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Keywords:

  • climate change;
  • trend;
  • climate jump;
  • Three Rivers Source Region

ABSTRACT

Changes observed in nine meteorological variables obtained from the Three Rivers Source Region (TRSR) between 1960 and 2009 were investigated using a fitted linear model, Mann–Kendall test, moving t-test, and Morlet wavelet. Analysis of the regionally scaled annual series from 1960 to 2009 showed that minimum (Tmin), maximum (Tmax), mean (Tmean) air temperature, precipitation (P), potential evaporation (Ep), and sunshine hours (SH) increased while relative humidity (RH) and wind speed (W) decreased. Trends were significant at a 99% confidence level for air temperature and at a 95% confidence level for Ep and W. With the exception of SH, regional scale changes observed in all variables in the past decade (2000–2009) when compared to climate norms (means of all climatic variables) from 1961 to 1990 were consistent with their corresponding linear trends from 1960 to 2009. Tmax, Tmean, and drought index (DI) exhibited one climate jump, Tmin and RH two, and SH, Ep, and W three at a significance level of α = 0.05. On a regional scale, the period from 1986 to 1997 experienced a warmer, drier climate due to higher than average air temperatures, lower P, and higher DI compared to means from 1960 to 2009. The majority of meteorological variables of the TRSR experienced significant (α = 0.05) short periodical cycling between 2 and 5 years. In terms of spatial distribution, seven out of 12 meteorological stations underwent warmer and wetter periods from 1960 to 2009, whereas the other five situated in the southeastern section of the TRSR underwent warmer, drier periods.