Number Theory: Four maps that capture the progress of monsoon | Latest News India - Hindustan Times
close_game
close_game

Number Theory: Four maps that capture the progress of monsoon

Jun 10, 2022 12:57 PM IST

Usually, this system arrives in India’s north-western parts only in the last week of June. Historically, either due to other pre-monsoon weather systems or the early arrival of monsoon, it has rained in around 90% of the country for at least one day in the first week of June.

New Delhi: June 1 is considered the beginning of the four-month summer monsoon in India because the weather system, generated by south-western winds, usually arrives at its first stop (the Kerala coast) on June 1. Usually, this system arrives in India’s north-western parts only in the last week of June. Historically, either due to other pre-monsoon weather systems or the early arrival of monsoon, it has rained in around 90% of the country for at least one day in the first week of June.

According to the India Meteorological Department’s (IMD) gridded dataset, India has received 17.7mm of rainfall so far this June (up to 8:30am on June 8). PREMIUM
According to the India Meteorological Department’s (IMD) gridded dataset, India has received 17.7mm of rainfall so far this June (up to 8:30am on June 8).

That has not happened this year -- neither the monsoon, nor other systems have resulted in rain in many parts of the country thus far this June. And even in regions where the monsoon has set in, its performance has lagged historical averages. Here are four maps that explain this.

June rainfall so far is 30th worst since 1901

According to the India Meteorological Department’s (IMD) gridded dataset, India has received 17.7mm of rainfall so far this June (up to 8:30am on June 8). This is 37.5% less than the 1961-2010 average of 28.3mm and the 30th lowest amount of rainfall since 1901 for this eight-day interval. The erratic beginning of this monsoon can be understood from rainfall last month. It rained more in the week ending May 14 (21mm) and May 21 (35.7mm) than it has so far in June. This may create problems for farmers, since IMD seems to have been hasty in declaring the onset of monsoon over Kerala. The deficit in rainfall has been in excess of 30% on five days in June and there was no surplus on any day.

Half the country has not received even a single day of rainfall in June

The high rainfall deficit this monsoon is not a result of only a few places receiving little rain. In most of the country, there has just been no rainfall at all. IMD’s gridded dataset gives rainfall for 4,685 grids or boxes bound by two adjacent latitudes and longitudes 0.25 degrees apart. For 88.6% of these grids, the average number of days it rained in the June 1-June 8 interval the 1961-2010 period is more than one day and for 35%, more than three days. Only 38.1% of grids have received more than one day of rain this June so far and 19%, more than three days. Almost half of the grids, 47%, have not received any rainfall at all. These no-rainfall grids cover almost all of northern and central India.

There is a deficit even where the monsoon has arrived

To be sure, since the monsoon is not due yet in many parts of the country, the rainfall thus far in June is not technically a sign of how the monsoon system is working in those places. Is it the case that the India average has been dragged down only because pre-monsoon rains are lacking? That may well be the case in the places where monsoon is not expected to arrive at this time of the month, such as northern and central India.

On the other hand, where the monsoon has arrived, it has not brought good rainfall. According to an IMD press release on June 8, the monsoon has arrived over Kerala, most of Tamil Nadu, and the southern half of Karnataka in the south, and over all north-eastern states. It was late by around three days in northern parts of Karnataka and Tamil Nadu and in Andhra Pradesh. Tamil Nadu and Andhra Pradesh show a surplus (in terms of rainfall since June 1) and Karnataka, a deficit small enough (1.8%) to be considered normal. It is Kerala, covered completely by monsoon, that has a 53% deficit, the 26th highest since 1901. In the north-eastern region, too, Tripura and Mizoram, states which are the closest to the Bay of Bengal and where monsoon arrived first, have the biggest deficits: 37% and 21% respectively. This is despite the fact that many parts of Kerala and the north-eastern states have received six or more days of rainfall (as the maps in the section above show).

To be sure, these deficits are with respect to historical averages, and does not mean that Kerala, Tripura, and Mizoram are facing dry weather and Tamil Nadu and Andhra Pradesh are rainy. The former have received more than 40 mm of rainfall this June and the latter, only up to 20 mm of rainfall.

 

Unveiling Elections 2024: The Big Picture', a fresh segment in HT's talk show 'The Interview with Kumkum Chadha', where leaders across the political spectrum discuss the upcoming general elections. Watch now!

Get Current Updates on India News, Election 2024, Mukhtar Ansari Death News Live, Bihar Board 10th Result 2024 Live along with Latest News and Top Headlines from India and around the world.

Continue reading with HT Premium Subscription

Daily E Paper I Premium Articles I Brunch E Magazine I Daily Infographics
freemium
SHARE THIS ARTICLE ON
Share this article
  • ABOUT THE AUTHOR
    author-default-90x90

    Abhishek Jha is a data journalist. He analyses public data for finding news, with a focus on the environment, Indian politics and economy, and Covid-19.

SHARE
Story Saved
Live Score
OPEN APP
Saved Articles
Following
My Reads
Sign out
New Delhi 0C
Friday, March 29, 2024
Start 14 Days Free Trial Subscribe Now
Follow Us On