Time change of water cycle in Huaihe River Basin

淮河流域位于重要的副热带锋，即所谓的梅雨锋在初夏停滞不前的地方。那里经常发生洪水和干旱。HUBEX(淮河流域实验)是GAME(Gewex亚洲季风实验)的一个子项目，将从1996财政年度开始进行，以阐明流域周围的水循环及其变化，以建立那里的水旱灾害的可预报性。本研究项目是在1995财政年度开展的，目的是通过日本气象学家和水文学家的合作以及中国的合作，对HUBEX进行初步研究。在HUBEX中，我们将在1998年进行密集的野外观测，如用于输入区域四维同化的密集雷电观测，日方用于产生雷达-Raingauge合成资料的三个多普勒雷达观测，以及中β尺度…热力学场的反演更多的云系，包括水文在内的陆面与大气相互作用过程的专门野外观测，以及中尺度大气和陆面耦合模式的建立。本文利用目前已有的资料对上述项目进行了检验，包括1991年夏季淮河流域大洪水的初步分析。日本科学家还访问了淮河流域，进行了数据和信息的调查。1996年3月在名古屋举行的HUBEX讲习班总结了这些成果和今后的问题。主要发现如下：1)1991年汛期，不仅有大量的南方水汽流入流域，而且出现了有效的大尺度辐合(北部边界的水汽流出很少)。局地蒸散对面雨量的贡献也不小。2)1979年夏季，百雨锋附近的几个地区出现了明显的日变化(夜间最大)的积雨云团。3)利用1988年7月的多普勒雷达观测资料和日本群岛附近的常规观测资料，通过对这些资料的反演，阐明了中-β尺度系统的维持过程。对不同积云参数化方案进行了敏感性试验，并以琵琶湖流域为例对SiBUC(包括城市冠层的简单生物圈模式)进行了收缩和校核。5)提出了利用常规地表气象资料估算地表热湿通量的方案。较少

Huaihe River Basin is located where the significant subtropical front, so-called the Meiyu (Baiu) front, stagnates in early summer. Floods and drought occur very often there. HUBEX (Huaihe River Basin Experiment) is one of the sub-project of GAME (GEWEX Asian Monsoon Experiment) and will be carried out from 1996 fiscal year to clarify the water cycle around the basin and its variation toward the establishment of predictability of the floods and the drought there. The present research project was carried out in 1995 fiscal year to clarify and their mechanisms by collaborating between the meteorologists and the hydrologists in Japan and China, as a pilot study of HUBEX.In the HUBEX,we will make intensive field observations in 1998, such as intensive rawinsonde observation for input the regional 4-dimensional data assimilation, three Doppler Radars observation by the Japanese side for producing the Radar-Raingauge Composite Data and for retrieval of thermodynamic fields of meso-beta-scale … More cloud systems, special field observations on interaction processes between land-surface and atmosphere including hydrology, and construction of the coupled meso-scale atmosphere and land-surface model.The present study examined the above mentioned items with use of the data available so far, including the pilot analysis of the case in summer of 1991 when the big flood occurred in the Huaihe River Basin The survey of data and informations was also made with visit of the basin by the Japanese scientists. These results and the future problems were summarized at the HUBEX workshop in Nagoya in March 1996. Main finding are as follows.1) In the flood period in 1991, not only large moisture inflow from the south into the basin persisted, but also effective macro-scale convergence (outflow from the northern boundary was very small) was also remarked. Contribution of local evapotranspiration to the areal precipitation was not so small even in that period.2) Cumulonimbus clusters with remarkable diurnal variation (maximum in the evening) was observed in the several regions adjacent to the Baiu frontal zone in summer of 1979. The role of the surface heating suggested to be rather different among these regions.3) With use of the Doppler Radar observation data together with the conventional ones around the Japan Islands in July 1988, maintenance process of a meso-beta-scale system was clarified by the retrieval of these data. Sensitivity test of the different cumulus parameterization was made for that case.SiBUC (Simple Biosphere Model including Urban Canopy) was contracted and checked by applying for the Biwa Lake basin. The distributed hydrological model, which can predict the river discharge, was also tried to be improved.5) Scheme for evaluating the surface heat and moisture fluxes over land with use of conventional surface meteorological data was contracted. Less