Quantifying changes in spatial patterns of surface air temperature dynamics over several decades

Abstract

We study daily surface air temperature (SAT) reanalysis in a grid over the Earth’s surface to iden- tify and quantify changes in SAT dynamics during the period 1979–2016. By analysing the Hilbert amplitude and frequency we identify the regions where relative variations are most pronounced (larger than ±50 % for the amplitude and ±100 % for the frequency). Amplitude variations are interpreted as due to changes in precipita- tion or ice melting, while frequency variations are interpreted as due to a northward shift of the inter-tropical convergence zone (ITCZ) and to a widening of the rainfall band in the western Pacific Ocean. The ITCZ is the ascending branch of the Hadley cell, and thus by affecting the tropical atmospheric circulation, ITCZ migration has far-reaching climatic consequences. As the methodology proposed here can be applied to many other geo- physical time series, our work will stimulate new research that will advance the understanding of climate change impacts.