Variation characteristics of agricultural boundary temperature in main agricultural regions in basins of the Brahmaputra River and its two tributaries in Xizang from 1981 to 2022
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 sta-tions 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 ad-vanced 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 dura-tion 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.
≥10℃ active accumulated temperatureinitial datefinal dateduration daysinterannual and interdecadal variationmutationthe Brahmaputra River and its two tributaries in Xizang
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