Abstract:

The mean daily temperature of 10 ℃ is the lower limit temperature for the suitable growth of thermophilic crop. The ≥10 ℃ active accumulated temperature (ATT₁₀) is one of the important indexes to measure the heat resources in the main agricultural regions of the Brahmaputra River and its two tributaries over Xizang (BRTX). Based on the daily average temperature data of 9 meteorological stations in BRTX from 1981 to 2022, the linear trend estimation, Pearson coefficient, Mann-Kendall test and R/S analysis method were used to analyze climate change characteristics of ≥10 ℃ boundary temperature (BT₁₀). The results are as follows: (1) With the increase of altitude, the BT₁₀ showed obvious vertical zonal characteristics in the main agricultural regions of BRTX, including the delay of initial date, the advance of the last day, the decrease of duration days and the ATT₁₀. (2) From 1981 to 2022, the initial date of BT₁₀ was advanced by -2.53 d·(10 a)^-1, and the final date delayed with a rate of 3.33 d·(10 a)^-1, the duration days and ATT₁₀ significantly increased with a rate of 5.87 d·(10 a)^-1 and 106.19 °C·d·(10 a)^-1, respectively. Compared with the Qinghai-Xizang Plateau, the magnitude of BT₁₀ change was significantly larger. (3) The 1980s was the decade with the latest initial date, the earliest final date, the shortest duration days and the lowest ATT₁₀ in the past 40 years, while the 21st century was the opposite. (4) The H indexes of the BT₁₀ were all greater than 0.65, indicating that in the future the BT₁₀ will maintain a strong persistence of earlier initial day, later final day, prolonged duration days and increased ATT₁₀. The mutation change of the initial date of BT₁₀ occurred in the early 1990s, while the abrupt change of the final date, duration days and ATT₁₀ occurred in the first decade of the 21st century.

Key words: ≥10 ℃ active accumulated temperature, initial date, final date, duration days, interannual and interdecadal variation, mutation, the Brahmaputra River and its two tributaries in Xizang

摘要：

日平均气温≥10 ℃是喜温作物适宜生长的下限温度。西藏“一江两河”主要农区≥10 ℃积温变化是判断该地区热量资源的关键指标。基于1981—2022年该区域9个气象站点的日平均气温数据，使用线性倾向估计、Pearson相关系数、Mann-Kendall检验和R/S分析法，分析≥10 ℃界限温度的气候变化特征。结果表明：（1）随着海拔高度的升高，≥10 ℃界限温度出现明显垂直地带性特征，包括≥10 ℃初日推迟、终日提前、持续日数与积温减少。（2）近42 a来，该地区≥10 ℃初日普遍提前，气候倾向率为-2.53 d·（10 a）^-1；终日延后，倾向率为3.33 d·（10 a）^-1；持续日数和积温均明显增加，倾向率分别为5.87 d·（10 a）^-1、106.19 ℃·d·（10 a）^-1。与青藏高原其他地区相比，这种变化更为明显。（3）20世纪80年代是过去40 a≥10 ℃初日最迟、终日最早、持续日数最短、积温最少的10 a，与之相对的是21世纪10年代的情况截然相反。（4）≥10 ℃界限温度的H指数均大于0.65，表明未来≥10 ℃界限温度初日提前、终日推迟、持续日数延长和积温增加的变化趋势将持续存在。

关键词: ≥10 ℃活动积温, 初日, 终日, 持续日数, 年际和年代际变化, 突变, 西藏“一江两河”