Temporal-spatial variability of modern climate in the Altai Mountains during 1970-2015

Zmeinogorsk to 0.75˚C/decade in Fuyun between 1970 and 2015. The rates in majority of sta- tions fall spanning from 0.20 to 0.40˚C/decade, that in four stations waved between 0.40 and 0.60˚C/decade, and that in two stations fluctuated between 0.60 and 0.80˚C/decade. The fastest increased rate of MAT was observed at Fuyun and Qinghe in the southeastern Altai Moun- tains. All stations significantly increased (from 0.43 to 0.84˚C/decade) in spring, larger than the increased trend of MAT. The rising rates in summer varied spanning from 0.05 (Altai and Qinghe) to 0.61 (Fuyun)˚C/decade, while the insignificant changes of some stations (i.e., Zmeinogorsk, Soloneshnoe, Altai and Qinghe) were observed. In autumn, except Soloneshnoe (0.04˚C/decade, P>0.05) station, others showed a warming rate ranging from 0.20 to 0.65˚C/ decade. In winter, a decreasing trend of temperature (−0.12˚C/decade) with no significance was detected at Zmeinogorsk. The winter air temperature at Ust-Coksa, Fuyun and Khovd experienced increasing trends which exceeded the 95% confidence level. The rates insignif- icantly increased between 0.02 and 0.20˚C/decade in other stations. As a whole, the temporal and spatial rates of temperature were varied in annual and seasonal scale and the warming cli- mate was found in the whole Altai Mountains during the past decades. Precipitation trend characteristics Fig 4 showed the trends of MAP and seasonal precipitation during 1970–2015 in the Altai Mountains. An increased rate about 4.82 mm/decade (P>0.05) was detected for MAP (Fig

4A). The MAP in 2015 increased 21.69 mm comparing with that in 1970. The changes of sea- sonal precipitation all did not exceed the significance level of 0.05 and their rates were 2.10 mm/decade in spring, 1.60 mm/decade in summer, 0.25 mm/decade in autumn and 0.93 mm/ decade in winter, respectively (Fig 4B–4E). The spatial changes of precipitation in annual and seasonal scale were presented in Fig 5. Four stations (Zmeinogorsk, Kyzyl-Ozek, Kosh-Agach and Olgiy) had decreasing trends of MAP with significant levels (P<0.05) and their rates were −4.68, −8.66, −7.29 and −4.99 mm/ decade, respectively. Although the positive trends of MAP were detected among other stations, the significant trends were only found in Soloneshnoe, Habahe, Aletai, Fuyun and Qinghe and their rates ranged from 1.14 (Khovd) to 17.97 (Soloneshnoe) mm/decade. In spring, two Fig 3. Spatial trends for annual and seasonal temperature during 1970–2015 over the Altai Mountains. https://doi.org/10.1371/journal.pone.0230196.g003 PLOS ONE Modern climate characters in the Altai Mountains PLOS ONE | https://doi.org/10.1371/journal.pone.0230196 March 17, 2020 5 / 15