intraseasonal Tropical Oscillations (PISTON) experiment with its R/V Sally Ride stationed in the northwestern tropical Pacific, CAMP2Ex documented diverse biomass burning, industrial and natural aerosol populations, and their interactions with small to congestus convection. The 2019 season exhibited El Nino conditions and associated drought, high biomass burning emissions, and an early monsoon transition allowing for observation of pristine to massively polluted environments as they advected through intricate diurnal mesoscale and radiative environments into the monsoonal trough. CAMP2Ex's preliminary results indicate 1) increasing aerosol loadings tend to invigorate congestus convection in height and increase liquid water paths; 2) lidar, polarimetry, and geostationary Advanced Himawari Imager remote sensing sensors have skill in quantifying diverse aerosol and cloud properties and their interaction; and 3) high-resolution remote sensing technologies are able to greatly improve our ability to evaluate the radiation budget in complex cloud systems. Through the development of innovative informatics technologies, CAMP2Ex provides a benchmark dataset of an environment of extremes for the study of aerosol, cloud, and radiation processes as well as a crucible for the design of future observing systems.

Recent upgrades, calibration, and scan-angle bias reductions to the Advanced Microwave Precipitation Radiometer (AMPR) have yielded physically realistic brightness temperatures ( T b ) from the Olympic Mountains Experiment and Radar Definition Experiment (OLYMPEX/RADEX) dataset. Measured mixed-polarization T b were converted to horizontally and vertically polarized T b via dual-polarization deconvolution, and linear regression equations were developed to retrieve integrated cloud liquid water (CLW), water vapor (WV), and 10-m wind speed (WS) using simulated AMPR T b and modeled atmospheric profiles. These equations were tested using AMPR T b collected during four OLYMPEX/RADEX cases; the resulting geophysical values were compared with independent retrieval (1DVAR) results from the same dataset, while WV and WS were also compared with in situ data. Geophysical calculations using simulated T b yielded relatively low retrieval and crosstalk errors when compared with modeled profiles; average CLW, WV, and WS root-mean-square deviations (RMSD) were 0.11 mm, 1.28 mm, and 1.11 m s −1 , respectively, with median absolute deviations (MedAD) of 2.26 × 10 −2 mm, 0.22 mm, and 0.55 m s −1 , respectively. When applied to OLYMPEX/RADEX data, the new retrieval equations compared well with 1DVAR; CLW, WV, and WS RMSD were 9.95 × 10 −2 mm, 2.00 mm, and 2.35 m s −1 , respectively, and MedAD were 2.88 × 10 −2 mm, 1.14 mm, and 1.82 m s −1 , respectively. WV MedAD between the new equations and dropsondes were 2.10 and 1.80 mm at the time and location of minimum dropsonde altitude, respectively, while WS MedAD were 1.15 and 1.53 m s −1 , respectively, further indicating the utility of these equations.

The United States Air Force's 45th Weather Squadron provides wind warnings, including those for downbursts, at the Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC). This study aims to provide a Random Forest model that classifies thunderstorms' downburst and null events using a 35-knot wind threshold to separate these two categories. The downburst occurrence was assessed using a dense network of wind observations around CCAFS/KSC. Eight dual-polarization radar signatures that are hypothesized to have physical implications for downbursts at the surface were automatically calculated for 209 storms and ingested into the Random Forest model. The Random Forest model predicted null events more correctly than downburst events, with a True Skill Statistic of 0.40. Strong downburst events were better classified than those with weaker wind magnitudes. The most important radar signatures were found to be the maximum vertically integrated ice and the peak reflectivity. The Random Forest model presented a more reliable performance than an automated prediction method based on thresholds of single radar signatures. Based on these results, the Random Forest method is suggested for continued operational development and testing.

Wind warnings are the second-most-frequent advisory issued by the U.S. Air Force's 45th Weather Squadron (45WS) at Cape Canaveral, Florida. Given the challenges associated with nowcasting convection in Florida during the warm season, improvements in 45WS warnings for convective wind events are desired. This study aims to explore the physical bases of dual-polarization radar signatures within wet downbursts around Cape Canaveral and identify signatures that may assist the 45WS during real-time convective wind nowcasting. Data from the 45WS's C-band dual-polarization radar were subjectively analyzed within an environmental context, with quantitative wind measurements recorded by weather tower sensors for 32 threshold-level downbursts with near-surface winds 35 kt (1 kt approximate to 0.51 m s(-1)) and 32 null downbursts. Five radar signatures were identified in threshold-level downburst-producing storms: peak height of 1-dB differential reflectivity Z(DR) column, peak height of precipitation ice signature, peak reflectivity, height below 0 degrees C level where Z(DR) increases to 3 dB within a descending reflectivity core (DRC), and vertical Z(DR) gradient within DRC. Examining these signatures directly in updraft-downdraft cycles that produced threshold-level winds yielded mean lead times of 20.0-28.2 min for cumulus and mature stage signatures and 12.8-14.9 min for dissipating stage signatures, with higher signature test values generally yielding higher skill scores. A conceptual test of utilizing signatures within earlier cells in multicell storms to indirectly predict the potential for intense downbursts in later cells was performed, which offered increased lead times and skill scores for an Eulerian forecast region downstream from the storm initiation location.