近56年乌鲁木齐市青草期水热气候条件时空变化

Spatio-temporal change in water and thermal climatic conditions during the green grass season in the Urumqi area from 1961 to 2016

基于乌鲁木齐市及其周边10个气象站1961-2016年逐日气象资料,以日平均气温稳定≥5℃的初、终日分别作为天然草地青草期初、终日指标,使用线性趋势分析以及ArcGIS的空间插值技术对近56年乌鲁木齐市青草期初、终日、青草期日数、平均气温、≥5℃积温、降水量和干湿指数等水热气候要素的时空变化规律进行了分析。结果表明,乌鲁木齐市天然草地青草期初日的空间分布具有"平原荒漠类草地早、山地草原和草甸类草地晚"的特点;青草期终日与初日相反,呈现"平原荒漠类草地晚、山地草原和草甸类草地早"的特点;青草期日数、平均气温、≥5℃积温均为"平原荒漠类草地多(高)、山地草原和草甸类草地少(低)",青草期降水量表现为"山地草甸和山地草原多、高寒草甸和平原荒漠类草地少",青草期干湿指数随海拔的升高而增大。1961-2016年,乌鲁木齐市青草期初日以每10年-0.424d的倾向率呈不显著(P>0.05)的提早趋势,青草期终日以1.455d·10a-1的倾向率呈显著(P<0.01)的推迟趋势,青草期日数、平均气温、≥5℃积温、降水量以及干湿指数分别以每10年1.879d、0.16℃、61.14℃·d、6.93mm和0.015的倾向率呈显著(P<0.05)的增多或上升趋势,但上述变化具有区域性差异。近26年(1991-2016年)较前30年(1961-1990年),除青草期初日提早幅度的空间差异不明显外,青草期终日的推迟幅度以及青草期日数、平均气温、≥5℃积温等要素的增多幅度表现出"平原荒漠类草地多、山地草原和草甸类草地少"的特点,青草期降水量和干湿指数增大幅度的空间分布呈现"平原荒漠类草地少、山地草原和草甸类草地多"的特点。

The fundamental spatio-temporal change characteristics of the start and end dates,duration,average temperature,accumulated temperature of≥5 ℃,precipitation,and arid-wet index of the green grass season were analyzed by using linear regression and mixed spatial interpolation technology based on ArcGIS,using the daily meteorological data collected from 10 meteorological stations in Urumqi City and its surroundings area from 1961 to 2016.The first and last dates when the daily mean temperature were stably≥5℃in a year were taken as the start date and end date of the growth of natural pasture and the green grass season,respectively.The main results showed that the spatial distribution of the above-mentioned climate factors were clearly varied among several observed locations in the Urumqi area.Generally,the start dates of the green grass season were earlier in the plain desert pastures than on the mountain grasslands and meadows.However,the end dates of the green grass season were later on the plain desert pastures than on the mountain grasslands and meadows.Several thermal elements,such as duration,average temperature and≥5 ℃ accumulated temperature of green grass season were higher on the plain desert pastures than on the mountain grasslands and meadows.Precipitation in the green grass season was higher on the mountain grasslands and meadows than on the alpine meadows and plain desert pastures.The arid-wet index of the green grass season increased with altitude.In the past 56 years,the start dates of the green grass season had shown an inconspicuous（P〉0.05）advancement at the rate of-0.424 d·10 a^-1,and the end dates have been significantly（P〈0.01）delayed,at the rate of 1.455 d·10 a^-1.At the same time,the duration,average temperature,accumulated temperature of≥5 ℃,precipitation,and arid-wet index of the green grass season significantly（P〈0.05）increased at the rate of 1.879 d·10 a^-1,0.16 ℃·10 a^-1,61.14（℃·d）·10 a^-1,6.93 and 0.015 mm·10 a^-1,respectively.However,these changes had regional differences.Comparing the last 30 a（1961-1990）with the most recent 26 a（1991-2016）the earlier days of the start of the green grass season showed little regional difference,and a greater increase in the delayed days of the green grass end dates,green grass season duration,average temperature,accumulated temperature of≥5℃ was observed on the plain desert pastures than on the mountain grassland and meadow,but the increments of precipitation and arid-wet index of the green grass season were greater on the mountain grasslands and meadows than on the plain desert pastures in the Urumqi City.