Current Science

Sulochana Gadgil ¹

Affiliations
1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560 012, IN

Abstract

No Abstract.

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Sulochana Gadgil ¹, P. A. Francis ²

Affiliations
1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
2 Indian National Centre for Ocean Information Services, Ministry of Earth Sciences, Hyderabad 500 090, IN

Abstract

We have addressed the question of whether the massive deficit of 42% in rainfall over the Indian region in June 2014 can be attributed primarily to the El Nino. We have shown that the variation of convection over the Northern part of the Tropical West Pacific (NWTP: 120-150E, 20-30N) plays a major role in determining the all-India rainfall in June with deficit (excess) in rainfall associated with enhancement (suppression) of convection over NWTP. In June 2014, the outgoing long wave radiation (OLR) anomaly over this region was unfavourable, whereas in June 2015, the OLR anomaly over NWTP was favourable and the all-India rainfall was 16% higher than the long-term average. We find that during El Nino, when the convection over the equatorial central Pacific intensifies, there is a high propensity for intensification of convection over NWTP. Thus, El Niño appears to have an impact on the rainfall over the Indian region via its impact on the convection over the West Pacific, particularly over NWTP. This occurred in June 2014, which suggests that the large deficit in June 2014, could be primarily attributed to the El Niño acting via intensification of convection over NWTP.

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Ashwini Kulkarni ¹, Sulochana Gadgil ², Savita Patwardhan ¹

Affiliations
1 Indian Institute of Tropical Meteorology, Pune, 411 008, IN
2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN

Abstract

The impact of the drought of the summer monsoon of 2015 has been particularly large in the Marathwada region of Maharashtra which is now facing unprecedented water scarcity and more than one thousand farmers have committed suicide. Substantial losses in the production of important crops such as pulses have been reported in Maharashtra. Naturally, the Marathwada drought has been extensively covered in the print and electronic media. The large impact has been attributed to exceptionally large deficit in rainfall by some journalists and politicians, to two successive droughts in 2014 and 2015 by some and some have considered the drought to be a manifestation of climate change. In this article, we present an analysis of the Marathwada monsoon rainfall from 1871 onwards and show that the quantum of deficit rainfall in 2015 as well as the occurrence of two successive droughts is within the observed variability of the Marathwada rainfall and the 2015 monsoon rainfall also cannot be considered as a manifestation of climate change. Thus the large impact of 2015 is a reflection of poor management of water resources and agriculture, despite the long experience of rainfall variability. We show that the prediction by the India Meteorological Department (IMD) of a high chance of below normal rainfall or a drought on the all-India scale and the occurrence of El Nino could have been used to anticipate large deficiency in Marathwada rainfall. We suggest that the problem of lack of progress in the production of rainfed crops such as pulses has to be addressed by using the rich rainfall data sets in the country to generate information which can be used by farmers and agricultural scientists to identify strategies, which are tailored to the entire spectrum of rainfall variability experienced. Towards this end an interactive software 'RAINFO' has been developed at the Indian Institute of Tropical Meteorology ((IITM), Pune to provide location-specific information derived from the IMD data, on the desired facets of rainfall variability.

Keywords

Marathwada Drought, Rainfall Variability, Rainfed Agriculture, RAINFO.

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Sulochana Gadgil ¹

Affiliations
1 A-18, Spring Flowers, Panchavati, Pashan, 411 008, IN

Abstract

D. R. Sikka's passionate affair with the Indian summer monsoon (as he called it) began in 1954, when he joined the India Meteorological Department (IMD), and ceased only with the end of his life on 18 March 2017.

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Sulochana Gadgil ¹, P. A. ², P. N. Vinayachandran ¹

Affiliations
1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 560 012, IN
2 Indian National Centre for Ocean Information Services (Ministry of Earth Sciences, Government of India), Hyderabad 500 090, IN

Abstract

The summer monsoon of 2019 began with a massive deficit in the all-India June rainfall of about 33% of the mean. This led to considerable anxiety since a large deficit in June had occurred last in the summer monsoon of 2014, which had turned out to be a drought. Here, we have attempted to unravel the factors that led to the deficit in June 2019 and also the above-normal rainfall in July. We show that the deficit in June 2019, as that of June 2014, can be attributed to the El Niño. The phase of the other important mode, Equatorial Indian Ocean Oscillation (EQUINOO), has been favourable throughout and led to the recovery of the monsoon in July when the El Niño weakened. It is expected that EQUINOO will play an important role in determining the rainfall in August and September, and hence the seasonal rainfall in 2019. Analysis of cases like 2003 and 2008, when the positive phase of EQUINOO lasted only during June and July and of 2007, when it lasted throughout the season has given an insight into the role of the sea surface temperature (SST) of the western equatorial Indian Ocean (WEIO) in sustenance of the positive phase of EQUINOO. We find that, unlike in 2003 and 2008, the SST of the WEIO has started increasing in late July, partly due to the mechanism which operated in 2007 and has led to a positive SST anomaly by 10 August, whereas sustained cooling has led to a negative SST anomaly over eastern equatorial Indian Ocean. Since conditions now appear to be favourable for sustenance of a positive phase of EQUINOO, it is expected that the seasonal rainfall will be above normal.

Keywords

Deficit Rainfall in June, ENSO, EQUINOO, Indian Summer Monsoon.

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Sulochana Gadgil ¹, P. A. Francis ², P. N. Vinayachandran ¹

Affiliations
1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bengaluru 500 012, IN
2 Indian National Centre for Ocean Information Services, Hyderabad 500 090, IN

Abstract

The summer monsoon of 2019 was rather unusual in terms of the all-India rainfall, with 32.8% deficit in June followed by rainfall being 4.6%, 15.4% and 52.3% above average for July, August and September respectively, resulting in the June–September rainfall being 10% above average (http://imdpune.gov.in/), on the borderline of excess rainfall. In an earlier study¹, we had analysed the performance of monsoon in June and July, and the important factors determining the interannual variation, viz. the El Niño Southern Oscillation (ENSO) and the Equatorial Indian Ocean Oscillation (EQUINOO).

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