An Application of the RAMS/FLUENT System on the Multi-Scale Numerical Simulation of the Urban Surface Layer A Preliminary Study   总被引：1，自引：0，他引：1  

李磊  胡非  姜金华  程雪玲 《大气科学进展》2007,24(2):271-280

The Regional Atmospheric Modeling System （RAMS） and the computational fluid dynamics （CFD） codes known as FLUENT are combinatorially applied in a multi-scale numerical simulation of the urban surface layer （USL）. RAMS and FLUENT are combined as a multi-scale numerical modeling system, in which the RAMS simulated data are delivered to the computational model for FLUENT simulation in an offline way. Numerical simulations are performed to present and preliminarily validate the capability of the multi-scale modeling system, and the results show that the modeling system can reasonably provide information on the meteorological elements in an urban area from the urban scale to the city-block scale, especially the details of the turbulent flows within the USL.  相似文献   

A Comparison of Two Canopy Radiative Models in Land Surface Processes     

DAI Qiudan  SUN Shufen 《大气科学进展》2007,24(3)

This paper compares the predictions by two radiative transfer models-the two-stream approximation model and the generalized layered model (developed by the authors) in land surface processes-for different canopies under direct or diffuse radiation conditions. The comparison indicates that there are significant differences between the two models, especially in the near infrared (NIR) band. Results of canopy reflectance from the two-stream model are larger than those from the generalized model. However, results of canopy absorptance from the two-stream model are larger in some cases and smaller in others compared to those from the generalized model, depending on the cases involved. In the visible (VIS) band, canopy reflectance is smaller and canopy absorptance larger from the two-stream model compared to the generalized model when the Leaf Area Index (LAI) is low and soil reflectance is high. In cases of canopies with vertical leaf angles, the differences of reflectance and absorptance in the VIS and NIR bands between the two models are especially large.Two commonly occurring cases, with which the two-stream model cannot deal accurately, are also investigated. One is for a canopy with different adaxial and abaxial leaf optical properties; and the other is for incident sky diffuse radiation with a non-uniform distribution. Comparison of the generalized model within the same canopy for both uniform and non-uniform incident diffuse radiation inputs shows smaller differences in general. However, there is a measurable difference between these radiation inputs for a canopy with high leaf angle. This indicates that the application of the two-stream model to a canopy with different adaxial and abaxial leaf optical properties will introduce non-negligible errors.  相似文献   

半干旱沙地樟子松林降雨再分配特征     

孙姗姗  刘新平  王翠萍  张铜会  何玉惠  吕朋  车力木格  张腊梅  王明明  程莉 《干旱区地理》2021,44(1):109-117

森林植被的降雨再分配过程是影响区域水资源利用效率以及生态系统生产力的重要因素.于2018年5—8月观测27 a生樟子松人工林降雨再分配特征,探究降雨再分配的比例变化对林地水分平衡的影响机制,分析、量化林内穿透雨、林冠截留、树干径流、枯落物层入渗部分产生的阈值.结果 表明:樟子松林内穿透雨量占同期降雨量的86.45％,穿...  相似文献   

SAR与光学遥感影像的玉米秸秆覆盖度估算     

刘之榆  刘忠  万炜  黄晋宇  王佳莹  郑曼迪 《遥感学报》2021,25(6):1308-1323

秸秆是农田生态系统的重要组成部分。秸秆覆盖度（CRC）的遥感估算可以大范围、快速地获取地面秸秆覆盖信息，对保护性耕作的推广具有十分重要的意义。基于Sentinel-1 SAR影像和Sentinel-2光学影像分别构建了雷达指数与光学遥感指数，结合吉林省梨树县春秋两期实地采样数据，探究遥感指数与玉米秸秆覆盖度的相关性。为进一步提升玉米秸秆覆盖度的估算精度，结合雷达指数与光学遥感指数，采用最优子集回归的方法建立玉米秸秆覆盖度的估算模型，完成研究区的玉米秸秆覆盖度估算制图。结果表明：土壤质地分区建模可有效解决土壤异质性问题，提升反演精度。各遥感指数在秋季高覆盖时期的表现均优于春季低覆盖时期。STI和NDTI指数在光学遥感指数中表现最好，R²分别为0.701和0.697，而在雷达指数中，基于余弦矫正法的γVH0指数与实测CRC的相关性最高，R²为0.564。结合雷达指数与光学遥感指数能够有效地提高秸秆覆盖度估算精度，在最优子集回归法下基于结合指数构建的回归模型最优，R²为0.799，RMSE为13.67%，达到了较高的精度。研究结果为秸秆覆盖度估算的精度提升提供了一种新思路。  相似文献   

计算机自动识别分类技术在森林遥感中的应用     

谈正  杜春华 《遥感学报》1988,(1)

本文叙述应用计算机自动识别分类技术在航天遥感图像中对森林资源进行分类的一些探索研究。本文介绍了采用自编程序“地理坐标系和图像坐标系的精密仿射变换”、“识别型增强技术”、“多光谱信息的特征提取”、“多光谱模糊算法聚类分析”等一系列算法后所取得的分类图像结果,与实地及目视解译相比较,森林分类相对精度达90％。  相似文献   

黑龙江省玉米干旱与低温冷害复合逆境对产量的影响   总被引：1，自引：0，他引：1  

姜丽霞  赵慧颖  曲辉辉  闫平  李秀芬  翟墨  于瑛楠 《气象》2021,(1):94-105

利用1981—2016年黑龙江省玉米农业气象观测站的资料,引入中华人民共和国气象行业标准中水分亏缺指数(KCWDI)、≥10℃积温距平(H)指标,分别对玉米出苗—乳熟期干旱、低温冷害进行判识,规定同一站、同一年内干旱、冷害均有发生为两种灾害复合发生,并分析其时空分布特征,以数理统计方法构建KCWDI和H与玉米产量的关系...  相似文献   

基于GIS的新疆呼图壁县制种玉米精细化气候区划          下载免费PDF全文

王森  张山清  刘纪疆  李战超  叶尔克江·霍依哈孜 《沙漠与绿洲气象(新疆气象)》2021,15(4):130-137

利用呼图壁县及周边15个气象站点1961-2018年气候资料和台站地理信息数据，应用地理信息系统(ArcGIS10.0)空间分析技术将新疆1:5万DEM数据转成分辨率为（100m×100m）的数字高程，并提取对应站点上的经度、纬度、海拔高度、坡度、坡向等，通过地统计回归和反距离权重等方法构建≥10℃积温、无霜期、7月平均气温、≥35℃高温日数等指标因子与地理因子的空间分析推算模型，获取制种玉米各区划指标因子的空间分布模拟值，并将实际值与模拟值之残差部分进行空间内插订正，结合制种玉米区划指标等级，最终得到制种玉米适宜种植精细化区划。区划结果表明，全县划分为最适宜区、适宜区、次适宜区、风险区和不适宜区5个分区。最适宜种植区分布在呼图壁县北部平原地带，包括呼图壁县、十里店镇、五工台镇、园户村镇和大丰镇等广大区域；适宜区分布在中部平原地带，包括独山子乡、龙王庙村、宁州户村、二十里店村等区域；次适宜种植区靠近丘陵、低山地带，包括石梯子乡。  相似文献