THE ISSUES IN THE IMPACT STUDY OF CLIMATE CHANGE ON THE TERRESTRIAL HYDROLOGICAL CYCLE

Abstract

The terrestrial branch of water cycle is mainly influenced by the climate and human activities, the interaction between these elements and hydrological process as well. With population growth and socio-economic development, the impact of human activities such as land use change, water use consumption and ecosystem environment change will be increasing. Recently, in some river basins located in North China, the impact of human activities such as groundwater overexploitation, irrigation loss and evaporation from reservoirs is exceeding the impact of climate variability and climate warming on terrestrial hydrological cycle. The changing terrestrial hydrological cycle leads to decreasing runoff in short and decadal time scale. The water and heat exchanges between land and atmosphere created by either nature or anthropogenic sources are important not only to atmosphere, but also bringing impact to the outcomes of soil moisture, evaporation and runoff directly. Having reviewed the above mentioned, the paper discussed the weakness of ongoing method in the study of climate change impact on hydrological cycle. Being one way from outputs of GCM as the climatic scenarios input to the hydrological model, the change in terrestrial hydrological cycle caused by climate warming and human activities can hardly be involved in the feedback to atmosphere. Considering the large contribution of land surface evaporation in precipitation over land, it thus leads to inaccurate rainfall prediction and incorrect describing the change of land surface hydrological cycle as well. Nowadays, both climatologists and hydrologists from geophysical science group have gained successfully in the study on land surface model in GCM and macroscale hydrological models respectively, which are two aspects of compensation each to other in describing the land surface hydrological cycle and will provide the possibility of coupled hydro-climate model in the future study of climate change impact. The human activities make additional difficulties to land surface parameterization. How to improve the description of terrestrial hydrological cycle in the changing environment from climate warming and intensive human activities is still the challenge for coupled hydrology climate models.