全球沙尘气溶胶源汇分布及其变化特征的模拟分析

根据全球沙尘气溶胶气候模式GEM-AQ/EC模拟的1995~2004年的沙尘起沙量和干湿沉降量,分析了沙尘气溶胶源汇的全球时空变化特征.全球沙尘起沙量集中在各个主要沙漠地区,北非对全球沙尘气溶胶贡献最大为66.6%.沙尘气溶胶沉降的高值区分布在沙漠源区及其紧临的下风地区.最大净沙尘气溶胶接收主要分布在沙漠周围地区并形成净接收量大于10t/(km2×a)的位于0°N~60°N之间的北非、欧亚大陆、西太平洋、北印度洋、北美和大西洋的带状分布.在北非、阿拉伯半岛、中亚、东亚和澳大利亚5个主要沙漠地区中,起沙量和沉降量都存在明显的季节变化,除中亚其他4个区域干湿沉降量和起沙的季节变化基本一致;东亚地区沙尘气溶胶起沙量和总沉降量的季节变化最为明显,而北非沙漠起沙量和总沉降量的季节变化最小,其他3个区域的季节变化幅度基本相同.中亚起沙峰值和阿拉伯半岛起沙次峰值出现在夏季,其他区域的峰值均出现在春季.10年间全球陆地年平均起沙量为(1500±94)Mt,保持略微上升趋势.以北非沙漠起沙量年际变化率最低(6.3%), 而以东亚(28.3%)和澳大利亚(45.0%)起沙量年际变化最为明显;全球陆地的沙尘气溶胶沉降量以约9.9Mt/a的速率递减,全球海洋的沙尘气溶胶沉降递增.

Modeling study on distributions and variations of global dust aerosol sources and sinks

Based on a 10-year (1995~2004) simulation of dust emissions and dry and wet depositions with the global air quality model system GEM-AQ/EC, the global spatial and temporal variations of the dust aerosol sources and sinks were characterized. Global dust emissions are centered over the major desert regions where the North African deserts are estimated with the largest emission contribution to the global dust aerosol up to 66.6%; the high dust aerosol depositions are concentrated over the desert sources and their immediately downwind areas. Thereby, the net dust aerosol sinks are largely distributed around the desert regions forming a receptor zone with the net sinks of greater than 10t/(km2×a) between 0°N and 60°N from North Africa, Eurasia, west Pacific Ocean, the north Indian Ocean, North America to the Atlantic ocean. In five major deserts of North Africa, Arabian Peninsula, Central Asia, East Asia and Australia, the dust emissions and depositions present the significant seasonal variations, The regional depositions expecting Central Asia experience almost the same seasonal cycle with the emissions; both dust aerosol emissions and depositions oscillate seasonally with the largest amplitudes in East Asia and with the lowest amplitudes in the North Africa. The seasonal dust emissions and depositions peak in summer over Central Asia and the Arabian Peninsula as well as during spring in the other three regions. Over the10 years, the global annual emission is averaged with (1500±94)Mt in a slightly rising trend. The inter-annual variability rate of dust emissions in North Africa is lowest (6.3%), up to 28.3% in East Asia and highest in Australia (45.0%). The dust aerosol depositions over global land decrease at a rate of around 9.9Mt/a, while they increase year to year over the oceans.