MC Interview | Delhi to begin seeing colder temperatures from October 15: IMD Chief

Also Read: Southwest monsoon withdraws from Delhi: IMD

Edited excerpts on how the Indian monsoon was saved from El Nino, winter outlook which estimates the country to see higher temperatures, rising extreme weather events indicating climate change, technical improvements, pilot use of AI by IMD below.

El Nino years are generally dry, with a severe lack of rainfall activity but the Indian southwest monsoon has done well despite having the driest August ever. What is the reason?

Monsoon this year is near normal. It was 94 percent of the long period average. Even though El Nino years are usually deficient, it was a combination of factors that saved us this time.

El Nino was countered by the development of the Indian Ocean Dipole in July, towards the end of August and in September. Further, the Mediterranean Oscillation in July helped increase convective clouds thereby leading to rainfall. Lastly, a higher number of low pressure systems in July and September led to further rain.

The rainfall pattern has been very erratic this year along with the range in temperatures. Temperatures rose in February; the onset of rainfall was delayed in June. So what is changing now?

There is no significant trend in the seasonal rainfall for the country as a whole. However, the number of days of occurrence of heavy rainfall has increased and the number of days of occurrence of light rainfall is decreasing. That means the dry spells are increasing and wet spells are decreasing, but whenever it is raining, it is raining heavily, leading to flash floods and other mishaps. If I consider data from 1970 to 2020, five decades, the number of extreme events has increased five times.

Similarly, temperatures are rising across the globe. Rising temperatures are more significant during winter months, that is January-February, followed by the post-monsoon months of October-November-December, and then pre-monsoon months March-April-May. The rise of temperature is lowest in monsoon months, that is June to September.

In winters, the number of cold wave days is decreasing and in pre-monsoon months, the number of heat waves is increasing. The duration of heatwaves as well as their severity is also increasing. Thus, the heat core zones including Northwest India and Central India are experiencing significantly severe heatwave conditions. Not only that, towards the peninsular area, the areas where there used to be no heat conditions, are now witnessing it.

What is the El Nino forecast for the coming winter months? 

El Nino will become stronger as we go ahead. El Nino conditions will continue not only for this year but up to early March of next year.

But El Nino will have different impacts on different regions. Northwest India can expect above-normal temperatures, as we are seeing in October as well. However, we expect good rainfall activity over Northeast and Southeast India especially in Tamil Nadu, Puducherry and Kerala as El Nino conditions will provide for more rainfall in these areas. On the cyclone disturbances, usually, October-December sees two to three cyclones. However, a study shows that during El Nino year the frequency and intensity of cyclones over the Bay of Bengal is relatively less. Another study says that the cyclones that develop during El Nino years move in southern latitude. That means during El Nino year, Tamil Nadu and South Andra Pradesh are more prone towards cyclone activity, unlike North Andhra Pradesh, Odisha and West Bengal. In El Nino year, this coast becomes more prone and more intense cyclones develop, and we are watching it closely.

Also Read: Monsoon ends with 'normal' rainfall as positive factors countered El Nino effect, says IMD

IMD has improved a lot when it comes to forecasts. It started giving regional forecasts which are more accurate. What can we expect for the future?

Yes, IMD has improved its capacity in terms of observational network, in terms of its computational network, modelling, forecasting, early warning, and reaching out the last mile.

We now have 37 radars and two satellites, we've got buoys and ships, and the number of rain gauges has also increased to almost 6,000, which we use to disseminate data every day.

The rainfall distribution is now provided location and district-wise. About 150 statistics are prepared every day with respect to rainfall. Similarly, with respect to temperature, information can now be found up to the village level. There may not be observations but Geographic Information Systems (GIS) analysis will tell you what the temperature is, which was not possible earlier.

IMD’s accuracy has also improved by at least 40-50 percent during the past five years as compared to the previous five years.

We are also using artificial intelligence in pilot mode and are collaborating with IITs to develop the system. IMD is also in talks with Google for a collaborative study to develop certain tools for artificial intelligence-based forecast products. It is a dual-engine concept. We will have dynamical models and artificial intelligence, both will complement each other to convert the data into value.