Spatio-Temporal Characteristics of Dry-Wet Conditions and Boundaries in Five Provinces of Northwest China from 1960 to 2020

Miao Wang,Lu Liu,Wenyang Si,Puxing Liu,Xuemei Qiao

doi:10.3390/atmos12111499

Abstract

The study of dry-wet climate boundaries in the context of climate warming is of great practical significance for improving the environment of ecologically fragile zones and promoting economic and natural sustainable development. In this study, based on the daily meteorological data of 110 stations, using the wetness index, empirical orthogonal function decomposition, regime shift detection test, Fourier power spectrum, and Kriging interpolation, the researchers analyzed the spatiotemporal characteristics of dry-wet conditions and boundaries in five provinces of Northwest China from 1960 to 2020. The results showed that the overall wetness index increased in the past 61 years, but with significant internal differences, among which the western and central climate tended to be warm and wet, and the eastern tended to be warm and dry. The annual wetness index changed abruptly in 1986 with cycles of 3.61 a, 7.11 a and 8.83 a. The mutations occurred correspondingly in spring, summer, autumn, and winter in 1972, 1976, 1983, and 1988, with periods of 3.88 a and 4.92 a, 2.18 a and 2.81 a, 2.15 a, and 2.10 a, respectively. The dry-wet climate boundary has fluctuated markedly since 1960. The extreme arid and arid regions boundary shifted southward and shrank in size until the extreme arid region disappeared in the 2010s. The arid along with semi-arid regions and semi-arid in addition to semi-humid regions boundaries both have two boundary lines, and show the shift of the northwestern boundary to the southeast and the southeastern boundary to the northwest, with the area of the arid together with semi-arid regions shrinking significantly by 5.64%, simultaneously, the area of the semi-humid region area expanding significantly by 84.11%. The boundary of semi-humid and relatively humid regions, and the boundary of relatively humid and humid regions all shifted to the southeast, moreover, the area of the relatively humid region and humid region shrank significantly by 12.08%. The expansion of semi-humid region and the contraction of other climate regions are characteristics of the dry-wet climate variability in five provinces of Northwest China. The area of the three arid climate zones dwindled by 9.61%, and the area of the three humid zones extended by 39.01%. Obviously, the climate inclined to be warm and humid in general.

Highlights

The empirical orthogonal function (EOF) combined with the North test are used to decompose the wetness index of 110 meteorological stations in five provinces of Northwest China from 1960 to 2020 [38], ArcGIS and Origin are deployed to plot the spatial distribution of the EOF decomposition and the corresponding temporal weight coefficients (Figure 2)
The annual wetness index in five provinces of Northwest China mutated in 1986 and scaled the heights of the relative wetness with periods of 3.61 a, 7.11 a, and 8.83 a, which are consistent with the cycles of atmospheric circulation and El Niño
1988, with periods of 3.88 a and 4.92 a, 2.18 a and 2.81 a, 3.61 a and 2.10 a, respectively, which are aligned with the period of atmospheric circulation

Summary

Introduction

The abnormal climate change events caused by global warming have become an issue of great concern all over the world. It has an impact on the dry-wet climate conditions, which will lead to a change in the dry-wet climate boundaries, the fluctuation of which visually reflects the dry-wet climate variability of a region. Thornthwaite [4] put forward the P-E index to estimate the possible evapotranspiration based on temperature, the sunshine hours in 1931, and revised the P-E index in 1948 and 1955. Holdridge [5] raised the calculation of the probable evapotranspiration rate (PER) based on the precipitation and plant bio-temperature in 1947.

Methods

Results

Discussion

Conclusion