Homogenized daily relative humidity series in China during 1960-2017

The relative humidity (RH) of atmosphere is a key element for weather/climate monitoring and research. However, RH is not as commonly applied in studying climate change, partly because the observation series of RH are prone to inhomogeneous biases due to non-climate changes in the observation system. A homogenized dataset of daily RH series from 746 stations in mainland China for the period 1960-2017, ChinaRHv1.0 , has been developed. Most (685 or 91.82% of the total) station series were found inhomogeneous with one or more break points. A major breakpoint occurred in the early 2000s for many stations especially in the humid and semi-humid zones, due to the implementation of automated observation across the country. The inhomogeneous biases associated with this change as detected via the Pettitt test and moving-t test are negative for most of the biased station series, suggesting that the early man-observed RH records are systematically larger than the recent automated records in most cases. There are more break points, mainly for the earlier times, detected by using the Multiple Analysis of Series for Homogenization (MASH) method, with biases mainly around -5% and 5%. The regional mean RH series of China shows little long-term trend during 1960-2017 [-0.008 % (10yr)⁻¹] according to the adjusted data, contrasting a significant decreasing trend [-0.414 % (10yr)⁻¹] in the raw data. This dataset can provide a reliable data basis for accurately evaluating the spatial and temporal change characteristics of relative humidity in China in recent decades and is of great significance to some related studies, such as haze, human comfort, and so on. There are two files in this dataset: one is the the homogenized daily relative humidity data and the other one is the corresponding station information. In Version 2.0, the earlier records are adjusted at the mean level and further homogenized to make it easy for users to download and use.