甘肃河西走廊实际水资源及其对林木适生程度的影响   总被引：5，自引：0，他引：5  

陈昌毓 《地理学报》1991,46(1):35-46

根据河西走廊近年来水资源研究中比较一致的结果,计算了各县市绿洲年、日平均气温≥10℃期间的实际水资源。采用张宝堃和H.L.彭曼的气候学方法,对各县市林木生长期的蒸散耗水量进行了估算,与实测和调查资料对照表明,两种估算值大致可分别反映林木基本正常生长和良好生长对水分的需求。提出了“实际干燥度”和“实际湿润度”的概念,并根据后者确定了各县市绿洲不同气候植被区林木的适生程度,以及应当选择的乔、灌木树种。  相似文献   

Water flux estimates from a Belgian Scots pine stand: a comparison of different approaches     

L. Meiresonne  D. A. Sampson  A. S. Kowalski  I. A. Janssens  N. Nadezhdina  J. Cermk  J. Van Slycken  R. Ceulemans 《Journal of Hydrology》2003,270(3-4):230-252

Four distinct approaches, that vary markedly in the spatial and temporal resolution of their measurement and process-level outputs, are used to investigate the daily and seasonal water vapour exchange in a 70-year-old Belgian Scots pine forest. Transpiration, canopy interception, soil evaporation and evapotranspiration are simulated, using a stand-level process model (SECRETS) and a soil water balance model (WAVE). Simulated transpiration was compared with up-scaled sap flow measurements and simulated evapotranspiration to eddy covariance measurements.

Reasonable agreement in the temporal trends and in the annual water balance between the two models was observed, however daily and weekly predictions often diverged. Most notably, WAVE estimated very low, to no transpiration during late autumn, winter and early spring when incident radiation fell below 50 W m⁻² while SECRETS simulated low (0.1–0.4 mm day⁻¹) fluxes during the same period. Both models exhibited similar daily trends in simulated transpiration when compared with sap flow estimates, although simulations from SECRETS were more closely aligned. In contrast, WAVE over-estimated transpiration during periods of no rainfall and under-estimated transpiration during rainfall. Yearly, total evapotranspiration simulated by the models were similar, i.e. 658 mm (1997) and 632 mm (1998) for WAVE and 567 mm (1997) and 619 mm (1998) for SECRETS.

Maximum weekly-average evapotranspiration for WAVE exceeded 5 mm day⁻¹, while SECRETS never exceeded 4 mm day⁻¹. Both models, in general, simulated higher evapotranspiration than that measured with the eddy covariance technique. An impact of the soil water content in the direct relationship between the models and the eddy covariance measurements was found.

The results suggest that: (1) different model formulations can reproduce similar results depending on the scale at which outputs are resolved, (2) SECRETS estimates of transpiration were well correlated with the empirical measurements, and (3) neither model fitted favourably to the eddy covariance technique.  相似文献   

Effect of potential evapotranspiration estimates on effective parameters and performance of the MIKE SHE-code applied to a medium-size catchment   总被引：3，自引：0，他引：3  

R. F. Vzquez 《Journal of Hydrology》2003,270(3-4):309-327

The effect of the method of calculating a time series of crop potential evapotranspiration (ET_p) on both the model performance and the magnitude of the main effective parameters of a distributed hydrological model was assessed on the basis of an independent multi-calibration. The ET_p was estimated as a function of the reference evapotranspiration (ET_o) by means of a crop coefficient approach. Three methods for deriving ET_o estimates were used in modelling a medium size catchment in Belgium: (A) Food and Agriculture Organisation (FAO) FAO-24 standard approach; (B) FAO-24 approach but used with coefficients, for both the wind and the Stefan-Boltzmann equations, differing from the standard formulation; and (C) FAO-56 standard approach. For assessing the performance of the estimation approaches, the point scale ET_o outputs of the generation methods were compared to local point scale ET_o guidelines derived from previous research. The outputs of generation method B and of the generation method C showed a close agreement with the local point scale ET_o guidelines. Their effect (to a catchment scale) on the performance of the hydrological model also seemed to be comparable. The best model performance was obtained by using the higher ET_o data generated by method A. The research also revealed a significant dependency of some of the effective parameters on the different ET_p estimates; especially of those parameters related to the computation of the actual evapotranspiration (ET_act).  相似文献   

Local Initiation of Deep Convection on the Canadian Prairie Provinces     

John M. Hanesiak  Richard L. Raddatz  Scott Lobban 《Boundary-Layer Meteorology》2004,110(3):455-470

Our study found that local mesoscale circulations associated with highlandareas, and transient evapotranspiration discontinuities, are likely to influencethe timing and location of the initiation of deep convection across the Canadianprairie provinces when synoptic-scale forcing is weak (e.g., weak low level windsand no frontal boundaries). The cumulus congestus and cumulonimbus clouds thatformed over the highland areas were initiated by anabatic wind induced mesoscalecirculations. These deep convective clouds generally formed relatively early in theday (about 1030 Central Standard Time (CST)). In the relatively flat cropped grasslandregion, transient evapotranspiration gradients influenced the location of deep convectioninitiation, and the average soil moisture in the root zone had a direct impact on theirtiming. As root zone soil moisture declined from greater than 70% to less than 30%,convection initiation was delayed from about 0930 to 1630 CST. Cumulus congestusand cumulonimbus clouds that formed over the ephemeral evapotranspiration gradientswere initiated by land-land circulations. The study has improved the understanding ofthe influence of local surface forcing on the development of deep convective cloud onthe Canadian prairie provinces. The identification of areas where deep convection islikely to be initiated with weak synoptic forcing will also aid in the forecasting ofthunderstorms in this region.  相似文献   

Complementary relationships for near-instantaneous evaporation     

Richard Crago  Raphael Crowley 《Journal of Hydrology》2005,300(1-4):199-211

The complementary relationship between actual and potential evaporation provides evaporation (i.e. evapotranspiration) estimates from minimal data. Some versions that require a land surface temperature instead of a humidity measurement could potentially be used with routine remotely sensed surface temperature data. A comparison of alternative complementary approaches, including those that require land surface temperatures, was made at small (10–30 min) time scales with point measurements spatially, using data from the FIFE, CASES, SGP, and Sahel field experiments. The advection-aridity version and a related version based on the Penman and the Priestley–Taylor equations performed the best overall. One of the four versions that incorporated land surface temperature performed fairly well. The complementary approach appears to remain viable, especially in remote sensing applications with sparse data.  相似文献   

TEST OF A SENSIBLE HEAT FLUX – RADIOMETRIC SURFACE TEMPERATURE RELATIONSHIP FOR HAPEX-SAHEL     

E. J. BURKE  J. B. STEWART 《Boundary-Layer Meteorology》1997,84(2):329-337

The estimation of the sensible heatflux from thermal infrared temperature requires anestimate of the excess resistance to be added to theaerodynamic resistance to the transfer of heat fromthe surface. This excess resistance can be expressedin terms of kB-1. An earlier studysuggested that the sensible heat flux over semi-aridregions could be derived from satellite thermalinfrared temperature using a value of kB-1= 7. Values of kB-1 were derived frommeasurements of sensible heat flux, radiometricsurface temperature, air temperature and wind speedtaken over millet, savannah and open forest sitesduring HAPEX-Sahel. These were comparable to valuesderived over similar sites during a previous study. Sensible and latent heat fluxes were estimated usingno excess resistance, kB-1 = 7 andkB-1 set to the values derived from theHAPEX-Sahel data set. There was an improvement on theestimated fluxes when an excess resistance wasincorporated. However, there was no apparentdifference between the errors in the estimated fluxeswith kB-1 set to either the derived orfixed values. This provides additional support forthe use of kB-1 = 7 in the derivation ofsurface fluxes from satellite data for sparsecanopies.  相似文献   

干旱缺水条件下麦田蒸散量的计算方法   总被引：20，自引：0，他引：20  

康绍忠  熊运章 《地理学报》1990,45(4):475-483

本文从试验资料出发,分析了干旱缺水条件下的麦田蒸散规律,以水量平衡方程为基础,且综合考虑影响麦田蒸散的天气条件、土壤水分状况和小麦本身的生物学特性,选用蒸发力、相对土壤有效含水量和作物的叶面积指数三因素建立了干旱缺水条件下麦田蒸散量的计算模型以及农田土壤水分变化的预测方法。  相似文献   

零通量面法和旱作麦田蒸散浅析     

张谋草  赵满来 《干旱气象》1995,(3)

利用西峰农业气象试验站１９８９－１９９０和１９９０－１９９１年度旱作麦田土壤水分观测资料，采用零通量面法计算农田蒸散。结果表明，在旱农地区存在稳定少变的零通量面位置；农田蒸散随时间的变化一般多呈双峰型，但其谷值均在８月８日。  相似文献   

Groundwater-supported evapotranspiration within glaciated watersheds under conditions of climate change   总被引：1，自引：0，他引：1  

Denis Cohen  Mark Person  Ronnie Daannen  Sharon Locke  Dave Dahlstrom  Victor Zabielski  Thomas C. Winter  Donald O. Rosenberry  Herb Wright  Emi Ito  John L. Nieber  William J. Gutowski  Jr 《Journal of Hydrology》2006,320(3-4):484-500

This paper analyzes the effects of geology and geomorphology on surface-water/-groundwater interactions, evapotranspiration, and recharge under conditions of long-term climatic change. Our analysis uses hydrologic data from the glaciated Crow Wing watershed in central Minnesota, USA, combined with a hydrologic model of transient coupled unsaturated/saturated flow (HYDRAT2D). Analysis of historical water-table (1970–1993) and lake-level (1924–2002) records indicates that larger amplitude and longer period fluctuations occur within the upland portions of watersheds due to the response of the aquifer system to relatively short-term climatic fluctuations. Under drought conditions, lake and water-table levels fell by as much as 2–4 m in the uplands but by 1 m in the lowlands. The same pattern can be seen on millennial time scales. Analysis of Holocene lake-core records indicates that Moody Lake, located near the outlet of the Crow Wing watershed, fell by as much as 4 m between about 4400 and 7000 yr BP. During the same time, water levels in Lake Mina, located near the upland watershed divide, fell by about 15 m. Reconstructed Holocene climate as represented by HYDRAT2D gives somewhat larger drops (6 and 24 m for Moody Lake and Lake Mina, respectively). The discrepancy is probably due to the effect of three-dimensional flow. A sensitivity analysis was also carried out to study how aquifer hydraulic conductivity and land-surface topography can influence water-table fluctuations, wetlands formation, and evapotranspiration. The models were run by recycling a wet year (1985, 87 cm annual precipitation) over a 10-year period followed by 20 years of drier and warmer climate (1976, 38 cm precipitation). Model results indicated that groundwater-supported evapotranspiration accounted for as much as 12% (10 cm) of evapotranspiration. The aquifers of highest hydraulic conductivity had the least amount of groundwater-supported evapotranspiration owing to a deep water table. Recharge was even more sensitive to aquifer hydraulic conductivity, especially in the lowland regions. These findings have important implications for paleoclimatic studies, because the hydrologic response of a surface-water body will vary across the watershed to a given climate signal.  相似文献   

海河及西北内陆河流域的水热平衡研究     

孙福宝  杨大文  刘志雨  丛振涛  雷志栋 《水文》2007,27(2):7-10

本文通过对海河流域的38个子流域及内陆河流域的7个子流域的逐年降水、径流及实际蒸散发和蒸发能力的分析,证明了基于Budyko假设的流域水热耦合平衡关系在海河及西北内陆河流域是成立的。根据各子流域的长期水量平衡结果,本文验证了水热耦合平衡模型中的唯一参数综合反映流域的下垫面条件且具有显著的区域分布规律,与此同时,本文还在海河流域及内陆河流域对根据流域平均坡度(tanβ),相对土壤最大蓄水能力(Smax/0)和相对土壤入渗能力(Ks/■r)估算模型参数■的经验公式进行了验证,计算结果较好。  相似文献