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利用WRF模式对2003年7月4-5日江淮地区的梅雨锋暴雨过程进行了数值模拟和诊断分析.结果表明:暴雨区处于高温高湿环境,高、低空急流的耦合和低层辐合以及高层辐散的配置有利于暴雨的产生发展.通过计算湿位涡还发现,ζMPV1高低层正负值区叠加的配置、ζMPV1<0及ζMPV2>0的演变,表明此次过程中不仅有对流不稳定能量存在,还有倾斜涡度的发展.ζMPV1和ζMPV2综合反映了暴雨区对流不稳定和斜压不稳定的增强. 相似文献
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北上台风暴雨过程涡散场的能量收支和转换特征 总被引：7，自引：2，他引：5
利用辐散风和旋转风的动能收支方程,对北方一次北上台风倒槽暴雨过程暴雨区内的涡散场能量收支和转换进行了计算.结果表明:暴雨区内动能的增加是暴雨增幅的一个主要原因.暴雨发展时,就旋转风动能(KR)而言,旋转风动能通量(HFR)辐合是主要能源,而旋转风的动能产生项(GR)是主要能汇;就辐散风动能(KD)而言,辐散风的动能产生项(GD)是主要能源,辐散风动能通量(HFD)辐散是主要能汇;总动能水平通量(HF)提供的辐合主要表现于对流层中、低层,这就使得低层辐合加强,上升运动加强,有利于暴雨的增幅.在暴雨过程中次网格尺度效应由能源转变为能汇,在暴雨发展之时能汇减小;能量的转换项C(KD,KR)总为正值,在转换项中,地转效应项的贡献很大.说明暴雨过程能量均由KD向KR转换,也就是说有效位能经KD向KR转换,充分说明了在整个暴雨过程中,尽管辐散风动能变化(∂KD/∂t)很小,但是它在其中充当“桥梁”作用,C(KD,KR)在暴雨发展时达到最大,此时能量转换最为旺盛;对流层低层辐散风动能向旋转风动能的转换是暴雨产生和发展的重要条件.此次暴雨过程,在暴雨区内表现为斜压不稳定和正压稳定共存的特征,其发展过程是系统斜压不稳定增长,正压稳定性减弱的过程,暴雨增幅的另一个重要原因就是暴雨区内低层斜压的发展. 相似文献
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一次大范围暴雨过程的诊断分析 总被引：1，自引：1，他引：0
用ECMWF 0.75°×0.75°, 6 h间隔再分析资料、地面加密观测资料、Micaps资料和云图TBB资料, 对2012年8月20日一次大范围暴雨过程进行诊断分析。结果表明:本次大暴雨过程是在高层急流入口辐散和中低层的低槽切变线的耦合作用以及台风的间接影响使得低槽系统移动缓慢和提供水汽的有利条件下产生的。暴雨带中水汽主要来源于南海和东海。从等熵位涡、湿位涡和总能量分析说明这次暴雨和大暴雨是在水汽条件充沛条件下, 对流不稳定叠加斜压不稳定和对称不稳定等共同作用下, 产生暴雨-大暴雨。另外, 南北两支气流在暴雨区强烈辐合(南侧为上升运动, 北侧为下沉运动)也起到了重要作用, 且总能量垂直廓线与雨团中心对流强度和强降水时段对应较好。低层东海东南暖湿气流和干冷的东北气流对本次大范围暴雨过程的产生起触发作用。 相似文献
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基于WRF模式的模拟结果,结合地面观测资料、雷达回波资料以及ECMWF ERA5再分析资料,对2010年10月1—8日发生在海南岛的一次持续性秋汛期特大暴雨过程中局地锋生与对流发展的相互作用机制进行了深入分析,发现:在海南岛秋汛期特大暴雨的锋生过程中,环境场起到主要作用。非绝热加热项F1和水平运动项F3在局地锋生的过程中贡献最大,且两者的正极大值区在强降水地区多时次重叠出现,表明非绝热加热和水平形变辐散是导致强降水区强烈锋生的主要原因。此外,模拟结果和实况观测对比分析发现,较低的凝结高度导致最强降水时段对流低层出现强潜热释放,对流区低层气团内部增暖,形成强烈锋生效应,低层强的锋生导致上升气流加速,深对流发展加强,暴雨增幅。与垂直运动有关的倾斜项F2相比,非绝热加热项F1和水平运动项F3贡献虽小,但在夜间有增大的现象,分析表明夜间暴雨区垂直速度ω水平分布的差异性对深对流的加强有重要作用。 相似文献
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2018年5月江苏极端降水事件发生前副热带高压异常及原因分析 总被引：1，自引：1，他引：0
本文利用NCEP/NCAR提供的2.5°×2.5°全球再分析数据,以2018年5月江苏两次极端降水事件发生前副高异常变化为研究对象,根据全型涡度方程定量计算了凝结潜热分布不均引起的涡源对副高迅速演变的诱发作用。研究发现,120°E处500 hPa 5月第1候副高脊线多年平均位置位于16°N附近,而2018年同期120°E的脊线则位于19°N附近,呈明显偏北的状态。2018年5月第1候东亚500 hPa位势高度距平场表现出南高北低的形态,有利于我国华东地区成为暖湿空气和干冷空气的交汇区,构成了江苏5月两次极端降水过程的有利环流背景。与对流层中层环流异常对应的是,同期115°~125°E之间850 hPa上8 g·kg-1等比湿线位于28°N附近,较多年气候态偏北15°,强降水区内同期850 hPa比湿较往年偏多2~4 g·kg-1,相应距平百分率可达50%~75%。且110°~120°E之间θse的340 K等值线5月第1候多年气候态位于13°N以南,但2018年同期却偏北至25°N附近,暖湿气团北进有利于强降水的发生。副高西伸北抬前,副高主体西侧和北侧均有凝结潜热加热区存在,说明潜热加热与副高演变关系密切。垂直剖面表明600 hPa为凝结潜热加热中心,向上加热率随高度减小,因此500 hPa处潜热加热率垂直梯度为负,使得500 hPa成为负涡源所在。因凝结潜热分布不均产生的负涡源,1~2 d便可形成与副高自身十分接近的负涡度值,足以诱发副高突变,该时间尺度与副高真实演变时间相符。负涡源中与凝结潜热垂直分布不均相关的部分起主要作用,而与凝结潜热水平分布不均相关的部分同时期产生的负涡度最多仅为前者的1/3左右,对副高突然西伸的作用较小。与凝结潜热相关的负涡源作为引发西太平洋副高异变的可能原因,其与副高的关系仍需进一步研究。 相似文献
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利用2010年1-2月深圳LAP3000型风廓线雷达资料, 对湍流耗散率进行了估算, 针对典型晴天条件下的湍流耗散率ε、折射率结构常数C2n、水平风速和风切变, 分析了其时空变化特征。得出如下结论: (1) 深圳地区低空大气ε的量级在10-7~10-1 m-2·s-3之间, 与理论模拟值基本一致; (2) 时间分布特征为, 2 km以下ε有很明显的日变化特征, 夜晚和上午ε较大, 下午及傍晚减少;(3) 空间分布特征表现为, ε随高度大致呈递减分布;ε量级达10-2.5 m2·s-3所在高度可作为深圳地区2010年1月14-15日边界层顶高度的判断依据。 相似文献
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利用美国新一代中尺度WRF(weather research and forecasting)模式,采用双向二重嵌套网格技术,对2005年7月1—2日山西的大暴雨天气过程进行数值模拟,并利用模式输出的高分辨率动力协调资料进行了初步诊断分析,着重分析了排熵指数与暴雨区的关系。结果表明:活跃的副高是造成此次强降水的主要影响系统,低空西南风急流为暴雨提供了充足的水汽及动力条件;大气排熵指数由高值向低值的演变有利于对流的发展,从而导致对流暴雨形成;负熵变区(IRE<0)对应着暴雨区,负熵变区的汇合反映了暴雨的落区;排熵指数与暴雨区有较好的对应关系。 相似文献
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采用地面、高空常规观测资料和NCEP全球再分析资料（空间分辨率1°×1°）,对2005年7月1日20时至2日20时（北京时）发生在山西的一次低涡暴雨过程从环流形势、物理量场方面进行了初步的分析,发现这次暴雨过程是受5OOhPa高空槽、副热带高压以及中尺度低涡等天气系统共同作用产生的。利用数值模拟输出的高时空分辨率资料探讨了此次暴雨过程的发生发展特征和机理,指出中低层中尺度涡旋是造成这次过程的主要天气系统,低涡的时空演变与暴雨中心的移动和雨强的变化有着较好的对应关系。湿位涡诊断表明：强降水发生时,暴雨区上空低层是不稳定区,湿位涡负中心出现在暴雨中心附近,且对流不稳定性远大于湿斜压性。地形的敏感试验进一步揭示了地形对暴雨的增幅作用。 相似文献
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Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter. 相似文献
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The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics. 相似文献
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Various features of the atmospheric environment affect the number of migratory insects, besides their initial population. However, little is known about the impact of atmospheric low-frequency oscillation(10 to 90 days) on insect migration. A case study was conducted to ascertain the influence of low-frequency atmospheric oscillation on the immigration of brown planthopper, Nilaparvata lugens(Stl), in Hunan and Jiangxi provinces. The results showed the following:(1) The number of immigrating N. lugens from April to June of 2007 through 2016 mainly exhibited a periodic oscillation of 10 to 20 days.(2) The 10-20 d low-frequency number of immigrating N. lugens was significantly correlated with a low-frequency wind field and a geopotential height field at 850 h Pa.(3) During the peak phase of immigration, southwest or south winds served as a driving force and carried N. lugens populations northward, and when in the back of the trough and the front of the ridge, the downward airflow created a favorable condition for N. lugens to land in the study area. In conclusion, the northward migration of N. lugens was influenced by a low-frequency atmospheric circulation based on the analysis of dynamics. This study was the first research connecting atmospheric low-frequency oscillation to insect migration. 相似文献
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The atmospheric and oceanic conditions before the onset of EP El Ni?o and CP El Ni?o in nearly 30 years are compared and analyzed by using 850 hPa wind, 20℃ isotherm depth, sea surface temperature and the Wheeler and Hendon index. The results are as follows: In the western equatorial Pacific, the occurrence of the anomalously strong westerly winds of the EP El Ni?o is earlier than that of the CP El Ni?o. Its intensity is far stronger than that of the CP El Ni?o. Two months before the El Ni?o, the anomaly westerly winds of the EP El Ni?o have extended to the eastern Pacific region, while the westerly wind anomaly of the CP El Ni?o can only extend to the west of the dateline three months before the El Ni?o and later stay there. Unlike the EP El Ni?o, the CP El Ni?o is always associated with easterly wind anomaly in the eastern equatorial Pacific before its onset. The thermocline depth anomaly of the EP El Ni?o can significantly move eastward and deepen. In addition, we also find that the evolution of thermocline is ahead of the development of the sea surface temperature for the EP El Ni?o. The strong MJO activity of the EP El Ni?o in the western and central Pacific is earlier than that of the CP El Ni?o. Measured by the standard deviation of the zonal wind square, the intensity of MJO activity of the EP El Ni?o is significantly greater than that of the CP El Ni?o before the onset of El Ni?o. 相似文献
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Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms. 相似文献
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Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d. 相似文献
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Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region. 相似文献
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Fei LIU Chen XING Jinbao LI Bin WANG Jing CHAI Chaochao GAO Gang HUANG Jian LIU Deliang CHEN 《大气科学进展》2020,37(7):663-670
正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment. 相似文献
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Yuepeng PAN Mengna GU Yuexin HE Dianming WU Chunyan LIU Linlin SONG Shili TIAN Xuemei Lü Yang SUN Tao SONG Wendell W. WALTERS Xuejun LIU Nicholas A. MARTIN Qianqian ZHANG Yunting FANG Valerio FERRACCI Yuesi WANG 《大气科学进展》2020,37(9):933-938
正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on 相似文献
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