雨区衰减及谱变化影响雷达测雨精度的数值模拟   总被引：4，自引：0，他引：4  

刘黎平 《南京气象学院学报》1994,17(2):255-258

用随机函数的方法，并假定雨滴谱为Ｇａｍｍａ分布，模拟并讨论了雨滴谱变化及雨区衰减对雷达和双线偏振雷达测雨误差的影响。结果表明：双线偏振雷达测雨精度受雨区衰减及滴谱变化的影响均小于普通雷达。雨区衰减使双线偏振雷达测雨产生小雨高估，大雨影响不大的现象，其主要原因可能是差反射率因子ＺＤＲ的测量误差。  相似文献   

MATHEMATICAL MODELING OF VARIATIONS ON STABLE ISOTOPIC RATIOS IN FALLING RAINDROPS   总被引：13，自引：0，他引：13  

章新平  谢自楚  姚檀栋 《Acta Meteorologica Sinica》1998,(2)

The variations of stable isotopic contents in falling raindrops are not only influenced by thehumidity conditions, but also by the stable isotopic contents in atmospheric vapor to a certainextent. If there is a difference between the isotopic contents in the vapor of the surrounding air andat the surface of the raindrops, the move of the isotopic contents from high to low values will beproduced. Usually. influenced by the evaporation process, the stable isotopic ratios in raindropsare constantly increased in the unsaturated atmosphere. The less the atmospheric humidity, themore obvious the increased range. As the enrichment rate of stable isotopes in raindrops is equal tothe outward isotopic move rate. the "pseudo-equilibrium state" appears. The influence ofevaporation on stable isotopic contents disappears in the saturated atmosphere, so that themagnitude of isotopic ratio in raindrops is dependent on the isotopic exchange between theraindrops and the surrounding atmosphere.  相似文献   

GBPP-100地面雨滴谱仪外场实用可行性研究   总被引：5，自引：0，他引：5       下载免费PDF全文

王祥国 《气象》1997,23(4):43-47

利用１９９３年４—６月共４次南京降雨过程中取到的ＧＢＰＰ－１００资料与滤纸斑点法所取资料，通过对应资料的雨滴谱基本参量的计算分析，研究ＧＢＰＰ－１００用于外场观测的可行性。结果表明：在瞬时雨强度变化缓慢且雨强小于１６０ｍｍ·ｈ－１的阵性降水和非阵性降水过程中，ＧＢＰＰ－１００完全可代替滤纸斑点法用于外场观测，对雨强变化迅速阵性降水ＧＢＰＰ－１００与滤纸斑点法取样结果差异较大，其原因还有待进一步研究。  相似文献   

下沉气流对Z-I关系的影响     

杨道侠  严采蘩 《气象》2002,28(4):9-14

采用伽玛分布形式的雨滴谱表达式，讨论了下沉气流W对Z－I关系的影响。发现随着W（向下为正）增大，关系式Z＝AI^b中系数A值减小,b值增大。利用地面实测雨滴谱资料计算出不同下沉气流下Z、I后回归得到的A、b值，以及根据由平均谱拟合得到的伽玛分布参数计算出A、b值，它们随W改变的变化趋势，均与理论分析结果一致。还讨论了环境气压场p对Z－I关系的作用，气压减小时，A值减小，b值增大，但变化不如W影响时的变化影响。此外，结合实测雨滴谱资料，分析了雨滴平均谱特征以及相关物理量的演变过程。  相似文献   

Locally modified surface winds on linear dunes as derived from directional raingauges     

David Sharon  Adina Margalit  Simon M. Berkowicz 《地球表面变化过程与地形》2002,27(8):867-889

The study deals with local airflow patterns induced by 12–16 m high, partly vegetated dunes, under various prevailing wind conditions. Detailed empirical data were derived by means of an unconventional use of directional raingauges. The utility and accuracy of the method have been previously tested in a combined empirical and numerical study over ridges on a similar scale. Results are presented on the nature, extent and intensity of locally modified patterns of surface flow and on their dependence on wind conditions and slope inclination. Results may serve to verify or refine existing perceptions or models of the flow affecting sand movement over dunes. For example, deflected surface wind flow and even stationary vortices were found to form under winds with resultant angles of incidence of only 5–10° relative to the axes of the dunes, and on slopes inclined only 12–15°, i.e. lower angles than often assumed in previous studies of dune morphology. Various effects of the resulting surface flow on the dune ecosystem are also referred to, e.g. the distribution of settling dust and seed dispersal. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Evaluation of an interrill soil erosion model using laboratory catchment data     

A. W. Jayawardena  Rezaur Rahman Bhuiyan 《水文研究》1999,13(1):89-100

Physically based soil erosion simulation models require input parameters of soil detachment and sediment transport owing to the action and interactions of both raindrops and overland flow. A simple interrill soil water transport model is applied to a laboratory catchment to investigate the application of raindrop detachment and transport in interrill areas explicitly. A controlled laboratory rainfall simulation study with slope length simulation by flow addition was used to assess the raindrop detachment and transport of detached soil by overland flow in interrill areas. Artificial rainfall of moderate to high intensity was used to simulate intense rain storms. However, experiments were restricted to conditions where rilling and channelling did not occur and where overland flow covered most of the surface. A simple equation with a rainfall intensity term for raindrop detachment, and a simple sediment transport equation with unit discharge and a slope term were found to be applicable to the situation where clear water is added at the upper end of a small plot to simulate increased slope length. The proposed generic relationships can be used to predict raindrop detachment and the sediment transport capacity of interrill flow and can therefore contribute to the development of physically‐based erosion models. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

秦岭山区东麓一次短时强降水特征及成因分析          下载免费PDF全文

刘胜男  冯典  郭大梅  肖贻青  王洁  刘菊菊 《中低纬山地气象》2023,47(1):82-89

利用陕西省区域自动站常规观测资料、NCEP 0.25°×0.25°再分析资料、华山站地面雨滴谱观测资料、商洛市雷达观测资料,从宏观和微观两方面对2021年7月22—23日秦岭山区东部1次强降水过程特征进行分析。结果表明：该次山区暴雨在实况上具有强降水范围小、持续时间长、短时雨量大、极易引发地质灾害的特点。该次山区暴雨发生在弱天气强迫和强层结不稳定的环境下,由地形抬升和850 hPa冷平流共同触发此次对流。高层辐散抽吸使得上升气流加强,合并商洛市山阳县特殊地形的增幅作用共同造成山阳县法官镇短时雨强的极端性,小尺度地形作用下风的辐合和温度差异使得强降水在局地长时间维持。强降水在微观层面上表现为高浓度的小雨滴和部分大雨滴的共同作用。850 hPa水汽通量在此次暴雨预报中具有一定的指示意义,22日20时山区强降水在发展之前,商洛市东南部水汽通量突增至20～30 g·cm^-1·hPa^-1·s^-1。雷达上表现为商洛市北部和南部30～45 dBz的大片层积混合云回波长时间维持,局地回波云团的合并对应降水增强。  相似文献   

坡面土壤侵蚀过程研究进展   总被引：42，自引：9，他引：33  

郑粉莉  高学田 《地理科学》2003,23(2):230-235

基于土壤侵蚀发生方式,重点评述了坡面雨滴溅蚀、薄层水流侵蚀、细沟侵蚀和浅沟侵蚀的研究进展,指出了各自研究中存在的问题,并提出坡面侵蚀过程中亟待加强的研究领域。  相似文献   

Analysis of the Microphysical Properties of a Stratiform Rain Event Using an L-Band Profiler Radar   总被引：2，自引：0，他引：2       下载免费PDF全文

RUAN Zheng  MING Hu  MA Jianli  GE Runsheng  BIAN Lingen 《Acta Meteorologica Sinica》2014,28(2):268-280

This paper investigates spatial and temporal distributions of the microphysical properties of precipitating stratiform clouds based on Doppler spectra of rain particles observed by an L-band profiler radar.The retrieval of raindrop size distributions（RSDs） is accomplished through eliminating vertical air motion and isolating the terminal fall velocity of raindrops in the observed Doppler velocity spectrum.The microphysical properties of raindrops in a broad stratiform region with weak convective cells are studied using data collected from a 1320-MHz wind profiler radar in Huayin,Shaanxi Province on 14 May 2009.RSDs and gamma function parameters are retrieved at altitudes between 700 and 3000 m above the surface,below a melting layer.It is found that the altitude of the maximum number of raindrops was closely related to the surface rain rate.The maximum number of large drops was observed at lower altitudes earlier in the precipitation event but at higher altitudes in later periods,suggesting decreases in the numbers of large and medium size raindrops.These decreases may have been caused by the breakup of larger drops and evaporation of smaller drops as they fell.The number of medium size drops decreased with increasing altitude.The relationship between reflectivity and liquid water content during this precipitation event was Z = 1.69×10~4M~（1.5）,and the relationship between reflectivity and rain intensity was Z = 256I~（1.4）.  相似文献   

Study of electrical property of precipitating clouds by point discharge current measurements near the ground     

A. M. Rao 《Pure and Applied Geophysics》1985,123(6):960-963

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