午夜欧美大片免费观看,欧美激情综合五月色丁香,亚洲日本在线视频观看,午夜精品福利在线

Based on monthly average soil temperature at the depths of 0 to 40 cm and the maximum and minimum 0 cm temperature from 1961 to 2011 and monthly average soil temperature at the depth of 80 cm, 160 cm, and 320 cm from 1981 to 2011, using the statistical diagnostic methods such as linear trend analysis, moving 〖WTBX〗t〖WTBZ〗 test and power spectrum, the variation trends and variation periods of average soil temperature, climate abrupt change, and anomalous years in Xi’an are studied.The results show that under the background of global warming, the annual and seasonal soil temperature at various levels, except in the near surface layer, showed warming trends, with the heating rate being 011 to 056 ℃ per 10 years. At the levels of 0 to 20 cm and 160 cm, the average soil temperature rising rate reached its maximum in spring; at the level of 40 cm and 320 cm, the largest was in winter, and at 80 cm that is in autumn; the minimum was in summer for all layers.The annual maximum surface temperature decreased slightly, and the minimum increased obviously; there was periodic variation in the annual mean soil temperature in the layer of 0 to 40 cm with the periods being 23 years and 36 to 46 years, as well as a long term oscillation of 32 years.There appeared abrupt changes in annual mean soil temperature in 1993 or 1994There appeared anomalous high annual mean soil temperature at various levels in the early and middle 2000s, except at 160 cm (no anomalous years) and 80 cm (anomalously low). Anomalous high soil temperature appeared mainly in spring, and anomalous low mainly in summer. The correlation between soil temperature at each depth and air temperature was greater than 082, which shows that air temperature variation is the main factor leading to soil temperature variation.