GFDL-ESM2M气候模式下京津冀地区未来潜在蒸散量时空变化

为探究未来潜在蒸散量时空变化特征,该研究以京津冀地区为例,基于美国GFDL提供的GFDL-ESM2M全球气候模式,得到京津冀地区92个格点2000-2050年的平均气温、最高气温、最低气温、太阳总辐射、平均相对湿度和近地面平均风速,应用Penman-Monteith公式计算京津冀地区未来92个格点的逐日潜在蒸散量(ET0),分析其时空分布特征及其与气象要素的相关关系。结果表明:未来年ET0总体呈增加趋势,RCP8.5情景下ET0上升速度最快,且随着时间推移增幅越来越大。夏季ET0增长速度最快,其次为春季、秋季与冬季,意味着未来ET0季节差异将愈加明显,可能出现更为严重的季节性干旱。ET0空间分布呈由西南向东北逐渐递减趋势,其中中部地区增速最快,增长趋势由中部向南北递减。不同气候情景下平均气温均呈逐年上升趋势,风速、太阳总辐射略微上升,而相对湿度下降。ET0与太阳总辐射的相关系数最大,呈由东北向西南递增趋势,其次为最高气温,呈由西北向东南递增趋势。ET0与相对湿度变化呈显著负相关,相关系数绝对值呈东北向西南递增趋势,ET0与风速相关度不明显。该研究可为农业需水预测与灌溉管理、科学应对气候变化提供基础支撑。

Spatiotemporal variations of future potential evapotranspiration in the Beijing-Tianjin-Hebei region under GFDL-ESM2M climate model

The temporal and spatial variation characteristics of future potential evapotranspiration (ET0) can provide basic data support for agricultural water demand prediction, irrigation management and rational response to climate change. This paper has made the temporal and spatial prediction based on the various parameters, including the average temperature, the maximum temperature, the minimum temperature, total solar radiation, relative humidity and near-surface wind speed, where the 92 grid points were obtained in the Jing-Jin-Ji region from 1960-2016. The feasibility of climate models was verified using the principle of probability distribution optimization. Using the global climate model of GFDL-ESM2M that provided by the United States (Geophysical Fluid Dynamics Laboratory, GFDL), the SS(Skill Score) value of annual mean temperature could reach 0.86, indicating good applicability for the simulation in the Jing-Jin-Ji region. The prediction period was set from January 1, 2021 to December 31, 2050, and the climate scenarios were selected RCP(representative concentration pathways)2.6, RCP4.5 and RCP8.5, respectively, representing low, medium and high RCP cases. The temporal and spatial distribution characteristics of the future daily ET0 and its correlation with climate elements were analyzed using the Penman-Monteith formula based on the measured 92 grid points in the Jing-Jin-Ji region. The simulated results found that the future ET0 showed an increasing trend during this period. The ET0 in the RCP8.5 scenario rose the fastest, with the increment increasing over time, especially in the 2040 period. The summer ET0 grew the fastest, followed by spring, autumn and winter, meaning that the distribution difference of the seasonal ET0 will dominate in the future. This phenomenon may cause more severe seasonal droughts. The spatial distribution of ET0 gradually decreased from southwest to northeast, specifically indicating that Shijiazhuang in the southern plain area had the largest ET0 (1 207-1 262 mm), while Zhangjiakou and Chengde in the northwest mountainous area had the lowest ET0 (938-974 mm). There was a high growth rate of ET0 in the central region, as decreasing from central region to north and south. The average temperature in each climate scenario increased year by year, the wind speed and total solar radiation increased slightly, while the relative humidity decreased. The correlation between ET0 and the total solar radiation was the most obvious, followed by the highest temperature, all showing an increasing trend from northwest to southeast. The ET0 had negatively correlation with the relative humidity, but the absolute value of its correlation coefficient increased from northeast to southwest. There was a relatively slight correlation between ET0 and the wind speed. The correlation coefficient between ET0 and the total solar radiation showed a declining trend from RCP2.6-RCP8.5 with the increase of the emission concentration, possibly resulting from the large amount of energy consumption. The energy consumption will lead to the increase of the aerosol content in the air and the increase of haze days, leading to the decrease of sunshine hours, and the reduction of the total solar radiation. The negative effect of the reduce in the sunshine hours may exceed the positive effect of the temperature rising. It is possible that the future ET0 will continue to rise due to the radiation and temperature. The ET0 increase in the future can deteriorate the water shortages and even severe droughts in the Jing-Jin-Ji region from 2021 to 2050.