Soumyajyoti Jana

Multi-technique observations of convective rain events at a tropical location

The effects of the convective rain on various atmospheric parameters have been investigated at Kolkata (22.57°N, 88.37°E), India, during pre-monsoon and monsoon period of 2013. Various parameters like cloud base height and depth, liquid water content, rain rate and rain drop size distribution (DSD) are observed concurrently. The atmospheric electric field measured with an electric field monitor and the attenuation and depolarisation of satellite signals measured by a Ku-band receiving system are also studied during rain events. The instability indices obtained from radiometric measurements and the rain height profiles from micro rain radar are used to classify rain into two types, namely, convective and stratiform. The signatures of rain events on multi-technique observations are studied to indicate the various aspects of convective processes at a tropical location.

Prediction of convective rainfall using multi-technique observations

Nowcasting of rain amount is extremely essential in various fields of life. In this paper, we have shown that monitoring of brightness temperature at 31.4 GHz, the frequency having strong absorption due to liquid water, can give an estimate of rain accumulation with a prediction efficiency of ~ 80 % and a lead time of 75 minutes. It has also been observed that atmospheric electric field also shows definite changes before rain the magnitude of which can be related with the rainfall amount.

Dependence of rain integral parameters on measured rain drop velocities at a tropical location

A study using a Laser Precipitation Monitor (LPM) for several rain events spanning the monsoon season of 2013 at Kolkata, India, reflects the effect of velocity measurements on Z-R and A-R relationship for both convective and stratiform events. Laser precipitation monitor measures ground based drop size distribution and drop velocity simultaneously. The presence of high velocity small drops (super-terminal) and low velocity large drops (sub-terminal) is abundantly experienced during different types of rain in the tropical region as observed by a Laser precipitation monitor (LPM). The number fraction of these drops is higher in convective rain than in stratiform rain. As the observed drop velocities show significant variation from the theoretically derived velocities, it is possible to get noticeable difference in rain rate calculations, Z-R and A-R relationships. The study involves a comparison of Z-R and A-R relations using both Gunn-Kinzer (GK) and actual observed velocity in convective and stratiform rain regimes separately as there was significant difference in number fraction of high velocity and low velocity rain drops in both the cases.