Do stratocumulus clouds detrain? FIRE I data revisited     

Stephan R. de Roode  Qing Wang 《Boundary-Layer Meteorology》2007,122(2):479-491

Analyses of aircraft observations of the stratocumulus-topped boundary layer during the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE I) show the frequent presence of clear, but relatively moist, air patches near the stratocumulus cloud-top interface. A conditional sampling of measurements in these clear air patches shows that their thermodynamic properties do more resemble boundary-layer air characteristics than those of free troposphere air. From an aircraft leg through cloud tops it is demonstrated that turbulent mixing across the cloud-top interface can lead to the local dissipation of the cloud top. Analogous to the terminology used for shallow cumulus parameterizations this process can be considered as detrainment, with which we mean that after a mixing event across the cloud-top boundaries, mixed unsaturated parcels become part of the clear environment of the cloud.  相似文献   

星载微波SSM/Ⅰ遥感在中国东北华北农田的辐射特征分析     

金亚秋 《遥感学报》1998,2(1):19-25

国家遥感应用工程技术研究中心ＮａｔｉｏｎａｌＥｎｇｉｎｅｅｒｉｎｇＲｅｓｅａｒｃｈＣｅｎｔｅｒｆｏｒＧｅｏｍａｔｉｃｓ（ＮＣＧ）国家遥感应用工程技术研究中心于１９９６年１２月２５日由国家科委正式批准组建（国科发计字［１９９６］６０３号文件）。中国科学...  相似文献   

星载微波SSM/Ⅰ遥感在中国东北华北农田的辐射特征分析   总被引：2，自引：1，他引：1  

金亚秋 《遥感学报》1998,2(1):19-25

本文研究了星载微波ＳＳＭ／Ⅰ１９９６年在中国东北华北平原农田上７个通道辐射亮度温度（ＴＢ）的遥感数据,提出用几个通道ＴＢ组合的散射指数和极化指数来分析中国平原地区农田的微波辐射特征,及其随生长季节的时间性变化。星载ＳＳＭ／Ⅰ数据可以监视农作物的生长和平原地区地面湿度的变化。本文还给出了大气和农作物地表矢量辐射传输的数值模拟结果。  相似文献   

基于DS1624的多点温度监测系统     

徐劲松  高玉平  袁海波 《时间频率学报》2007,30(2):105-110

为了减少温度变化对高精度时间比对的影响,设计了一种由带存储功能的数字温度计DS1624构建的、基于I2C总线的温度监测系统,并给出了系统的构成及软件、硬件实现方法和详细实验结果。分析表明,以温度监测系统为关键部分的温度控制系统是高精度时间比对所必要的。  相似文献   

Spatial variability of snowmelt timing from AMSR‐E and SSM/I passive microwave sensors,Pelly River,Yukon Territory,Canada     

Joan M. Ramage  Jeremy D. Apgar  Rose A. McKenney  Wade Hanna 《水文研究》2007,21(12):1548-1560

Spring snow melt run‐off in high latitude and snow‐dominated drainage basins is generally the most significant annual hydrological event. Melt timing, duration, and flow magnitude are highly variable and influence regional climate, geomorphology, and hydrology. Arctic and sub‐arctic regions have sparse long‐term ground observations and these snow‐dominated hydrologic regimes are sensitive to the rapidly warming climate trends that characterize much of the northern latitudes. Passive microwave brightness temperatures are sensitive to changes in the liquid water content of the snow pack and make it possible to detect incipient melt, diurnal melt‐refreeze cycles, and the approximate end of snow cover on the ground over large regions. Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR‐E) passive microwave brightness temperatures (T_b) and diurnal amplitude variations (DAV) are used to investigate the spatial variability of snowmelt onset timing (in two stages, ‘DAV onset’ and ‘melt onset’) and duration for a complex sub‐arctic landscape during 2005. The satellites are sensitive to small percentages of liquid water, and therefore represent ‘incipient melt’, a condition somewhat earlier than a traditional definition of a melting snowpack. Incipient melt dates and duration are compared to topography, land cover, and hydrology to investigate the strength and significance of melt timing in heterogeneous landscapes in the Pelly River, a major tributary to the Yukon River. Microwave‐derived melt onset in this region in 2005 occurred from late February to late April. Upland areas melt 1–2 weeks later than lowland areas and have shorter transition periods. Melt timing and duration appear to be influenced by pixel elevation, aspect, and uniformity as well as other factors such as weather and snow mass distribution. The end of the transition season is uniform across sensors and across the basin in spite of a wide variety of pixel characteristics. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

A longer XMM–Newton look at I Zwicky 1 – distinct modes of X-ray spectral variability     

L. C. Gallo  W. N. Brandt  E. Costantini  A. C. Fabian 《Monthly notices of the Royal Astronomical Society》2007,377(3):1375-1382

  相似文献   

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张彩红  谭凯  杨少敏 《大地测量与地球动力学》2015,35(2):183-185

??Bernese??????ж??ο???????????????????????t??????λ??????λ??,??????????13??????????2013\|07\|23??29?????????е??????????GPS??λ????????????????????????λ???????cm??????????λ???????mm??????  相似文献   

一种新的北斗Klobuchar模型及其精度分析     

徐李冰  蔡成林  陈光喜  李春华 《大地测量与地球动力学》2015,35(5):788-792

针对传统Klobuchar模型电离层延迟修正精度不高的问题,提出一种新的Klobuchar模型,以提高北斗导航系统的精度。利用欧洲定轨中心CODE的全球格网数据作为参考,使用松弛搜索法分别对覆盖中国区域的格网点和9个测站的观测数据进行算例分析。比较两种方法得出,新模型的修正精度相对于广播模型有大幅提高;新模型预报7d内的电离层时延值修正效果也比广播模型有明显改善;格网点上的平均修正精度从67.89%提高到78.44%,观测数据的平均修正精度从69.81%提升至82.34%。  相似文献   

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刘俊  何秀凤  刘炎雄 《大地测量与地球动力学》2014,34(4):117-122

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王志平  陶庭叶  高飞 《大地测量与地球动力学》2014,34(4):161-164

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