Scaling of heavy rainy days with upper air profiles over Chennai during Northeast monsoon

Abstract

This study aims to scale the heavy rainy days (rainfall > 64 mm per day) with the surface and upper-air parameters overChennai (12.80° N and 80.03° E), located on the east coast of India, during the Northeast (NE) monsoon (October toDecember) from 2001 to 2015. The daily rainfall and radiosonde observations that are available from India MeteorologicalDepartment (IMD), Outgoing Long-wave Radiation (OLR) from Very High Resolution Radiometer (VHRR) Kalpana-1Indian satellite, and Total Column Liquid Water (TCLW) and vertical velocity from ERA-Interimre analysis are used. Thestudy commences with the comparison of mean daily Integrated Water Vapor (IWV) and rainfall over Chennai. Further, thestudy proceeds ahead by analyzing the IWV, TCLW, Instantaneous Condensation Rate (ICR) and precipitation extremeefficiency during the heavy rainy days. The results are such as (i) the heavy rainy days are better scaled using IWV andTCLW than with surface air temperature and OLR (ii) ICR during the all heavy rainfall days found high at 700 mb level,and (iii) the precipitation extreme efficiency which is estimated using the ratio of precipitation extreme (obtained fromvertical velocity, specific humidity gradient) and the ICR has shown a linear relationship with the surface reaching rainfallthrough the temporal and spatial smearing of raindrops expected.