AWTP指数在广西农业干旱分析中的应用

基于广西32个测站1961-2007年的逐日降水量资料,应用降水的平均等待时间(AWTP)指数作为衡量干旱的标准,分析了广西农业干旱的时空分布特征.结果表明,就气候平均状况而言,广西秋季的相当干期最长,其次是冬季,春季和夏季的最短.从时间变化看,广西春、夏季相当干期主要以年际、年代际变化为主,而秋、冬季的相当干期除了显...     

粤西北一次连续型霜冻过程诊断分析

通过利用热力学方程对粤西北一次全区性较长的连续7d左右的霜冻过程进行诊断分析,得到以下结论:(1)持续性霜冰冻开始出现在较强冷空气影响粤西北时锋面过境后,较强冷平流使地面气温降得较低,等压线变得稀疏,使地面风速减小;(2)持续性霜冰冻过程中,地面一直受冷高压控制,持续较长过程中有冷空气不断补充影响使冷高压维持;(3)持续性霜冰冻发生过程中,粤西北中低层02时相对湿度较小,并持续几天,一般处于高空槽后.不易成云,利于地面辐射降温成霜冰.     

ON THE RELATIONSHIPS BETWEEN THE SUMMER RAINFALL IN CHINA AND THE ATMOSPHERIC HEAT SOURCES OVER THE EASTERN TIBETAN PLATEAU AND THE WESTERN PACIFIC WARM POOL

The relationships between the summer rainfall in China and the atmospheric heat sources over the eastern Tibetan Plateau and the western Pacific warm pool were analyzed comparatively, using the NCEP/NCAR reanalysis daily data. The strong (weak) heat sou…     

南海夏季风爆发前后低纬大气环流突变特征

利用1982～1996年15年平均的NCEP再分析资料,研究南海夏季风爆发前后低纬大气环流的突变特征。结果表明,东南亚地区对流层中上层厚度（温度）场、高低风场和大气层顶净辐射加热率（QRT）都有突变发生。海温场的变化相对其他要素较为缓慢,但也存在明显的转折点。QRT突变最早,其次是海温场变化出现明显转折,再是厚度（温度）场、低层风场突变,高层风场的突变最迟;低层风场突变最快,其次是厚度（温度）场,最后是QRT和高层风场。南海地区的降水,水汽场的突变发生在南海夏季风爆发前,而且突变较快。     

近50a广东登陆热带气旋的若干气候特征

利用《台风年鉴》／《热带气旋年鉴》[3，4]和广东降水资料，研究了近52a(1949～2000年)来广东登陆热带气旋的时、空变化特征。结果表明，52a间，登陆广东的热带气旋总数占全国总数的38％，居沿海各省之首。每年可有1到7个数量不等的热带气旋登陆广东，年平均数为3．9个。小波分析结果表明，至少对于广东的登陆热带气旋而言，70年代中期是一个明显的气候跃变期。前期(1949～70年代中)，登陆热带气旋数存在三种主要变化周期，即准3a(2～4a)、准7a(6～8a)和准12a(10～16a)周期的变化；后期(70年代中～2000年)，主要的变化周期为4～6a和7～9a。在年代际尺度上，登陆广东的热带气旋较多的时段为：1949～1954年、1959～1965年、1972～1976年1982～1987年和1991～1996年等。登陆广东的热带气旋总数与广东7～9月累计雨量有较类似的变化趋势。热带气旋主要在6～9月登陆广东，高峰期是7～9月。热带气旋登陆地点分布特征是，西多东少，粤西(珠海及其以西)沿海登陆的热带气旋总数占广东登陆总数的63％。     

前、后冬的东亚冬季风年际变异及其与东亚降水的关系

利用ERA-Interim的再分析资料和NOAA海温、降水量等资料对前、后冬的东亚冬季风的年际变异特征及其与东亚降水的关系进行对比分析,并讨论了热带和中高纬系统影响东亚冬季风变异的相对重要性。前冬的东亚冬季风变异的主导模态为东亚全区一致变异型,即一致的北风偏弱或偏强;其次为南部变异型,主要表现为在我国南方-南海北部的东北风偏弱或偏强。而后冬的东亚冬季风变异的主导模态则为南部变异型,其次为东亚全区一致变异型。从前冬到后冬,东亚冬季风的主要变异模态的次序出现交叉更替。前、后冬的冬季风主要模态以年际变化为主,但后冬主导模态还显示出冬季风有变强的趋势。前、后冬的东亚冬季风的主导变异模态也影响东亚降水异常的位置。在前冬,冬季风异常主要影响我国华北、渤海-黄海海域以及朝鲜半岛和日本南部区域的降水异常,而后冬的冬季风异常则主要导致我国东南地区及其东侧附近的西北太平洋海区的降水异常。前冬的东亚冬季风的前两种主要变异模态都受到印度洋-太平洋海温和中高纬环流系统共同的影响;后冬的东亚冬季风的前两种主要变异模态则分别主要受ENSO和中高纬系统的影响。      

Relative Roles of Intraseasonal and Above-seasonal Components in the South China Sea Summer Monsoon Onset

Multi-scale contributions are involved in the South China Sea (SCS) summer monsoon (SCSSM) onset process. The relative roles of intraseasonal oscillation and above-seasonal component in the year-to-year variation of the SCSSM onset are evaluated in this study. The 30-90-day and above-90-day components are major contributors to the year-to-year variation of the SCSSM onset, and the former contributes greater portion, while the 8-30-day component has little contribution to the onset. In the early onset cases, the 30-90-day westerly winds move and extend eastward from the tropical Indian Ocean (TIO) to the SCS monsoon region relatively earlier, and replace the easterly winds over the SCS with the cooperation of the 30-90-day cyclone moving southward from northern East Asia. The westerly anomalies of the above-90-day component in spring jointly contribute to the early SCSSM onset. In the late onset cases, the late eastward expansion of 30-90-day westerly wind over the TIO, accompanied by the late occurrence and weakening of the 30-90-day anticyclone over the SCS, and its late withdraw from the SCS, as well as the persistent easterly anomalies of above-90-day component, suppress the SCSSM onset. However, the SCSSM outbreaks in the obvious weakening stage of 30-90-day easterly anomalies. The easterlies-to-westerlies transition of the 30-90-day 850- hPa zonal wind over the SCS in spring is closely associated with sea surface temperature in the tropical western Pacific in preceding winter and spring, while the interannual variation of the above-90-day zonal wind in April-May is closely related to the decaying stage of the El Ni?o-Southern Oscillation events.     

东亚冬季风异常对西北太平洋海温的影响

利用1950—1998年的月平均海温资料和NCEP/NCAR月平均大气环流再分析资料,研究了东亚冬季风的异常对西北太平洋海温的作用过程。结果表明,南海—台湾附近海域—日本南部以南海域(简称东亚邻海)是海-气热通量异常的显著区。弱东亚冬季风在东亚邻海有偏南风距平,抑制相应海域海-气界面上由海表向大气释放的热通量,从而使得海表温度出现正距平。强冬季风则反之。这种大气-热通量-海温的异常影响过程所需的响应时间约为1个月。东亚邻海冬季发生的海温异常可持续到下一年的夏季。     

2011年秋季海南强降水过程分析

对2011年9月下旬至10月上旬,发生在海南的强降水过程特征以及不同的季内周期振荡对其影响进行了分析。结果表明,对此次强降水过程有显著影响的振荡周期为2~7 d和45~90 d。2~7 d的振荡以TD型波动为主,表现为从热带西太平洋-海洋性大陆向西北传播的特征。而45~90d的振荡在9—10月初期间表现为东西双向传播并在海南汇合的特征,有利于在南海北部出现持续的对流环流系统。该次海南强降水过程发生在La Nina事件期间,热带印度洋和热带西北太平洋为大范围的暖异常,位于南海北部的季风槽和强劲的西南季风有利于热带气旋的生成和海南强降水过程的发生及维持。     

EVOLUTION OF TROPOSPHERIC TEMPERATURE FIELDS AND CORRESPONDING THERMAL MECHANISMS BEFORE/AFTER ONSET PERIODS OF ASIAN SUMMER MONSOON

The evolution of the tropospheric temperature fields over Indian and South China Sea monsoon areas and their thermal mechanisms are compared and analyzed during the period from March to June, 1996. The results show that the onsets of the Indian and South China Sea summer monsoons are closely associated with the seasonal warming in the troposphere over the zonal belt of 10°N～30°N in these areas, which leads to the inversion of meridional temperature gradient. During the pre-onset period, the warming over the South China Sea monsoon region is mainly due to the warm horizontal advection and diabatic (latent) heating processes. Meanwhile, the warming is suppressed by the vertical adiabatic process (cooling). In spring over the Indian monsoon region, the significant adiabatic heating due to the subsidence motion, which compensates the cooling due to the strong cold advection and diabatic cooling processes, results in a larger warming rate than over the South China Sea monsoon region. However, the meridional temperature gradient over the Indian monsoon region is so large during the late winter and early spring that it takes longer time to warm the troposphere to have the reversion of meridional temperature gradient than it does over the South China Sea monsoon region. It results in the phenomenon that the South China Sea summer monsoon generally breaks out earlier than the Indian summer monsoon.