排序方式： 共有38条查询结果，搜索用时 15 毫秒
1.
选取2014年7月31日安徽滁州一次飑线过程,使用地基雨滴谱仪资料分析此次过程的雨滴谱特征。根据雷达回波和地面降水强度将这次降水过程划分为对流降水、过渡性降水和层云降水,并以10 mm·h-1为临界值将对流降水进一步划分为对流前沿降水、对流中心降水、对流后沿降水。结果表明:对流中心降水、过渡性降水、层云降水的质量加权直径均比较稳定,平均值分别为1.8 mm, 1.0 mm, 1.7 mm。对流降水的标准化截距相比层云降水更大。对流中心降水各粒径段雨滴数浓度均较高;层云降水小雨滴浓度较低,且有少量大雨滴;过渡性降水由小雨滴组成。当雨水含量相同时,层云降水的质量加权直径相比对流降水更大。当雨强相同时,层云降水的反射率因子相比对流中心降水更大。更为精细的降水类型划分可有效改善Z-I关系。 相似文献
2.
A Comparison of De-noising Methods for Differential Phase Shift and Associated Rainfall Estimation 
下载免费PDF全文
下载免费PDF全文 Measured differential phase shift ΦDP is known to be a noisy unstable polarimetric radar variable, such that the quality of ΦDP data has direct impact on specific differential phase shift KDP estimation, and subsequently, the KDP-based rainfall estimation. Over the past decades, many ΦDP de-noising methods have been developed; however, the de-noising effects in these methods and their impact on KDP-based rainfall estimation lack comprehensive comparative analysis. In this study, simulated noisy ΦDP data were generated and de-noised by using several methods such as finite-impulse response(FIR), Kalman, wavelet,traditional mean, and median filters. The biases were compared between KDP from simulated and observedΦDP radial profiles after de-noising by these methods. The results suggest that the complicated FIR, Kalman,and wavelet methods have a better de-noising effect than the traditional methods. After ΦDP was de-noised,the accuracy of the KDP-based rainfall estimation increased significantly based on the analysis of three actual rainfall events. The improvement in estimation was more obvious when KDP was estimated with ΦDP de-noised by Kalman, FIR, and wavelet methods when the average rainfall was heavier than 5 mm h-1.However, the improved estimation was not significant when the precipitation intensity further increased to a rainfall rate beyond 10 mm h-1. The performance of wavelet analysis was found to be the most stable of these filters. 相似文献
3.
江淮之间夏季雨滴谱特征分析 总被引：11，自引：3，他引：8
分析了2011—2013年夏季(6—8月)滁州地基雨滴谱观测资料,根据雨强及其随时间的变化将降水分成对流降水和层云降水,分析不同降水类型的雨滴谱特征。结果表明:滁州地区对流降水的质量加权直径Dm和标准化参数lgNw的平均值分别为1.67 mm和3.91 mm-1·m-3,层云降水Dm和lgNw的平均值分别为1.18 mm和3.57 mm-1·m-3,对流降水雨滴平均尺度更大。Nw相比Γ分布参数N0能更好地反映总数浓度Nt的大小。Γ分布3参数均随雨强的增大而减小,当雨强增长到一定程度时,μ(谱型)和Λ(斜率)趋于常数。研究了μ-Λ关系和Z(反射率因子)-R(雨强)关系。对流降水和层云降水的Z-R关系分别为Z=408R1.20和Z=301R1.21。新的Z-R关系和经典Z-R关系(Z=300R1.40)反演的雨强相比实际观测值均偏小,但新的Z-R关系反演的雨强与实际观测值更接近。 相似文献
4.
5.
Analysis of the Characteristics of Turbulent Flux and Its Footprint Climatology at An Agricultural Site 总被引：1，自引：0，他引：1
Based on quality controlled data from eddy covariance system and automatic weather station collected at Guantao farmland site from 2008 to 2010, the characteristics of diurnal, seasonal and annual variations of turbulent flux were reported. The corresponding source areas of flux measurement at different temporal scales were analyzed in detail, using arithmetic-averaged and flux-weighted footprint climatology calculation method, respectively. The main findings are as follows. Firstly, sensible heat and latent heat flux both show consistent diurnal variation throughout the year, while CO2 fluxes only have significant diurnal variation in growing season with an opposite trend. The seasonal variation of the turbulent flux is mainly affected by the crop type and its growth status in different phenological periods. During growing season, latent heat flux and CO2 flux are the dominant flux exchange items whose value are significantly higher in their middle growth stage than other ones during which latent heat and CO2 flux exchange of the summer corn is stronger than winter wheat. Secondly, with combined effects of wind, turbulence and surface condition, the source area of flux measurement change most significantly at daily scale, less obvious at seasonal scale and smallest at annual scale. Finally, compared with arithmetic-averaged footprint climatology method, flux-weighted footprint climatology is a more reasonable method to calculate the source areas of the flux measurement, in that they account for the time change of the actual turbulent flux. The arithmetic-averaged results are most likely to overestimate the size of source area during small observed flux due to its weak turbulent exchange. 相似文献
6.
利用NCEP再分析资料、常规气象资料分析淮河流域2007年雨季洪水期间大气环流及影响系统的时空分布,对雨季偏长及致洪暴雨气象成因进行了探讨.结果发现淮河流域雨季偏长与西太平洋副热带高压(副高)伸入大陆稳定脊线位置以及中高纬度建立稳定的阻塞高压有密切的关系;出现的持续性暴雨都与中纬度附近稳定的横槽或低压带有关;暴雨都是多个影响系统叠加的结果,与它们的位置有一定的对应关系.影响系统主要有低层切变线、西南涡和急流.2007年淮河雨季期间来自西北太平洋副热带高压西侧的东南气流和来自孟加拉湾的西南气流对淮河流域降水区水汽的输送起主要作用;低层辐合、高层辐散增强了上升运动,为持续强降雨提供了动力条件,并触发能量的释放. 相似文献
7.
对流云是我国南方地区主要的降水云系, 含有丰富的云水资源, 是南方人工增雨作业的主要对象。为了研究江淮地区对流云发生发展规律, 利用双多普勒雷达反演技术分析了发生在2004年7月31日的一块对流云不同发展阶段的垂直运动结构。对流云在发展阶段以上升气流为主, 底层辐合明显, 结构紧密; 成熟阶段的上升与下沉气流势力相当, 且比发展阶段强盛, 强回波位置下移, 结构较发展阶段松散; 减弱阶段上升和下沉速度均减小, 水平辐散增强。结果表明:反演的不同阶段对流云垂直运动结构合理, 可以利用双多普勒雷达反演技术进行对流云三维运动结构研究。 相似文献
8.
9.
10.
基于MODIS数据的淮北地区云特性研究 总被引：1，自引：1，他引：0
利用2006年—2015年MODIS云产品数据(MYD06),对淮北地区不同云相态、不同相态云粒子有效半径和云顶温度逐月概率分布进行了统计对比分析,同时对四季云水路径逐年变化进行了研究。研究表明:淮北地区夏秋冬季水云出现的概率较高,春夏季冰云出现的概率较高。水云年均发生概率是冰云的近2倍,晴空和冰云相当,混合相态云较少。除7月份,水云有效半径概率逐月分布逐年有所变化,主要分布在5—30μm。冰云有效半径主要分布在15—35μm,且10年间4、5和8月份概率分布较为一致。混和相云有效半径主要分布在10—40μm,逐月发生概率在10—20μm和25—35μm出现两个峰值,这与水云和冰云不同,且在春秋冬较为明显。10年间淮北地区上空云水路径年均值低于300 g/m~2。冬季年均云水路径相对较低且逐年呈现减少的趋势。春秋冬季云顶温度逐月概率分布逐年变化较大。春冬季冷云发生的概率较大,夏秋季暖云出现的概率要高于冷云。 相似文献