Characteristics of thermal finestructure in the southern Yellow Sea and the East China Sea from airborne expendable bathythermograph measurements

Four surveys of airborne expendable bathythermograph with horizontal spacing of about 35 km and vertical spacing of 1 m extending from the surface down to 400 m deep are used to analyze thermal finestructures and their seasonality in frontal zones of the southern Yellow Sea and the East China Sea. Finestructure characteristics are different not only among fronts but also along the same front, implying different mixing mechanisms. Summer thermocline intrusions with thickness from few to 40 meters, generated by the vertically-sheared advection, are identified along the southern tongue of the Cheju-Yangtze Front (especially south of Cheju Island). The finestructures south of the Yangtze Bank (i.e. the western tip of the southern tongue) produced by strong along-frontal currents are not as rich as elsewhere in the southern tongue. The Cheju-Tsushima Front presents mixed finestructures due to confluent currents from various origins. The irregular-staircase finestructures in the Kuroshio region (below the seasonal thermocline), driven by double-diffusive mixing, show seasonal invariance and vertical/horizontal coherence. The strength of mixing related to finestructure is weaker in the Kuroshio region than in the Cheju-Tsushima Front or south of Cheju Island. The profiles in the Tsushima Warm Current branching area show large (∼50 m thick), irregular-staircase structures at the upper 230 m depth, which coincides roughly with the lower boundary of the maximum salinity layer. The finestructure at depths deeper 230 m is similar to that in the Kuroshio region. The possible mechanisms for generating the finestructures are also discussed.     

南印度洋海区大风天气气旋概念模型研究

本文根据多年的天气图、卫星云图以及1980～1990年的NCEP再分析资料,通过统计分析和合成分析等方法建立了能够在南印度洋特定海区引起12m/s以上大风天气的中高纬气旋型天气概念模型,井对该天气概念模型作了详细的阐述.该天气概念模型主要发生在南半球的冬季和初春,在该模型中,气旋从高纬低压中分裂出来,快速东移赶上位于其东部的高位低压并发展至其北部.气旋冷锋最终在南印度洋东部引起大风.该天气概念模型的建立对南印度洋海区大风的预报可起到一定指导作用.     

呼和浩特地区一次对流天气过程分析

利用多普勒雷达资料的强度场、速度场、垂直累积液态水含量等资料,对2009年7月29日呼和浩特市及以西地区的1次中到大雨天气过程进行了分析。结果表明:由不同仰角的PPI图和多普勒雷达径向速度场的变化来判断未来雷达回波的强度及移动方向,对临近预报有重要作用;观测垂直累积液态含水量VIL值的变化可以预报对流天气形成的可能性。     

T639和EC模式对内蒙古主要天气系统的预报性能检验

利用2012年T639和EC模式500hPa高度场预报产品及ECMWF客观再分析资料,采用天气学检验方法,对内蒙古主要天气影响系统之西风槽、贝加尔湖冷涡、蒙古冷涡和东北冷涡数值产品的预报性能进行检验。检验结果表明:T639和EC模式产品对内蒙古影响系统具有较好的预报性能,36h内的预报性能更为显著。EC模式产品预报准确率优于T639模式产品,但对内蒙古东部地区影响系统的预报稳定性相对较差。T639模式产品在36h的预报能力比较高,对影响系统的生成时间、槽线位置、移动速度及中心强度4项检验指标预报准确率均在80%以上。EC模式预报产品,48h内对影响系统4项检验指标预报准确率均在80%以上。随着预报时效延长,T639和EC模式产品预报能力均有所下降。两套模式产品与实况相关系数空间分布在各时效均具有显著的相关关系,并且对应相关系数空间分布,T639和EC模式产品标准差的大值中心与相关系数的低值中心基本一致。     

Satellite Passive Sensing of the Marine Atmosphere Associated With Cold‐Air Mesoscale Cyclones

Contemporary research into extratropical cloud systems optimizes the increase in resolution of visible (VIS) and thermal infra‐red (IR) sensors, and the ability to retrieve wind and atmospheric moisture variables at mesoscales using microwave radiometry. These passively‐acquired remote sensing data are used to develop synoptic climatological (conceptual and simple statistical) ‘models’ of mesoscale cyclones in cold‐air outbreaks (mesocyclones, ‘polar lows’) occurring over the otherwise data‐void southern oceans. Mesocyclones present a limitation to successful weather forecasting for New Zealand and coastal Chile, southern Australia and South Africa, during the cold season. The synoptic climatological analyses show that: 1) the patterns of mesocyclone cloud vortex origins, movement and dissipation (‘mesocyclone regimes’), exhibit spatial dependence and have associations with upper‐ocean conditions; 2) mesocyclone ‘outbreaks’ are embedded within characteristic larger‐scale anomaly fields of tropospheric pressure, height, and layer thickness (mean temperature); and 3) composite (statistical average) models of cloud system structure based on the microwave retrievals of marine weather reveal mesocyclones to be relatively dry in comparison with synoptic cyclones, yet very windy. These analyses should permit the development of methods to better predict these important cold‐season storms over southern middle latitudes, and a fuller assessment of their significance for the larger hydroclimatic system.     

台湾海峡地区雾形成的天气类型分析

利用 1 980— 1 997年东亚逐日 0 8时地面天气图资料 ,归纳并分析了台湾海峡地区(2 0°— 2 7°N ,1 1 5°— 1 2 5°E)形成雾的 4种天气类型 ,它们分别是冷平流主导型、暖平流主导型、均压场型和台风外围型 ,为台湾海峡地区雾的预报提供天气学参考。     

2000年春季中国北方沙尘暴天气气候成因研究

从环境背景和天气气候成因两个方面,分析了2000年春季中国北方沙尘暴频繁爆发的原因。结果表明,① 2000年春季中国北方大风沙尘暴的源地、路径和天气形势可归纳为三种类型;②近年来中国北方干旱加剧土地荒漠化严重,使原本广阔的戈壁沙漠面积逐步扩大,为沙尘暴天气的爆发提供了物质基础;③ 2000年处于反厄尔尼诺(拉尼娜)事件的高峰期,使东亚冬季风加强;同时2000年春季极涡位于东半球新地岛附近,冷空气频繁南下,易形成大风天气;④ 2000年春季我国北方干旱少雨,气温回升迅速且温度偏高,使解冻的地表土层疏松,又提供了丰富的沙尘源。     

0601号强台风“珍珠”路径变化因子及降水特征

利用天气学诊断分析方法,结合气象卫星云图、多普勒雷达回波、总能量场和中尺度自动气象站记录资料等,分析0601号强台风“珍珠”路径变化的原因以及逐时降水动态变化特点,并探讨了台风影响过程中强降水的主要成因．指出副高、西风槽、高能区对台风运动的影响;台风中心降水和外围降水强弱有反相关的关系,降水较集中在台风路径的左侧;台风“珍珠”登陆前持续加强和对流强烈发展所形成的深厚系统是出现强降水的重要基础,在卫星云图上密实的螺旋结构和中尺度对流云团的生成是台风云带中出现强降水的显著特征,而特定区域地形的多方面影响是降水幅度增加的原因．     

Trends in Interdiurnal Temperature Variation for the Central United States, 1945–1985

Temporal variation in the absolute value of interdiurnal variability (AIDV) of January maximum temperatures is examined for the period 1945–1985 in the central United States (90°–105°W). AIDV indicates the magnitude of day-to-day changes in the maximum temperature. Five-year running-mean AIDV values decreased significantly throughout the period. This trend was apparent for the region overall and for the 10 of the 20 study sites analyzed individually. Temporal variation in AIDV values was significantly related to mid-tropospheric flow patterns over the central United States. Meridional circulation was associated with smaller AIDV values in all sites except those in the northwestern and southeastern corners of the study area, whereas zonal flow was linked to larger interdiurnal temperature change. The analysis of selected individual years indicated that mid-tropospheric circulation patterns were more persistent with meridional flow, and surface cyclones and their associated surface fronts tracked through the study area less frequently than in years with zonal flow. Analysis at a daily temporal resolution revealed an added dimension of trends in temperature variability beyond those apparent with a coarser monthly resolution. These results emphasize the importance of finer temporal resolution in the analysis of both past and projected climate change; regionally summarized monthly temperature values mask important variation in temperature trends apparent at shorter temporal and more local spatial scales.     

背景西风对由局地天气尺度波所形成阻塞的影响

本文从理论上研究了在不同的背景西风条件下阻塞胚胎与局地天气尺度波之间的相互作用。结果发现合适的弱西风对阻塞的形成是至关重要的 ,较强的背景西风不利于阻塞的形成。同时局地天气尺度波的位置也起着重要作用。