珠海凤凰山林地下垫面观测通量的贡献区分析

根据安装在珠海凤凰山亚热带常绿阔叶林区内的陆―气相互作用与碳通量观测塔观测数据，利用K-M模型计算了对应时刻的通量贡献区，分析得到不同大气稳定度、不同季节、不同时刻下通量贡献区分布的变化规律。提出一种切实可行的评价地表均一性的标准，即计算每个子区域表面积与其地表投影区域表面积的比值，以此确定K-M 模型对该站点的适用性。结果表明：通量贡献区范围的分布，在大气稳定度＞0.1 的情况下与主风向分布范围相近，而在大气稳定度＜-0.1 的情况下与主风向分布范围不完全一致。在冬季，通量贡献区主要分布在北部和东部方向；在季风爆发前的春季，通量贡献区分布和冬季大体相近；在季风爆发后的春季和夏季，通量贡献区在西南方向和东南方向较为集中，这一规律和风速风向的分布规律一致。对于日变化来说，在夜间通量贡献区范围大于白天，其中贡献区最大范围多出现在夜间，但随着季风的爆发，贡献区最大范围出现的时间从T 02:00左右推迟到T 04:00 左右，这可能是由不同季节大气达到最稳定的时段不同所致。贡献区范围最小的情况出现在T 07:00―09:00 之间，这段时间往往也是湍流活动性最强的时段。

Analysis on the Source Area of Forest Site in Phoenix Mountain of Zhuhai

Based on the data of CO2 flux and interaction between land and atmosphere from the observing tower in Phoenix Mountain of Zhuhai, the study computes the source area of corresponding time in evergreen broadleaved forest in the mountain, and analyzes the change rule with different atmospheric stability conditions, different seasons and different time using K-M model. We develop a series of standards, which can judge the uniform lever and certify the applicability of the K-M model by computing the ratio between the projected area and the surface area. The results show that the distribution of source areas is similar to that of the main wind direction in stable atmospheric condition, and not completely similar to the main wind direction distribution in unstable atmospheric condition. In winter, the source area is mainly distributed in the northern and eastern directions. In spring, before the onset of the monsoon, the source area distribution is similar to that in winter. After the onset of the monsoon, the distribution of the source area is relatively concentrated in the southwest and southeast directions. The rule is similar to that of the distribution of wind direction. As for daily variation, the area range at night is larger than that in the day. The maximum range more likely appears at night. With the monsoon onset, the time delays from T02:00 to 04:00. The cause is probably that the atmosphere in different seasons reaches the most stable condition in different time. The minimum range of the source area occurs in the period between T 07:00-09:00, when the turbulent activity is the strongest.