Long-term meteorological trends in the Naiman County of northern China

The annual trends of six meteorological variables (precipitation, evaporation, relative humidity, sunshine hours, and wind-speed and air temperature) were analyzed by wavelet analyses and mutation analyses of Mann-Kendall method based on daily average data observed from Naiman National automatic meteorological station from 1970 to 2014. Results indicated: (1) The ranges of annual mean precipitation, evaporation, relative humidity, daily sunshine hours, wind-speed and air temperature were 213 similar to 567 mm, 1408 similar to 2192 mm, 46%similar to 58%, 7 similar to 9 h, 2.7 similar to 3.8 m/s and 5.8 similar to 8.6 degrees C, respectively. (2) Air temperature and daily sunshine hours had increased by 0.29 degrees C /10a and 0.11h/10a (P<0.01) respectively over 45 years (1970 similar to 2014); (3) Wavelet analysis indicated that wind-speed had a long cycle (26 years); the cycle for daily sunshine hours was somewhat shorter (18 years); evaporation had no obviously cycle; and the other three variables had both shorter and longer cycles. (4) Mutation analysis determined six meteorological parameters that differed from each other, e.g., evaporation had a mutation from low to high occurred in 2001; relative humidity had a mutation from high to low occurred in 2000; daily sunshine hours had a mutation from low to high occurred in 1993.