Climate variability in the northern and southern Altai Mountains during the past 50 years.

The Holocene drying trend in the northern Altai Mountains and the wetting trend in the southern Altai Mountains inferred from the paleoclimatic studies indicated it is needed to understand the modern climatic characters in this region. However, a detailed analysis of modern climate variations in the northern and southern Altai Mountains is lacking. Here, we investigate the monthly temperature and monthly precipitation data from seventeen meteorological stations during 1966-2015 in the northern and southern Altai. The result shows that temperature increases significantly in the northern (0.42 °C/10 yr) and in the southern (0.54 °C/10 yr). The precipitation decreases insignificantly (-1.41 mm/10 yr) in the northern, whereas it increases significantly (8.89 mm/10 yr) in the southern. The out-of-phase relationship of precipitation changes is also recorded at different time-scales (i.e., season, year, multi-decades, centennial and millennial scales), indicating the Altai Mountains are an important climatic boundary. Based on the analysis of modern atmosphere circulation, the decreased precipitation in the northern corresponds to the decreasing contribution of 'Northern meridional and Stationary anticyclone' and 'Northern meridional and East zonal' circulation and the increased precipitation in the southern are associated with the increasing contribution of 'West zonal and Southern meridional' circulation.