Observed Characteristics of Rainfall Indices and Outgoing Longwave Radiation over the Gangetic Plain of India

Abstract

Rainfall indices during the summer monsoon season may be used for assessment of drought and flood characteristics as well as for agricultural practices and water resources. Therefore, rainfall indices are evaluated over the meteorological subdivisions, namely Bihar, East Uttar Pradesh (UP), and West UP, over the eastern Gangetic Plain of India, which is densely populated and largely depends on agricultural production for the livelihood of the population. For the period 1980–2018, the present study considers the gridded rainfall data of the India Meteorological Department (IMD) at a resolution of 0.25° × 0.25° and outgoing longwave radiation (OLR) data of the National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) at a resolution of 1° ×1°. Rainfall indices including total rainfall in wet days (PRCPTOT) when daily rainfall is greater than or equal to 1 mm, the number of consecutive dry days (CDD) when daily rainfall is ≤ 1 mm, the number of consecutive wet days (CWD) when daily rainfall is ≥ 1 mm, the number of days when daily rainfall is ≥ 10 mm (Rx10) and the number of days when daily rainfall ≥ 20 mm (Rx20) are analyzed over the meteorological subdivisions. The PRCPTOT, CDD, CWD, Rx10, and Rx20 show an increasing/decreasing trend at a 95% confidence level. The rainfall indices CDD and CWD show positive and negative correlations with OLR, respectively, over the meteorological subdivisions.