Era-interim Forced Simulation of the Indian Summer Monsoon     

Lav Kumar  Nishtha Agrawal  Abhishek K. Rai  Shailendra K. Mishra  Vinay S. Pandey 《Marine Geodesy》2013,36(6):558-574

Abstract

In the present study, mean rainfall for the months of June-July-August-September (JJAS) during summer monsoon is simulated over India and its adjoining regions for a period between 1982 and 2006. The study was carried out using Regional Climate Model (RegCM) version 4.6 at a resolution of 25?km. The simulated mean JJAS monsoon rainfall was validated against the observational IMD data. Comparison of JJAS seasonal mean summer rainfall for the first decade 1982–1991, with the later decade 1997–2006 indicate that the intensity of rainfall increases over Indian land-mass during the later decade under the forced conditions of Era-Interim. The observed JJAS mean rainfall indicates two maximum rainfall areas i.e. the Western Ghats and the Himalayan region. A significant bias is observed in the central and Jammu and Kashmir (J&K) region. The JJAS mean seasonal surface air temperature distribution at 0.25?×?0.25-degree grids resolution shows a decreasing trend of temperature over the Indian landmass.  相似文献   

Recharge and salination processes in the carbonate aquifers in Israel     

A. S. Issar 《Environmental Geology》1993,21(3):152-159

Limestone and dolostone aquifers play a major role in the water supply system of Israel. In many cases, there are brackish to saline springs at their outlets. The source of the saline water and the mechanism of salinization differ from place to place. In some cases, it is due to mixing with seawater (Mediterranean or Dead Sea) at the fresh-saline water interface, while in other cases deepseated brines emerge along regional faults. The general policy for reclaiming the fresh component of the water before mixing with the saline component is to try to catch the fresh water as far as possible upstream from the outlet. In most cases, this is the area where the mixing takes place. The main case histories in Israel are discussed in this paper.  相似文献   

Application of isotope tracers in continental scale hydrological modeling     

Balzs M. Fekete  John J. Gibson  Pradeep Aggarwal  Charles J. Vrsmarty 《Journal of Hydrology》2006,330(3-4):444-456

Isotope tracers are widely used to study hydrological processes in small catchments, but their use in continental-scale hydrological modeling has been limited. This paper describes the development of an isotope-enabled global water balance and transport model (iWBM/WTM) capable of simulating key hydrological processes and associated isotopic responses at the large scale. Simulations and comparisons of isotopic signals in precipitation and river discharge from available datasets, particularly the IAEA GNIP global precipitation climatology and the USGS river isotope dataset spanning the contiguous United States, as well as selected predictions of isotopic response in yet unmonitored areas illustrate the potential for isotopes to be applied as a diagnostic tool in water cycle model development. Various realistic and synthetic forcings of the global hydrologic and isotopic signals are discussed. The test runs demonstrate that the primary control on isotope composition of river discharge is the isotope composition of precipitation, with land surface characteristics and precipitation-amount having less impact. Despite limited availability of river isotope data at present, the application of realistic climatic and isotopic inputs in the model also provides a better understanding of the global distribution of isotopic variations in evapotranspiration and runoff, and reveals a plausible approach for constraining the partitioning of surface and subsurface runoff and the size and variability of the effective groundwater pool at the macro-scale.  相似文献   

Spatial and temporal variation in evapotranspiration using Raman lidar     

W.E. Eichinger  D.I. Cooper  L.E. Hipps  W.P. Kustas  C.M.U. Neale  J.H. Prueger 《Advances in water resources》2006

The Los Alamos Raman lidar has been used to make high resolution (25 m) estimates of the evapotranspiration rate over adjacent corn and soybean canopies. The lidar makes three-dimensional measurements of the water vapor content of the atmosphere directly above the canopy that are inverted using Monin–Obukhov similarity theory. This may be used to examine the relationship between evapotranspiration and surface moisture/soil type. Lidar estimates of evapotranspiration reveal a high degree of spatial variability over corn and soybean fields that may be associated with small elevation changes in the area. The spatial structure of the variability is characterized using a structure function and correlation function approach. The power law relationship found by other investigators for soil moisture is not clear in the data for evapotranspiration, nor is the data a straight line over the measured lags. The magnitude of the structure function and the slope changes with time of day, with a probable connection to the amount of evapotranspiration and the spatial variability of the water vapor source. The data used was taken during the soil moisture–atmosphere coupling experiment (SMACEX) conducted in the Walnut Creek Watershed near Ames, Iowa in June and July 2002.  相似文献   

Inter-annual Variability of Moisture Flux from the Prairie Agro-ecosystem: Impact of Crop Phenology on the Seasonal Pattern of Tornado Days   总被引：1，自引：0，他引：1  

R. L. Raddatz  J. D. Cummine 《Boundary-Layer Meteorology》2003,106(2):283-295

This study, through the inclusion of a simpleparameterization of the phenologicaldevelopment of spring wheat in evapotranspirationsimulations for 1988–2000, at a representativearid grassland and a representative transitionalgrassland site, delineated the inter-annualvariability of the seasonal moisture flux from theCanadian Prairie agro-ecosystem. Theagro-ecosystem's contribution to atmospheric boundary-layermoisture, at these representative sites, wasrelated to the seasonal pattern of tornado days in thegrassland eco-climatic zone for the averageyear, for a warmer/drier year and for a cooler/wetteryear. The following conclusions were drawn:(1) The moisture flux from the Prairie agro-ecosystemdisplays considerable inter-annualvariability due, in the main, to the rate andtiming of crop phenological development andassociated biophysical parameters, and (2) themoisture flux from the Prairie agro-ecosystemtranslates directly into changes in atmosphericboundary-layer moisture, which subsequentlyaffects the magnitude of the potential energyavailable for deep convection and the seasonalpattern of tornado days. For expansive agriculturalareas, representing the inter-annual variabilityof crop phenological development in land surfacemodels is critical to the successful simulationof the surface moisture flux, and thus thethermodynamic properties of the atmospheric boundarylayer. Therefore, it is of particularimportance to Prairie climate and climate change modelling.  相似文献   

非均匀地表条件下区域蒸发散通量计算方法的研究   总被引：11，自引：1，他引：11       下载免费PDF全文

刘晶淼  余锦华等 《应用气象学报》2002,13(3):288-298

文章改进了计算蒸发散通量的 Kotada-Barton模式（K-B模式)。经长江三角洲地区和淮河流域试验区各种不同陆面条件（水面，森林，麦田和水稻田）下的实际应用并通过和其它方法比较，认为该方法计算精度与涡动相关法及鲍恩比法相当，不论是计算蒸发散通量的瞬时值或日值都具有较高的可信度。该方法的最大优点在于它仅仅依赖于土地资源遥感信息、常规气象资料和基础地理信息如地面高程，而到目前为止上述资料均可以通过卫星等手段及常规观测得到。利用此方法计算了长江三角洲地区各种地表面上1995年各月的蒸发散量及该地区的区域平均蒸发散量。结果证明此方法具有较高的精确度，且基础资料容易得到，是一种估计不同地表覆盖条件下的蒸发散量和具有复杂的地形和土地利用条件下的区域平均蒸发散量的有用工具。  相似文献   

基于GRACE数据的天山阿克苏河流域水储量变化分析     

王志成  张辉  李万江  邓海军 《沙漠与绿洲气象(新疆气象)》2017,11(6):1-8

水储量变化可视为气候变化对水文系统影响的指示器。基于GRACE数据,结合气候数据和冰川积雪数据,分析了近10 a年来阿克苏河流域的水储量变化。研究结果表明:(1)过去10 a间阿克苏河流域的水储量呈递减趋势,减少速率为-0.12±0.85 cm/a,且春季表现为正距平,而秋季表现为负距平;(2)山区冰川退缩和积雪消融是该流域山区水储量减少的主要原因,近半个世纪以来冰川物质平衡为负平衡,同时近十年来积雪面积递减速率为-24 km~2/a;(3)阿克苏河流域的耕地面积的迅速增加导致了地下水过度超采,是绿洲区水储量减少的主要驱动因子。  相似文献   

陆面模式中土壤湿度影响蒸散参数化方案的评估     

肖宇  马柱国  李明星 《大气科学》2017,41(1):132-146

本文将四个常见陆面模式CLM3.5（Community Land Model Version 3.5）、Noah_LSM（The Noah Land Surface Model）、VIC（Variable Infiltration Capacity）以及SSiB（The Simplified Simple Biosphere Model）中土壤湿度影响蒸散的参数化方案进行简化,并利用实验观测资料对不同参数化方案进行评估,探究不同陆面模式对土壤湿度与蒸散关系的模拟差异,从而为提高模式的模拟能力提供依据。结果表明,（1）CLM与SSiB中计算土壤湿度影响裸土蒸发的参数化方案较Noah_LSM和VIC更接近真实的物理过程,同时CLM与SSiB模式中土壤湿度对蒸发的影响程度较Noah_LSM和VIC大;而对于下垫面有植被条件下的蒸散而言,CLM中包含了植被光合作用、呼吸作用等生物物理学过程,与实际情况更为接近,并且CLM与SSiB中土壤湿度对植被蒸散的影响程度大于VIC,Noah_LSM最低;（2）根据干旱区、半干旱区、半湿润区以及湿润区各站点的分析可知,CLM、SSiB与Noah_LSM中土壤湿度影响蒸散的参数化方案的拟合效果较VIC好,同时在部分站点CLM与SSiB的参数化方案稍优于Noah_LSM。区域之间比较说明,四个模式对干旱半干旱区的模拟效果明显较半湿润区和湿润区好。  相似文献   

甘肃干旱半干旱地区林木蒸散量估算和水分适生度研究   总被引：18，自引：1，他引：17       下载免费PDF全文

陈昌毓  董安祥 《应用气象学报》1998,9(1):79-87

采用张宝堃和H.L.彭曼的气候学方法,对甘肃干旱半干旱区各县、市林木生长期的蒸散耗水量进行了估算,并与实测和调查资料进行了对比,结果表明:两种估算值大致可反映乔木薪炭林和乔木用材林生长对水分的需求。文中还给出了各县、市年和日平均气温≥10℃期间的实际水资源。根据各地林木生长期的耗水量指标和实际水资源,采用实际湿润度方法确定了各地不同气候植被区林木的水分适生度。  相似文献   

基于机器学习的参考作物蒸散量估算研究   总被引：2，自引：0，他引：2  

毛亚萍  房世峰 《地球信息科学学报》2020,22(8):1692-1701

参考作物蒸散量（Reference Evapotranspiration, ET₀）的准确估算对区域水资源管理和分配、流域水量平衡以及气候变化等研究具有重要作用。新疆地处我国西北干旱地区,水资源供需矛盾尖锐,精确估算该地区的ET₀有助于其科学合理地调配水资源,缓解水资源供需压力。FAO推荐的Penman-Monteith法是计算ET₀的标准方法,但该方法需要多项气象因子,而新疆地区气象站点较少且分布不均,精确完备的气象数据在新疆大部分区域难以获取。因此,如何使用有限气象因子获取高精度的ET₀在新疆地区备受关注。本文基于中国气象数据网提供的新疆地区1980—2019年的地面气候资料日值数据集,在日和月尺度下,通过对最高气温T_max、最低气温T_min、平均气温T_avg、风速U₂、相对湿度RH和日照时数n共6项气象因子进行敏感性分析,形成不同的气象因子组合;然后使用SVM、RF、GBDT和ELM 4种机器学习算法,以FAO-56 PM计算值为标准值,对新疆地区的ET₀进行了拟合建模;最后,从拟合精度、稳定性和计算代价3个方面对模型进行评价。研究表明：① 在新疆地区,ET₀对RH、T_max和U₂敏感系数级别为高,平均敏感系数分别为-0.516、0.283和0.266;n为中等,平均敏感系数为0.124;T_min和T_avg为低,平均敏感系数分别为-0.016和-0.003;② 在日尺度,各算法在RH、T_max、U₂和n这4项气象因子为输入时精度较高（RMSE<0.5 mm/day,R²>0.95）,可对ET₀进行精确估算;在月尺度,各算法使用RH、T_max和U₂这3项参数便可对ET₀进行精确估算。SVM和GBDT这2种算法在日尺度和月尺度都有较好的适用性,可在相应尺度下使用较少气象因子替代FAO-56 PM公式对ET₀进行估算。  相似文献