1961-2014年华北平原二十四节气热量资源的时空分布变化分析

通过推算历年二十四节气的划分时间,利用华北地区63个气象站点1961-2014年逐日地面观测资料,分析每个节气期间平均气温、最高/低气温、≥0℃积温的线性变化趋势;基于春分、秋分日计算分析研究区各站点无霜期的终/始日与春分/秋分日差值和无霜期≥0℃积温的时空分布变化特征.结果表明,华北平原气温(平均、最高、最低)最高为大、小暑节气,最低为小、大寒节气.无霜期由北向南递增,终霜日平均发生在春分节气,沿纬度方向由南向北推迟,初霜日平均发生在霜降节气,沿纬度方向由南向北提前.1961-2014年华北地区二十四节气内热量资源(气温、≥0℃积温)均呈现上升趋势,冬春季的节气升温幅度大于夏秋季.雨水节气平均气温、最高、最低气温增幅在二十四节气中最大,分别为0.63、0.74和0.53℃·10a-1.最低气温增幅大于平均气温和最高气温,对气候增暖的贡献较大.近54a来研究区无霜期内≥0℃积温平均增加442.8℃·d.气候变暖同时延长了华北地区的无霜期,研究区无霜期气候倾向率平均为3.9d·10a-1,该变化由初/终霜日的变化共同作用引起,且春季终霜日提前(气候倾向率为2.1d·10a-1)比秋季初霜日推迟(气候倾向率为1.9d·10a-1)更明显.

Spatiotemporal Distribution and Variation of Heat Resources in the Twenty-Four Solar Terms in North China Plain over the Period 1961-2014

By calculating the dividing time of the twenty-four solar terms in each year, average values and climate trends for temperature (average temperature, maximum and minimum temperature) and accumulated temperature over 0℃ in each solar term were analyzed based on the observed data from 63 meteorological stations in North China Plain from 1961 to 2014. Spatial distribution of the deviation days between last / first frost date and Vernal Equinox/Autumnal Equinox date, as well as accumulated temperature over 0℃ in frost-free period and their changing rates, were also studied. Results showed that the Great Heat and Slight Heat solar terms exhibited the largest heat resources, on the contrast, the Great Cold and Slight Cold solar terms exhibited the smallest heat resources. The days of frost free period increased from north to south in the study area. The last frost date averagely occurred in the Vernal Equinox, postponed from south to north along the latitude direction, and the first frost date occurred in the Hoar-frost Falls on the average, advanced from south to north along the latitude direction. Each solar term in North China Plain in 1961-2014 showed a significant increasing trend for heat resources, and the highest warming rate occurred in the Rains solar term with average temperature, maximum and minimum temperature increasing trend values 0.63, 0.74 and 0.53℃·10y-1, respectively. The minimum temperature had greater contribution to climate warming than maximum temperature because of its higher increasing trend. Accumulated temperature over 0℃ in frost-free period in the study area increased by 442.8℃·d in recent 54 years. Climate warming has also prolonged frost free period in North China at increasing trend 3.9d·10y-1 due to the changes in both the first and last frost date, and the advanced last frost date in spring (climate tend rate 2.1d·10y-1) was more significant than the delayed first frost date in autumn (climate tend rate 1.9d·10y-1) .