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.
- 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.
- 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.
- 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
- 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.