卫星微波被动遥感云中液态水的研究进展   总被引：3，自引：1，他引：2  

姚展予  彭亮 《气象学报》2009,67(2):331-341

卫星微波被动遥感云中液态水的研究在近30年中取得了较大的进展.卫星遥感仪器的不断进步、探测精度的不断提高为卫星微波被动遥感云中液态水提供了技术和资料保障,在此基础上针对卫星微波被动遥感云中液态水技术而发展的一些统计反演方法和物理反演方法不断地得到改进、完善和提高.文中主要就各个时期发展的主要反演方法做了简要回顾,概括了这些反演方法的关键技术,评述了各自的优点和局限性.由于海表和陆表的辐射特性的巨大差异,分别就海洋上空和陆地上空云中液态水的统计和物理反演技术方法进行了综述,并进行了比较.针对地表比辐射率这一制约陆地上空云中液态水反演技术发展的瓶颈问题,也进行了相关评述和讨论.  相似文献   

地形动力作用对华北暴雨和云系影响的数值研究   总被引：9，自引：4，他引：5       下载免费PDF全文

廖菲  胡娅敏  洪延超 《高原气象》2009,28(1):115-126

为了进一步研究地形对华北暴雨的影响,本文从云微物理学的角度出发,选取了2005年7月22～24日的一次华北暴雨过程为研究对象,利用中尺度数值模式ARPS,通过地形高度敏感性试验,详细讨论了地形高度变化对流场、云及降水微物理过程的影响.结果表明:地形高度变化对水平和垂直流场的大小和分布都有较大影响;地形高度增加有利于迎风坡附近水平风场辐合和垂直上升运动发展,这对云的垂直和水平发展影响都很大,尤其是对中高层云的发展影响最明显,并且能明显扩大地面降水的分布范围,地面最大降水量也有所增多.这主要是由于地形高度增加后能促进中高层云水的产生,尤其是零度层之上的过冷云水含量的增多,这大大促进了冰相粒子(雪和霰)的增多,从而使得以冷云过程为主的此次降水过程中,冰相粒子融化形成的雨水含量增多.虽然地形高度的增加会抑制云系发展前期的暖云过程,但对冷云过程有持续加强作用,而且不会明显改变云内降水的形成机制,冷云过程依然是降水的最大贡献项,总体上促进了云和降水的发展.  相似文献   

气溶胶对北京中尺度对流系统影响的数值试验   总被引：7，自引：5，他引：2       下载免费PDF全文

马贤芳  刘长海  刘晓东  付丹红  潘翻番 《气象科学》2010,30(1):21-26

利用可分辨云模式(WRF),模拟研究了不同气溶胶浓度对北京地区2001年8月23日一次产生强降水和冰雹的对流天气的影响。结果表明,气溶胶浓度的增加不利于对流云的发展,导致地面降水减小,但是对降水结构没有明显影响。气溶胶浓度增加导致云中水成物数浓度和质量浓度均发生变化,其中云水、冰晶和雪含量增加,而雨水、霰和雹含量减小。从云微物理学分析发现,气溶胶浓度减小有利于高层云的形成,云滴有效半径随着气溶胶浓度增加而减小。  相似文献   

A comparison of MODIS-derived cloud amount with visual surface observations   总被引：6，自引：0，他引：6  

Andrzej Z. Kotarba   《Atmospheric Research》2009,92(4):522-530

Two main sources for global cloud climatologies are visual surface observations and observations made by spaceborne sensors. Satellite observations compared with surface data show in most cases differences ranging from − 15% up to − 1%, depending on sensor and observation conditions. These differences are partially controlled by sensors' cloud detection capabilities — a higher number of spectral bands and higher spatial resolution are believed to allow discrimination of clouds from land/ocean/snow background. A Moderate-Resolution Imaging Spectroradiometer (MODIS) produces images of the atmosphere in 36 spectral bands with a spatial resolution of 250–1000 m, thus having a capacity for cloud detection far more advanced than other operating sensors. In this study, instantaneous MODIS cloud observations were compared with surface data for Poland for January (winter) and July (summer) 2004. It was found that MODIS observed 4.38% greater cloud amount in summer conditions and 7.28% in winter conditions. Differences were greater at night (7–8%) than in daytime (0.5–7%) and correlations ranged between 0.577 (winter night) and 0.843 (winter day, summer day and night).  相似文献   

Relationship between radar reflectivity and the time scale of warm rain formation in a global cloud-resolving model     

Kentaroh Suzuki  Graeme L. Stephens   《Atmospheric Research》2009,92(4):411-419

The connections between radar reflectivity and the time scale of warm rain formation are examined within a global cloud-resolving model. The parameterizations formulae of auto-conversion and accretion processes in the model reveal specific relationships between the time scale for auto-conversion and radar reflectivity of cloud water as well as between the time scale for accretion and radar reflectivity of rain water. The overall time scale for warm rain formation, determined by combined contributions from these processes, is found to relate with total radar reflectivity in the manner that varies with cloud-rain composition between auto-conversion and accretion limits. The global statistics from the model output reveals that the time scale is closely related with the total radar reflectivity, thus suggesting that the radar reflectivity is a gross measure of the warm rain time scale. The relationship developed is applied to both model-simulated and CloudSat-observed radar reflectivities to compare the time scales of warm rain formation between observation and the model. Comparison of the time scale so derived reveals significant differences between the model and CloudSat observations. These differences suggest that the simulated cloud-rain composition in the model is biased toward larger rain water contents and smaller content of cloud water compared to reality due to an accelerated cloud-to-rain water conversion in the model.  相似文献   

Analysis of microsecond- and submicrosecond-scale electric field pulses produced by cloud and ground lightning discharges     

Amitabh Nag  Brian A. DeCarlo  Vladimir A. Rakov 《Atmospheric Research》2009,91(2-4):316-325

We examined microsecond- and submicrosecond-scale pulses in electric field records of cloud and cloud-to-ground lightning discharges acquired in summer 2006, in Gainesville, Florida. A total of 12 cloud and 12 ground flashes were analyzed in detail, with the electric field record length being 96 or 200 ms and sampling interval being 4 or 10 ns. The majority of pulses in both cloud and ground discharges analyzed in this study were associated with the initial breakdown process and were relatively small in amplitude and duration. The typical durations were an order of magnitude smaller than tens of microseconds characteristic of “classical” preliminary breakdown pulses. We estimated that 26% of the pulses in the 12 cloud discharges and 22% of the pulses in the 12 cloud-to-ground discharges had total durations less that 1 µs.  相似文献   

FY-2C云迹风资料在中尺度数值模式中的应用研究   总被引：6，自引：1，他引：5  

李华宏  王曼  薛纪善  杞明辉 《气象学报》2008,66(1):50-58

利用探空观测资料对FY-2C云迹风资料进行统计检验和误差分析,并针对其误差特征进行偏差订正和热成风原理两种方法的质量控制.然后通过GRAPES-3Dvar同化到GRAPES-Meso模式中,对2005年7月1日00时至7月2日00时发生在中国西北部的一次暴雨过程进行了数值对比试验.结果表明:云迹风数量在垂直方向上主要集中分布于500 hPa以上的对流层中高层,在250 hPa附近数量分布概率最大;高度在500 hPa以下云迹风存在明显的风向误差和很大的风速误差,而且误差分布发散,可用性较差.500 hPa以上层次的云迹风误差较小,且误差分布呈高斯分布具有一定的系统特性,可用性较好;通过质量控制后,可以把风向错误或风速偏差太大的云迹风予以剔除,进一步提高云迹风的精度;同化云迹风资料后,在暴雨区附近初始风场低层的西南气流明显加强,有利于暴雨区水汽输送和水汽辐合,最终能很好地改善24 h暴雨预报的强度和落区.  相似文献   

The coalescence of water drops II. The coalescence problem and coalescence efficiency     

Nitza Arbel  Zev Levin 《Pure and Applied Geophysics》1977,115(4):895-914

By the use of the model of approaching drops (Arbel and Levin, 1977) the coalescence efficiencies of drops are computed. It is found that for interactions of drops at their terminal velocities the coalescence depends both on the size of the large drop and on the size ratio of the interacting drops in agreement with the experimental results of Whelpdale and List (1971) and Levin and Machnes (1977).The results were found to be sensitive to the assumption of the drops deformation and to the critical separation distance. This distance is defined as the distance at which the drops begin to merge. The variations of the coalescence efficiency with these parameters is discussed.Appendix: List of symbols D distance between the deformed surfaces of the drops - D _o initial value ofD - D _s stop distance, the distance at which the impact velocity vanishes - D _c critical coalescence distance - E collection efficiency - E ₁ collision efficiency - E ₂ coalescence efficiency - E _2R coalescence efficiency for collisions with stationary targets - F _c centrifugal force - p ratio of the radii of the interacting drops - r _o initial distance between drops' centers - R _L radius of larger drop - R _s radius of smaller drop - R _D radius of deformation - v approach velocity of two deformed surfaces - v _o initial value ofv - V _i impact velocity (given negative sign when drops approach each other) - V _c critical impact velocity - W _i velocity of the smaller drop at infinity for it to reachD _o with velocityv _o - x _i impact distance, the distance between the trajectories of the two drops - x _c critical impact distance for coalescence -  average critical impact distance for coalescence - X _c critical impact distance for collisions - coefficient of deformation given in equation 1 - _i impact angle defined byWhelpdale andList (1971) given also inArbel andLevin (1977) - coefficient of deformation given in equation 2 - viscosity of air - _i impact angle used inArbel andLevin (1977) and here - _c critical angle for coalescence - average critical angle for coalescence On sabbatical leave (1976–77) from the Department of Geophysics and Planetary Sciences, Tel Aviv University, Ramat Aviv, Israel.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

Research Status and Progress of Balloon-borne Cloud and Precipitation Particles Probe     

Peng Wang  Lei Liu  Xichuan Liu  Shuai Hu  Shijun Zhao  Wenming Ji  Taichang Gao 《地球科学进展》1986,35(7):704-714

The accurate observation of the microphysical structure of cloud and precipitation plays an important role in understanding the formation of clouds and precipitation. In-situ measurement using measuring instruments carried by meteorological balloons is an effective way to obtain the microphysical properties of cloud and precipitation particles, which is a supplementary means for aircraft to observe cloud and precipitation particles. This observation method plays a more and more important role in in-situ measurement. According to the difference of the working principle of the existing balloon-borne cloud and precipitation particles probes, the detectors can be divided into particle impact-sampling sensors, particle imaging sensors, light-scattering sensors, light intensity attenuation sensors and charge measurement sensors. The working principles, key technologies and main advantages and disadvantages of typical instruments were summarized, and their applications to detailed cloud structure acquisition, cloud remote sensing method establishment, cloud and precipitation physical process research and parameterization, and scientific observation of thunderstorm clouds were briefly introduced. Finally, the development trend of balloon-borne cloud precipitation particle detectors was prospected, which will provide reference for related technical research and equipment development.  相似文献   

IAU-Replay初始化方法在华南暖区暴雨模拟中的应用研究          下载免费PDF全文

陈浩伟  徐道生  高翠翠  乐迁  刘涛  张邦林 《气象科学》2023,43(5):600-611

基于TRAMS （Tropical Regional Atmospheric Model System）区域模式和ECMWF （European Centre for Medium-range Weather Forecasting）全球分析场资料，对一次华南暖区暴雨过程进行IAU-Replay模拟试验。由于本次个例模拟试验的分析时刻ECMWF分析场和TRAMS模式正好处于比较协调的状态，直接使用全球分析场进行冷启动也不会激发虚假高频短波，因此IAU-Replay方法对于模拟结果的初始平衡性影响较小。从动力场和水物质场的对比可以发现，IAU-Replay方法通过提前启动模式有效避免了Spin-up过程的影响，这对于降水预报具有明显的改进效果。对IAU-Replay中不同预热时间的敏感性进行测试，发现当预热时间从6 h延长至12 h后模式可以更加合理地模拟出与对流系统中直接相关的中小尺度信息，从而使降水预报效果更接近实况。连续一周的预报结果评估进一步验证了IAU-Replay技术的有效性。  相似文献