Temporal variations of frequency of occurrence, horizontal size, height and aspect ratio of radar echoes from convective clouds around Delhi during monsoon season

Abstract

Temporal variations of frequency of occurrence, diameter (<i>D</i>), height (<i>H</i>) and aspect ratio (<i>H/D</i>) of radar detected precipitation echoes from convective clouds in Delhi region during the monsoon season have been studied. The study is based on hourly radar observations of precipitation echoes from 2467 convective clouds made during the monsoon seasons of 3-year period, 1977-79. Radar observations were taken mainly between 1000 and 1700 IST (0430 and 1130 UTC). Frequency of occurrence of such precipitation echoes has been found to be more in afternoon and less in morning. Similar trend has been observed in the temporal variations of height and aspect ratio of precipitation echoes of these clouds. On the other hand, diameter of the echoes has been found to be maximum in the morning and minimum at noon. The study has also shown that the echo diameter has a liner relationship with its height. The relationship can be expressed by a regression equation, <i>D = aH + b</i>, where <i>a</i> and <i>b</i> are the coefficients to describe the equation.