摘要:利用2006～2017年风云气象卫星资料和气象再分析资料，对华北及周边5～8月对流活动和地面感热加热进行统计分析。分析表明，华北及周边白天平均感热加热和地形关系密切，内蒙古中部和东南部、华北北部和华北西部山区感热加热较强，最强感热加热出现在5月和6月，7月和8月明显减弱。和感热加热强度相对应，对流活动频率较高的月份同样出现在5月和6月，其中5月以弱对流为主，6月华北中北部强对流最活跃，另外，环渤海区域6～7月强对流相对频繁。5～8月日平均感热加热和对流频率趋势呈现一致的减弱对应关系。上午，感热加热引起河北西部和北部对流层低层出现辐合气流，700 hPa以下出现不同程度的增温，上升气流可达对流层中层，东侧的平原地区出现补偿下沉运动，升温和上升运动触发对流，在有利条件下发展东移。不同月份和区域对流频率日变化呈现明显差异，6月对流频率日变化显著，8月最弱，山区对流频率日变化显著，东部渤海及周边对流频率日变化较小。对流频率的月平均分布和日变化均表现出和地形相关的感热加热差异的特征。
关键词:风云卫星/
华北地形/
感热加热通量/
对流频率
Abstract:This paper represents statistical analysis of the convective activities and surface sensible heat fluxes from May to August in North China and its surrounding areas based on meteorological satellite and reanalysis data from 2006 to 2017. The results show that the daytime average sensible heat flux is closely related to the topography in North China and its surrounding areas. The sensible heat flux is stronger in the central and southeastern Inner Mongolia and the northern and the western mountainous areas of North China. The strongest sensible heat flux occurs in May and June whereas it obviously weakens in July and August. The higher convection frequency corresponding to the intensity of the sensible heat flux also occurs in May and June. In May, most of the convections are weak. The deep convections are most active in the north-central part of North China in June and are relatively frequent in the area around the Bohai Sea from June to July. The trend of the corresponding relationship between the daily average sensible heat flux and convection frequency shows consistent weakening from May to August. In the morning, sensible heat causes various degrees of convergence and warming in the lower troposphere below 700 hPa in the Western and Northern Hebei Province. The ascending motion reaches the middle troposphere, and the compensating descending motions occur in the eastern plains. The warming up and ascending motion trigger convection, which can develop rapidly when it moves eastward under favorable conditions. The diurnal variation in convection frequencies in different months and regions obviously differs. In June, the diurnal variation in the convection frequencies is significant, whereas it is the weakest in August. Regionally, the diurnal variation in the convection frequencies in mountainous areas is significant, whereas it is the weakest in the eastern Bohai Sea and its surrounding areas. Both the monthly mean distribution and diurnal variation in the convection frequency have a close relationship with the surface sensible heat flux generated by the topography.
Key words:Fengyun satellite/
Topography of North China/
Sensible heat flux/
Convection frequency
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http://www.iapjournals.ac.cn/qhhj/article/exportPdf?id=18161
