Don’t compare us with western nations: IMD chief Ajay Kumar
There is good news for Mumbaikars as the Indian Meteorological Department (IMD) has predicted that the city will this year receive normal monsoon in comparison to last year. But Mumbaikars have to be careful for the next couple of days as the temperature will rise up to 37 degree celsius. In an exclusive interview with Swapnil Mishra, IMD director, Ajay Kumar discusses the weather conditions and rainfall in Mumbai, installation of the Doppler Radar and much more.
How will the summer be this year and are there any chances of a heatwave again in parts of Maharashtra?
AK: In the coming week, the city will witness normal temperature of 33 to 34 degree celsius, but the humidity level may increase due to which the mercury level might increase. The temperature in some parts of Marathwada, Vidharbha and North Central Maharashtra will be constant and vary between 42 to 44 degree celsius for the next four to five days. But there will be no heatwaves in these areas.
How does global warming impact IMD predictions? How has that affected the weather?
AK: It will be difficult to say that global warming impacts IMD predictions and affects weather since global warming may be of two types — one is natural and the other manmade. It is difficult to distinguish one from the other. When temperature increases, both air and ocean get heated. When air temperature increases more, it holds more water vapour which brings more rain. Also, higher temperature means that oceans can release more moisture in the air by evaporation which leads to more rainfall. However, in some areas, the atmosphere can become drier and drought can occur in such places.
The movement of clouds and rains are based on mathematical calculations. However, modern satellites help in making more accurate predictions. Why is the IMD then being criticised for faulty predictions?
AK: A numerical weather prediction (NWP) model helps in predictions based on mathematical equations a week in advance. But satellite pictures provide information of the cloud pattern at a particular time. It helps the forecaster to identify the areas of significant clouds. But forecasts fail due to uncertainty in NWP models. Apart from the models, there are many other phenomena and different parameters like temperature, humidity and uplifting of air which help us make predictions. IMD has its own models which help us predict weather.
What kind of rainfall will Mumbai and Maharashtra witness this year? What are your predictions?
AK: IMD has predicted 97 per cent of the long period average (LPA) rainfall in the month of June-September. The LPA is average rain across the country from 1951 to 2000, estimated to be 89 cm. The monsoon is considered normal at 96-104 per cent of the LPA. Low rainfall is expected to be weak during the start of the monsoon season in June. The Indian Ocean Dipole (IOD), another critical factor influencing the monsoon, is also projected to be weak but will occur only at the later stages. Also, most global monsoon models are predicting ‘normal’ rainfall for India this year.
We will update this forecast in June when we issue region-wise forecasts. The preliminary indications are that rainfall could be fairly distributed across most parts of the country, barring south and northeast India. On the regional level, IMD will give a geographical forecast of rainfall for the North-West India and southern India in the mid-June. On a local level, we do not give any prediction but we keep giving warning of rainfall.
Where do we stand in terms of accuracy of weather prediction compared to the West? What is the percentage?
AK: IMD’s predictions cannot compare with those in western countries because they have a different weather system. India falls in tropical region, that is ‘30 degree north to 30 degree south latitude’ therefore rainfall occurs due to ‘convective activity’. The temperature is more in the reason which leads to the sudden formation of clouds due to moisture and that is why we cannot say what the prediction percentage is. Western countries fall in higher latitude, which means they have an extratropical system where convective types of clouds are not formed. Due to movement of these weather systems western countries’ predictions are more accurate compared to India.
(Convective Activity is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to increased winds, cumulus cloud development, and decreased surface dew points. Moist convection leads to thunderstorm development, which is often responsible for severe weather throughout the world).
Bombay High Court had directed to install 22 rain gauge in two weeks after the Chitale committee submitted the report to the civic corporation? Till now, how many Doppler radars have been installed and why are they getting delayed?
AK: I cannot say when Doppler Radar will be installed. So far we have only selected the location — ‘Veravali reservoir’— where the second radar will be installed. Under the supervision of the court, the land was handed over to IMD. Currently, there are many procedures for budgeting, tendering and many others due to which it is getting delayed but once everything is done it will be installed.
Last year, the Brihanmumbai Municipal Corporation (BMC) had blamed IMD for wrong predictions? This year, what is your action plan with the railway authorities and the civic corporation during monsoon?
AK: There is no action plan, but like every year, we will issue a warning about the rainfall according to which they will make their arrangements. We are always ready to help BMC and railways during monsoon and if they are planning to come meet me and plan some action during monsoon, they are welcome.
IMD predictions cannot be compared with those made in western countries. They have a different weather system due to which their predictions are more accurate compared to India. It will be normal rainfall this season. Most global monsoon models are predicting ‘normal’ rainfall for India this year. The preliminary indications are that rainfall could be fairly distributed across most parts of the country, barring south and northeast India.