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Spatial-Temporal Variability of Droughts during Two Cropping Seasons in Sri Lanka and Its Possible Mechanisms

Shelton, Sherly and Ogou, Faustin Katchele and Pushpawela, Buddhi (2022) Spatial-Temporal Variability of Droughts during Two Cropping Seasons in Sri Lanka and Its Possible Mechanisms. Asia-Pacific Journal of Atmospheric Sciences, 58 (1). pp. 127-144. ISSN 1976-7633. doi:10.1007/s13143-021-00239-0.

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Drought management in Sri Lanka is mostly limited to relief provision due to the shortage of scientific details to develop sufficient drought risk management. Therefore, spatio-temporal variability of droughts in two cropping seasons, Yala (May–August) and Maha (October–March) in Sri Lanka, have been investigated using the Standardized Precipitation Evapotranspiration Index (SPEI). The SPEI-4 at August (SPEI-4August) shows an apparent decadal variation over wet, intermediate, and dry climate regions in the country, which is coherent with the decadal shift of rainfall in 1999. For the Yala season, the number of drought events (SPEI-4_(August) < −1) in the late period (2000–2015) is higher than that in the early period (1985–1999). On the other hand, the decadal variation of SPEI-6_(March) is not distinguished; however, the number of drought events (SPEI-6_(March) < −1) in all climate regions is less after 2003 as compared to the early period. The principle component time series of SPEI-4_(August) and rainfall in Yala seasons (r = 0.93) have closely associated, which implies that rainfall received in the Yala season can ascribe the observed decadal variation in SPEI-4_(August). In the Yala season, less moisture transport towards Sri Lanka is observed in the late period due to the weakening of 850 hPa wind circulation and increasing of 500 hPa geopotential height, which causes more moisture divergence and ultimately affects the decreasing rainfall over the country. Meanwhile, the observed rainfall variability in cropping seasons, especially in the Yala season, is characterized by the large-scale circulation at interannual (Nino3.4) to decadal-scale (Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO).

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Ogou, Faustin Katchele0000-0002-0342-7929
Additional Information:© This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2021. Received 07 June 2020; Revised 26 March 2021; Accepted 28 March 2021; Published 17 May 2021. We are thankful to the Meteorological Department of Sri Lanka for providing weather data. The first author acknowledges the CAS–TWAS President’s Fellowship Program for International Ph.D. student, China–Sri Lanka joint Center for Education and Research (CSL-CER), Industrial Technology Institute–Sri Lanka. No potential conflict of interest was reported by the authors.
Funding AgencyGrant Number
Chinese Academy of SciencesUNSPECIFIED
China-Sri Lanka Joint Center for Education and Research (CSL-CER)UNSPECIFIED
Industrial Technology Institute (Sri Lanka)UNSPECIFIED
Subject Keywords:SPEI, Yala and Maha seasons; Drought variability; Decadal shift of rainfall; Large-scale circulation indices
Issue or Number:1
Record Number:CaltechAUTHORS:20210602-135902735
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Official Citation:Shelton, S., Ogou, F.K. & Pushpawela, B. Spatial-Temporal Variability of Droughts during Two Cropping Seasons in Sri Lanka and Its Possible Mechanisms. Asia-Pacific J Atmos Sci 58, 127–144 (2022).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:109349
Deposited By: Tony Diaz
Deposited On:02 Jun 2021 21:09
Last Modified:28 Jan 2022 19:23

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