Researchers Reveal Snow Phenology in the Tienshan Mountains of Central Asia

Snow cover is a major component of the cryosphere. Satellite measurements and surface observations provide evidence that the spatial extent of annual snow cover in the Northern Hemisphere has undergone significant reductions in recent decades. The Tienshan Mountains provide the source for the glacier and snow cover meltwater that supplies the major rivers in Central Asia. Previous studies mainly focused on changes in the extent and depth of snow cover, while spatial and temporal patterns of snow cover start and melt dates for the Tienshan Mountains have received less attention. Moreover, the combined effects of climate and topography on snow phenology have not yet been described in detail.

Researchers from Xinjiang Institute of Ecology and Geography of Chinese Academy of Sciences use the MODIS daily snow cover fraction products to produce daily cloud-free snow cover products over the Tienshan Mountains for each hydrological year during 2002/03-2017/18. The spatial and temporal patterns of SCD, SOD, and SED in different elevation zones were analyzed and attributions of the driving factors of snow phenology anomalies were identified using climate data.

Research indicates: (1) For the entire Tienshan region, SCD showed a non-significant increasing trend at a rate of 0.31 day per year (p>0.05), associated with both earlier SOD (-0.25 d/a, p>0.05) and SED (-0.001 d/a, p>0.05). (2) Trend analysis shows that SCD decreases below 1,500 m a.s.l., but increases between 1,500-4,000 m a.s.l., indicating SCD at high and low altitudes show a contrasting response to climate change. Meanwhile, the increase of SCD in the north-facing areas is greater than that in the south-facing areas. (3) Temperature plays a more important role than precipitation in SOD and SED changes. The temperature decline in mid-latitude was attributed to changes in the Arctic system and the recent Pacific Ocean cooling effect in winter.

Research results entitled Climate and Topographic Controls on Snow Phenology Dynamics in the Tienshan Mountains, Central Asia was published in the Atmospheric Research.

Article link: https://doi.org/10.1016/j.atmosres.2019.104813