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A detailed report published by Changing Monsoon Dynamics: A district-level retrospective of Monsoon 2023
73% of the country gets normal rains but district-wise data reveals opposite trends
Changing Monsoon Dynamics: A district level retrospective of Monsoon 2023
73% of the country gets normal rains but district-wise data reveals opposite trends
Key Highlights
● About 6% of the 81,852 normal district rain days during the monsoon
● Over 60% of district-wise daily rainfall data showed large deficits (deficits of over
60%) or no rain
● The country saw second second-highest number of heavy rain events (over 115.6 mm of rainfall
received) in the last five years
● August was the worst performing month, with over 76% of district rain days
registering large deficits or no rain
● India recorded 544 floods and heavy rainfall events during the entire season
● Himachal Pradesh ranked one with 123 extreme events, followed by Maharashtra
with 69 events, Uttarakhand with 68 events
● Nine out of 10 years in the last decade, the East & Northeast region has recorded
negative rainfall
● Despite an active monsoon in September, the Standardised Precipitation Index (SPI)
data for the period from June 1, 2023 to October 4, 2023 shows meteorological
drought conditions
Southwest Monsoon 2023 recently concluded with ‘below-normal’ rainfall to the tune of 94%
of the long-period average (LPA) against the forecast of 96% with an error margin of +/-4%.
However, increasing variability of rainfall continued to dominate the four-month-long season.
The month of July was the best performer and a saviour from a possible disaster. It recorded
13% excess rainfall, which was the second highest since 2005. The month compensated for
the underperformance of June that had ended with a deficit of 10% rainfall.
Halfway through the season, August, the core monsoon month collapsed completely with
36% rainfall deficiency. The country was plunging into despair with drought threats looming
large on account of building El Nino in the Pacific Ocean. However, the oceanic phenomena
of Indian Ocean Dipole (IOD) and Madden Julian Oscillation (MJO), both associated with
increasing rains over India, turned the tables by triggering back-to-back monsoon
low-pressure systems over the Bay of Bengal in September. With this, the timely revival of
the monsoon saved the country from the scare of yet another potential drought.
Out of 36 meteorological subdivisions in the country, 26 subdivisions recorded normal
rainfall, constituting 73% of the area of the country. Meanwhile, seven subdivisions recorded
deficit rainfall that covers 18% of the area of the country. Only three subdivisions witnessed
excess rainfall amounting to an area of 7%.
The real picture behind ‘normal’ rainfall:
A look at the district-wise distribution of rainfall through the four months of Monsoon 2023
offers a glimpse of how distorted the picture of “normalcy” really is. An analysis of the daily
district rainfall sheets from June up to the last week of September suggests barely any
sense of normalcy in the distribution of rainfall. About 6% of the 81,852 district rain days
during the monsoon analysed by CarbonCopy and Climate Trends registered normal
rainfall. Analysis of daily district-level rainfall through the four-month season reveals the
volatile nature of “normalcy” – over 60% of the district-level daily rainfall observations
registered Large Deficits or No Rain while almost 20% of the observations showed Large
Excesses By comparison, over 60% of the district-wise daily rainfall data showed large deficits (deficits
of over 60%) or no rain. It is understood that normal rainfall data has been averaged out over
several years and cannot be expected to indicate the consistency of rainfall, but the
relatively miniscule number of “normal” rainfall days experienced by India’s 718 districts
does reflect a reality of being swung between extremes.
Days registering “Large Excess” (where excess is over 60% of the LPA) rainfall was the next
most prevalent category, indicating the violent shifts between dry and wet through the
season.
August was the worst-performing month, with over 76% of district rain days registering large
deficits or no rain. The week-by-week rainfall performance assessment of India’s 36
meteorological sub-stations over 17 weeks of the monsoon, reveal that almost half of all
weekly observations experienced rainfall deficits of at least 20%. This denotes that almost
two-thirds of the district rainfall days either registered large deficits or no rain, raising a
question on the definition of seasonal normalcy.
Analysis of daily district-level rainfall through the four-month season reveals the volatile nature of
“normalcy” – over 60% of the district-level daily rainfall observations registered Large Deficits or No
Rain while almost 20% of the observations showed Large Excesses | Data: IMD Daily observations;
Original analysis done By: CarbonCopy/Climate Trends
The spells of excessive rainfall, particularly in July, and a generous peppering of very heavy
and extreme rain events resulted in an averaging of a normal monsoon season. Despite
ending the season with just 94% of the LPA rainfall, the country saw the second highest
number of heavy rain events (over 115.6 mm rainfall received) in the last five years. In 2019,
when the country saw 3056 heavy rain events, about 10% higher than this year’s 2742
events, seasonal rainfall recorded was 110% of the LPA. While almost half of all heavy rain
events this year came in the month of July, June observed the highest number by far in the
last five years despite registering a substantial deficit in rainfall over the country.
“Monsoon variability is definitely increasing. When global warming happens not only means
but also extremes will increase.
This monsoon will be known for its large spatial and temporal variability and is typical of any year.
The issue however is not seasonal rainfall but large intra-seasonal variability with extended active and weak phases. Data suggest this
variability is increasing manifold. So, we need to predict this spatial distribution very well and it is very important for us to learn to adapt to this increasing variability,” said Dr Madhavan Rajeevan, Former Secretary, the Ministry of Earth Sciences and Climate Scientist.
Complete Report read the report at source
