我国西北降水变化趋势和预估

doi:10.12006/j.issn.1673-1719.2021.281

摘要/Abstract

摘要：

利用观测资料、GPCC再分析资料和第六次耦合模式比较计划（CMIP6）模拟结果，研究了我国西北地区近几十年及未来降水变化趋势。结果表明，1979—2019年我国西北干旱半干旱区降水在全年各季节均有显著增加，其中秋季增加最多。CMIP6模拟结果显示，随着全球变暖，我国西北地区降水在2015—2100年将继续增加。至21世纪末，在SSP2-4.5和SSP5-8.5情景下，我国西北地区年平均降水量将分别增加约13.7%（37 mm）和25.8%（78 mm)，其中降水量增加最多的季节分别为夏季和春季。考虑到西北地区蒸发量也将随全球变暖而增加，模式平均的结果显示西北地区年平均净降水量在两种情景下的增幅分别约1.4%和4.9%，表明我国西北地区未来气候呈现显著的变湿趋势。进一步分析表明，西北地区未来降水增加可能与局地大气低层位势高度降低和上升运动加强有关。

关键词: 西北变湿, 降水, 全球变暖, 土壤湿度, 未来预估

Abstract:

Using the observational data and simulation results from the Coupled Model Intercomparison Project Phase 6 (CMIP6), precipitation changes in Northwest China during 1979-2019 and under future global warming conditions are studied. Observations show that annual mean precipitation increased significantly in the arid and semi-arid areas of Northwest China over 1979-2019. Precipitation increased significantly in all seasons, with the largest increase in autumn. CMIP6 projection simulations show that precipitation in Northwest China will continue to increase from 2015 to 2100 along with global warming. Compared with that of the other regions in China, the increase of precipitation percentage is the largest in Northwest China. According to the projection of multi-mode ensemble mean, under the SSP2-4.5 and SSP5-8.5 scenarios, the increasing rates of annual mean precipitation in Northwest China are about 1.6%/(10 a) and 3.0%/(10 a), respectively. By the end of the 21st century, the annual mean precipitation in Northwest China will increase by ~13.7% (37 mm) for SSP2-4.5 and ~25.8% (78 mm) for SSP5-8.5. The seasons with the largest increase in precipitation are summer for SSP2-4.5 and spring for SSP5-8.5. Considering that evaporation in Northwest China will also increase with global warming, the annual mean net precipitation in Northwest China will increase by ~1.4% for SSP2-4.5 and ~4.9% for SSP5-8.5 at the end of the 21st century. Consequently, the increase of near surface soil moisture in Northwest China are ~10% for SSP2-4.5 and ~20% for SSP5-8.5. These results indicate that there is a significant wetting trend in Northwest China in the future. Further analysis also shows that future precipitation increasing in Northwest China are due to decreases of geopotential heights at the lower troposphere, which enhances upward motions.

Key words: Wetting in Northwest China, Precipitation, Global warming, Soil moisture, Future projection

张诗妍, 胡永云, 李智博. 我国西北降水变化趋势和预估[J]. 气候变化研究进展, 2022, 18(6): 683-694.

ZHANG Shi-Yan, HU Yong-Yun, LI Zhi-Bo. Recent changes and future projection of precipitation in Northwest China[J]. Climate Change Research, 2022, 18(6): 683-694.

图/表 10

表1 本文所用的25个CMIP6模式模拟结果

Table 1 The 25 CMIP6 models and their outputs used in this study

图1 1979—2019年GPCC再分析资料和我国台站观测资料中年降水量（a,b）气候平均态和（c,d）变化趋势注：图(c)中打点区域和图(d)中实心圆表示降水变化通过95%的信度检验，下同。

Fig. 1 Climatological annual mean precipitation (a, b) and precipitation trends (c, d) over 1979-2019. (Regions with dots in plot (c) and solid circles in plot (d) indicate that precipitation changes are statistically significant at the 95% confidence level, with the Student t-test, the same below)

图2 1979—2019年西北地区月降水量变化趋势注：*表示降水变化趋势通过了95%的信度检验。

Fig. 2 Trends in monthly mean precipitation in Northwest China over 1979-2019. (Asterisks indicate that the trends are statistically significant at the 95% confidence level)

图3 CMIP6模拟的1979—2014年年降水量(a)、变化趋势(c)及分别与GPCC资料结果的偏差(b, d)

Fig. 3 Climatological annual mean precipitation (a) and precipitation trends (c) over 1979-2014 in CMIP6 historical simulations, as well as their differences (b, d) from GPCC

图4 观测和模拟的1979—2100年我国西北地区季节平均降水变化量时间序列注：降水变化量为减去起始5年（1979—1983年）的平均降水量；灰色、黄色和红色阴影分别表示历史模拟、SSP2-4.5和SSP5-8.5情景下试验的模式间离散度。

Fig. 4 Time series of seasonal mean precipitation anomalies in Northwest China over 1979-2100. (Precipitation anomalies are calculated by subtracting the mean precipitation of the first 5 years (1979-1983) of the time series. Gray, yellow and red shadings indicate the inter-model spreads of precipitation in the historical, SSP2-4.5 and SSP5-8.5 simulations, respectively)

图5 CMIP6预估的2015—2100年我国年平均降水量（a,b）、蒸发量（c,d）和净降水量（e,f）变化趋势百分比

Fig. 5 CMIP6 projected percentage of annual mean precipitation (a, b), evaporation (c, d) and net precipitation (e, f) changes in China over 2015-2100

图6 CMIP6的 25个模式预估的2015—2100年西北地区平均年降水量、蒸发量和净降水量变化趋势百分比注：×表示模式集合平均值。圆圈表示单个模式的结果，其中实心圆表示趋势通过95%信度检验。

Fig. 6 CMIP6 projected percentage of annual mean precipitation, evaporation and net precipitation changes in Northwest China over 2015-2100. (× denotes the ensemble mean. Circles denote results of individual models)

图7 CMIP6预估的2015—2100年SSP2-4.5情景(a)和SSP5-8.5情景(b)下我国年平均近地面土壤湿度变化趋势百分比

Fig. 7 Projected percentage of trends in annual mean near surface soil moisture in China by CMIP6 for SSP2-4.5 (a) and SSP5-8.5 (b)

图8 2015—2100年SSP2-4.5 (a)和SSP5-8.5情景(b)下西北地区降水量回归的700 hPa位势高度纬向距平变化趋势注：等值线表示模式模拟的700 hPa位势高度气候平均场的纬向距平（减去纬向平均)，等值线间隔为10 m。填充色表示位势高度的变化趋势，打点区域表示位势高度的变化趋势通过95%信度检验。

Fig. 8 Trends of annual mean 700 hPa geopotential heights over 2015-2100 regressed against the precipitation in Northwest China for SSP2-4.5 (a) and SSP5-8.5 (b). (Contours indicate climatological zonal anomalies of geopotential heights, and contour intervals are 10 m. Color shading indicates trends in geopotential heights)

图9 2015—2100年SSP2-4.5 (a)和SSP5-8.5 (b)情景下西北地区降水量回归的700 hPa大气垂直速度变化趋势注：等值线表示模式模拟的700 hPa垂直速度气候平均场（正值表示下沉运动，负值表示上升运动，等值线间隔为10-3 Pa/s)。填充色表示垂直速度的变化趋势。

Fig. 9 Trends of annual mean 700 hPa vertical velocity over 2015-2100 regressed against the precipitation in Northwest China for SSP2-4.5 (a) and SSP5-8.5 (b). (Contours indicate climatological vertical velocity, and contour intervals are 10-3 Pa/s. Color shading indicates trends in vertical velocity)

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