"India's monsoon midpoint: Extreme wet and dry spells define July rainfall"
Long Period Average (LPA)
mean rainfall over a region computed across 30–50 years, used as the monsoon benchmark
Low-Pressure System (LPS)
region of reduced surface pressure where warm moist air rises, the primary monsoon rain-bearing mechanism
The Southwest monsoon is the defining climatic event of the Indian subcontinent, delivering approximately 70–80% of the country's annual rainfall between June and September. Its spatial and temporal distribution is governed by a complex interplay of large-scale atmospheric circulation, sea surface temperatures, and mesoscale weather systems. The India Meteorological Department (IMD), operating under the Ministry of Earth Sciences, is the nodal agency for monsoon forecasting, issuing weekly and seasonal outlooks calibrated against the Long Period Average (LPA) — the mean rainfall over a region computed across a multi-decade span of 30 to 50 years.
The monsoon's advance across India follows a broadly predictable trajectory, typically reaching Kerala by early June and covering the entire country by mid-July. However, year-to-year variability is substantial, driven by phenomena such as the El Niño–Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD), and the position of the monsoon trough — an elongated low-pressure zone extending from Pakistan to the Bay of Bengal. Low-pressure systems (LPS) forming over the Bay of Bengal are the primary rain-bearing mechanisms during the monsoon season, responsible for the bulk of rainfall over central and peninsular India.
Historically, a deficit June followed by a recovery in July is not unprecedented, but the co-occurrence of record-breaking rainfall events alongside prolonged dry spells and heatwaves within the same calendar month represents an intensification of within-season variability that climate scientists increasingly attribute to a warming atmosphere's capacity to hold more moisture and release it in concentrated bursts.
The monsoon trough is a critical structural feature of the South Asian monsoon. When it lies close to the Himalayan foothills, rainfall intensifies over the plains of north India; when it shifts southward toward the peninsula, central India receives heavy rainfall. Its position in early and late July was favourable, enhancing rainfall over central and northwest India.
Low-pressure systems (LPS) form when warm, moist air rises, creating a region of reduced surface pressure. During the monsoon, these systems typically originate over the Bay of Bengal and track westward or northwestward across the Indian landmass, delivering heavy rainfall along their path. A system that intensifies beyond a threshold becomes a deep depression and, further, a cyclonic storm. The slow movement of an LPS is particularly consequential: a slow-moving system deposits far more rainfall over a given area than a fast-moving one, increasing flood risk. …
With reference to 'Indian Ocean Dipole (IOD)' sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?
1.IOD phenomenon is characterised by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
2.An IOD phenomenon can influence an El Nino's impact on the monsoon.
Select the correct answer using the code given below:
With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct?
1.OMT is measured up to a depth of 26°C isotherm which is 129 metres in the south-western Indian Ocean during January-March.
2.OMT collected during January-March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.
Which of the statements given above is/are correct?
The seasonal reversal of winds is the typical characteristic of
With reference to the India Meteorological Department's (IMD) rainfall classification, which of the following statements is/are correct?
1.Rainfall within ±19% of the Long Period Average (LPA) is classified as 'normal'.
2.The LPA is computed over a fixed 30-year period updated every decade.
3.'Exceptionally heavy' rainfall refers to 24-hour rainfall exceeding 210 mm at a location.
Select the correct answer using the code given below:
Consider the following statements about low-pressure systems (LPS) during the Indian monsoon:
1.LPS primarily originate over the Arabian Sea and track eastward across the Indian landmass.
2.A slow-moving LPS deposits more rainfall over a given area than a fast-moving one.
3.When an LPS intensifies with sustained winds of 52–61 km/h, it is classified as a deep depression.
Which of the statements given above is/are correct?
The 'monsoon trough' is best described as:
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