Variability of extreme rainfall events over India during southwest monsoon season

Pattanaik, D. R.; Rajeevan, M.

doi:10.1002/met.164

Cited by 135 publications

(62 citation statements)

References 31 publications

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“…Rainfall also shows an increase of about 1.3 mm/year in this period. Decreasing trends in Indian summer monsoon rainfall in last 50 years (Lau and Kim, 2010) and increasing number of extreme rainfall events (Goswami et al, 2006;Pattanaik and Rajeevan, 2010) have been repeatedly reported over this region in recent studies. Our analysis indicates that increasing CAPE over the Indian region may be responsible for increase in frequency of extreme events.…”

Section: Discussionmentioning

confidence: 68%

Trends of Convective Available Potential Energy over the Indian region and its effect on rainfall

Murugavel

Pawar

Gopalakrishnan

2011

Intl Journal of Climatology

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Many studies in recent times have suggested that long-term changes in Convective Available Potential Energy (CAPE) are associated with the changes in convective activity and atmospheric energy budget and, hence, the changes in CAPE could be used as a potential indicator of climate change. Here, we analyse daily radiosonde data of 32 stations over the Indian region from 1984 to 2008 (25 years), to study the climatology and long-term changes in CAPE, lower troposphere moisture content and upper tropospheric temperature. Using gridded daily rainfall data over this region, the relationship between average CAPE and average rainfall as well as the trends in CAPE and its effect on rainfall pattern are also examined during different seasons of this region. All the coastal and island stations, as well as some stations in the foothills of the Himalayas, show higher values of CAPE compared to other inland stations. This study clearly demonstrates that CAPE values have been systematically increasing over most parts of the Indian region during last 25 years. The increase in CAPE is found to be due to increase in low-level moisture content and decrease in upper level temperature over the last 25 years. The seasonal variations show that the CAPE is higher during the monsoon compared to pre-monsoon or post-monsoon seasons and it suggests that thermodynamic conditions favourable for high CAPE together with large-scale dynamics are necessary for organized monsoon convections over this region. In comparison with a large increase in the allIndia average of CAPE during monsoon season, which is about 38 J Kg −1 year −1 , the all-India summer monsoon rainfall increases about 1.3 mm year −1 . The systematic increasing trend in CAPE may be compensating for weakening of monsoon circulation and, thus, maintaining the monsoon rainfall over the Indian region.

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Section: Discussionmentioning

confidence: 68%

Trends of Convective Available Potential Energy over the Indian region and its effect on rainfall

Murugavel

Pawar

Gopalakrishnan

2011

Intl Journal of Climatology

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“…For instance, studies have found a rise in the summer monsoonal precipitation extremes over central India and northeastern Pakistan [15][16][17][18][19][20]. In contrast, precipitation extremes feature a falling trend over southwestern Pakistan [20], the eastern Gangetic plains and some parts of Uttaranchal, India [21].…”

Section: Introductionmentioning

confidence: 99%

Rising Precipitation Extremes across Nepal

Karki

Hasson

Schickhoff

et al. 2017

Climate

208

140

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Abstract:As a mountainous country, Nepal is most susceptible to precipitation extremes and related hazards, including severe floods, landslides and droughts that cause huge losses of life and property, impact the Himalayan environment, and hinder the socioeconomic development of the country. Given that the countrywide assessment of such extremes is still lacking, we present a comprehensive picture of prevailing precipitation extremes observed across Nepal. First, we present the spatial distribution of daily extreme precipitation indices as defined by the Expert Team on Climate Change Detection, Monitoring and Indices (ETCCDMI) from 210 stations over the period of . Then, we analyze the temporal changes in the computed extremes from 76 stations, featuring long-term continuous records for the period of 1970-2012, by applying a non-parametric Mann−Kendall test to identify the existence of a trend and Sen's slope method to calculate the true magnitude of this trend. Further, the local trends in precipitation extremes have been tested for their field significance over the distinct physio-geographical regions of Nepal, such as the lowlands, middle mountains and hills and high mountains in the west (WL, WM and WH, respectively), and likewise, in central (CL, CM and CH) and eastern (EL, EM and EH) Nepal. Our results suggest that the spatial patterns of high-intensity precipitation extremes are quite different to that of annual or monsoonal precipitation. Lowlands (Terai and Siwaliks) that feature relatively low precipitation and less wet days (rainy days) are exposed to high-intensity precipitation extremes. Our trend analysis suggests that the pre-monsoonal precipitation is significantly increasing over the lowlands and CH, while monsoonal precipitation is increasing in WM and CH and decreasing in CM, CL and EL. On the other hand, post-monsoonal precipitation is significantly decreasing across all of Nepal while winter precipitation is decreasing only over the WM region. Both high-intensity precipitation extremes and annual precipitation trends feature east−west contrast, suggesting significant increase over the WM and CH region but decrease over the EM and CM regions. Further, a significant positive trend in the number of consecutive dry days but significant negative trend in the number of wet (rainy) days are observed over the whole of Nepal, implying the prolongation of the dry spell across the country. Overall, the intensification of different precipitation indices over distinct parts of the country indicates region-specific risks of floods, landslides and droughts. The presented findings, in combination with population and environmental pressures, can support in devising the adequate region-specific adaptation strategies for different sectors and in improving the livelihood of the rural communities in Nepal.

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“…The rainfall events were classified based on India Meteorological Department [ Table 1 of Pattanaik and Rajeevan (2010)]. The total number of rainy days were 109, 111 and 91, respectively, for 2014-2016, of which light rain (daily rainfall < 10 mm) constituted around 76% of total rainfall events.…”

Section: Wavelet Analysismentioning

confidence: 99%

Investigation of scale interaction between rainfall and ecosystem carbon exchange ofWestern Himalayan Pine dominated vegetation

Mukherjee

Sekar

Lohani

et al. 2018

Preprint

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Abstract. Forests of the Western Himalaya, India, are impacted by the summer monsoon and winter seasonal rainfall events and associated changes in the meteorology. Here, we assess the scale interactions between observed forest ecosystem fluxes and meteorological parameters, particularly rainfall seasonality and extremes. The scale interactions were investigated using daily observed fluxes and meteorological parameters of 1080 days of 2014–2016 from a Pinus roxburghii dominated forest and using wavelet spectral analysis method. The mixed forest of this study was a sink of CO2 having the average NEE −3.21 gC m−2 day−1 for the period of observations. Result of the wavelet coherence analysis from observed data indicated a statistically significant correlation (> 0.7 at 95 % confidence level) between daily average NEE and daily total rainfall having band periods of 70–120 days, 35–64 days and 60–90 days of monsoon periods of 2014–16, respectively, where rainfall leading to NEE. Impact of heavy rainfall events of monsoon periods over NEE of the forest patch was found to have average band periods of 4 days; whereas, the winter time heavy rainfall events were having average band periods of 15 days with very high local correlation (> 0.7 at 95 % confidence level) inferring that ecosystem exchange rate was mirroring rainfall events. Although CASA-GFDE3 model simulated daily NEE values of 2014–15 were found have a low fraction of explained variance (= 0.08) with respect to observations, modeled NEE-rainfall relationship of 2014 was found to corroborate well with the observed pattern; however for 2015, the phase relationship between modeled NEE and rainfall around band period of 100 days was opposite to the flux tower observations. Subsequently, heavy rainfall events and daily average air temperatures were also found to be coherent during monsoon period having wavelet coherences > 0.8 indicating a cause and effect relationship between both parameters, and rainfall events were mirroring temperature variations. Therefore, it is anticipated that the Pinus roxburghii dominated forest productivity of Western Himalaya, India, are expected to increase even with the increment of heavy rainfall events in the near 20 future.

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Variability of extreme rainfall events over India during southwest monsoon season

Cited by 135 publications

References 31 publications

Trends of Convective Available Potential Energy over the Indian region and its effect on rainfall

Trends of Convective Available Potential Energy over the Indian region and its effect on rainfall

Rising Precipitation Extremes across Nepal

Investigation of scale interaction between rainfall and ecosystem carbon exchange ofWestern Himalayan Pine dominated vegetation

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