On the freeze–thaw cycles of shallow soil and connections with environmental factors over the Tibetan Plateau

Changes in the freeze–thaw cycles of shallow soil have important consequences for surface and subsurface hydrology, land–atmosphere energy moisture interaction, carbon exchange, ecosystem diversity productivity. This work examines cycle on Tibetan Plateau (TP) using in–situ temperature observations 0–20 cm layer during July 1982–June 2017. The domain averaged beginning frozen day is November 18 delays by 2.2 days per decade; ending March 9 advances 3.2 number 109 shortens 5.2 decade. Altitude latitude combined could explain spatial patterns annual mean status well. Stations located near 0 °C contour line experienced dramatic changes as seen from subtropical mountain coniferous forest southern TP. Soil completely freezes to 20-cm depth 15 while thaws 10 average. Near-surface displays more pronounced than deeper soil. Surface air strongly influences but snow exerts limited effects. Different thresholds definition lead differences multiple-consecutive-day approach appears be robust reliable. Gridded products resolve pattern observed some extent further improvement needed.