| Using multisource satellite remote sensing data and assimilation,the spatio-temporal characteristics,main mechanisms and its influence on precipitation over India southern of the southern Bay of Bengal(BOB)cold pool(SCP)were analyzed,which enhanced the understanding of the SCP in the Bay of Bengal.The SCP appeared early in May,peaked in August,weakened in October,and then gradually disappeared.The multi-source satellite remote sensing data showed that 2018 and 2015 were the typical years of dramatic and weak cooling,with anomalies of-0.55℃ and 0.43℃ respectively.So,we analyzed the typical cold pool events in the southern Bay of Bengal in 2018 and 2015.In 2018,the positive wind stress anomaly controlled the SCP,while the net heat flux decreased and the vertical entrainment increased,resulting in the cooling of the SCP.The opposite process was appeared in 2015.The analysis of the heat budget showed the advection effect was the main cause of the cryogenic seawater in 2018 and 2015,accounting for 49.2% and80.7% respectively.The cooling difference of SCP mainly occurred in June,which was 2.76 times that of 2015 in 2018,and the net heat flux item was the main contribution.Multisource satellite remote sensing data and assimilation have been applied to explore the interannual variability in the SCP and its relationship with El Ni(?)o–Southern Oscillation(ENSO)events for the period 1982–2020.The anomalous SST of the SCP in the summer following the peak phase(i.e.,winter)of the ENSO was closely related to the ENSO events.El Ni(?)o(La Ni(?)a)-induced the warm(cold)anomaly of the SCP starting from May and persisted throughout August with a peak value appearing in June during the El Ni(?)o(La Ni(?)a)decaying years.In the El Ni(?)o decaying years,the southwest monsoon current(SMC)was weakened,forced locally by the weakening southwesterly wind and remotely by the easterly wind anomaly at the equator associated with El Ni(?)o.The El Ni(?)o-related weakening SMC and the associated less cold advection led to the warm anomaly of the SCP.In addition,El Ni(?)o-related atmospheric heating also made a comparable contribution to the evolution of the SCP’s SST.In the early stage(15 May to 10 June),its contribution to the warming of the SCP was much larger than that of the SMC,whereas from mid-June to August,it reversed to have a cooling effect and partially offset the advection heating induced by the SMC on the SCP.In the La Ni(?)a decaying years,similar oceanic and atmospheric processes operated but in an opposite way.Finally,based on the analysis of multi-source satellite remote sensing and assimilated data,we analyzed the influence of the difference of sea surface temperature(dSST)of the SCP and the warm water in the northern Bay on precipitation in southern India and its interannual variabilities during the summer period from 1982 to 2020.When dSST appeared positive anomaly,the cold pool SST anomaly and high pressure anomaly will be transmit to southern India through Rossby wave,which will cause negative near-surface temperature anomaly in southern India,and also cause local circulation anomaly in the southeast Arabian Sea and the northern Bay of Bengal.This circulation anomaly will lead to the strengthening westerly wind over southern India.During the negative dSST anomaly years,the process was reversed.What’s more,the atmospheric circulation anomalies made the air temperature appear negative anomalies and the positive relative humidity anomalies in south India,which was conducive to the formation of precipitation in the positive dSST anomaly years.In the 200 h Pa wind field,the upper troposphere over the Tibetan Plateau was controlled by anticyclonic circulation anomaly,leading to the intensification of South Asian High,which strengthened the southwest monsoon process,and thus enhanced the precipitation over India southern in wet events.During the dry events,the process was reversed.The analysis suggested that the effect of dSST on precipitation in India southern could last until September. |
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