Spatial-Temporal Variations of Temperature and the Cause Analyses in the Yellow River Valley during Recent 50 Years

Spatial-temporal variations of temperature in the Yellow River valley were detailedly analysed by using 142 station observation data from 1961 to 2010. With respect to spatial distribution, the temperature increases from west to east and from north to south. Empirical orthogonal function (EOF) analysis reveals that the principal EOF mode is a consistent warming over the whole valley, with the strongest warming in the upper reaches of the Yellow River 0.40℃ (10 a)^-1. Secondly, the EOF mode shows opposite variations in the eastern and western regions. Thirdly, it shows opposite variations in the southern and northern regions. The warming rate is the highest in winter 0.52℃ (10 a)^-1, and then spring 0.30℃ (10 a)^-1, autumn 0.26℃ (10 a)^-1, and summer 0.14℃ (10 a)^-1. Further analysis reveals that, in addition to the global warming impact, the warming in the Yellow River valley during recent 50 years can be attributed to large-scale interdecadal warming in the mid-1980s and the late 1990s. These two interdecadal warming events occurred synchronously with the interdecadal shifts of the East Asian monsoon.