INTEGRATED STUDY ON WATER/ENERGY/MATERIAL CYCLE PROCESSES INCLUDING SNOW SEASON-LAKE BIWA PROJECT 4TH STAGE-

为了启动自1992年以来一直不是琵琶湖工程目标的冷季水文过程，在Yodo河流域的发源地约果山地区建立了新的观测系统。为了了解温带大雪区积雪和融化过程，观测了积雪深度和相关气象要素，通过非静力气象模式(ARPS-SIBUC，CReSiBUC)的各种数值试验，研究了地面加热和土壤水分状况对对流雨形成的影响。在实际变化范围内，初始土壤水分分布的差异确实会影响降雨的位置和强度。这一结果表明土壤水分的逐日变化在短期数值天气预报中的重要性。在本研究中，使用陆地表面模式SiBUC估计了日本大部分地区(不包括冲绳)的陆地表面状态(例如土壤水分和雪水当量)。SiBUC的大气强迫数据是使用JMA提供的业务气象数据(例如AMeDAS，地面天气观测)创建的。这次陆地再分析历时18年(从1991年到2008年)，水平分辨率约为10公里。将雪水当量的时间序列和水平分布与观测值和其他模型产品进行了比较。

To start the cold season's hydrological processes which have not been a target of the Lake Biwa Project since 1992, new observation system was established in Yogo mountain area, the origin of Yodo River Basin. To understand the snow accumulation and melting processes in the heavy snow area in temperate climate zone, snow depth and related meteorological elements are observed.Through various kinds of numerical experiments by nonhydrostatic meteorological models (ARPS-SiBUC, CReSiBUC), impacts of surface heating and soil moisture status for the formation of convective rain were investigated. The difference in the initial soil moisture distribution within realistic variation range does influence the location and intensity of rainfall. This result suggests the importance of day-to-day variation of soil moisture in short-range numerical weather prediction.In this study, land surface state (e.g. soil moisture and snow water equivalent) is estimated using land surface model SiBUC for the most part of Japan (excluding Okinawa). The atmospheric forcing data for SiBUC is created using operational meteorological data provided by JMA (e.g. AMeDAS, surface weather observation). This land reanalysis was carried out for 18 years (from 1991 to 2008) with about 10km horizontal resolution. The time series and horizontal distribution of snow water equivalent are compared with observation and other model product.