Monsoon

  • A Monsoon can be stated as a seasonal shift in the prevailing wind direction that usually brings with it a different kind of weather. It almost always refers to the Asian monsoon, a large region extending from India to Southeast Asia where monsoon conditions prevail.
  • During the winter monsoon, a persistent and large high pressure zone over Asia drives cool, dry air soutward toward the tropics. This provides the monsoon region with its dry season.
  • Then during May and June of each year, the summer monsoon arrives with persistent southerly wind flow driven by a warm air mass with low pressure at the surface that forms over southern Asia as it is warmed by the sun. Air from the relatively higher pressure air mass over the Indian and tropical western Pacific Ocean flows northward toward the low pressure over land, bring with it torrential rains. A late arrival of the monsoon can be bad for agriculture, as the monsoon rains are necessary for summer crops.
  • According to IMD, there is a declining trend for the monsoon as well. “The 2018 Northeast monsoon season (October-December) rainfall over the country as a whole was substantially below normal (56 per cent of LPA, 1951-2000 average). This was 6th lowest since 1901.
  • In India the dry northerly wind flow over India changes direction, and warm humid air from the Indian Ocean flows from the south, gradually overspreading the Indian subcontinent. Widespread torrential rains, and even severe thunderstorms, large hail and tornadoes can accompany the onset (arrival) of the summer monsoon.
  • The Indian Ocean version of the hurricane, which is traditionally called a "CYCLONE" in the Indian Ocean, can also form and move ashore in association with the onset of the monsoon.
  • These cyclones have at times killed many thousands of poor people who live in the low-lying areas along the eastern coast of India and Bangladesh.

Quick Facts on Monsoon

  • The India Meteorological Department (IMD) on January 16, 2019, declared that 2018 was the sixth - warmest year in the last 117 years or since 1901, when recording started. Pointing towards changing weather and climate parameters, it also noted that the last monsoon rainfall was the sixth-lowest since 1901.
  • The 2018 annual mean land surface air temperature for the country was +0.41°Cabove the 1981-2010 average, thus making 2018 the sixth-warmest year on record since 1901
  • That India is witnessing consistent warmer seasons is clear from the IMD’s analysis that pointed out that 11 out of 15 warmest years were in the last 15 years (2002-2018). The last year was also the consecutive third-warmest year after 2016 and 2017.
  • According to the report titled “South Asia's Hotspots: Impacts of Temperature and Precipitation Changes on Living Standards”, rising temperatures and erratic rainfall pattern could cost India 2.8 per cent of its GDP.
  • Approximately 60 crore Indians live in areas where changes in average temperature and precipitation will negatively impact living standards. These areas, called hotspots, were identified using spatial granular climate and household data analysis. The analysis was done for two scenarios—one indicating a pathway where climate change mitigating actions were taken and the other where current trends of carbon emissions continued.

Monsoon Mission Initiative

Objectives:

–To improve Seasonal and Intra-seasonal Monsoon Forecast

–To improve Medium Range Forecast

Participating Institutions:

–Indian Institute of Tropical Meteorology (IITM), Pune

–National Centre for Medium Range Weather Forecast, Noida (NCMRWF)

–India Meteorological Department (IMD), New Delhi

Monsoon has always been critical for India’s economy. The current prediction capabilities are not adequate.In recent times, several new approaches (high resolution, super parameterizations, data assimilation etc.) have shown that the variability in tropics can be reasonably resolved, thereby creating a great scope for improving the monsoon prediction.

The mission will support focused research by national and international research groups with definitive objectives and deliverables to improve models in the short, medium, extended and seasonal range scales through setting up of a framework for generating dynamical forecasts and improving skill of forecasts. The mission will also support observational programs that will result in better understanding of the processes.

Type of Disturbances

Associated Wind Speed in the Circulation

Low pressure Area

Less than 17 knots (<31 kmph)

Depression

17 to 27 knots (31 to 49 kmph)

Deep Depression

28 to 33 knots (50 to 61 kmph)

Cyclonic Storm

34 to 47 knots (62 to 88 kmph)

Severe Cyclonic Storm

48 to 63 knots (89 to 118 kmph)

Very Severe Cyclonic Storm

64 to 119 knots (119 to 221 kmph)

Super Cyclonic Storm

119 knots and above (221 kmph and above)

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