| Climate change has become a global issue of common concern, the issues such as droughts, floods, extreme weather and others induced by the climate change have had the negative effects to our lives, so to understand the characteristics of climate change and how to effectively use the climate change, which have the extremely important meanings for guiding our lives. The study area weibei Dryland located in the central of Shaanxi Province is the region's important agricultural base and the fruit industry base, at the same time, the ecological environment of which is a fragile and sensitive region. The ecological environmental degradation and natural disasters from climate change have had a profound and far-reaching impact to the agriculture, water resources, ecological environment and people's lives of Weibei Dryland, and as a major constraint factor to social and economic development of Weibei Dryland.This paper selects the data of the month, quarter, annual precipitation and average temperature from 1961 to 2007 of 11 representative meteorological stations in Weibei Dryland, at the same time, the selected data had been supplemented by consult the yearbooks and other literatures of each region to ensure the completeness and correctness of the data. Based on referring to the available research results about climatic characteristics from predecessors' works, combined with the actual situation of the study area, we have analyzed the temporal and spatial variation characteristics of the temperature and precipitation of Weibei Dryland. Used the methods of the linear estimation tendency, the climate trend coefficient, the anomalous precipitation, the moving average and others, the temperature and precipitation analysis in the time series of the annual and seasonal climate change characteristics are carried out, in addition to, analyzing the variation characteristics of the maximum temperature and the minimum temperature of the study area, In the spatial characteristics analysis, the geodetic coordinates generated by software Geomap3.2 combine with the selected meteorological data, and then the GRID data generated by software Surfer8.0 generate the contours using the contour function of software Surfer8.0, then the generated contours are being into the base map of software CorelDRAW 12 using the coordinates superposition, at last the contours have been drafted after the manual intervention, and then the spatial analysis of temperature and precipitation have been discussed. The main conclusions as follows: 1. the temperature aspects:(1)the annual average temperature of Weibei Dryland in recent 47 years has shown the characteristics that the wavelike rising rate is at 0.24℃per 10 years and the annual average temperatures seem to be more obvious wavelike increasing trend since the mid-80's and similar with the country temperature change trend, the warmer years are mainly concentrated in after 90's. And the analysis indicated that the temperature of abnormal high year is 2006 and the abnormally low year is 1984, compared with the national, abnormally high temperature year is earlier than the national for one year. (2)the temperature tendency rate of four seasons is respectively at 0.33℃/10a in spring, negative 0.04℃/10a in summer,0.17℃/10a in fall and 0.46℃/10a in winter. Mmong them, the greatest rate is in winter which shows the biggest increase range in winter temperatures, the summer's is negative indicating the temperature having a slight downward trend and the spring and the winter for the biggest contribution to climate warming.(3) the downward trend rate of extreme high temperature is 0.11℃/10a while the downward trend rate of extreme minimum temperature is 0.29℃/10a in Weibei Dryland since 47 years. (4) the results of the temperature spatial analysis in study area indicate:The northern area and the area around Chunhua are the areas of the temperature more significant increase that the trend is well represented in the spring, autumn and winter, similar variation tendency with the annual average temperature. The difference is that the temperature change range in the northern and central of the study area is less, and showing an increasing trend, oppositly, the temperature change range in the southern is bigger, and showing a decreasing trend.2. the precipitation aspects:(1)the reducing rate of annual total precipitation in Weibei Dryland is 12.49mm per 10 years, the rate of annual total precipitation in study area-induce about 58.7mm, similar with rate of the national's, and the reduce trend is very significant.(2)Seasonal precipitation tendency rate:the maximum rate of fall precipitation (-14.6 mm/10a), followed by spring (-10.63mm/10a), the minimum of winter (1.8 mm/10a) and with a very weak rate, the summer precipitation rate is 9.8 mm/10a. Mmong them, the precipitation in summer and winter is an increasing trend, while in spring and autumn precipitation is decreased.(3)the results of the precipitation spatial analysis in study area indicate:the southern is the area with the most significant precipitation rate in spring, summer and winter, and with the smallest rate of annual total precipitation. The season with the larger rate in the northern is autumn and the same trend as the total precipitation rate. The spring precipitation rate is similar with the summer's, and the autumn's and the annual's trend similar to the total in the central region.The temperature and precipitation of the mutation test analysis in Weibei Dryland using Mann-Kendall method indicate:the mutation from the low value to the high value of the annual average temperature in study area maybe occur in 1997 and the mutation from the low value to the high value of the spring maybe occur in 1999, the summer temperature had a large transition in 1966 and maybe have a mutation phenomenon in 1972. there was no mutation occurring in autumn temperature, the mutation from the low value to the high value of the winter temperature maybe occur in 1992. However, the precipitation mutation process is much more complex than the temperature's, the total precipitation had no obviously mutation phenomenon, and had several transition phenomenons which mainly occurred in the late 60s, late 70s and mid-80s. There may be three mutation phenomena in the spring precipitation, no mutation phenomenon occurring in summer precipitation, the mutation from the high value to the low value of the autumn precipitation maybe occur in 1967-1969, while the mutation of the winter precipitation trend was more complexity than the other seasons'.The analysis of the climate change character istics in Weibei Dryland indicated that the climate in this area present the warming and drying trend, and the trend of climate would have a effect on the agriculture, especially for the planting which are very sensitive to the climate change, more attention should be paid, further this research would have some decision-making roles on the economic development for this area, but also there would provide an typical area example for the climate change characteristics study of other areas of the country. |
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