City-based Indian Institute of Tropical Meteorology (IITM) is set to enter the second year of its three-year cloud seeding experiment series in the ‘rain shadow’ region of Solapur in Maharashtra this monsoon. The experiment series, which began last year with ground-based observations, is aimed at improving the understanding of clouds and rainfall patterns.An analysis of the results of the experiment series will be carried out once it ends in the monsoon of 2019.
Unlike the conventional cloud seeding, which is carried out to bring artificial rains in drought-hit areas, the IITM experiment series aims at acquiring detailed observations of atmospheric states, particulates, clouds and rainfall.
As part of the project, a C-band radar has been installed in Solapur to monitor clouds and precipitation, and to suitably select clouds for seeding.
“The seeding will be done with an aircraft, which will dispense hygroscopic particles near the cloud base. This year, we have set up a dual polarised C-band radar at Solapur, which will monitor clouds and rainfall within the 200 km radius, where seeding experiments will take place,” said Thara Prabhakaran, senior IITM scientist and project director of Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX).
The advantage of having such a radar is its potential to detect ice processes within the clouds. The radar will monitor clouds and rainfall, their characteristics in both the seeded and unseeded clouds. “With the dual polarisation feature, the radar will be capable of monitoring a ‘seedable’ cloud with more accuracy, while the aircraft will target those clouds in the identified area,” added Prabhakaran.
In support, another aircraft equipped with instruments will monitor particulates of the size ranging from a few nanometer to the size that of a raindrop that is a few milli-metres. This will also help document the activities unfolding inside the chosen cloud, which will be monitored continuously throughout its life cycle. In addition, the aircraft will have instruments to monitor air motions and vertical velocities that are crucial in the cloud development.
During the previous CAIPEEX experiments, the team of scientists managed to document micro-physical observations without actually seeding the cloud. The team also attempted randomised seeding. However, only a few cases were obtained for statistical evaluation.
The senior scientist said, “The current experiment is expected to add to the number of cases that can be statistically evaluated. The results will be used to formulate guidelines for precipitation enhancement.”
Ever since CAIPEX experiments were first carried out, researchers have understood the mixed phase process in clouds and ice water content, the indirect effects of aerosol, elevated aerosol layers and mechanism of their formation, actual identification of key raindrop formation processes in monsoon clouds, how raindrops are formed in these clouds and their pathways, and aerosol-cloud-precipitation interactions in natural clouds, which paved the way for carrying out the current seeding experiment.