December 10, 2023

Syllabus– General Studies 1(geography, disaster management)/3 (environment) 


Recently, the director-general of the IMD gave a brief about climate change and weather forecasting; the advances that have been made, and the challenges that remain.

India’s Geographical Location:

  • India falls in the tropical region; 
    • Extra-tropical regions are in the middle and higher latitudes where most of Europe, northern United States and Canada are located. 
  • The weather of the Location:
    • The weather in the tropical region is different from that of the extra-tropical regions. 
    • 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’s weather forecasting:

  • Tropical Cyclones:
    • There has been tremendous improvement in the forecasting of tropical cyclones in the last 10 years. 
    • The accuracy of monsoon forecasts, especially of extreme rainfall events, has increased from about 60 per cent 10 years ago to over 80 per cent now.
    • Even for thunderstorms, the potential zone of occurrence is being predicted five days in advance. 
      • These are not easy to predict because they are localised in about a 1-10-km area, and last barely half an hour to three hours. 
      • The specific location is predicted at least three hours in advance. 
      • In this India’s accuracy is among the best in the world.
  • Lightning is a major killer during thunderstorms. 
    • India is one of the very few countries that provide lightning forecasts. 
    • This is constantly being improved. 
    • IMD scientists and equipment are able to identify potential hotspots 14 days in advance, and a lightning warning is issued every three hours on the day of the occurrence from over 1,000 stations across the country. 
    • IMD have an app called Damini;
      • It 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.
  • Heatwaves:
    • A large number of deaths used to happen because of heatwaves until a few years ago. 
    • Because of an accurate forecasting system, and effective communication and dissemination of information, the loss of lives due to heatwaves has come down to single digits now. 
    • India is also working on cold wave predictions.

Visible trends of 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. 
  • It’s getting hotter not just on the surface, but also in the troposphere, increasing its water-holding capacity. 
  • Studies show that with a rise of 1 degree Celsius, moisture-holding capacity increases by about 7 per cent. 
  • If the atmosphere has the capacity to hold more moisture, it will have the capacity to cause more rainfall.
  • So, the probability of occurrence of heavy rainfall has increased. 
  • Studies also show an increase in the frequency of heavy rainfall events. 
  • These are events when 24-hour accumulative rainfall on a particular day is more than 15 cm. 
  • Such events are increasing over the tropical belt as a whole, including in India. 
    • This trend is more evident in Maharashtra, Gujarat, Odisha, and West Bengal.
  • Rainfall:
    • On average, the number of light rainfall and moderate rainfall days is decreasing, while the number of extreme rainfall events is 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.
  • Heatwaves:
    • The increase is more in the central and northern parts of India. 
    • Cold wave conditions are likely to decrease because of the increase in temperature. 
  • Thunderstorm and Cyclones:
    • Lightning also shows an increasing trend. 
    • There has been an increase in thunderstorms because of the rise in the moisture content in the atmosphere due to temperature increases.
    • 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.

Future projections of weather:

  • In the business-as-usual scenario, the temperature can rise as high as 4 to 5 degrees Celsius by the end of this century. 
  • But this will most likely not be the case in view of our efforts to reduce emissions of greenhouse gases. 
  • Even so, heatwave conditions (area, duration, and frequency) are likely to increase.
  • Monsoon rainfall is projected to increase, and so are events of extreme rainfall. 
  • Rainstorm events, which are related to floods, are also expected to increase.
  • In general, extreme events will become more frequent and more intense, going by the current projections.

Limitation of weather predictions:

  • As you go towards extremes, their occurrence becomes very rare, and as the event becomes rare, the probability of prediction decreases gradually. 
  • For a granular prediction, say over a small area of a city or a town, there are limitations with current resources and technology. 

IMD 3 main objectives for future weather prediction:

  • To ensure that no severe weather goes undetected and unpredicted. 
    • In the next five years, IMD will have augmented our observational system that will enable it to detect, and predict every severe weather event. 
    • The idea is to enhance capacities so that even small-scale events can be predicted at the granular level with longer lead times.
  • To improve impact-based forecasts. 
    • To have very realistic impact-based forecasts incorporating hazards, vulnerability and risk analysis, for four significant severe weather events i.e., 
      • Tropical cyclones, 
      • Heavy rainfall, 
      • Thunderstorms, and 
      • Heatwaves. 
    • They result in major losses of life and property, and IMD hopes to minimise the losses through effective forecasts.
  • To make updated weather information available to everyone, every hour. 
    • For this, observation and communication systems have to be improved, mobile apps have to be developed.

The Indian Express link- 

Question- Indian Meteorological Department’s role in weather forecasting has helped in major advances in disaster mitigation. Comment.

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