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

为了启动1992年以来琵琶湖工程没有涉及的寒冷季节水文过程，在有多河流域的起源约哥山区建立了新的观测系统。为了了解温带地区大雪区的积雪和融化过程，对雪深和相关气象要素进行了观测。通过非水静力气象模式（ARPS-SiBUC、CReSiBUC）的多种数值试验，研究了地表加热和土壤水分状况对对流雨形成的影响。土壤初始水分分布在实际变化范围内的差异确实会影响降雨的位置和强度。这表明土壤湿度日变化在短期数值天气预报中的重要性。在本研究中，使用SiBUC陆地表面模型估算了日本大部分地区（不包括冲绳）的陆地表面状态（如土壤湿度和雪水当量）。SiBUC的大气强迫资料是利用日本气象厅提供的业务气象资料（例如AMeDAS、地面天气观测）编制的。从1991年到2008年进行了18年的土地再分析，水平分辨率约为10km。将雪水当量的时间序列和水平分布与观测和其他模式产品进行了比较。

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.