Published on: April 15, 2022
The India Meteorological Department (IMD), while forecasting a “normal” southwest monsoon and average rainfall for the year 2022
WHAT DID IMD SAY
- India would get 99% of the long period average (LPA) rainfall — changed from 89 cm to 88 cm in 2018, and in the periodic update in 2022, again revised to 87 cm
- The IMD does not expect an El Nino, a phenomenon associated with a warming of the Central Pacific and drying up of the rains over northwest India, the coming monsoon
- Currently La Nina conditions are prevailing over equatorial Pacific. The latest forecasts indicates it will continue during the monsoon
- Current indications suggest “normal” to “above normal” rainfall in the northern parts of peninsular India, central India and the Himalayan foothills
- Many parts of northeast India and southern parts of South India are expected to see a subdued monsoon
WHAT – A seasonal reversing wind accompanied by corresponding changes in precipitation
- Monsoons are seasonal winds which reverse their direction with the change of season.
- They flow from sea to land during the summer and from land to sea during
- Countries like India, Indonesia, Bangladesh, Myanmar etc. receive most of the annual rainfall during south-west monsoon season whereas South East China, Japan etc., during north-east rainfall season.
- During the summers of northern hemisphere, North India receives high insolation and generates low pressure.
- This low pressure attracts winds from all direction. Heating of Tibetan plateau also plays role here.
- During the same time, Inter-Tropical convergence zone also shifts to the north and as a result trade winds starts blowing towards India carrying moisture with them.
- The shift in the position of the ITCZ is also related to the phenomenon of the withdrawal of the westerly jet stream from its position over the north Indian plain, south of the Himalayas.
- The easterly jet stream sets in along 15°N latitude only after the western jet stream has withdrawn itself from the region. This easterly jet stream is held responsible for the burst of the monsoon in India.
- Normal or Near Normal: When per cent departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA
- Below Normal: When departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA
- Above Normal: When actual rainfall is 104-110% of LPA
- Deficient: When departure of actual rainfall is less than 90% of LPA
- Excess: When departure of actual rainfall is more than 110% of LPA
LONG PERIOD AVERAGE (LPA)
- It is the average rainfall recorded during the months from June to September, calculated during the 50-year period, and is kept as a benchmark while forecasting the quantitative rainfall for the monsoon season every year
- IMD maintains an independent LPA for every homogeneous region of the country, which ranges from 71.6 cm to 143.83 cm
- Climate pattern that describes periods of below-average sea surface temperatures across the east-central Equatorial Pacific
- Considered to be the counterpart to El Nino, and its impacts tend to be opposite those of El Niño
- Together, they form the “cold” (La Nina) and “warm” (El Nino) phases of the El Nino-Southern Oscillation (ENSO)
INDIA METEOROLOGICAL DEPARTMENT
- IMD was established in 1875
- It is an agency of the Ministry of Earth Sciences of the Government of India
- It is the principal agency responsible for meteorological observations, weather forecasting and seismology
BENEFITS OF NORMAL MONSOON
- The monsoon is critical for agriculture in the country since nearly 60% of India’s net arable land lacks irrigation. The monsoon delivers about 70% of India’s annual rainfall and determines the yield of several grains and pulses, including rice, wheat, and sugarcane
- Will help to contain food price pressures, especially in cereals and pulses. It is also crucial to keep up the rural demand
- Replenish nearly 100 large reservoirs critical for drinking water and power generation across the country
- Most major sectors of the economy like to base their sales and distribution activities on the monsoon’s behavior
- A normal monsoon will also lead to reservoirs across India, which are responsible for water supply in cities, filling up.Thus it will also lead to an increase in production of hydro power which is a cleaner form of energy