南疆短时强降水概念模型及环境参数分析

利用南疆2010-2016年自动气象站及区域自动气象站逐小时降水量资料,NCEP/NCAR 1°×1°再分析资料以及探空资料,分析不同强度的短时强降水的时空分布,得出南疆短时强降水事件的天气型有明显的季节性特点和区域性特征。总结了典型短时强降水过程的环境背景场特征,建立了短时强降水的三种概念模型:中亚低槽(涡)型、西伯利亚低槽(涡)型和西风短波型。通过7个探空站的温湿廓线形态、地面露点温度、T_(850)-T_(500)、T_(700)-T_(500)、对流有效位能(CAPE)、对流抑制能量(CIN)、抬升凝结高度、0～6 km垂直风切变等分析了南疆短时强降水的环境背景:短时强降水Ⅰ型(整层湿)、短时强降水Ⅱ型(上湿下干)和短时强降水Ⅲ型(上干下湿)发生前大气水汽含量充沛、存在一定的CAPE和较明显的垂直风切变以及0℃层高度偏低、暖云层厚度偏厚等特征,而合适的CIN,有利于对流不稳定能量的积聚和爆发,促进短时强降水的发生;短时强降水Ⅳ型(干绝热型)存在大气层结较干和较大的T_(850)-T_(500)、T_(700)-T_(500);Ⅰ型和Ⅱ型是南疆短时强降水的主要类型,常出现在南疆中部、西部地区的盛夏和夏末,多为西伯利亚低值系统(低涡、低槽)型和中亚低值系统(低涡、低槽)型影响。     

Recent Change of the South Asian High

This paper investigates the variability of the summer （May-September） South Asian Iligh （SAIl） for the period 1979-2012. Results show that the intensity and the area of the summer SAH decreased around 2002 at the decadal scale; and the East Asian westerly jet suppressed at the north edge of the SAH, which is consistent with the SAH variation. The precipitation pattern over eastern China also shifted during the same periods, with increased rainfall in the Huang-Huai River region and South China and decreased rainfall in the Yangtze River region. The relationship between the two variations is evidently strengthened via changes in moisture flux.     

南海夏季风持续异常的特征及其对全球环流的影响II.数值试验

利用T42L9全球大气环流谱模式进行数值试验 ,以揭示南海夏季风强度异常的特征及其影响。控制试验结果表明 ,该模式不仅能够很好地模拟出气候平均的西风带槽脊和高低空气流分布以及它们的季节性变化 ,而且对于与亚洲季风有关的各个主要系统 ,如南亚高压、副高进退及越赤道气流等都有较强的模拟能力。在亚洲季风区及热带太平洋这一大范围区域的大气内部热源异常强迫下 ,模式显示出了南海夏季风持续异常的特征、北半球热带外环流的响应以及亚洲季风区降水异常分布。南海夏季风长时间强度异常所引起的大气内部热源异常 ,一方面通过三维垂直环流的异常联结着南海夏季风对北半球热带内外环流的影响 ,另一方面它又通过持续异常期的波列传播 ,即能量的传播 ,不仅影响我国长江流域降水 ,还会逐渐影响到北半球中高纬环流结构。这样西风带环流形势将会发生相应的变化和调整 ,南海夏季风持续异常影响到了北半球大气环流和天气气候的变化。     

South-north dipolar pattern around mid-1990s in Korean summer rainfall variability

From the time series of rainfall in summer (June, July and August) in South and North Koreas for recent 28 years (1981–2008), rainfall has significantly increased in South Korea while it has significantly decreased in North Korea since 1996. In particular, the decreasing trend of summer rainfall in North Korea was more conspicuous during the second Changma (late August – mid-September). This characteristic was also found in the south-north dipolar pattern based on 1996 by empirical orthogonal function analysis using summer rainfall observed in all weather observation stations in South and North Korea.The decreasing rainfall trend in North Korea was found to be associated with the weakening of convection by anomalous northeasterlies from anomalous anticyclone centered on around Baikal Lake during summer. On the other hand, the increasing rainfall trend of South Korea was associated with the strengthened anomalous cyclone in the southern region of China, which in turn strengthened anomalous southwesterlies.     

夏季南亚高压与邻近上对流层下平流层区水汽变化的联系

利用1979-2015年ERA-interim月平均再分析资料,分析了夏季南亚高压（SAH）与邻近上对流层下平流层（UTLS）区水汽空间分布特征,讨论了二者的相关关系和因果联系。结果表明:（1）在对流层上层,水汽大值区位于南亚高压的东南侧,并随高度升高向西北倾斜到100 hPa,水汽大值中心基本位于南亚高压中心附近。（2）南亚高压偏强（弱）时,南亚高压东部UTLS区水汽显著偏多（少）,而南亚高压西北部水汽异常不显著。（3）南亚高压偏强（弱）时南亚高压中部UTLS区水汽偏多（少）可能与南亚高压对水汽的抽吸和对水汽输送屏障有关。（4）而南亚高压东南侧UTLS区水汽偏多（少）时南亚高压偏强（弱）可能与深对流输送的水汽潜热释放有关。      

北半球平流层极涡崩溃早晚的环流特征及其对5月南亚降水的影响

本文采用1979—2014年NCEP/NCAR月平均再分析资料、CMAP和GPCP月平均降水资料,分析了北半球平流层极涡崩溃早晚的环流特征及其与南亚降水的关系。结果表明,北半球平流层极涡崩溃时间存在明显的年际变化特征。极涡崩溃偏早(偏晚)年,自3月开始异常信号从平流层向下传播,之后的4月,从平流层到对流层高层极区温度异常偏高(偏低),极涡异常偏弱(偏强),极夜急流异常偏弱(偏强)。结果还表明,5月南亚降水异常与平流层极涡崩溃时间的早晚存在显著相关,5月南亚降水异常与平流层极涡崩溃早晚年平流层异常信号的下传有关。当平流层极涡崩溃偏晚年,4月平流层极区表现为位势高度异常偏低,而中纬度则位势高度场异常偏高,并伴随位势高度异常场的向下传播,5月该位势高度异常场下传至阿拉伯海北部大陆上空对流层顶,形成有利于降水的环流场,导致南亚降水偏多。反之,则相反。     

Strengthened Relationship between the Antarctic Oscillation and ENSO After the Mid-1990s during Austral Spring

This paper documents a decadal strengthened co-variability of the Antarctic Oscillation(AAO)and ENSO in austral spring after the mid-1990 s.During the period 1979–93,the ENSO(AAO)spatial signatures are restricted to the tropics–midlatitudes(Antarctic–midlatitudes)of the Southern Hemisphere(SH),with a weak connection between the two oscillations.Comparatively,after the mid-1990 s,the El Ni o-related atmospheric anomalies project on a negative AAO pattern with a barotropic structure in the mid–high latitudes of the SH.The expansion of El Ni o-related air temperature anomalies have a heightened impact on the meridional thermal structure of the SH,contributing to a weakened circumpolar westerly and strengthened subtropical jet.Meanwhile,the ENSO-related southern three-cell circulations expand poleward and then strongly couple the Antarctic and the tropics.Numerical simulation results suggest that the intensified connection between ENSO and SST in the South Pacific since the mid-1990 s is responsible for the strengthened AAO–ENSO relationship.     

华南及邻近海域夏季深对流活动气候特征

利用具有较高时空分辨率与很好时空完整性的11年(1996—2007年，无2004年)6—8月静止卫星数字红外云图和TBB资料，给出了华南及邻近海域夏季深对流活动气候分布特征，并同文献中给出的雷暴日分布和闪电分布进行了对比分析。结果表明，华南及邻近海域夏季深对流活动有5个活跃中心，其月变化特征与大尺度环流背景密切相关。6月华南陆地区域深对流活动较活跃，7、8月南海海域深对流活动较活跃。华南及邻近海域深对流活动具有间歇性发展特征，其周期大约为3～5候，但华南海岸线附近为海陆过渡区域，深对流活动持续比较活跃且间歇性特征不突出；深对流活动旬与候变化特征表明华南陆地区域和南海海域深对流活动呈现反相关变化趋势。深对流活动的日变化特征显示该区域陆地与海洋、山地与盆地的热力差异所导致的海陆风环流与山谷风环流使得华南海岸线附近区域的深对流活动具有午后向陆地传播、午夜后向海洋传播的特征，山地与盆地的深对流活动具有显著的午夜后向盆地传播的特征。深对流活动日变化特征还表明该区域不仅具有一般热对流、海洋深对流和双峰型深对流等多种类型对流活动，且两广海岸线邻近区域具有持续时间长、日变化较不显著的海岸线深对流和其它天气系统触发和维持的深对流。     

The Possible Mechanism of a Type of Vortex Heavy Rainfall during the Pre-Rainy Season in South China

In this paper,NCEP reanalysis data,intensive observation data collected from field experiment,model simulation data,and topographic trial data are fully analyzed to study a severe heavy rainfall event during 5 6 June 2008 in South China.Unlike most warm region rainfall cases,this one is associated with an obvious vortex system,which draws in water vapor and energy from the southwest monsoon surges ahead of a low trough above the Bengal Bay (BLT,Bengal Low Trough).At the lower troposphere,three currents,especially the southwest current and the east current,converge into the southeast of the vortex.Thus,the distributions of strong vorticity,water vapor,and ascending motion cause frequently occurrence and growth of convection there.The possible reasons for this rainfall event are summarized as a conceptual model.     

一次南亚高压中期活动过程的数值研究

本文利用1965—1984年6—9月逐日08时850hPa历史天气图上分析的ITCZ,统计出ITCZ频数分布图,研究了南海—西太平洋地区ITCZ的气候特性和季节性进退,揭示了ITCZ具有与副热带高压同步北跳现象和频数突增现象。发现:西太平洋上的ITCZ容易在12°N和20°N附近形成和维持,使ITCZ频数图上出现南、北两个多频带.这一分支现象与热带低层赤道西风和高层热带东风的分支现象密切相关。由于ITCZ存在着活跃与间歇的低频振荡,加上海陆、地形和热带气旋活动的影响,以及ITCE的结构特点,因而月平均多云带和最小OLR轴位置比流场ITCZ显著偏南,而且在南海地区出现偏离季风槽而沿地形槽的走向.对比分析表明,用OLR标准差与平均值之比值X来表征ITCZ的位置可能比直接用最小OLR轴更合理.