The Indian summer monsoon rainfall (ISMR) during June-September in 2022 was above normal with respect to its climatology. Rainfall during the 2022 Southwest Monsoon Season was above normal. The all-India monsoon seasonal rainfall during 1 June to 30 September was 925.0 mm compared to its climatology value 868.6 mm based on 1971-2020 data (Fig. 1 and Fig.2). It can be seen that although all India rainfall was above normal, the Indo-Gangetic plains (Nagaland, Manipur, Mizoram & Tripura, Gangetic West Bengal, Jharkhand, Bihar, and east & west Uttar Pradesh) received severe deficient rainfall. Rainfall averaged over All India was the fifth highest since 2001 after the years 2019(970.8 mm), 2007(966.6 mm), 2020 (959.3 mm), and 2013 (943.4 mm). The ISMR was above normal three out of the last four years (2018-2022) comes after normal to below normal ISMR for five years during 2014-2018 (Fig. 2)
Figure 1: Observed (left), climatology (middle), and anomaly (right) of rainfall over India for June-September 2022 (Climatology and anomaly based on 1971 to 2020 period). *Based on Realtime Data [Source: IMD]
Figure 2: Year-to-year variability of Indian summer monsoon rainfall for the period 1901-2022 with respect to 1971-2020 climatology.
The southwest Monsoon set in over Kerala on 29th May against the normal date of 01st June i.e. 3 days ahead of its normal date (Fig. 3) and covered the entire country by 2nd July against normal date of 8th July (6 days before the normal date of covering entire India). Withdrawal of southwest monsoon began from southwest Rajasthan and adjoining Kutch on 20th September 2022 against its normal date of 17th September (Fig 3). Southwest monsoon withdrawn from entire country on 23 October (Fig 3).
Figure 3: Onset and withdrawal of Indian summer monsoon during 2022 and its comparison with normal onset and withdrawal date.
The rainfall statistics for all India and four homogeneous zones are given in Figure 4 and its month wise spatial rainfall distribution of rainfall anomaly is given in Figure 5. The rainfall realized over south peninsular India was 122% of LPA, over Central India 119 % of LPA, over northwest India 101% of LPA and over east & northeast India 82 % of LPA.
Figure 4: Rainfall statistics (All India and four homogeneous regions) for the southwest monsoon season during June - September 2022. [Source: IMD]
Figure 5: Observed (left), climatology (middle), and anomaly (right) of rainfall over India for tJune, July, August and September 2022 (Climatology and anomaly based on 1971 to 2020 period). [Source: IMD]
Figure 6: Daily rainfall time-series for All India and four homogeneous regions from 1 June to 30 September 2022. [Source: IMD]
The large-scale climate modes such as ENSO and IOD that prevailed during the summer monsoon 2022 are presented in Figure 7, 8 and 9. La Nina conditions were prevailing over Pacific Ocean which strengthened from July to September. At the same time negative Indian Ocean Dipole (IOD) was observed over Indian Ocean from July to September 2022. The strength of negative IOD was weakened from July to September 2022.
Figure 7: Sea surface temperature (SST) anomaly (C) from June to September 2022. [SST data: NOAA ERSSTv5]
Figure 8: ENSO indices (Nino3.4, Nino3, Nino4, Nino1+2, and Modoki) for the past 12 months period from Oct 2021 to Sep 2022. [SST data: NOAA ERSSTv5]
Figure 9: IOD indices (DMI, WEIO, and EEIO) for the past 12 months period from Oct 2021 to Sep 2022. [Dipole Mode Index (DMI), West Equatorial Indian Ocean (WEIO), East Equatorial Indian Ocean (WEIO) index.
Apart from ENSO and IOD, the Madden Julian Oscillation (MJO) is known to influence the Indian summer monsoon rainfall. The MJO phase diagram from April to June and from July to September 2022 is given below. The MJO was over western hemisphere and Africa from 1 June to 20 June and then the MJO observed over Indian Ocean from 21 June to 30 June. During the 1st week of July, the MJO was observed over the Maritime continent and then it was weakened to strengthen again around 21 July over western hemisphere and Africa. The MJO was entered Indian Ocean around 27 July but with weak intensity. The MJO was weak during most of the month of August except a few days from 21 to 30 August over the Indian Ocean. The MJO was weak and inactive during the month of September.
Figure 10: The MJO phase diagram from April to June and from July to September 2022 [Source: http://www.bom.gov.au/climate/mjo/]
References:
https://www.imdpune.gov.in/swmonsoon22.php
https://www.satyabanbratna.com/
Comments
Post a Comment