THE DAYTIME PBL HEATING PROCESS OVER COMPLEX TERRAIN IN CENTRAL JAPAN UNDER FAIR AND CALM WEATHER CONDITIONS .2. REGIONAL HEAT-BUDGET, CONVECTIVE BOUNDARY-LAYER HEIGHT AND SURFACE MOISTURE AVAILABILITY

The daytime PBL heating process and the air-land heat budget are analyzed for central Japan under fair weather and weak synoptic wind conditions, making use of routine observational data. The convective boundary layer (CBL) depth increases as the PBL heating rate Q(s) increases. According to the horizontal distribution of Q(s), the depth of the CBL is larger over the inland basin and inland plain areas, while it is smaller over the coastal and mountainous areas. The mountainous area has a large CBL height (ASL) in spite of small values of Q(s) due to the higher ground level. The CBL height increases monotonically from the coastal region toward inland areas. The air-land heat budget is estimated for 11 sub-regions. Overall, there is no significant difference in the heat budget among the sub-regions, except that the Kanto Plain has a somewhat larger sensible heat flux and smaller latent heat flux, due to having the smallest percentage of vegetated area and the largest percentage of urban area. The Bowen ratio is estimated as 1.03 when averaged over central Japan. Surface moisture availability beta, the ratio of the bulk latent heat transfer coefficient to the sensible heat transfer coefficient, is estimated as 0.29 for the mean value during the spring season over central Japan. Regional variation of beta ranges from 0.16 to 0.46 over all the sub-regions.