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Lanzhou University (兰州大学) 2015

Enhanced Arid and Semi-arid Warming Over Mid-high Latitudes of Northern Hemesphere

季飞

  • Titre : Enhanced Arid and Semi-arid Warming Over Mid-high Latitudes of Northern Hemesphere

Auteur : 季飞

Grade : Doctoral Dissertation 2015

Université : Lanzhou University (兰州大学)

Résumé partiel
By analyzing the high resolution data from Climate Research Unit (monthly precipitation and mean surface air temperature) version TS3.1, we examined the trends of annual mean surface air temperature as function of climatological mean precipitation. It’s found that the warming was particularly enhanced over the mid-high latitude semi-arid areas of Northern Hemisphere, especially a warming of the winter periods. The warming over semi-arid areas is faster than any other regions and contributes most to the global warming. From this perspective, we define a new trend by the spatial-temporally multidimensional ensemble empirical mode decomposition (MEEMD) method, diagnose the evolution of global land surface air temperature trend in the past century, analyze the temporal and spatial characteristics of dry/wet variation at the surface of North America and Eurasia, and their correlations with the enhanced warming. At the end of this study, we define a Modulated Annual Cycle (MAC) of land surface air temperature at each grid point, then we study the evolution of MAC trend, and characteristics of the changes of MAC under different timescales, on which basis we evaluate the correlations between MAC changes and the enhanced arid and semi-arid warming over the mid-high latituds of Northern Hemisphere. The main results are summarized :(1) The entire globe is warming from 1900 onward. The noticeable warming first started around the regions circling the Arctic and subtropical regions in both hemispheres. But the largest warming to date has been at the northern mid-high latitudes which include most of the arid and semi-arid regions, Asia, Europe and North America have been experiencing the largest warming since 1900. Before 1950, there were both moderate warming and weak cooling regions. The cooling regions shrank and most of them turned into warming regions with an accelerated pace of warming over the next three decades. By 1980, except for the weak cooling in the northern tip of Greenland and in the vicinity of the Andes, almost all the global land had been warming.

Mots clés : arid and semi-arid regions ;evolution of SAT trend ;dry/wet variation ;modulated annual cycle ;multi-timescale ;

Présentation (CNKI)

Page publiée le 10 avril 2022