IMD study clocking climate change suggests more agroclimatic zones

Agroclimatic classification is based on the type of vegetation, soil and climate. Crop planning, selection of the crop, time of sowing and other parameters are based on the agroclimate of the region.

Reclassification will further divide the 127 agroclimatic zones. It will refine crop planning and help in increasing crop productivity of wheat, rice, cotton and other crops.

The IMD study that analysed temperature, both maximum and minimum, and rainfall trends for 30 years from 1985 said both parameters necessary for crop cultivation had undergone significant change.

The study showed increasing average minimum temperature in the agroclimatic zones in the northern plains. Konkan and central Maharashtra, including Pune district, but excluding Vidarbha, showed a warming trend in the post-monsoon months ranging from 0.02° celsuis to 0.09° celsius per year. Central and peninsular India posted increasing frequency of heavy rainfall events during the pre- and monsoon months.

The study indicated change in climatic parameters from pre-1990 to post-1990s. “These changes can impact the agroclimatic zones which should be reclassified under the climate change scenario,” Nabansu Chattopadhyay, former deputy director general and head of the agricultural meteorology division, IMD, Pune Chattopadhyay said.

“When there were heavy rainfall events during the monsoon between July and September, many agroclimatic zones in the Indo-Gangetic plains up to the northeast showed a decreasing trend (–0.25 to –0.07 events per year). On the contrary, from July to September, and during the pre-monsoon, the number of agroclimatic zones in the central and western parts, and peninsular India showed increasing trend (0.05–0.23 events per year). Pune district showed an increasing trend in heavy rainfall events for September,” Chattopadhyay added.

Pulak Guhathakurta, one of the researchers involved in the study, said the analysis of the minimum temperature trends in the country indicates no significant changes in various regions but significant warming trends were observed over most of the states during the monsoon season in various temporal scales.

Guhathakurta heads the Climate Application and User Interface, Office of Climate Research and Services, IMD in Pune. Other IMD scientists involved in the study included A K Sahai, S Dutta, A K Srivastava, among others.

“The same trend of increase in minimum temperature is noticed in the monsoon months in Bihar and adjoining Jharkhand, in the range 0.03°–0.06°C per year. Central Odisha region exhibits a

trend of 0.01° to 0.03°C per year,” he added.

The study showed that the highest warming, increase in the upper and lower range of average maximum temperature, was observed over most of the agroclimatic zones of peninsular India. These areas included Maharashtra, Rajasthan, some parts of Gujarat and states of the northeast India during the periods studied.

“The study between two episodes from 1951 to 1980 and from 1981 to 2010 suggests that peninsular India, Gujarat and states of the northeast are warming more at 0.01°C per year when compared with the northern states. The dry farming tracts of the country are experiencing a decreasing trend in the rainfall activity,” he said.