CHENNAI: As frequency of deficit rainfall years are on the rise affecting both urban populace and farming community as a whole, Indian Institute of Tropical Meteorology (IITM), under the aegis of Ministry of Earth Sciences, is fast tracking a research programme called Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) to derive a strategy for weather modification programme in the country.
CAIPEEX is basically understanding rain formation in clouds and make a distinction between seedable clouds and non-seedable clouds.
As things stand today, artificial rain making techniques involving cloud seeding cannot be used for bringing rain clouds to rainfall deficit/drought areas. These techniques can only induce potential pre-existing clouds with adequate cloud droplets, to produce enhanced quantity of rain. And, for cloud seeding experiments to be successful, there has been a scientific understanding on which clouds to be seeded.
Thara V Prabhakaran, Project Director of CAIPEEX, said understanding clouds and associated processes were important for making better forecast of surface rainfall. Aerosol particles can impact cloud processes in a dramatic way by changing the cloud micro and macrostructure.
She was speaking at an event organised by Regional Meteorological Centre (RMC), Chennai, on the occassion of World Meteorological Day 2017, which is celebrated with the theme ‘Understanding Clouds’.
Thara said currently a major field campaign using aircraft, C-band radar and other atmospheric profilers, Lidars and particle counters and weather balloon flights is underway over rain shadow region for scientific evaluation.
The objective was to make observational data from these efforts available to a greater research community for further modelling.
“Already, 820 hours of airborne observations have been done. Three major airborne surface field campaign were carried out over Ganges Valley and airbone observations over western ghats in 2014 and 2015,” she said.
Demand for cloud seeding
The interior part of peninsular India is rain shadow region. The seasonal monsoon rainfall is lower compared to all India mean monsoon rainfall. The rainfall variability is larger.
The region is drought prone. In the prolonged monsoon-dry conditions, there are demands for cloud seeding operations from State governments. Cloud seeding programmes with modern technology have been carried out by Karnataka, Andhra Pradesh and Maharashtra governments in 2003-2005.