Climatological Characteristics and Long-Term Trend of Relative Humidity in Wuhan

Based on the homogeneity test and correction of the relative humidity series, climatological characteristics and long-term trend of relative humidity in the urban area of Wuhan are analyzed. The results showed that:(1) The non-homogeneity deviation caused by relocated stations in the relative humidity series is prodigious, and the deviation caused by relocation of Wuhan station in 2010 is 8%. (2) Annual average relative humidity in the urban area of Wuhan remains high, and the values vary between 75%-85% with the highest value occurring at Wuhan station. (3) The relative humidity gradually increases from January to June, and then begins to decrease slowly after reaching its peak value in June. Monthly differences are pretty small with the values within 0.1%-2.5%. Seasonal characteristics of relative humidity in the urban area of Wuhan show that the RH is the highest in the summer and lowest in the winter during the whole year. (4) From 1961 to 2015, the average relative humidity in the urban area of Wuhan urban area exhibited a long-term decreasing trend, and the linear trend was accelerated after the 1990s. (5) In the past 55 years, time series of average relative humidity in the spring, autumn, and winter all show declining trends in varied degrees, of which the trend in the spring is more obvious, and a significant rising trend is found in the summer. However, the annual and seasonal means are showing a significant downward trend after 1991.