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241.
K. Blümel 《Boundary-Layer Meteorology》1998,86(2):193-232
By means of the algorithm presented here, the temporal course H(t) and the daily mean H¯ of the sensible heat flux H can be estimated from measurements of the thermodynamic surface temperature (as a function of time) and from a one-time-of-day air temperature observation. In addition to these temperatures, one needs estimates for daily mean wind speed, for the roughness lengths of momentum and heat transfer, and for the displacement height. First, a quite general solution of the equation for heat conductance (equation for the vertical profile of potential temperature (z,t)) in the dynamic sublayer will be presented. The undetermined parameters in this solution will be defined with the aid of the above mentioned measurements. The influence of horizontal advection will be taken into account. After that, the sensible heat flux can be evaluated from the temperature difference between surface and air with the well known resistance formulae. In this paper the algorithm is derived for areas with homogeneous surfaces, i.e., with uniform surface temperatures. Finally, the method will be verified by measurements taken during the field campaigns HIBE 89 (Hildesheimer Börde in Germany) and EFEDA 91 (Spain). The root mean square errors (RMSE) for the comparison between measurement and model with regard to the temperature difference of surface and air amount to one or two degrees Kelvin, and the error of H¯ reaches 10 to 25 per cent. The method can be used to determine the sensible heat flux from measurements of surface temperatures by satellites (e.g., METEOSAT), but can also be applied to ground based measurements. For instance, horizontal temperature advection can be estimated from measurements at a single location, especially if more than one near-surface air temperature is available. The procedure can be generalized for larger areas, which consist of various surface types with different surface temperatures. This generalization of the algorithm is in progress and will be addressed in a subsequent paper. It will allow us to improve the estimates for H(t) by means of temperature measurements from, e.g., NOAA/AVHRR or LANDSAT/TM, taking into account the heterogeneity of the area that is contained in one METEOSAT pixel. 相似文献
242.
The approach to remote sensing of water vapor by using global positioning systems(GPS)isdiscussed.In order to retrieve the vertical integrated water vapor(IWV)or the precipitable water(PW),the weighted“mean temperature”of the atmosphere,T_m would be estimated to the specificarea and season.T_m depends on surface temperature,tropospheric temperature profile,and thevertical distribution of water vapor.The surface temperature dependence is borne out by acomparison of T_m and the values of surface temperature T_s using radiosonde profiles of BeijingStation(No.54511)throughout 1992.The analysis of radiosonde profiles spanning a one-yearinterval(1992)from sites in eastern region of China with a latitude range of 20-50°N and alongitude range of 100-130°E yields the coefficients α and b of a linear regression equation T_m=α bT_s. 相似文献
243.
244.
长江三峡地区枯水期强降水过程的水汽图象 总被引:5,自引:3,他引:2
通过对1996年11月4 ̄6日长江三峡地区强降水过程的水汽图象、红外及可见光云图和常规气象资料的诊断分析,证灾了在水汽图象上可以看到红外云图和可见光云图上看不到的信息,而这信息对强降水预报是重要的。 相似文献
245.
246.
THE STUDY OF RETRIEVAL THEORY AND METHODS FROM SATELLITE REMOTE SENSING FOR METEOROLOGICAL PARAMETERS OVER EASTERN ASIA—PART Ⅱ:ISPRM AND VSPRM2
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Based on the practice of improved simultaneous physical retrieval model(ISPRM),in the lightof the functional analysis approach,the variational simultaneous physical retrieval model(VSPRM)has been developed.Its approximation of 1st degree is VSPRM1,which is identicalwith the ISPRM.Its approximation of 2nd degree is VSPRM2,more advanced than the VSPRM1.This paper has analyzed the function of VSPRM2,pointing out the potentiality of synergy retrievalof this model.Also,it has dealt with the problem of parameterization of water vapor's kernelfunctions and retrieval of water vapor remote sensing.Because of the characteristics of this strong ill posed inverse problem,prior information mustbe used wisely in order to get the accurate calculation of radiance R.In the previous paper,wediscussed how to build the best first guess field,the way to determine the P_s and to correct thecalculation of radiance.In this paper,we continue discussing in depth about the calculation oftransmittance,the determination of surface parameters and the selection for an optimumcombination of channels for the low-level sounding.The long-term experiment and comparison work under operational environment have shownthat the ISPRM is useful for retrieval of temperature and water vapor parameters over Chinaincluding the Tibetan Plateau,and it further proves the scientific nature of well-posed inversetheory. 相似文献
247.
《水文科学杂志》2013,58(5)
Abstract Modelling of the rainfall–runoff transformation process and routing of river flows in the Kilombero River basin and its five sub-catchments within the Rufiji River basin in Tanzania was undertaken using three system (black-box) models—a simple linear model, a linear perturbation model and a linear varying gain factor model—in their linear transfer function forms. A lumped conceptual model—the soil moisture accounting and routing model—was also applied to the sub-catchments and the basin. The HEC-HMS model, which is a distributed model, was applied only to the entire Kilombero River basin. River discharge, rainfall and potential evaporation data were used as inputs to the appropriate models and it was observed that sometimes the system models performed better than complex hydrological models, especially in large catchments, illustrating the usefulness of using simple black-box models in datascarce situations. 相似文献
248.
The use of drilled shafts to stabilize an unstable slope has been a widely accepted practice. There are two basic design and analysis issues involved: one is to determine the global factor of safety of the drilled shafts stabilized slope and the other one is to determine the design earth thrust on the drilled shafts for structural design of the shafts. In this paper, a limiting equilibrium method of slices based solution for calculating global factor of safety (FS) of a slope with the presence of a row of drilled shafts is developed. The arching mechanisms due to the presence of the drilled shafts on slope were taken into account by a load transfer factor. The method for calculating the net force applied to the drilled shaft from the soil mass was also developed. The interrelationships among the drilled shaft location on the slope, the load transfer factor, and the global FS of the slope/shaft system were derived utilizing the developed numerical closed‐form solution. An illustrative example is presented to elucidate the use of the solution in optimizing the location of the drilled shafts on slope to achieve the desired global factor of safety of the slope/shaft system. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
249.
万瑜 《沙漠与绿洲气象(新疆气象)》2024,18(4):9-16
利用高空、地面常规观测资料、NCEP/NCAR再分析资料,诊断分析了2017年2月新疆天山北坡一次区域性暴雪过程的特征及成因,结合GDAS再分析资料并采用HYSPLIT模式,模拟追踪水汽源地、主要水汽输送通道及其对水汽输送的贡献。结果表明:此次天山北坡暴雪是在典型后倾结构的高低空系统配置下产生的,中、高纬地区短波槽在东移过程中同位相叠加,为暴雪长时间维持提供了稳定的天气尺度背景;暴雪发生时位势不稳定性加强,中低层持续冷垫抬升是主要的动力机制,较强垂直风切变是降雪强度较大的重要原因,高低空急流耦合激发中尺度垂直上升支和次级环流圈,地形作用对暴雪有增幅作用;暴雪主要水汽源地位于阿拉伯半岛西侧的红海和伊朗高原西南侧的波斯湾至阿拉伯海北部一带,水汽通道主要集中在500~850 hPa,水汽辐合区位于700~850 hPa,中高层有偏西气流、中层有西南气流、低层有西北急流将水汽接力输送至暴雪区;利用HYSPLIT模式模拟发现,暴雪期间,西、东、南边界水汽输入均起重要作用,主要水汽输送通道分别为偏西路径、偏西南路径、局地水汽路径,1500 m高度的追踪,三者贡献率大致相当,3000 m高度,局地水汽和偏西路径水汽贡献率更大。 相似文献
250.