Extreme weather events will become more frequent and more intense- IMD

Extreme weather events will become more frequent and more intense- IMD

Subject: Environment

Context: Rising frequency and intensity of extreme weather events

Trends in extreme weather events:

• Globally, temperatures have risen by about 1.2 degrees Celsius compared to 100 years ago. Over India, the rise has been about 0.6 degrees Celsius.
• The rise has been more in the northern, central, and eastern parts, and less over peninsular India.
• This rise in temperature has an impact on extreme weather events. The probability of occurrence of heavy rainfall has increased. This trend is more evident in Maharashtra, Gujarat, Odisha, and West Bengal.

Rainfall days, heat waves, cyclones:

• On average, the number of light and moderate rainfall days are decreasing, while the number of extreme rainfall events are increasing.
• But total rainfall during the monsoon season has remained largely unchanged. This means when it rains, it rains heavily, and when it doesn’t rain, it doesn’t rain at all.
• This trend is quite significant across the country’s central belt.
• A decrease in rainfall activity has been observed over Kerala and Jharkhand and adjoining areas, but an increase in West Bengal, western Uttar Pradesh, and parts of Karnataka.
• The intensity of cyclones in the Bay of Bengal does not show any significant change, but Arabian Sea cyclones are showing an increase in intensity.

India and Weather Forecasting Model

• Until 2010, the IMD used only statistical models (Traditional Model) to forecast the monsoon.
• These involved identifying climate parameters linked to the performance of the monsoon. For example, the sea surface temperature gradient between North Atlantic and North Pacific, the volume of warm water in the equatorial Pacific, the Eurasian snow cover.
•  IMD started testing a dynamical system around 2015: This simulates the weather at a chosen set of locations on a given day — the land and ocean temperature, moisture, wind speeds at various heights, etc — and powerful computers calculate how these weather variables will change over days, weeks, months.
• These models are also useful for anticipating heat-wave or a cold-wave and therefore useful to urban planners and government.

Is developed nations weather forecast more accurate?

• The weather in the tropical region (ex. India) is different from that of the extratropical regions where most of Europe, northern United States, and Canada are located.
• Cyclones, the monsoon, thunderstorms are characteristic of tropical weather systems.
• Tropical weather is associated with convective forces of the atmosphere.  The intense heating of the Earth’s surface plays a dominant role in the genesis, evolution, characteristics, propagation, and movement of the weather in these areas.
• Extra-tropical weather systems are more systematic and periodic, and therefore, in general, easier to predict.
• In comparison, the weather in the tropical zones is a little less predictable.
• India Meteorological Department (IMD) operates a dedicated weather and climate monitoring, detection and warning services useful for various sectors of economy.
• Monsoon prediction and the weather forecasting systems in the country are comparable to the best in the world. However, efforts are continuously being made to further enhance the level of efficiency of the forecasting systems.
• To improve the prediction of Monsoon, the National Monsoon Mission was launched in 2012. Under the National Monsoon Mission initiative, the Indian Institute of Tropical Meteorology (IITM), Pune
• The monsoon forecast for the country is prepared by the Climate Prediction Unit of Climate Research and Services Division (CR&S), IMD, Pune.
• India is one of the very few countries that provide lightning forecasts.  An app called Damini provides location-specific information about the occurrence of lightning during the past 5, 10, and 15 minutes, and a lightning forecast for the next 45 minutes.
• We have three main objectives for future forecasts:
  • First, to ensure that no severe weather goes undetected and unpredicted.
  • The second objective is to improve impact-based forecasts.
  • The third objective is to make updated weather information available to everyone, every hour.