Analysis of Dry/Wet Variations in the Poyang Lake Basin Using Standardized Precipitation Evapotranspiration Index Based on Two Potential Evapotranspiration Algorithms

Weilin Liu,Lina Liu

doi:10.3390/w11071380

Abstract

Global warming has resulted in unevenly distributed changes in precipitation and evapotranspiration, which has some influence on dry/wet conditions, thus exerting a tremendous impact on national life and the social economy, especially agricultural production. In order to characterize the dry/wet variations in the Poyang Lake basin during 1958–2013, based on the potential evapotranspiration (PET) estimated by the Thornthwaite (TH) and Penman–Monteith (PM) formulas, two types of Standardized Precipitation Evapotranspiration Index (SPEI), namely SPEI_th and SPEI_pm, were calculated in this study. The characteristic of dry/wet variations in the Poyang Lake basin was analyzed and a comparative analysis of two SPEIs was conducted. The results indicate that both SPEI series showed a wet trend in the Poyang Lake basin on an annual scale as well as seasonal scales during 1958–2013, except for spring and autumn. A drying trend was observed in spring, while in autumn, the dry and wet conditions in two SPEIs had opposite trends. However, all trends from two SPEIs were not significant, except for summer SPEI_pm. Meanwhile, significant positive correlations were detected between precipitation and two SPEIs, with the correlation coefficients above 0.95, whereas negative correlations were detected between PET and two SPEIs, with the correlation coefficients ranging from −0.17 to −0.85. This indicates that precipitation was the main climatic factor to determine change in dry/wet conditions in the Poyang Lake basin. Although there were obvious differences between the accumulated values of the Penman–Monteith-based PET (ET_pm) and Thornthwaite-based PET (ET_th), trends in the SPEI_pm series were generally consistent with those in the SPEI_th series, revealing that the method for PET calculation was not critical to the change in dry/wet conditions. Moreover, the results of the conditional probability of SPEI_pm and SPEI_th show that both SPEI_pm and SPEI_th could detect wet or dry events that were identified by SPEI_pm or SPEI_th.

Highlights

According to the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC), global warming is prevailing throughout the world, with the global temperature rising by0.91 ◦ C over the past 100 years, and the global warming trend will continue [1]
3- and time scales1958–2013 were calculated precipitation and two sets of potential evapotranspiration (PET) data, in which PET was estimated by the TH and FAO56 PM
Obtain the overall Standardized Precipitation Evapotranspiration Index (SPEI) values of Poyang Lake basin, using the precipitation and PET averaged over all formulas, respectively

Summary

Introduction

According to the fifth assessment report of the Intergovernmental Panel on Climate Change (IPCC), global warming is prevailing throughout the world, with the global temperature rising by0.91 ◦ C over the past 100 years, and the global warming trend will continue [1]. Changes in precipitation and evapotranspiration will affect the balance of the surface water budget. It is of great importance to further study the characteristics of dry and wet variations for efficient water resource management and adaptation strategies development of climate change. With global warming, variations in evapotranspiration caused by remarkable changes in surface meteorological factors, such as temperature, have had an important impact on dry and wet conditions over the past several decades [16,17]. The indicators constructed by the single variable of precipitation cannot reflect the influence of warming or cooling on dry and wet conditions, precipitation is still an important factor determining the dry and wet changes of the surface [18]

Objectives

Methods

Discussion

Conclusion