一次“梅中返春”稳定性持续暴雨过程的预报失误分析

使用NCEP-FNL资料对杭州湾一次稳定性持续暴雨过程进行分析,发现冷暖气流在浙江不断交绥形成持续降雨,低层冷空气和东南暖湿气流的不断增强,使大气斜压扰动发展,锋区降雨增强,暴雨发生。此次过程,由于数值模式预报出现偏差而导致杭州湾24h大雨、暴雨预报出现较大失误。检验结果,GFS模式36h预报时效内对冷暖系统预报较好,但对低层锋区的风场预报有偏差,从而对中低层辐合、水平锋生和水汽输送产生影响,大雨、暴雨落区出现偏差。另外,模式对杭州湾南岸冷空气影响预报偏弱也是暴雨漏报的一个重要因素。稳定性降雨预报中,预报员需重视模式在预报临近时刻的调整,根据实况监测和雨带的移动、演变对冷暖气流影响作甄别,从而及时调整降雨落区和影响时间,对预报做出有益修正。     

2017年10月大气环流和天气分析

2017年10月环流特征如下：极涡呈偶极型,中高纬地区西风带为4波型分布,西太平洋副高强度较常年偏强、位置明显偏西。全国平均降水量46.2 mm,较常年同期（35.8 mm）偏多29%,为1961年以来第八高;全国平均气温10.6℃,较常年同期（10.3℃）偏高0.3℃。10月我国的大范围降水过程有6次,主要冷空气过程3次,其中8—10日降水过程伴随冷空气活动,给西北地区东部、华北中南部、东北南部带来该地区该季节较罕见的大范围强降水。2017年第20号台风卡努10月中旬登陆广东雷州半岛,给华南带来大风、降水。下旬我国北方出现一次雾 霾天气过程。     

泰山酸雨特征及影响因素分析

利用2006—2015年泰山气象站的降水pH、电导率、降水量和风向风速资料,统计分析了泰山酸雨特征和变化趋势,探讨了降水量和风向风速对酸雨的影响。结果表明,泰山降水年均pH变化范围为4.31～4.99,酸雨发生频率达到69.3%;pH随降水量的增加而趋于5.60（中性）;5月至次年1月的月均pH与月平均过程降水量的变化趋势一致;月均电导率与月平均过程降水量的变化趋势相反。泰山降水期间盛行西南风,在南风和东北风条件下,酸雨出现频率最高且酸性最强,这主要是风速风向因素和人为排放源分布共同导致的。近10 a泰山降水酸性程度有所减弱,酸雨频率明显下降,表明近年来酸雨污染情况有所改善,有利于保护泰山生态环境。     

2018年4月大气环流和天气分析

2018年4月大气环流的主要特征是极涡偏强且呈偶极型分布,中高纬环流呈4波型,西太平洋副热带高压强度较常年偏弱,南支槽强度较常年偏强。4月全国平均气温12.4℃,较常年同期偏高1.4℃;全国平均降水量43.6 mm,比常年同期（44.7 mm）偏少2.5%。月内我国有3次冷空气过程,其中2—7日为一次全国性强冷空气过程,造成大范围剧烈降温和雨雪天气;北方地区出现5次沙尘过程;南方地区出现3次暴雨过程,其中22—24日的暴雨过程给长江中下游地区造成严重的暴雨洪涝灾害。     

一次冻雨天气的云雷达回波特征分析

利用2014年12月10—12日的地面和探空资料、ECWMF再分析资料、Ka波段毫米波云雷达资料,采用特征分析、物理诊断量方法及回波特征分析方法,得到了较天气雷达更精细的垂直微观特征,对贵州冻雨的形成和演变提供了新的观测事实。结果表明:(1)此次冻雨过程地面温度在0℃附近,且云系形成后的温度随高度下降始终维持在-10～0℃之间,为过冷暖雨过程。(2)冻雨在初生、成熟及消亡阶段的回波强度随高度下降逐渐增大,强度值为-30～12dBz。空气垂直速度集中在-0.4～1.6m/s之间,粒子下落速度集中在2.4m/s以内。(3)冻雨初生及消亡阶段上升运动弱,粒子尺寸小。成熟期间,上升气流加强,小粒子所占比例减小,大粒子增多。云体中下部谱宽大值区和强反射率因子对应,反映了液态过冷水下落过程中的碰并增长结果。     

雨雪冰冻监测系统的设计与应用

雨雪冰冻气象灾害会严重影响交通、电力等各行各业,通过建设雨雪冰冻监测系统,增加积雪深度、称重降水、实景观测等观测要素,加强积雪、固态降水自动化监测。利用OpenCV技术对雪深监测数据进行质量控制,采用等值线wContour类库画图方法绘制等值线图,结合实景拍摄及时准确反映雨雪冰冻情况。通过分析显示系统,综合各类气象观测资料,为气象工作者或决策部门提供直观、准确的气象信息,为气象防灾减灾提供有效的技术手段,提高气象服务水平。     

北京市快速城市化对短时间尺度降水时空特征影响及成因

快速城市化对区域降水过程的影响已成为人类活动对不同时空尺度水循环影响研究的热点。基于北京全区2011-2015年20个自动气象站逐小时降水资料,利用Circular统计法等多种方法,在揭示北京市降水总体特征基础上,进一步从日、场次、小时等多种精细化时间尺度来探究北京市不同类型降水特征。研究表明：① 场次暴雨平均降水量、场次降雨持续时间及降水强度高值中心主要位于北京城区,与郊区降水过程相比,城区总体降水过程历时较长、雨量较大。城市雨岛效应可能是上述降水指标在城区具有高值中心的原因之一。② 北京全区降水日分布不均,不同区域降水类型有较大差异。北京市的暴雨雨型主要以午后型为主,占总雨型的47.53%。山区总体及北部近郊、远郊区、南部近郊分别以午后型、正午型、夜晚型降水为主。而城区的暴雨类型显示出主城区的东西两侧有较大的差异,西侧受山谷风环流及热岛环流影响类型较为复杂,东侧以傍晚型为主。③ 场次暴雨的降水峰值出现时间主要集中在12:00-19:00,且城区降水峰值发生时间较郊区降水峰值发生时间推迟。海拔的升高会使日降水峰值的出现时间的不确定性增大。④ 极端降水量指标及持续干燥、湿润指标均在城区显示出高值区,极端降水频率指标高值区位于城区下风向。城市化可能通过人口膨胀、土地利用类型变更等方式间接提高极端降水发生的风险。     

Mesoscale and Microphysical Characteristics of a Double Rain Belt Event in SouthChina on May 10–13, 2022

A second rain belt sometimes occurs ahead of a frontal rain belt in the warm sector over coastal South China,leading to heavy precipitation. We examined the differences in the mesoscale characteristics and microphysics of thefrontal and warm sector rain belts that occurred in South China on May 10–13, 2022. The southern rain belt occurred in anenvironment with favorable mesoscale conditions but weak large-scale forcing. In contrast, the northern rain belt wasrelated to low-level horizontal shear and the surface-level front. The interaction between the enhanced southeasterly windsand the rainfall-induced cold pool promoted the persistent growth of convection along the southern rain belt. The con vective cell propagated east over the coastal area, where there was a large temperature gradient. The bow-shaped echo inthis region may be closely related to the rear-inflow jet. By contrast, the initial convection of the northern rain belt wastriggered along the front and the region of low-level horizontal shear, with mesoscale interactions between the enhancedwarm-moist southeasterly airflow and the cold dome associated with the earlier rain. The terrain blocked the movement ofthe cold pool, resulting in the stagnation of the frontal convective cell at an early stage. Subsequently, a meso-γ-scalevortex formed during the rapid movement of the convective cell, corresponding to an enhancement of precipitation. Therepresentative raindrop spectra for the southern rain belt were characterized by a greater number and higher density ofraindrops than the northern rain belt, even though both resulted in comparable hourly rainfalls. These results help us betterunderstand the characteristics of double rain belts over South China.     

2016年5月大气环流和天气分析

北半球极涡呈偶极型分布,极涡主体分别位于格陵兰岛以西以及贝加尔湖北部附近,强度较常年同期偏强;中高纬环流呈4波型分布特征,长波槽分别位于北美西部、格陵兰岛东部、里海西部和贝加尔湖北部;西太平洋副热带高压较常年同期面积明显偏大,588 dagpm等高线东西伸展经度跨度很大,接近环绕全球。5月全国平均气温16.3℃,较常年同期（16.2℃）偏高0.1℃;全国平均降水量82.8 mm,较常年同期（69.5 mm）偏多19.1%。月内我国主要天气特点是：南海夏季风5月下旬爆发;西南地区东部、江南、华南南暴雨过程频发;强对流过程影响范围广、过程强度大、雷暴大风和冰雹灾害较多。     

CHARACTERISTICS OF THE LATENT HEAT DUE TO DIFFERENT CLOUD MICROPHYSICAL PROCESSES AND THEIR INFLUENCE ON AN AUTUMN HEAVY RAIN EVENT OVER HAINAN ISLAND

We analyzed cloud microphysical processes’ latent heat characteristics and their influence on an autumn heavy rain event over Hainan Island, China, using the mesoscale numerical model WRF and WRF-3DVAR system. We found that positive latent heat occurred far above the zero layer, while negative latent heat occurred mainly under the zero layer. There was substantially more positive latent heat than negative latent heat, and the condensation heating had the most important contribution to the latent heat increase. The processes of deposition, congelation, melting and evaporation were all characterized by weakening after their intensification; however, the variations in condensation and sublimation processes were relatively small. The main cloud microphysical processes for positive latent heat were condensation of water vapor into cloud water, the condensation of rain, and the deposition increase of cloud ice, snow and graupel. The main cloud microphysical processes for negative latent heat were the evaporation of rain, the melting and enhanced melting of graupel. The latent heat releases due to different cloud microphysical processes have a significant impact on the intensity of precipitation. Without the condensation and evaporation of rain, the total latent heating would decrease and the moisture variables and precipitation would reduce significantly. Without deposition and sublimation, the heating in high levels would decrease and the precipitation would reduce. Without congelation and melting, the latent heating would enhance in the low levels, and the precipitation would reduce.