Dominant pattern of year-to-year variability of summer precipitation in Nepal during 1987–2015

Sharma, Shankar; Hamal, Kalpana; Khadka, Nitesh; Joshi, Bharat Badayar

doi:10.1007/s00704-020-03359-1

Cited by 34 publications

(32 citation statements)

References 56 publications

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“…ERA5 is a recently released fifth‐generation global atmospheric reanalysis project developed by the European Centre for Medium‐Range Weather Forecasts, which provides improved data for atmospheric models and assimilation systems (C3S, 2017). Recently, Sharma et al (2020d) validated the ERA5 precipitation product using an extensive gauge network (220) from Nepal during 1987–2015, revealing that ERA5 is a good alternative for precipitation monitoring in the country.…”

Section: Methodsmentioning

confidence: 99%

Assessment of drought impacts on crop yields across Nepal during 1987–2017

Hamal

Sharma

Khadka

et al. 2020

Meteorological Applications

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Drought influences agriculture, hydrology, ecology and socioeconomic systems globally. As agriculture is the primary source for livelihoods and contributes to $27% of Nepalʼs total gross domestic product, it is essential to understand the impact of drought on maize and wheat crop yields to minimize the droughtrelated risks. This study presents insights about agricultural drought across Nepal during 1987-2017 using the Standardized Precipitation Evapotranspiration Index (SPEI). The temporal evolution of SPEI time series has revealed frequent occurrences of drought episodes during the cropping cycle of summer maize and winter wheat crops. Moreover, the turning point of the drought was detected in 2000 (1987-2000, 2001-2017) in different regions. The averaged frequency for the SPEIs (1, 3, 6 and 12) of drought years for summer maize (winter wheat) in the western, central and eastern regions increased by 13% (12.5%), 6% (7.5%) and 7% (8%), respectively, from 1987-2000 to 2001-2017. The relationship between Standardized Yield Residual Series, the detrended SPEI at 1-12 lags and soil moisture was observed for both crops. The most correlated crop growth period for summer maize and winter wheat was the sowing and growing period, respectively, indicating the sensitive period of water deficit. Besides, the correlation performed in the two sub-periods (1987-2000 and 2001-2017) shows that drought impacts increased in the western and central regions, whereas they substantially decreased in the eastern region during the cropping period of summer maize. However, the drought sensitivity for winter wheat was decreased in the western region but significantly increased in the central and eastern regions of Nepal. The results of this study provide important information useful for policymakers in monitoring and mitigating the drought-related risks on maize and wheat crops in Nepal.

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Section: Methodsmentioning

confidence: 99%

Assessment of drought impacts on crop yields across Nepal during 1987–2017

Hamal

Sharma

Khadka

et al. 2020

Meteorological Applications

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“…A significant correlation was found between the SPI and SST anomalies over the Pacific Ocean, suggesting that the ENSO is the prominent forcing for the interannual variability of annual and summer drought in Nepal. The warm SST anomalies over the Pacific disturbed the monsoon circulation by delaying monsoon precipitation and causing a precipitation deficit in South Asia (Mishra et al, 2016;Joshi and Kar, 2018;Sharma et al, 2020b).…”

Section: Discussionmentioning

confidence: 99%

“…Based on climatology, the four distinct seasons of Nepal are spring (March-May), summer monsoon (June-September), autumn (October-November) and winter (December-February). Moreover, the mean summer precipitation over the country during the period 1987-2015 is 1,685 mm (Sharma et al, 2020b).…”

Section: Study Areamentioning

confidence: 99%

Drought characteristics over Nepal Himalaya and their relationship with climatic indices

Sharma

Hamal

Khadka

et al. 2021

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Understanding drought characteristics is vital for sustainable societal and ecosystem functioning, especially in ongoing climate change. The study investigates the drought characteristics over the Nepal Himalaya using the standardized precipitation index (SPI) based on monthly precipitation data from 220 ground stations between 1980 and 2016 at seasonal and annual timescales. The results show that occurrences of drought are more frequent after the 2000s, intensifying their severity and duration. The cumulative probabilities of short-term (SPI3) and long-term (SPI12) drought during the period 1980-2016 were 17.1% and 23.5%, respectively. The short-term drought over Nepal occurred with an average duration of 2.8 months and a severity of −4.3, whereas for long-term drought the duration and severity were 8.6 months and −13.9, respectively. Meanwhile, the seasonal drought shows that the spring and autumn drought events were slightly higher than summer and winter drought. The wavelet power spectrum shows the variability signals of winter, spring and summer drought were 2-8 and 8-16 years; however, the autumn drought index only varied at 2-8 years. The NINO3.4 is the primary controlling mode of variability for summer and annual drought, whereas the dipole moment index (DMI) is used for the autumn drought at an interannual timescale. The decadal variability of summer and annual drought is linked with the Pacific Decadal Oscillation, whereas winter and spring drought are linked to the Arctic Oscillation. Furthermore, the study contributes to the understanding of the drought characteristics and its controlling factors of variability over Nepal.

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“…Monsoon enters Nepal from the east and advects toward the west, covering the whole country within a week. Generally, summer monsoon is characterized by widespread rainfall [7,59], whereas, pre-monsoon season is characterized by localized afternoon thundershowers [7]. Furthermore, post-monsoon and winter seasons are relatively dry seasons.…”

Section: Study Areamentioning

confidence: 99%

Assessment of GPM-Era Satellite Products’ (IMERG and GSMaP) Ability to Detect Precipitation Extremes over Mountainous Country Nepal

et al. 2021

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The reliability of satellite precipitation products is important in climatic and hydro-meteorological studies, which is especially true in mountainous regions because of the lack of observations in these areas. Two recent satellite rainfall estimates (SREs) from Global Precipitation Measurement (GPM)-era—Integrated Multi-Satellite Retrievals for Global Precipitation Measurement (IMERG-V06) and gauge calibrated Global Satellite Mapping of Precipitation (GSMaP-V07) are evaluated for their spatiotemporal accuracy and ability to capture extreme precipitation events using 279 gauge stations from southern slope of central Himalaya, Nepal, between 2014 and 2019. The overall result suggests that both SREs can capture the spatiotemporal precipitation variability, although they both underestimated the observed precipitation amount. Between the two, the IMERG product shows a more consistent performance with a higher correlation coefficient (0.52) and smaller bias (−2.49 mm/day) than the GSMaP product. It is worth mentioning that the monthly gauge-calibrated IMERG product yields better detection capability (higher probability of detection (POD) values) of daily precipitation events than the daily gauge calibrated GSMaP product; however, they both show similar performance in terms of false alarm ratio (FAR) and critical success index (CSI). Assessment based on extreme precipitation indices revealed that the IMERG product outperforms GSMaP in capturing daily precipitation extremes (RX1Day and RX5Day). In contrast, the GSMaP product tends to be more consistent in capturing the duration and threshold-based precipitation extremes (consecutive dry days (CDD), consecutive wet days (CWD), number of heavy precipitation days (R10mm), and number of extreme precipitation days (R25mm)). Therefore, it is suggested that the IMERG product can be a good alternative for monitoring daily extremes; meanwhile, GSMaP could be a better option for duration-based extremes in the mountainous region.

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Dominant pattern of year-to-year variability of summer precipitation in Nepal during 1987–2015

Cited by 34 publications

References 56 publications

Assessment of drought impacts on crop yields across Nepal during 1987–2017

Assessment of drought impacts on crop yields across Nepal during 1987–2017

Drought characteristics over Nepal Himalaya and their relationship with climatic indices

Assessment of GPM-Era Satellite Products’ (IMERG and GSMaP) Ability to Detect Precipitation Extremes over Mountainous Country Nepal

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