In this study,we investigate the complex relationship between western disturbances(WDs),the El Ni?o–Southern Oscillation(ENSO),and extreme precipitation events(EPEs) in the western Himalaya(WH) during the extended wi...In this study,we investigate the complex relationship between western disturbances(WDs),the El Ni?o–Southern Oscillation(ENSO),and extreme precipitation events(EPEs) in the western Himalaya(WH) during the extended winter season(November–March).WDs west of WH coincide with 97% of recorded EPEs,contributing substantially(32% in winter,11% annually) to total precipitation within WH.WDs are 6% less frequent and 4% more intense during El Ni?o than La Ni?a to the west of WH.During El Ni?o(compared to La Ni?a) years,WDs co-occurring with EPEs are significantly more intense and associated with 17% higher moisture transport over “WH box”(the selected region where most of the winter precipitation over WH occurs).This results in twice the EPE frequency during El Ni?o periods than La Ni?a periods.A substantial southward shift(~180 km) of the subtropical jet(STJ) axis during El Ni?o brings WD tracks further south towards their primary moisture sources,especially the Arabian Sea.We have shown that WDs that are both more intense and pass to the south of their typical latitudes have higher levels of vertically integrated moisture flux(VIMF)within them.VIMF convergence in the most intense pentile of WDs is 5.7 times higher than in the weakest,and is 3.4 times higher in the second lowest latitude pentile than in the highest.Overall,this study demonstrates a direct link between changes in the latitudinal position and intensity of WDs associated with the winter STJ,and moisture convergence,which leads to the occurrence of EPEs over WH during ENSO phases.展开更多
基金the Ministry of Science and Technology,Government of India,and Council of Scientific and Industrial Research(CSIR)(09/081(1371)/2019-EMRI)for its funding,supported by a NERC Independent Research Fellowship(MITRE,NE/W007924/1)。
文摘In this study,we investigate the complex relationship between western disturbances(WDs),the El Ni?o–Southern Oscillation(ENSO),and extreme precipitation events(EPEs) in the western Himalaya(WH) during the extended winter season(November–March).WDs west of WH coincide with 97% of recorded EPEs,contributing substantially(32% in winter,11% annually) to total precipitation within WH.WDs are 6% less frequent and 4% more intense during El Ni?o than La Ni?a to the west of WH.During El Ni?o(compared to La Ni?a) years,WDs co-occurring with EPEs are significantly more intense and associated with 17% higher moisture transport over “WH box”(the selected region where most of the winter precipitation over WH occurs).This results in twice the EPE frequency during El Ni?o periods than La Ni?a periods.A substantial southward shift(~180 km) of the subtropical jet(STJ) axis during El Ni?o brings WD tracks further south towards their primary moisture sources,especially the Arabian Sea.We have shown that WDs that are both more intense and pass to the south of their typical latitudes have higher levels of vertically integrated moisture flux(VIMF)within them.VIMF convergence in the most intense pentile of WDs is 5.7 times higher than in the weakest,and is 3.4 times higher in the second lowest latitude pentile than in the highest.Overall,this study demonstrates a direct link between changes in the latitudinal position and intensity of WDs associated with the winter STJ,and moisture convergence,which leads to the occurrence of EPEs over WH during ENSO phases.
