Anik Das

Category: Research

  • Multi-Platform Observations of Southern Ocean MBL Clouds and Drizzle

    Highlights

    Cloud and drizzle properties in Southern Ocean (SO) marine boundary layer clouds were examined using aircraft (SOCRATES), shipborne (MARCUS), and satellite (CloudSat, EarthCARE) observations to compare how different observational platforms detect and characterize the similar cloud regimes sampled over the same SO region during the austral summer season.

    What are the main findings?

    • A synergistic analysis of the radar-only and combined radar-lidar observations across the three platforms was conducted. The total cloud fractions (CFTs) derived from the three radars show excellent agreement. All three radars detect large drizzle drops, but marine M-WACR and airborne HCR excel at detecting smaller cloud droplets that are often missed by CloudSat CPR. Combining radar and lidar observations enhanced cloud detection by 20%–60%. The results from this study provide new insights for designing future cloud radar systems.
    • Consistent cloud–drizzle retrievals across platforms. The reflectivity–retrieval framework provides consistent macrophysical and microphysical properties of liquid-dominant SO MBL clouds and drizzle from all three-platform observations.
    • Retrieved cloud structures are physically realistic, while instrumental limitations explain most differences. The retrieved vertical distributions of cloud and drizzle properties are consistent with the dominant physical growth processes. Differences among the three platforms reflect variations in radar sensitivity, vertical resolution, and sampling strategy.

    What are the implications of the main findings?

    • Toward unified cloud–drizzle retrievals. A single in situ-derived reflectivity–microphysics framework can be applied across airborne, ship-based, and satellite radars, enabling more coherent multi-platform cloud and drizzle climatologies.
    • Stronger confidence in MBL cloud process interpretation. The retrieved cloud–drizzle structures across platforms support robust physical interpretations of SO MBL clouds and provide a benchmark for improving retrievals and climate model evaluation.

    Related Publication

    • Das, A., Dong, X., & Xi, B. (2026). Cross-Platform Comparison of Marine Boundary Layer Cloud and Drizzle Properties over the Southern Ocean Using Airborne, Shipborne, and Satellite Observations. Remote Sensing, 18(13), 2262. https://doi.org/10.3390/rs18132262
    • Dong, X., Das, A., Xi, B., Zheng, X., Behrangi, A., Marcovecchio, A. R., & Girone, D. J. (2025). Quantifying the differences in Southern Ocean clouds observed by radar and lidar from three platforms. Geophysical Research Letters, 52, e2024GL112079. https://doi.org/10.1029/2024GL112079

    Conference Presentations:

    • Das, A., Dong, X., Xi, B.(2026). Investigation of Marine Boundary Layer Cloud and Drizzle Microphysics using Multi-Platform Observations over the Southern Ocean. Presentation at the 17th Conference on Cloud Physics, Session: High-Latitude Cloud, Precipitation and Radiation Processes II, AMS Madison Summit 2026. American Meteorological Society (AMS).
    • Dong, X., Das, A., Xi, B., Brendecke, J. (2026). Consistency of Cloud Amount and Vertical Structure Derived from Surface, Airborne, and Spaceborne Cloud Radar Measurements. Presentation at the 17th Conference on Cloud Physics, Session: Remote Sensing of Clouds I, AMS Madison Summit 2026. American Meteorological Society (AMS).
    • Dong, X., Das, A., Xi, B., Girone, D., Marcovecchio, A. R., Zheng, X., & Behrangi, A. (2025). Quantifying the differences of clouds observed by radar and lidar from three platforms over the Southern Ocean. Presentation at the 105th AMS Annual Meeting 2025. American Meteorological Society (AMS). https://ui.adsabs.harvard.edu/abs/2025AMS…10551658D/abstract

  • Southern Ocean MBL Cloud Microphysics and Radar Retrievals

    Highlights

    Understanding marine boundary layer (MBL) cloud and drizzle microphysics is essential for improving cloud–radiation feedback in models and satellite retrievals, which are sensitive to regional conditions, observation methods, and instrument characteristics. Since cloud and drizzle droplets follow distinct size distribution patterns, accurate retrievals require case-specific analyses.

    In this work, we analyze droplet size distributions from in situ cloud and drizzle probes onboard the research aircraft during the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) airborne field campaign over the Southern Ocean. Empirical relationships linking effective radius and liquid water content to radar reflectivity are derived, providing a useful reference for retrievals across different observational platforms and microphysical regimes. The results show that microphysical properties vary systematically with reflectivity, supporting the use of radar measurements to derive time-resolved vertical profiles of cloud and drizzle structure.

    Related Publication

    • Das, A., Dong, X., & Xi, B. (2026). Deriving Empirical Relationships between MBL Cloud Microphysical Properties and Radar Reflectivity Using Airborne In Situ Measurements over the Southern Ocean. Journal of Atmospheric and Oceanic Technology, 43(4), 425-443. https://doi.org/10.1175/JTECH-D-25-0069.1

    Conference Presentations

  • Marine Boundary Layer Cloud Characterization

    Highlights

    The Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) was an aircraft-based campaign (15 January–26 February 2018) that deployed in situ probes and remote sensors to investigate low-level clouds over the Southern Ocean (SO).

    A novel methodology was developed to identify cloud boundaries and classify cloud phases in single-layer, low-level marine boundary layer (MBL) clouds below 3 km using the HIAPER Cloud Radar (HCR) and in situ measurements. Radar-derived cloud base and top heights agreed well with corresponding lidar-based and in situ estimates of cloud boundaries, with mean differences below 100 m. An empirical liquid water content–reflectivity (LWC-Z) relationship was used to retrieve the LWC and liquid water path (LWP) from HCR profiles. The cloud phase was classified using HCR measurements, temperature, and LWP, yielding 40.6% liquid, 18.3% mixed-phase, and 5.1% ice samples, along with drizzle (29.1%), rain (3.2%), and snow (3.7%) for drizzling cloud cases. The classification algorithm demonstrated good consistency with established methods.

    The resulting framework provides a robust approach for characterizing Southern Ocean MBL clouds and supports future satellite retrieval and climate-model evaluation efforts.

    Related Publication

    • Das, A., Xi, B., Zheng, X., & Dong, X. (2025). Marine Boundary Layer Cloud Boundaries and Phase Estimation Using Airborne Radar and In Situ Measurements During the SOCRATES Campaign over Southern Ocean. Atmosphere, 16(10), 1195. https://doi.org/10.3390/atmos16101195

    Conference Presentation:

  • Associations of Trace Gases and Meteorological Parameters and Particulate Matter with Ozone under Smog Conditions

    Associations of Trace Gases and Meteorological Parameters and Particulate Matter with Ozone under Smog Conditions

    Highlights

    This work investigated the connection between O3 and other pollutants and meteorological conditions during a smog episode in Delhi. Ozone concentrations varied from site to site (150~269 µg/m3). A significant negative correlation has been observed between O3 and its precursor gases. Wind speed showed a positive correlation, but high wind usually dilutes the pollutant concentrations. Thus, a positive correlation with wind speed represents ozone transport from other locations to observational sites. The high ratio of PM2.5 to PM10 indicates a predominance of human involvement. Toluene and benzene ratios(T/B) are estimated to understand the nature of emission sources and the lifetime of pollution. The analysis of the benzene and toluene fractions indicates anthropogenic air masses’ dominance. Very high T/B values at several sites indicated that benzene was emitted from vehicular emission while toluene was from point sources. Ozone formation potential analysis showed that toluene and p-xylene are the prime contributors to ozone.

    Related Publications:

    Conference Presentation:

    • Tewari, A., Srivastava, N., & Das, A. (2021). Ozone connections with VOCs, precursors, and meteorological conditions during severe smog condition over Delhi. Paper presented at the International Symposium on Tropical Meteorology (INTROMET-2021), On Changing Climate: Consequences and Challenges (C4-21), November 23–26, 2021, Cochin Chapter of the Indian Meteorological Society (IMS), Cochin University of Science and Technology (CUSAT), Cochin.
  • Quantifying the Differences in Southern Ocean Clouds Observed by Radar and Lidar From Three Platforms

    Quantifying the Differences in Southern Ocean Clouds Observed by Radar and Lidar From Three Platforms

    Find it online: https://doi.org/10.1029/2024GL112079

    A synergistic analysis of the radar-only and combined radar-lidar observations across the three platforms was conducted. To align with well-calibrated CloudSat cloud profiling radar (CPR) (and HCR) reflectivity measurements, a constant 4.5 dB offset was applied to all M-WACR reflectivitives during the MARCUS. This brings M-WACR data into better agreement with both HCR and CPR reflectivity measurements and facilitates a more reliable cloud fraction (CF) comparison. The total CFs (CFTs) derived from the three radars show excellent agreement. All three radars detect large drizzle drops, but M-WACR and HCR excel at detecting smaller cloud droplets that are often missed by CPR. The underestimated CFs by CPR are due to increased attenuation of CPR measurements below 3 km, and the combined effects of attenuation and surface clutter below 1 km. Combining radar and lidar observations enhanced cloud detection by 20%–60%. The results from this study provide new insights for designing future cloud radar systems.

    Cite Paper: Dong, X., Das, A., Xi, B., Zheng, X., Behrangi, A., Marcovecchio, A. R., & Girone, D. J. (2025). Quantifying the differences in Southern Ocean clouds observed by radar and lidar from three platforms. Geophysical Research Letters, 52, e2024GL112079. https://doi.org/10.1029/2024GL112079

    Conference Presentation:

    Dong, X., Das, A., Xi, B., Girone, D., Marcovecchio, A. R., Zheng, X., & Behrangi, A. (2025). Quantifying the differences of clouds observed by radar and lidar from three platforms over the Southern Ocean. Presentation at the 105th AMS Annual Meeting 2025. American Meteorological Society (AMS).

    Presentation Abstract: https://ui.adsabs.harvard.edu/abs/2025AMS…10551658D/abstract