利用最大熵增方法估计青藏高原地面热源

Estimating surface heat source in the Qingzang plateau using the Maximum Entropy Production model

  • 摘要: 研制能够满足气候监测和预测业务时效需求、覆盖时间长且准确度较高的青藏高原地区地面热源数据集(包括地表感热通量(SH)和潜热通量(LE))有科学价值和实际意义。在多种大气再分析资料中,NCEP-II大气再分析资料能够满足气候监测与预测业务时效,但其基于经典莫宁-奥布霍夫相似理论计算的SH和LE误差较大。虽然以往的研究已经采用最大熵增模型(Maximum Entropy Production,MEP)以及卫星遥感和大气再分析等多源数据建立了青藏高原地区SH和LE数据集,然而这些数据集的时间较短且不能满足气候监测、预测业务的时效需求,因此文中采用MEP和能够满足气候监测和预测时效的NCEP-II大气再分析资料的日平均地表净辐射、地表温度和表层土壤含水量数据,建立了1980—2023年青藏高原地区SH和LE的格点数据集,用青藏高原地面加密观测站资料验证了新建数据集的可靠性,并分析SH和LE的时、空变化特征。结果表明:用MEP计算的月平均SH(SHMEP)和LE(LEMEP)与观测的相关系数分别为0.93和0.82,均方根误差分别为11.91和13.80 W/m2,优于ERA5、ERA-Interim、MERRA-2、JRA-55和NCEP-II大气再分析资料的SH和LE,能够满足气候监测和预测业务时效及质量需求。分析表明,1980—2023年夏季青藏高原SHMEP呈现显著的下降趋势(-0.48 W/(m2·10 a)),而LEMEP呈现不显著的上升趋势。

     

    Abstract: It is practical significance to develop a long-term, high-accuracy dataset of the surface heat sources (including surface sensible heat flux (SH) and latent heat flux (LE)) in Qingzang plateau, which can meet the time requirement of climate monitoring and prediction. Among various atmospheric reanalysis data, the NCEP-II atmospheric reanalysis data can meet the operational time requirement of climate monitoring and prediction. However, the NCEP-II SH and LE calculated based on the classic Monin-Obukhov similarity theory have large errors. Previous studies have developed SH and LE datasets in the Qingzang plateau using the Maximum Entropy Production (MEP) model and the multi-source datasets including satellite remote sensing data and atmospheric reanalysis data. However, these SH and LE datasets are short in time and cannot meet the timeliness requirements. In this paper, using the MEP model and daily average net radiation, surface temperature, and soil moisture data extracted from the NCEP-II atmospheric reanalysis dataset, we establish SH and LE in the Qingzang plateau area from 1980 to 2023. We verify the reliability of the new dataset by using the Qingzang plateau intensive observation data and analyze the temporal and spatial variation characteristics of SH and LE. The result shows that the correlation coefficients between monthly mean MEP SH (SHMEP) and LE (LEMEP) and the observations are 0.93 and 0.82, respectively, and the root mean square errors(RMSE) are 11.91 and 13.80 W/m2, respectively. The results are better than those of the ERA5, ERA-Interim, MERRA-2, JRA-55, and NCEP-II atmospheric reanalysis data, and can meet the timeliness and quality needs of climate monitoring and prediction operations. Moreover, for the period 1980—2023, summer SHMEP exhibits a significant downward trend, with a linear trend of -0.48 W/(m2·10 a), while LEMEP shows an unsignificant upward trend.

     

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