Validating the Estimates of Grobal Water Balance by Global River Runoff Dataset

作为估算全球土壤水分分布的一项努力，全球土壤湿度计划(GSWP)应运而生。利用一个1度×1度的全球河网--总径流积分路径(TRIP)，计算了250个业务测站上游流域的平均径流。从世界上150个主要流域的这些站收集了1987和1988年的径流观测数据，并与LSM产品进行了比较。研究发现，对于雨量观测密度较高(30/lmil)的流域地区，LSM对年径流量的估计效果较好，相对根值误差为40[%]。平方。Km)，用来准备强迫降水。误差大约相当于年蒸散量的18%。LSM还被发现有低估年度径流的趋势。这可能是由于在强风条件下低估了雨量，特别是对雪，因为所有LSM都低估了位于高纬度的大多数流域的径流量。LSM的全球径流产品采用线性河流径流模型，并在250个测站进行了分析。引入路径后，大多数LSM的月径流实测值与模拟值的相关性都得到了改善。河流径流信息是验证大陆尺度水循环的有效手段，开发了具有图形用户界面的GSWP产品数据库，并通过Internet向公众开放。这些由水和能量平衡组成的全球数据集引起了公众的极大关注，专用网页自开放以来的访问量正在增加。目前每月访问数据库的次数超过5，OOO请求。

As one effort to estimate the global soil moisture distribution, the Global Soil Wetness Project (GSWP) was conceived. A gridded 1 degree by 1 degree global river channel network, named Total Runoff Integrating Pathways (TRIP) is used to calculate mean runoff estimated by the LSMs for drainage areas upstream of 250 operational gauging stations. Runoff observations from these stations in 150 major river basins of the world have been collected for years in 1987 and 1988, and were compared with the LSM products. It was found that LSMs estimated annual runoff fairly well with a relative root mean, square error of 40 [%] for drainage areas with a fairly high density of raingauge observations (30/lmil. sq. km) which was used to prepare the forcing precipitation. The error corresponds to approximately 18 [%] of annual evapotranspiration. LSMs are also found to have a tendency to underestimate the annual runoff. It may be caused by underestimation of raingauges under strong wind conditions, especially for snow, as all of the LSMs underestimated the runoff for most of the drainage areas located in higher latitudes. A linear river routing model was applied for the global runoff products from the LSMs and analyzed at 250 gauging stations. The correlations between observed and simulated monthly runoff were improved for most of the LSMs by introducing the routing. River runoff information was found to be effective for the validation of water cycles on the continental scale.A database for the GSWP products was developed with graphical user interface, and opened for the public accesses through the Internet. These global datasets consisting water and energy balances drew magnificient attention from public and the number of the access to the dedicated web page is increasing since its opening. Currently the access to the database is more than 5,OOO request per month.