中国年均地温的估算方法研究

Methods for Estimation of Mean Annual Soil Temperature in China

年均地温是土壤重要的物理性质,对区域农业生产有着重要意义。对中国1981—2010年间895个气象站的地面气候资料进行整理,按全国一级标准耕作制度分区分析。结果表明:各区5~40 cm内各深度年均地温均高于相应气象站点的年均气温。同一分区内,各气象站点5~40 cm年均地温随深度增加未表现出相同的变化规律;不同深度的年均地气温差平均值在5~20 cm深度范围内变化≤0.1℃,在20~40 cm深度范围变化较大,个别分区达0.4℃。各分区之间比较,5~40 cm年均地气温差平均值存在地域差异性:自北向南,年均地气温差平均值表现为先减小后增加的变化规律;自东向西,纬度接近的分区年均地气温差平均值逐渐增大;不同分区年均地气温差平均值的变化较大,20 cm深度为1.4~3.9℃,40 cm深度为1.1~4.3℃。利用回归方程法和年均地气温差平均值法,在各标准耕作制度一级区分别建立年均地温估算公式,回归方程法的准确性高于年均地气温差平均值法,但青藏高原区和内蒙古高原及长城沿线区的估算公式未达到很好的估算效果。对各分区5、10、15、20和40 cm年均地温观测数据完整的262个气象站的数据进行分析表明,5~40 cm深度范围内,多数分区年均地温每5 cm变化量的均值≤0.1℃,20~40 cm深度的变化量更小。对于单一估算点,其40 cm和50 cm年均地温的最大差距≤0.4℃,所以,在中国土壤系统分类中,可以考虑用40 cm的地温代替50 cm的地温。

【Objective】Mean annual soil temperature is an important physical property of soil and of great significance to regional agricultural production.The purpose of this study is to explore regional characteristics of mean annual soil temperature relative to soil depth in China,and define an applicable method for accurate estimation of mean annual soil temperature.【Method】Ground meteorological data accumulated in the 895 meteorological stations in China during the period from 1980 to 2010 were collated and mean annual soil temperature analyzed based on zoning by Grade I standard farming system in China.Two methods were tested for estimation of mean annual soil temperature in China.The first one is a multiple regression equation established on the basis of SPSS Statistics 17.0 for regression of mean annual soil temperature with mean annual air temperature,latitude,longitude and altitude,and the second one is to estimate mean annual soil temperature based on the mean annual air temperatures and regional mean air temperature already available.【Result】 Results show that the mean annual soil temperature in various soil layers 5 to 40 cm in depth in all the regions was higher than the mean annual air temperature monitored at the meteorological stations of corresponding regions.In the same meteorological zone,regardless of meteorological stations,mean annual soil temperature varied with soil depth within 5~40 cm,but the variation did follow the same trend.Mean annual soil and air temperatures differed in the range of ≤0.1℃ in all the soil layers from 5 to 20 cm in depth,but varied more,significantly in the soil layers from 20 to 40 cm in depth,and the difference in some individuals zones reached 0.4℃.Comparison between meteorological zones shows that the difference between mean annual soil and air temperatures varied regionally,that is,declining first and then rising from north to south,and gradually increasing from east to west;in some zones the difference varied in the range of 1.4~3.9℃at 20 cm in soil depth and in the range of1.1~4.3℃ at 40 cm in soil depth.Compared with the estimation model based on zoning by Grade I standard farming system,the regression equation was higher in accuracy,but it was not so significant in the Qinghai-Tibet Plateau,Inner Mongolia and zones alongside the Great Wall.Analysis of the data of mean annual soil temperatures in soil layers at 5,10,15,20 and 40 cm in depth at all the 262 meteorological stations that had kept complete data shows that in the soil layers 5~40 cm in depth,mean annual soil temperature varied in the range of ≤0.1℃ at 5 cm and much less in the soil layers 20~40 cm in depth.Based on a single estimation site,the estimated mean soil temperature in the soil layer at 50 cm differed from the value at 40 cm to the extreme by ≤0.4℃.【Conclusion】The estimation of mean annual soil temperature using the mean annual soil and air temperature difference method is quite low in accuracy and the method is recommended for use only in the Middle and Lower Reaches of the Yangtze River,Jiangnan region,Sichuan Basin and Yunnan-Guizhou Plateau,and the regression equation method is quite high in accuracy in all the zones of Grade I standard farming system,except for QinghaiTibet Plateau,Inner Mongolia and zones alongside the Great Wall.In farming zones where the distribution of meteorological stations is dense and little in elevation variation,the regression equation based model is the more higher in accuracy with little variation in mean annual soil temperature in the soil layer 40~50 cm in depth.Therefore,it is advisable to use the soil temperature at 40 cm to replace that at 50 cm in the prevailing ＂Chinese Soil Taxonomy＂.