三亚降水日变化特征及其影响机制OA北大核心CSTPCD

Based on hourly precipitation data during 2011-2020,the characteristics and mechanisms of diurnal variation of precipitation in Sanya from June to October are studied.The results show that diurnal variation of precipitation in Sanya exhibits a bimodal pattern,with a primary peak at 05-08 LST and a secondary peak at 15-17 LST.Spatial distribution differences are observed in the diurnal variation,with peak values predominantly in the afternoon for inland mountainous areas and in the morning for coastal areas.Rainy days are divided into days with early morning peaks and days with afternoon peaks.In terms of atmospheric circulation,early morning peak rainfall days are featured by consistent westward low-eastward high pattern in the geopotential height anomaly along with southeaster anomaly,while afternoon peak rainfall days are featured by a low-pressure anomaly near 115°E over the South China Sea and northeaster anomaly.Regarding the influencing mechanisms,for morning peak rainfall days,there is a low-pressure anomaly and positive specific humidity anomaly at night.Continuous strong convergence is present near the surface in the Sanya region,accompanied by a deep ascending motion system in the vertical circulation,which is the primary factor leading to nighttime precipitation.For afternoon peak rainfall days,negative specific humidity anomalies are observed at night,and a deep descending circulation prevails at 500～600 hPa in the vertical circulation,suppressing nighttime precipitation.Local wind circulation in the afternoon leads to persistent strong near-surface convergence anomalies near the mountainous areas.Throughout the vertical circulation,there is a deep ascending motion circulation,serving as the main reason for afternoon precipitation.