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A Satellite Observation-based Analysis of Aerosol-cloud-precipitation Interaction during the February 2016 Unseasonal Heatwave Episode over Indian Region

Category: Aerosol Physics and Instrumentation

Accepted Manuscripts
DOI: 10.4209/aaqr.2018.04.0144
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Sunny Kant1, Jagabandhu Panda 1, M.G. Manoj2

  • 1 Department of Earth and Atmospheric Sciences, National Institute of Technology Rourkela, Odisha-769008, India
  • 2 Cochin University of Science and Technology, Kerala- 682022, India

Highlights

  • ACP interaction during an unseasonal heatwave episode over India is analysed.
  • Meteorological conditions supported moisture transport and cloud formation.
  • Radiative and microphysical effect observed during pre-mature and mature phases.
  • Invigoration effect seen during dissipating phase of the unseasonal heatwave episode.

Abstract

Aerosol-cloud-precipitation (ACP) interaction during the February 2016 unseasonal heatwave episode over India is analyzed and presented. Moderate Resolution Imaging Spectroradiometer (MODIS) datasets from the Aqua satellite are used to discuss the relationship between aerosol and cloud parameters viz. aerosol optical depth (AOD), Angstrom Exponent (AE), cloud fraction, ice and liquid cloud effective radius, cloud optical depth, cloud top temperature and ice and liquid cloud water path. Further, the Tropical Rainfall Measuring Mission (TRMM) dataset is used for analyzing the rainfall during the dissipating phase of the heatwave episode. Prevailing meteorological conditions during pre-mature, mature and dissipating phases of the episode are analysed using ERA-Interim 0.25o resolution datasets by considering near-surface temperature, relative humidity, and vertical integrated moisture flux convergence. Back–trajectory analysis is carried out for determining the origin of air mass and possible aerosol transport. Hot and dry westerly winds are found to be dominating during pre-mature and mature phases, and consequently, significant aerosol transport is observed. The variation of AOD is up to 1.6 during the three phases with AE being in the range 0.8-1.7, indicating the presence of both fine and coarse-mode aerosols. Clouds respond to aerosols reasonably well in the presence of favorable dynamic and thermodynamic atmospheric conditions through relevant microphysical processes. Suppression of precipitation during pre-mature and mature phase is primarily attributed to weak aerosol-cloud interaction. A major rainfall event over a region comprising northern Odisha, eastern Jharkhand and most parts of West Bengal, and situated in the north of minimum vertical integrated moisture flux zone, is realized during the dissipating phase. This rainfall event resulted from unseasonal moisture transport from neighboring Bay of Bengal, the presence of appreciable aerosol loading and the consequent ACP interaction.

Keywords

Aerosol-cloud interaction Heatwave Aerosol optical depth (AOD) Rainfall


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