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Observational inter-annual variations in the seasonal freezing depth across China during 1965–2013

Kun Xia*, Bin Wang

*Corresponding author:

ABSTRACT: Long-term changes in the soil freezing-thawing depth are an important indicator of climate change. Based on data from 764 meteorological stations across China, we analysed the climatology and variability in the seasonal frozen depth (SFD) during 1965–2013 and investigated the connections among changes in the SFD, meteorological factors (temperature, precipitation, snow depth, freezing index and thawing index) and atmospheric circulations (the East Asian winter monsoon (EAWM) and the North Atlantic Oscillation (NAO)) in each of four sub-regions: northwestern China (W), the Tibetan Plateau (TP) and eastern China (E1 and E2). In addition, the contributions of two different factors to the variation in the SFD were quantified. The results reveal that during 1965–2013, the SFD noticeably changed from positive to negative anomalies in approximately 1988 for all the studied regions, exhibiting a significant decreasing trend, and the rates of decrease are 0.23±0.03 cm/yr, 0.08±0.01 cm/yr, 0.26±0.03 cm/yr, and 0.24±0.03 cm/yr in E1, E2, W and the TP, respectively. The air freezing index is strongly correlated with the SFD in the E2 and TP regions, and it accounts for 82.6% and 84.9% of the change in the SFD, respectively. Snow depth shows a significant association with the variability in the SFD just in the E1 region. Compared to the NAO, the EAWM plays an important role in changes in the SFD. These findings have implications for further understand the mechanisms of cold environment changes across China.