南海港口大风的环流特征及其预报指标——以海南洋浦港为例

Circulation Characteristics and Forecasting Indicators of High Wind in a Port of South China Sea:Taking Yangpu Port as an Example

本文以海南洋浦港为例,利用2015—2019年大风资料,通过合成分析等方法深入探讨了不同类型大风过程的环流特征、发生机制及其预报指标。结果表明:(1)洋浦港大风过程按照影响系统可分为冷空气型、切变线型、热带气旋型和热低压型4种。(2)冷空气型大风主要是由强冷平流引发的;当925hPa关键区24h降温超过6℃且北风分量大于11.5m/s时,洋浦港6h后易发生冷空气型大风;切变线型大风主要产生于强对流引发的雷暴大风、飑线等;当925hPa低空切变线、500hPa南支槽等天气尺度系统出现有利配置,对流有效位能CAPE≥1500J·kg^(-1),且具有较合适的对流抑制能量CIN值时,易发生切变线型大风;热低压型大风与海陆热力差异引起的海风锋密切相关;当海南岛西北部陆地与近海海面的6h变温之差≥3.5℃,CAPE≥1500J·kg^(-1),CIN≤20J·kg^(-1)时,海风锋极易触发雷暴大风等强对流天气;热带气旋型大风主要发生在TC中心附近的等压线密集带以及外围螺旋雨带的中小尺度对流系统中。业务预报时可在数值预报基础上结合统计规律以及卫星、雷达等实况资料综合判定风力等级。

Taking Yangpu Port of Hainan as an example,using wind data from 2015 to 2019,the circulation characteristics,inducing mechanism and forecasting indicators of different kinds of High Wind Processes(HWPs)are investigated in this paper.Results suggest that:(1)HWPs of Yangpu Port can be divided into four types,namely cold-air type,shear-line type,tropical-cyclone(TC)type and thermal-low type,according to their influencing systems.(2)The cold-air HWP is mainly due to the advection of cold air.When the decreasing of the temperature in the critical area at 925 hPa is greater than 6 ℃ and the magnitude of north wind is greater than 11.5 m/s,it indicates that the cold-air HWP will occur in 6 hours;the shear-linear HWP is mainly caused by thunderstorm gales and squall lines induced by severe convection;when favorable configuration appears in synoptic-scale systems such as 925 hPa low shear-line and 500 hPa south trough,CAPE≥1500 J·kg^(-1) with appropriate CIN value,the shear-linear HWP is prone to occur;the thermal-low HWP is closely related to the sea breeze front caused by the difference of sea-land heat;when the difference of the increasing temperature between northwest inland and offshore sea surface in 6 hours is greater than or equal to 3.5 ℃,CAPE≥1500 J·kg^(-1),CIN≤20 J·kg^(-1),the sea breeze front is prone to trigger severe convection such as thunderstorms and gales;the TC HWP mainly occurs in the isobaric dense belt near the TC center and the mesoscale convective systems in the peripheral spiral rain belt.The wind scale can be determined synthetically based on the numerical forecast and combined with the statistical law,satellite,radar,and other monitoring data in the operational forecast.