Cooling of land due to ongoing wet spell won't affect monsoon arrival: Scientists

While the ongoing wet spell over large parts of India is unusual, the cooling of the landmass due to it will not delay the arrival of monsoon, senior scientists said on Tuesday.

The Indian monsoon is driven by the temperature and pressure difference between the Indian landmass and the Indian Ocean.

During the summer months, the landmass heats up, creating a low-pressure zone that draws in moist air from the ocean, resulting in rainfall.

There have been concerns that the cooling of the landmass due to the ongoing prolonged wet spell may weaken the low-pressure zone and there will be less force to draw in the moisture-laden air from the ocean. As a result, the arrival of monsoon rains may be delayed.

According to the India Meteorological Department's (IMD) data, the maximum temperature has remained below the 40 degrees Celsius mark across India for the last three days.

"There is no relationship as such (between the cooling of land due to the ongoing wet spell and the weakening of the monsoon winds)," Mrutyunjay Mohapatra, Director General of Meteorology, IMD, told PTI.

There is enough time for land heating to take place, he said.

While a long, wet spell over large parts of the country simultaneously is very rare, it is not going to affect the arrival of monsoon, said G P Sharma, president (meteorology), Skymet Weather, a private weather-forecasting agency.

"There is still a month to go if we go by the usual date (for the arrival of monsoon), that is, June 1. It is a very long time. This spell will possibly be over in another week. The usual conditions of the pre-monsoon season -- heat and thunderstorms -- will commence after this," Sharma said.

Roxy Mathew Koll, climate scientist at the Pune-based Indian Institute of Tropical Meteorology, said land surface temperatures at this time alone do not drive monsoon.

"Even though land surface temperatures cool with rains, the (latent) heat is released to the troposphere or the atmosphere over the land.

"I will be more concerned about the teleconnections with El Nino during the monsoon season. An El Nino can enhance the tropospheric temperature gradient by increasing the temperatures over Eurasia and thereby, weaken the monsoon winds," he said.