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1.
THE RELATIONSHIP OF THE PRECEDING WINTER MJO ACTIVITIES AND THE SUMMER PRECIPITATION IN YANGTZE-HUAIHE RIVER BASIN OF CHINA 总被引:2,自引:0,他引:2
The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China’s 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases. 相似文献
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By employing the singular value decomposition(SVD) analysis, we have investigated in the present paper the covariations between circulation changes in the Northern(NH) and Southern Hemispheres(SH) and their associations with ENSO by using the NCEP/NCAR reanalysis, the reconstructed monthly NOAA SST, and CMAP precipitation along with NOAA Climate Prediction Center(CPC) ENSO indices. A bi-hemispheric covariation mode(hereafter BHCM) is explored, which is well represented by the first mode of the SVD analysis of sea surface pressure anomaly(SLPA-SVD1). This SVD mode can explain 57.36% of the total covariance of SLPA. BHCM varies in time with a long-term trend and periodicities of 3—5 years. The long term trend revealed by SVD1 shows that the SLP increases in the equatorial central and eastern Pacific but decreases in the western Pacific and tropical Indian Ocean, which facilitates easterlies in the lower troposphere to be intensified and El Ni觡o events to occur with lower frequency. The spatial pattern of the BHCM looks roughly symmetric about the equator in the tropics, whereas it is characterized by zonal disturbances in the mid-latitude of NH and is highly associated with AAO in the mid-latitude of SH. On inter-annual time scales, the BHCM is highly correlated with ENSO. The atmosphere in both the NH and SH responds to sea surface temperature anomalies in the equatorial region, while the contemporaneous circulation changes in the NH and SH in turn affect the occurrence of El Ni觡o/La Ni觡a. In boreal winter, significant temperature and precipitation anomalies associated with the BHCM are found worldwide. Specifically, in the positive phase of the BHCM,temperature and precipitation are anomalously low in eastern China and some other regions of East Asia. These results are helpful for us to better understand interactions between circulations in the NH and SH and the dynamical mechanisms behind these interactions. 相似文献
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对1991—1992年厄尔尼诺事件形成的一种看法 总被引:1,自引:0,他引:1
本文对1991-1992年厄尔尼诺事件前兆及形成过程进行了分析,与1982-1983年和1986-1987年厄尔尼诺事件进行了对比。对自西向东传播的厄尔尼诺事件的形成特点及传播规律进行了解释。 相似文献
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肇庆市PM2.5重污染天气形势及冬季典型污染过程输送特征研究 总被引:8,自引:1,他引:8
为了揭示肇庆市颗粒物重污染过程的发生与发展规律,利用2013—2014年PM2.5监测数据,分析该区域两年间的空气质量整体变化情况以及PM2.5污染过程的季节变化规律,统计两年间所有颗粒物重污染过程,并根据污染过程的天气形势展开分析,运用空气质量数值模型(WRF-Chem)对冬季一次典型重污染过程进行模拟研究。结果表明,肇庆2013—2014年共发生27次PM2.5重污染过程且主要出现在秋冬季,结合气象场的分布特征,总结出四种诱发重污染过程发生的天气形势,分别是高压出海型(48%)、热带低压型(22%)、锋面影响型(19%)及冷高压控制型(11%)。在四种天气形势的影响下,肇庆整体风向以东南风和南风为主,大气处于静稳状态,导致污染物的积累并诱发重污染过程。WRF-Chem模拟结果进一步发现,不利气象条件及本地排放源是造成肇庆冬季重污染过程发生的主要原因。结合四维通量模型对肇庆边界污染物输送情况进行定量分析后发现,肇庆PM2.5以输出为主,其中硝酸盐与氨盐的输出通量较大。此外,模型还揭示了肇庆境内的主要污染物输送通道呈东南-西北走向,外地输入的污染物也通过此通道影响肇庆的空气质量 相似文献
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运用农业气象学、气象学等理论建立了一个冬小麦群丛反射率农业气象数值模式。模式由辐射日变化反演、土壤反射率日变化反演以及植被反射率模拟等子模式耦合而成,运用该模式可以利用常规气象资料对冬小麦群丛反射率日变化进行较准确的模拟,实测验证结果表明模拟最大相对误差为12.1%,平均相对误差为6.3%,该模式为进一步估算农田热量平衡以及进行农业微气象研究提供了理论方法,并可充当作物生长数值模式中的一个子模式。 相似文献
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冬小麦生长发育的模拟模式 总被引:3,自引:0,他引:3
根据冬小麦生长发育及其与环境条件关系的机理研究,建立了模拟冬小麦发育阶段和各器官生物量变化的动态模式。其中包括3个环境要素子模式,分别计算温度、辐射和水分,5个生物学过程子模式,分别模拟冬小麦的发育、光合、呼吸、同化物分配和叶面积系数。用镇江和海安共8个播期的实测资料对模式进行验证,并对模式进行了初步数值试验应用。 相似文献
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华南及邻近海域夏季深对流活动气候特征 总被引:8,自引:0,他引:8
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。 相似文献
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Due to the higher temporal and spatial resolution and the better integrality of long-term satellite infrared(IR) Brightness Temperature(TBB) data,a climatology of deep convection during summer over South China and the adjacent waters is presented in this paper based on the 1-hourly infrared IR TBB data during June-August of 1996-2007(except 2004).The results show that the geographic distribution of deep convection denoted by TBB ≤-52℃ over South China and the adjacent waters are basically consistent with previous statistical results based on surface thunderstorm observations and low-orbit satellite lightning observations.The monthly,ten-day,five-day and diurnal variations of deep convection in this region are focused on in this paper.There are 5 active deep-convection areas in June-August.The monthly variations of the deep convection are closely associated with the large-scale atmospheric circulations.The deep convection over the land areas of South China is more active in June while that over the South China Sea is more active in July and August.The development of deep convection is prominently intermittent and its period is about 3 to 5 five-day periods.However,the deep convection over the coastal areas in South China remains more active during summer and has no apparent intermittence.The ten-day and five-day variations of deep convection show that there are different variations of deep convection over different areas in South China and the adjacent waters.The tendency of deep convection over the land areas of South China is negatively correlated with that over the South China Sea.The diurnal variations of deep convection show that the sea-land breeze,caused by the thermal differences between land and sea,and the mountain-valley breeze,caused by the thermal differences between mountains and plains or basins,cause deep convection to propagate from sea to land in the afternoon and from land to sea after midnight,and the convection over mountains propagates from mountains to plains after midnight.The different diurnal variations of deep convection over different underlying surfaces show that not only there are general mountainous,marine and multi-peak deep convection,but also there is longer-duration deep convection over coastal areas and other deep convection triggered and maintained by larger-scale weather systems in South China during summer. 相似文献
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文中利用NCEP/NCAR 2 0 0 1年 9~ 10月的全球日平均资料和中央气象台的逐日 0 8时 2 4h降水资料 ,着重分析了 2 0 0 1年秋季黄淮、江淮地区持续干旱时期的水汽收支及动力条件。结果表明 ,2 0 0 1年 9~ 10月该地区大气水汽含量比常年同期明显偏小 ,水汽以支出为主 ,并且南边界的水汽输出与多雨时期的情况截然不同 ;与之相反 ,有两支水汽通道将大量水汽输送到中国华西地区 ,为该地区提供了丰富的水汽。在此期间 ,江淮、黄淮地区大气层结稳定或成中性 ,对流弱 ,基本为下沉气流控制 ,使得该地区缺乏有利的动力条件 ,无法形成降水。通过分析发现 ,造成 2 0 0 1年秋季江淮、黄淮地区持续干旱时期水汽和动力条件异常的主要原因是亚洲中高纬地区盛行纬向环流 ,西风锋区位于 5 5°N附近 ,比常年同期偏北约 5个纬距 ;西北太平洋副热带高压持续偏西偏北 ,是近 2 6年来同期副热带高压脊线位置持续在 2 5°N以北时间最长的一年 ;同时 ,2 0 0 1年 9月份东亚 -西太平洋低纬度地区大气活动异于常年 ,吕宋岛附近维持一个强盛的对流中心 ,这在历史上是少有的。 相似文献
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Synoptic systems and microphysical properties associated with a sea fog event are
analyzed based on the measurements of visibility, meteorological elements and fog droplet
spectrum from a comprehensive field campaign in Xiamen, Fujian province during spring 2013.
The influences of meteorological elements on the microstructures of the sea fog are also
discussed. The results showed that the wind speed and direction changed suddenly during the
intermittent and disperse phases of the sea fog. Liquid water content, number concentration
and average diameter varied obviously in the development, mature and disperse phases of the
sea fog. The burst re-enforcement of sea fog was accompanied by explosive broadening of fog
droplet spectrum; average diameter, number concentration and liquid water content increased
sharply; and background meteorological conditions also changed significantly. The
microstructures fluctuated intensely due to changes in turbulence, radiation and
meteorological conditions at different stages, including nucleation, condensation,
coagulation, and evaporation, as well as the discontinuity of spatial distribution of
droplets. 相似文献
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A NUMERICAL EXPERIMENT STUDY ON THE FORMING MECHANISMS OF LOW-LATITUDE CIRCULATION CELLS AND PRECIPITATION DURING AN EAST ASIAN COLD SURGE
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The forming mechanisms of low-latitude circulation cells and precipitation during an East Asian cold surge have been studied by using a five-layer primitive equation model.Numerical experiments show that in mid-high latitudes,the propagation of the East Asian winter monsoon is nearly a dry process;in low-latitudes,the effects of cumulus convection intensify the northeast monsoon and northeast trade wind;however,they also prevent the intertropical convergence zone(ITCZ) from further southward invasion,and strengthen the meridional and zonal cells over East Asia. Numerical results also indicate that the winter monsoon precipitation in Indonesia and Northern Australia can exist independently.Both the South China Sea(SCS) cold surge and the West Pacific northeast cross-equatorial trade wind are of importance for the formation of the Northern Australia summer monsoon and its precipitation.Numerical results show that the development of cumulus convection,triggered by the SCS cold surge,is a crucial factor in forming the heavy monsoon precipitation and low-level stationary disturbances in Indonesia and Borneo.The tropical topography and northeast trade wind disturbances only affect the intensity of precipitation there. 相似文献
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Analyzing observations of wintertime air temperature in both indoor and outdoor surroundings in
Kunming, a city lying in low latitudes, characteristics of temperature and humidity have been studied for the interior of rooms facing north-south under different weather conditions. Significant warming effect has been identified in terms of lowest and daily-mean indoor temperature in the area of Kunming. The heating amplitude ranges from 7.7°C to 10.0°C and from 4.6°C to 5.8°C for the interior part of rooms facing the south and from 4.6°C to 7.0°C and from 1.3°C to 4.4°C for the interior part of rooms facing the north, respectively for the two elements. The highest air temperature is higher indoor than outdoor for rooms facing the south, but otherwise is usually true for rooms facing the north. Additional findings point out that buildings not only help maintain relatively warm indoor temperature but delay its variation. The diurnal cycle of temperature indoor is smaller and ranges by 40% ~ 48% for south-facing rooms, and by 20% ~ 30% for north-facing rooms, than outdoor, and the highest temperature is about 2 hours late inside the room than outside. It shows how inertly indoor temperature varies. The work also finds that relative humidity is less indoor in southward rooms than in northward ones and difference is the largest on fine days but the smallest when it is overcast. For the diurnal variation, the indoor relative humidity is large at nighttime with small amplitude but small during daytime with large amplitude. The above-presented results can be served as scientific foundation for more research on climate in low-latitude cities and rational design of urban architectures. 相似文献
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1993年世界气候异常原因及大气对东传型ENSO事件响应的诊断分析 总被引:5,自引:0,他引:5
主要用气候统计方法,按不同标准对1949-1992年影响我国(进入防线)的西太平洋台风资料进行过滤分析。确定台风突然加强的标准,在此基础上对它们进行分类,给出各类的时空分布特点及高低层平均环境场,得出的结论是(1)影响我国的突然加强的台风主要出现在每年7-10月,并集中的南海中部,东海出现的个例减少。(2)按中心气压和近中心的最大风速变化的先后,突然加强台风可分为三类,第三类与第一、二类高低层的产 相似文献
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