土壤热异常对地表能量平衡影响初探

将来自土壤深部的热通量引入off line的陆面过程模式 (NCAR—LSM ) ,通过长达 2a的数值试验对比分析了它对各层次土壤温度和地表能量平衡的影响。　　在土壤底部引入 5W /m2 的热通量使底层土壤显著升温 ,但升温随着接近表层而迅速衰减。积分 3个月后 ,由地下进入地表的热流量增幅可达 1W/m2 以上 ,并持续增大到 5W /m2 ,地表最大升温约 0 .5K ,同时地表感热、蒸发潜热及长波辐射通量均有 1W /m2 左右的正异常 ;若将土壤热传导系数放大一个量级以加速热量交换 ,则地表升温提高到 1K以上 ,长波辐射增加 3W /m2 以上 ,超过了气溶胶全球平均的辐射效应。结果表明 :一定量值的土壤热异常对地表能量平衡和短期气候变化 (10 -1～ 10 1a)有着不可忽略的影响。同时 ,深入的资料分析、完善的陆面过程模式以及它与大气模式的耦合试验也是亟待进行的相关工作。

PRELIMINARY STUDY ON THE EFFECTS OF SOIL THERMAL ANOMALY ON LAND SURFACE ENERGY BUDGET

Effects of geothermal flux on soil temperature and land surface energy budget are discussed by introducing a soil heat flux into an off-line land surf acemodel(NCAR LSM) and integrating for 2 years.Remarkable increase in soil temperature at deepest level is detected given a geothermal flux of 5 W/m².Additional heat flux from soil into land surface exceeds 1W/m² after integrated for 3 months.The flux keeps in-creasing until reaches 5 W/m².Amaximum anomaly of 0.5K is found in ground temperature.Correspondingly,there are positive anomalies of around 1 W/m² in surface sensible,latent and outgoing long-wave radiation fluxes.Increase in ground temperature can be even greater than 1 K given an enlarged soil thermal conductivity by one order of mag nitude to accelerate the heat transfer process through soil layers.In this case,surface long-wave radiation flux is then enhanced not ably by 3 W/m²,which is larger than the global radiative effects of sulfate aerosol.The results imply that soil thermal anomaly on a certain scale should not be ignored to land surface energy balance and short-term climate change.Meanw hile,some related studies,such as dat a analyses,improvement of land surface model and land-at mosphere coupled model are also in greatneed for better under-standing this issue.