半干旱地区草地与裸地水热通量的研究

Moisture and Heat Fluxes over Grassland and Bare Soil in Semi-arid Area

沙尘暴的发生与土体缺乏草本、灌木有效保护和植被覆盖度低有关,定量地研究半干旱地区草地与裸地水热通量具有十分重要的意义。涡度相关技术是直接测定下垫面和大气之间水热通量的相对标准观测方法,利用其测量草地和裸地水热通量(潜热和显热通量),结果发现草地晴天白天的潜热明显大于显热,其最大值大约是显热的一倍;而裸地恰好相反,显热明显大于潜热,其最大值大约是潜热的一倍。草地阴天白天的潜热略大于显热;而裸地的显热仍明显大于潜热,其最大值大约是潜热的一倍以上;同时存在能量不闭合问题。草地发挥降温增湿等生态效应,对减少沙尘暴、维护生态平衡具有极其重要的作用。

Sandstorm has something with inadequatesoil protection by the grasses,the shrubs,and low vegetation coverage. It＇s very important for us to study the moisture and heat fluxes quantitatively over the grassland and the bare soil in the semi-arid area. Eddy covariance technique is the relatively standard method, which is used to measure the moisture and heat fluxes between the different underlying surfaces and atmosphere. Therefore the two fluxes were measured over the grassland and the bare soil. The result indicated that in sunny daytime over the grassland,the latent heat flux was much greater than the sensible one. The maximum of the latent heat was twice as that of the sensible heat. On the contrary ,the sensible heat was much greater than the latent heat over the bare soil. The maximum of the sensible heat was twice as that of the latent heat. However,the latent heat flux was a little greater than the sensible heat flux in cloudy daytime over the grassland. The sensible heat was still much greater than the latent heat over the bare soil. The maximum of the sensible heat was over twice as that of the latent heat. The energy imbalance existed. Grassland has the ecological effect in decreasing temperature and enhancing moisture. It will play important part in decreasing the sandstorm and maintaining ecological balance.