| Hulunbuir forest-steppe ecotone is a China’s existing forest-steppe ecotone with more complete and high research value in large scale ecological ecotone, which is closely related and mutually dependent with well-known Daxinganling forest and Hulunbuir prairie symbiotic zone at the same time.Ecotone with specially natural and geographical characteristics was very sensitive to climate change, so climate change was first shown here. At the background of the study of the Hulunbuir forest-steppe ecotone climate, therefore, it could provide judgment basis for government departments. Besides, it could provide theoretical basis for climate change, ecological planning, disaster prevention, disaster reduction work and so on. Furthermore, it could provide important reference for production practice in agriculture, animal husbandry and forestry. Meanwhile, it lays theoretical foundation on the interdisciplinary research of forest-steppe ecotone in future.We take the Hulunbuir forest-steppe ecotone (46°94’N～51°50’N and118°30’E-122°55’E) as the research area in this study. It illustrates long-term temporal dynamic change rules of the temperature, precipitation, sunshine, evaporation, relative humidity, wind and other meteorological elements through the collection of measured meteorological data, using MATLAB mathematical statistics, Kriging interpolation and wavelet analysis method in the research area and adjacent meteorological stations from1971to2010. It talks about the main weather systems of Hulunbuir forest-steppe ecotone and circulation characteristics ofthe seasons in large scale from circulation background. It also comprehensively reveals of climate background in this research area. The results show that:1) The temperature rose with climate tendency rate of0.10℃/a. The mean temperature of the seasons, the mean maximum and minimum temperatures rose significantly in the study area for near40years. The spring and summer played a great role in the warming in1970s and the lowest temperature climate tendency rate was1.44times of the maximum temperature.2) Precipitation reduced with climate tendency rate for2.29mm/a in the climate change of Hulunbuir forest-steppe ecotone from1971to2010, besides, climate change in warming and dry almost synchronized. Besides, there was clear periodic change in annual amount of precipitation with12-16a and16-20a in the interannual scale and the precipitation will increase relatively in future years;Meanwhile,the daily range of temperature was gradually reduced and summer precipitation reduction mainly resulted from annual rainfall decrease in the study area;Precipitation days with more than or equal to0.1mm will increase by1.4rainy days every10years and precipitation days in other magnitudes will rise slowly. However, the period of rainstorm will remain stable and the rainfall intensity will reduce. The longest continuous days without precipitation will reduce too.3) Daily sunshine hours, sunshine hours for four seasons, average wind speed, and the gale days, annual evaporation, relative humidity, average wind speed and gale days for the four seasons presented decreasing trends on the whole for40years in this study area. The decreasing sunshine duration in spring, summer and autumn was resulted from natural fluctuations in climate. Relative humidity decreased mainly in winter, summer and autumn. The interannual changes were relatively small and the annual evaporation decreased remarkably with the same those of spring and summer. The gale days were most in the spring, and with the average wind speed maximum.4) The Mongolia high pressure mostly influences the winter. The Northeast cold vortex, the Mongolia cold vortex and the Lake Baikal are the main summer precipitation systems, especially the Northeast cold vortex with maximum. The Lake Baikal appears relatively more in spring and autumn and cold wave weather is often caused by the Mongolia cyclones. |
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