《海洋预报》| 三亚降水日变化特征及其影响机制

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2025-02-17 17:08

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三亚降水日变化特征及其影响机制

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作者：蓝欣^{1 2}冯箫^{1 3}

单位：1. 海南省南海气象防灾减灾重点实验室, 海南海口 570203;2. 海南省三亚市气象局, 海南三亚 572000;3. 海南省气象台, 海南海口 570203

分类号：P426.61+4

出版年·卷·期（页码）：2024·41·第六期（71-81）

摘要：利用 2011—2020年逐时降水数据，研究了三亚 6—10月降水日变化特征及其影响机制。结果表明：三亚降水日变化呈双峰特征，主峰出现在 05—08时，次峰出现在 15—17时。降水日变化存在空间分布差异，内陆山区峰值以午后为主，沿海地区以晨峰为主。将降雨日按峰值时间分为晨峰雨日和午峰雨日，在环流差异上，晨峰雨日的位势高度距平场呈一致的西低东高和东南风异常，午峰雨日则表现为在南海上空115°E附近存在一个低压异常和东北风异常；在影响机制上，晨峰雨日夜间存在低压异常和比湿正距平，近地面存在持续较强的辐合，垂直环流上存在一个深厚的上升运动系统，是导致夜间降水发生的主要原因，而午峰雨日夜间存在比湿负距平，500～600 hPa垂直环流上维持一个深厚的下沉环流，抑制了夜间降水，午后局地风场环流导致山区附近出现持续较强的近地面辐合异常，垂直环流上整层存在深厚的上升运动环流，是午后降水发生的主要原因。

关键词：降水日变化三亚晨峰雨日午峰雨日

Abstract：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.

Key words：diurnal variation of precipitation; Sanya; early morning peak rainy days; afternoon peak rainy days