Redai dili (Dec 2022)
Analysis of Regional Variation Characteristics and Influencing Factors of Pan Evaporation in the Yangtze River Basin
Abstract
Evaporation is an important component of both hydrological and energy cycles and is very sensitive to climate change. In the context of global warming, rising temperature leads to a series of changes in hydrological factors, such as precipitation, evaporation, soil moisture, and groundwater flow, which have significant impacts on the natural environment, ecosystems, and social economy. Pan Evaporation (PE) is a vital climatic factor for estimating the atmospheric evaporation demand, and its change has been recognized as an integrative indicator of the hydrological response to climate change. Therefore, it is of great theoretical and practical significance to analyze the variation characteristics of PE and its influencing factors for water resource evaluation, hydrological process research, agricultural irrigation, and evaporation monitoring under climate change. The Yangtze River Basin (YRB) is a densely populated and highly developed area that plays an important role in the development of China's national economy. To discuss the variations in PE in the YRB and its main influencing factors, previous studies only divided the basin into upper, middle, and lower reaches based on natural and social factors. However, the area of the YRB is vast, and the PE varies greatly among the different regions of the basin under the influence of terrain and climate conditions. It is not sufficient to discuss the variation characteristics of regional PE from upstream, middle, and downstream. Additionally, most time series remained around 2000 in the existing studies, and the analysis of change characteristics of recent PE time series and its influencing factors have not been reported. Therefore, it is essential to conduct consistent regionalization for PE in the YRB and to identify the factors influencing PE variations in the subregions in recent decades. In this study, the Rotating Empirical Orthogonal Function (REOF) and Fuzzy C-Means clustering algorithm (FCM) were applied to form subregions based on pan observation data from 148 meteorological stations in the Yangtze River Basin during 1980-2017. Then, the variation characteristics and main influencing factors of PE in each sub-region were analyzed using the modified Mann-Kendall test and multivariate stepwise regression analysis. The results are as follows: (1) The first four REOF modes revealed five principal PE anomaly sensitive areas in the basin: southeast Poyang Lake plain, southwest Hengduan Mountain, northern Nanyang Basin, western Sichuan Plateau, and Central Sichuan Basin. Based on these spatial modes, the PE in the basin can be divided into nine subregions. (2) At the annual scale, PE in respective regions shows an increasing trend with the highest rate (111.28 mm/10 a) in the central basin and the lowest rate (12.5 mm/10 a) in the western plateau region. At the seasonal scale, PE in autumn and winter showed an increasing trend in the whole basin, while the variation in PE in spring and summer showed obvious regional differences, and PE in some areas showed a decreasing trend. (3) The main factors affecting the change in PE differ from region to region; however, in most of the sub-regions, PE variations are closely related to the changes in mean temperature and vapor pressure deficit. Our results are conducive to a better understanding of the temporal changes in PE in other regions of the world. In particular, the results can contribute to the development of more efficient methods for modeling and predicting PE variations by focusing on the main influencing factors under changing climatic conditions.
Keywords
