Temporal And Spatial Variation And Its Influencing Factors Of The Cold Period In Qaidam Basin From 1961 To 2013

There is no doubt that global climate warming, many changes observed since the mid twentieth Century is unprecedented. More noteworthy is that, since at the begin of the 21 st century, extreme low temperature events of Eurasian Continental region where global warming response is most significant happen frequently and have the characteristic of wide affect range, long duration, large intensity and disaster losses, in sharp contrast to the warming background since the 1980 s. Chose Qaidam Basin for the study in this paper, using temperature data of 102 grid points from 1961 to 2013, by calculating of the pentad average temperature, defining cold period, counting the onset and upset pentad of cold period, using the climate tendency rate and spatial interpolation and correlation analysis method, analyzing the spatial and temporal characteristics and mechanism of the onset and upset pentad pentads of the cold period in Qaidam Basin. The main conclusions of this paper are as follows:(1) From the time point of view, in the la st 53 years, the average annual value of the cold period in Qaidam Basin is 37.6P, the cold period showed a shortening trend and tendency rate is-0.704P/10a; the average annual value of the onset pentad is 57.2P, the onset pentad is postponing trend and the tendency rate is 0.333P/10a; the average annual value of the upset pentad is 21.8P, the upset pentad is constantly advancing trend and the tendency rate is-0.37P/10 a. It is in the 1990 s that the cold period shorting,the onset pentad postponing and the upset pentad advancing is most significant, it is in the1960 s that the cold period prolonging, the onset pentad advancing and the upset pentad postponing is the most significant, 1960 s is relatively cool, 1990 s is relatively hot.(2) ArcGIS interpolation showed that the space distribution of the onset and upset pentad and pentads of cold period in Qaidam Basin have significant differences, coupled with the influence of topography, geomorphology, altitude and climate factors, resulting in the spatial distributions showed complexity and disunity, particularly performance from the center of the basin to the surrounding mountains with the increase of altitude, the cold period continue to extend, the onset pentad advance, the upset postpone, forming distinct vertical differentiation characteristics.(3) The onset and upset pentad and pentads of cold period in Qaidam Basin in the last 53 years by Mann Kendall method analysis showed that: It is in 1993 that the Qaidam Basin cold period was significantly shortened, the point mutation; it is in 1990 that the onset pentad postponed, the mutation point; it is in 1996 the upset pentad advanced, the point mutation. The mutation year of the upset pentad and cold period in Qaidam basin compared with the onset pentad postponed 3 and 6years respectively. The onset and upset pentad and pentads of cold period in Qaidam Basin have the vibration characteristics of a multi frequency, quasi periodic. Therein, the cold period exist the cycle of 2, 4, 8 and 12 years; the onset pentad exist the cycle of about 2, 5, 8, 10 and 21 years; the upset pentad exist the cycle of 2, 4 and 10 years. And the three have same short periods, different mesoscale cycle, indicating that the onset and upset pentad and pentads of cold period in Qaidam Basin is not only affected by the atmospheric circulation and El Nino, may also be affected by solar activity.(4) Principal component analysis showed that the main influences of the length of the cold period in Qaidam Basin is altitude and the ?0? accumulated temperature, the annual evaporation and annual amount of radiation has certain influence, but average wind speed for cold period has little effect. With the increase of altitude, the cold period showed a trend of extension with 0.33P/50m; the onset pentad constantly advanced with-0.12P/50m; the upset pentad constantly postponed with 0.2P/50 m. North-south less span in latitude, east-west larger span in longitude something, with increasing latitude, cold period was shortened trend with the linear rate of change for-0.65 P / 0.5 ° N; the onset pentad constantly postponed with the linear change rate for 0.20P/0.5N; the upset pentad continues to advance with linear change rate for-0.48P/0.5N. With the increase of longitude, the cold period was prolonged trend with linear change rate for 0.35P/0.5E; the onset pentad is continuous advance with the linear change rate for-0.15P/0.5E; the upset pentad continue to postpone with linear change rate for 0.20P/0.5E.(5) Remote correlation analysis indicated that the decreases of northern hemisphere and Asia polar vortex area and the weakening of the polar vortex intensity in the 90 s of the 20 th century directly affect that the onset pentad postponed, the upset pentad advanced and cold period shortened in Qaidam Basin. The northern hemisphere subtropical high intensity index in summer was significantly stronger and Indo Burma trough slowing down or stagnation during the eastward process may also affect the length of the cold period. In addition, Vail Huo Jens gram- oymyakon and Eurasian meridional circulation positively correalated with the cold period and the upset pentad and negatively correlated with the onset pentad. R/S show that the last 53 years the shortened trend of the cold period will continue to shorten in the future, the postponed trend of the onset pentad continue postpone in the future, the constantly advanced trend of the upset pentad will contine to advance in the future, and this continuous trend onset pentad is more significant than the upset pentad.