共查询到20条相似文献，搜索用时 31 毫秒
1.
ABSTRACT Daily average net radiation （DANR） is an important variable for estimating evapotranspiration from satellite data at regional scales, and is used for atmospheric and hydrologic modeling, as well as ecosystem management. A scheme is proposed to estimate the DANR over large heterogeneous areas under clear-sky conditions using only remotely sensed data. The method was designed to overcome the dependence of DANR estimates on ground data, and to map spatially consistent and reasonably distributed DANR, by using various land and atmospheric data products retrieved from MODIS （Moderate Resolution Imaging Spectroradiometer） data. An improved sinusoidal model was used to retrieve the diurnal variations of downward shortwave radiation using a single instantaneous value from satellites. The downward shortwave component of DANR was directly obtained from this instantaneous value, and the upward shortwave component was estimated using satellite-derived albedo products. Four observations of air temperature from MOD07_L2 and MYD07_L2 data products were used to derive the downward longwave component of DANR, while the upward longwave component was estimated using the land surface temperature （LST） and the surface emissivity from MOD1 l_L2. Compared to in situ observations at the cropland and grassland sites located in Tongyu, northern China, the root mean square error （RMSE） of DANR estimated for both sites under clear-sky conditions was 37 W m-2 and 40 W m-2, respectively. The errors in estimation of DANR were comparable to those from previous satellite-based methods. Our estimates can be used for studying the surface radiation balance and evapotranspiration. 相似文献
2.
Xia Zhang 《Asia-Pacific Journal of Atmospheric Sciences》2012,48(1):97-105
A soil-atmosphere-transfer model (SATM) was evaluated using observational data from the Tongyu Cropland Station and Audubon Research Ranch in semiarid areas, where the land cover was nearly bare soil during the simulation period. Simulations by the SATM at both sites were conducted using the new and original surface thermal roughness length parameterization schemes, respectively. Comparisons of simulations and observations have demonstrated that using the new surface thermal roughness length scheme in this model made sound improvements in the simulation of soil surface temperatures, sensible heat fluxes and net radiation fluxes in the daytime at both sites, compared to the original scheme, because the new scheme produced a larger aerodynamic resistance for turbulent heat transfer in the daytime. With respect to latent heat fluxes, the improvement was not as obvious as that attained for soil surface temperature since the soil water content in the surface layer in a semiarid area is a more important factor than surface soil temperature in controlling evaporation rate. Accordingly, it can be concluded that the new surface thermal roughness length parameterization scheme could improve the ability of the SATM to simulate bare soil surface energy budget with latent heat flux component being innegligible in semiarid areas. 相似文献
3.
青藏高原西部冬季地表净辐射与中国降水的关系 总被引：6，自引：9，他引：6
本文利用1982年8月－1983年7月在青藏高原地区进行的辐射平衡观测资料，计算了高原西部地区历年冬季（11－2月）的地表净辐射。通过对高原西部冬季地表净辐射的分析阐明了高原西部地表加热场的特征，并讨论了它与我国的西南秋雨、长江流域伏旱以及黄河上游雨季降水等的关系。 相似文献
4.
5.
Zhengfang Wu Haibo Du Dongsheng Zhao Ming Li Xiangjun Meng Shengwei Zong 《Theoretical and Applied Climatology》2012,108(3-4):495-503
Daily global solar radiation is an important input required in most crop models. In the present study, a sunshine-based model, the ?ngstr?m–Prescott model, is employed to estimate daily global solar radiation on a horizontal surface during the growing season in Northeast China. Data from six control groups are used. The controls include the entire sequence, precipitation days, and non-precipitation days both during the growing season and year-round. Estimations are validated by comparing the calculated values with the corresponding measured values. The results indicate that estimating daily global solar radiation during the growing season using data only from the growing season is better than using year-round data. Classifying days with respect to precipitation and non-precipitation is also unnecessary. The performance on estimating daily global solar radiation during the growing season using the entire data in growing season performs best. A sunshine-based equation is obtained using our method to estimate growing season daily radiation for all meteorological stations in Northeast China. The approved approach is expected to be beneficial to crop models and other agricultural purposes. 相似文献
6.
利用全国95个气象站点逐日地表太阳总辐射和日照时数资料,通过最小二乘法拟合回归建立地表太阳总辐射气候学计算模型。通过对比分析以日值和月值为起点的地表太阳总辐射计算模型的精度,确定了全国不同省份和区域的不同时间尺度（月、季节、生长季和年）地表太阳总辐射计算模型,并探讨了经验系数a、b值的分布及变化特征。结果表明,以日值和月值为起点建立的月、四季、生长季和年地表太阳总辐射计算模型精度无显著性差异,相对误差均低于8.5%,但以日值为起点的计算模型a、b值变异性更小。在以日值为起点建立计算模型的前提下,全国各地a、b值自西北部向南部减小,且从四季到生长季再到年尺度,随着时间尺度增大,a、b值振幅减小。根据不同省份年地表太阳总辐射计算模型经验系数a、b值,全国可划分为新甘蒙地区、青藏高原地区和中东部地区3个区域,分别确定了每个区域四季、生长季和年尺度下地表太阳总辐射计算模型。各区域不同时间尺度地表太阳总辐射计算模型均通过了显著性检验（p<0.01）,其中青藏高原地区和新甘蒙地区模型相对误差低于8.0%,模拟精度较高。 相似文献
7.
阿尔卑斯山杉林冠层影响辐射传输的个例分析 总被引：3，自引：1，他引：2
利用瑞士Alptal观测站杉树林冠层上方、下方的辐射观测资料,分析了冠层对短波辐射的减弱及对长波辐射的增幅作用及其季节变化。结果表明,对比较密集的常绿针叶林,冠层对入射短波辐射的透过率随着太阳高度的降低而减小,春季以后趋于稳定;冠层对长波辐射的增幅作用随天气状况而变化,这种增幅作用在晴空条件下最显著,可达1.5倍。在冬季,因为太阳辐射较弱,冠层对长波辐射的增幅作用超过对短波辐射的减弱从而增加地面净辐射。在其它季节,太阳辐射比较强,冠层对短波辐射的减弱超过对长波辐射的增幅作用而减少地面净辐射。地面净辐射与冠层上方气温的变化趋势虽然在有些时段一致,但在伴随降雪过程的降温时段,地面净辐射与气温的变化趋势近乎反相,在积雪融化时段,地面净辐射的增加比气温升高更显著,尤其是在白天。 相似文献
8.
YANG Xingguo QIN Dahe ZHANG Tingjun KANG Shichang QIN Xiang LIU Hongyi 《Acta Meteorologica Sinica》2010,24(6):680-698
Ground-based measurements are essential for understanding alpine glacier dynamics, especially in remote
regions where in-situ measurements are extremely limited. From 1 May to 22 July 2005 (the spring-summer
period), and from 2 October 2007 to 20 January 2008 (the autumn-winter period), surface radiation as well
as meteorological variables were measured over the accumulation zone on the East Rongbuk Glacier of Mt.
Qomolangma/Everest at an elevation of 6560 m a.s.l. by using an automatic weather station (AWS). The
results show that surface meteorological and radiative characteristics were controlled by two major synoptic
circulation regimes: the southwesterly Indian monsoon regime in summer and the westerlies in winter. At the
AWS site on the East Rongbuk Glacier, north or northwest winds prevailed with high wind speed (up to 35 m
s-1 in January) in winter while south or southeast winds predominated after the onset of the southwesterly
Indian monsoon with relatively low wind speed in summer. Intensity of incoming shortwave radiation was
extremely high due to the high elevation, multiple reflections between the snow/ice surface and clouds, and
the high reflective surrounding surface. These factors also caused the observed 10-min mean solar radiation
fluxes around local noon to be frequently higher than the solar constant from May to July 2005. The mean
surface albedo ranged from 0.72 during the spring-summer period to 0.69 during the autumn-winter period.
The atmospheric incoming longwave radiation was greatly affected by the cloud condition and atmospheric
moisture content. The overall impact of clouds on the net all-wave radiation balance was negative in the Mt.
Qomolangma region. The daily mean net all-wave radiation was positive during the entire spring-summer
period and mostly positive during the autumn-winter period except for a few overcast days. On monthly
basis, the net all-wave radiation was always positive. 相似文献
9.
By using the climatological calculating method for each component of slope surface net radiation proposed by the authors,calculations and analyses are done of the distribution features of slope net radiation in China with emphasis on the discussion of variations of slope net radiation in typical stations and sites with slope direction,slope,latitude and season.The distribution features of net radiation on the north and south slopes are,for the first time,mapped and discussed,revealing the great difference on the national basis,and thus acquiringa new interesting result that the negative-value area of winter net radiation on the north slope(20°)can reach Yunnan and Guizhou Provinces and middle and upper reaches of the Changjiang River. 相似文献
10.
以较为精确的大气辐射传输模式为基础,研制出晴天地表总辐射和净辐射瞬时值的计算方案。与以往的经验计算方法不同,该方案将辐射传输带模式的思路引入地面太阳辐射计算,并尽可能将大气中吸收和散射物质对太阳辐射的影响考虑进去,从而使该方法具有较好的精确性和普适性。在此基础上采用了Kokhanovsky等人提出的大气气溶胶反射率和透过率参数化方案,使得气溶胶对地面总辐射和净辐射的影响得到较好的处理。采用的自变量都是数值预报模式或卫星观测能提供的气象要素,因此该方案即可用于数值预报模式或陆面过程模式计算地表辐射平衡,又可以利用卫星观测或再分析资料估算地面太阳能资源分布。利用美国能源部三个大气辐射观测站点2005年全年的观测资料及欧洲宇航局提供的卫星反演气溶胶资料对计算方案进行了检验。结果表明,该方法十分精确,所有点的平均相对误差都小于6%,误差的均方差都小于0.3 W•m-2。 相似文献
11.
Results of one-year simulations using the Weather Research and Forecast (WRF) model, with the use of different radiation schemes (RRTM, RRTMG, CAM, New Goddard and Goddard), are evaluated for China. The observations used in the model assessment include station data from the China Meteorological Administration, 14 flux field sites arranged in a coordinated observation network, and Global Land Data Assimilation System (GLDAS) data. Specifically, based on a Taylor diagram, the temperature differences between the radiation schemes are small, and the best annual mean spatial pattern and average value for China as a whole is produced by RRTMG. For the rainfall and net radiation annual mean simulation, the New Goddard and CAM schemes present better results than the RRTMG scheme. With respect to low cloud cover, all the schemes have similar reproduction without high cover on east of Tibet Plateau. Overall, the New Goddard and CAM schemes are suitable for longtime simulation without nesting and nudging options. 相似文献
12.
对临海沙漠地区非均匀地表区域地表能量通量和蒸发(蒸散)的研究,是一个十分重要但又是一个难点问题。本文提出了1个基于卫星遥感和地面观测的参数化方案,并把其应用于沙特阿拉伯吉达地区,利用1个景的陆地资源卫星Landsat-7E^TM^ 资料进行了分析研究,得到了一些有关临海沙漠地区非均匀地表区域地表特征参数、植被参数和地表能量通量的新概念。最后讨论了所提出的参数化方案的适用范围和需改进之处。 相似文献
13.
青藏高原地区大气顶净辐射与地表净辐射的关系 总被引：14，自引：0，他引：14
地表净辐射为地气系统净辐射与大气层净辐射之差。对大气层净辐射作不同的假定，可将地表净辐射与大气顶辐射收支之间的关系表示成不同的形式。本文利用１９８２年８月—１９８３年７月青藏高原地区地面辐射收支观测资料及同期ＮＯＡＡ－７辐射收支资料，用统计方法讨论了大气顶净辐射与地表净辐射之间的相关性，建立了两者之间的回归方程，并在此基础上分析了青藏高原地区月平均地表净辐射的时空分布特征。 相似文献
14.
Xiangxiang ZHANG Yongjiu DAI Hongzhi CUI Robert E. DICKINSON Siguang ZHU Nan WEI Binyan YAN Hua YUAN Wei SHANGGUAN Lili WANG Wenting FU 《大气科学进展》2017,34(9):1035-1046
Given the crucial role of land surface processes in global and regional climates, there is a pressing need to test and verify the performance of land surface models via comparisons to observations. In this study, the eddy covariance measurements from 20 FLUXNET sites spanning more than 100 site-years were utilized to evaluate the performance of the Common Land Model(Co LM) over different vegetation types in various climate zones. A decomposition method was employed to separate both the observed and simulated energy fluxes, i.e., the sensible heat flux, latent heat flux, net radiation, and ground heat flux, at three timescales ranging from stepwise(30 min) to monthly. A comparison between the simulations and observations indicated that Co LM produced satisfactory simulations of all four energy fluxes, although the different indexes did not exhibit consistent results among the different fluxes. A strong agreement between the simulations and observations was found for the seasonal cycles at the 20 sites, whereas Co LM underestimated the latent heat flux at the sites with distinct dry and wet seasons, which might be associated with its weakness in simulating soil water during the dry season. Co LM cannot explicitly simulate the midday depression of leaf gas exchange, which may explain why Co LM also has a maximum diurnal bias at noon in the summer. Of the eight selected vegetation types analyzed, Co LM performs best for evergreen broadleaf forests and worst for croplands and wetlands. 相似文献
15.
Toby R. Marthews Yadvinder Malhi Hiroki Iwata 《Theoretical and Applied Climatology》2012,107(3-4):461-477
Field measurements of radiation fluxes—notably downwelling longwave radiation flux (LW flux)—are as yet rare or nonexistent outside a very select number of sites in the tropics. Data gaps can only be filled through the use of estimation schemes based on measurements of other meteorological variables, and there is a need for recommendations on best practice in this area. We selected 18 contrasting semi-empirical estimation schemes for downward longwave radiation, based on air emissivities, combined with six different sky cover estimation schemes and compared the expected longwave flux with hourly observations from a flux tower at Caxiuan? in Brazil. Of all schemes tested, the Dilley–Kimball emissivity scheme combined with Kasten and Czeplak’s sky cover scheme during the day and Dilley and O’Brien’s model B scheme at night proved to be the most reliable, yielding estimates of LW flux generally within 20?W/m2 of measurements across all time points. 相似文献
16.
An evaluation of Arctic cloud and radiation processes during the SHEBA year: simulation results from eight Arctic regional climate models 总被引：1，自引：1，他引：0
K. Wyser C. G. Jones P. Du E. Girard U. Willén J. Cassano J. H. Christensen J. A. Curry K. Dethloff J.-E. Haugen D. Jacob M. Køltzow R. Laprise A. Lynch S. Pfeifer A. Rinke M. Serreze M. J. Shaw M. Tjernström M. Zagar 《Climate Dynamics》2008,30(2-3):203-223
Eight atmospheric regional climate models (RCMs) were run for the period September 1997 to October 1998 over the western Arctic
Ocean. This period was coincident with the observational campaign of the Surface Heat Budget of the Arctic Ocean (SHEBA) project.
The RCMs shared common domains, centred on the SHEBA observation camp, along with a common model horizontal resolution, but
differed in their vertical structure and physical parameterizations. All RCMs used the same lateral and surface boundary conditions.
Surface downwelling solar and terrestrial radiation, surface albedo, vertically integrated water vapour, liquid water path
and cloud cover from each model are evaluated against the SHEBA observation data. Downwelling surface radiation, vertically
integrated water vapour and liquid water path are reasonably well simulated at monthly and daily timescales in the model ensemble
mean, but with considerable differences among individual models. Simulated surface albedos are relatively accurate in the
winter season, but become increasingly inaccurate and variable in the melt season, thereby compromising the net surface radiation
budget. Simulated cloud cover is more or less uncorrelated with observed values at the daily timescale. Even for monthly averages,
many models do not reproduce the annual cycle correctly. The inter-model spread of simulated cloud-cover is very large, with
no model appearing systematically superior. Analysis of the co-variability of terms controlling the surface radiation budget
reveal some of the key processes requiring improved treatment in Arctic RCMs. Improvements in the parameterization of cloud
amounts and surface albedo are most urgently needed to improve the overall performance of RCMs in the Arctic. 相似文献
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18.
采用2002年1月、2月、7月、8月每日8～16时(北京时间)的GMS-5卫星云图资料以及相同时次的漠河和郑州两个辐射站的地面净辐射资料，通过读取红外1、红外2、水汽和可见光云图上的卫星计数值，并将卫星计数值按照GMS-5定标表转换成亮度温度和反射率，最终形成一套利用卫星资料研究云对地面净辐射影响的数据集。采用统计的方法将地面净辐射与影响地面净辐射的各因子：太阳天顶角、地面及云面反射率等有关因子进行拟合，发现地面净辐射与这些因子之间有很好的相关性，特别在引入卫星红外通道亮温值减水汽通道亮温值这一因子后，在有云状况下，拟合的相关系数有较明显的提高，原因可能是这一因子包含了云分类的信息，这一方法的提出为利用卫星资料研究云对地面净辐射的影响提出了一个新的思路。 相似文献
19.
甘肃马衔山区陆面过程与降水的研究 总被引：1，自引：0，他引：1
采用定西的麦田微气象观测,定西、兰州的辐射观测和马衔山区34个气象、水文和雨量站的气候资料,结合NOAA-16卫星的AVHRR资料以及反演的地表植被盖度和反射率,并用SEBAL算法推导出夏季地表净辐射、感热、潜热、土壤热通量密度的区域分布特征,并分析陆面过程对降水的影响。结果表明:本区降水的空间分布与夏季植被盖度对应最好,相关系数高达0.722,其次是土壤热通量和潜热通量,相关系数分别为-0.65和0.615。这表明森林通过降低地表反射率和表面温度,不仅增加地表净辐射,而且减少其用于感热和土壤热通量的消耗。由于林区地表水分多,从而将接收较多的太阳辐射能主要用于蒸散,增加边界层中的水汽。故林区降水远大于植被稀疏的半干旱黄土梁。 相似文献
20.
We examine the performance of several methods to estimate meteorological inputs for modelling dispersion in urban areas during
convective conditions. Sensible heat flux, surface friction velocity and turbulent velocities are estimated from measurements
of mean wind speed and the standard deviation of temperature fluctuations at a single level on a tower at two suburban sites
and at one urban site in Riverside, California. These estimates are compared with observations made at these sites during
a field study conducted in 2007. The sensible heat flux is overestimated in the urban area, while it is underestimated at
a suburban site when temperature fluctuations are used in the free convection formulation to estimate heat flux. The bias
in heat flux estimates can be reduced through a correction that depends on stability. It turns out that the bias in heat flux
estimates has a minor effect on the prediction of surface friction velocity and turbulent velocities. Estimates of sensible
heat flux, surface friction velocity and turbulent velocities are sensitive to estimates of aerodynamic roughness length,
and we suggest estimating the aerodynamic roughness length through detailed micrometeorological measurements made during a
limited field study. An examination of the impact of the uncertainty in estimating surface micrometeorology on concentrations
indicates that, at small distances from a surface release, ground-level concentrations computed using estimates of heat flux
and surface friction compare well with the those based on observed values: the bias is small and the 95% confidence interval
of the ratio of the two concentrations is 1.7. However, at distances much larger than the Obukhov length, this confidence
interval is close to 2.3 because errors in both friction velocity and heat flux affect plume spread. Finally, we show that
using measurements of temperature fluctuations in estimating heat flux is an improvement on that based on the surface energy
balance, even when net radiation measurements are available. 相似文献