Max-Planck-Institut für Chemie, Joh.-Joachim-Becherweg 27, 55128 Mainz, Germany.
Science. 2011 Sep 23;333(6050):1737-9. doi: 10.1126/science.1207824.
Megacities are immense sources of air pollutants, with large impacts on air quality and climate. However, emission inventories in many of them still are highly uncertain, particularly in developing countries. Satellite observations allow top-down estimates of emissions to be made for nitrogen oxides (NO(x) = NO + NO(2)), but require poorly quantified a priori information on the NO(x) lifetime. We present a method for the simultaneous determination of megacity NO(x) emissions and lifetimes from satellite measurements by analyzing the downwind patterns of NO(2) separately for different wind conditions. Daytime lifetimes are ~4 hours at low and mid-latitudes, but ~8 hours in wintertime for Moscow. The derived NO(x) emissions are generally in good agreement with existing emission inventories, but are higher by a factor of 3 for the Saudi Arabian capital Riyadh.
特大城市是空气污染物的巨大来源，对空气质量和气候有重大影响。然而，许多特大城市的排放清单仍然高度不确定，特别是在发展中国家。卫星观测允许对氮氧化物（NO(x) = NO + NO(2)）进行自上而下的排放量估算，但需要对 NO(x)寿命的先验信息进行量化。我们提出了一种从卫星测量中同时确定特大城市 NO(x)排放量和寿命的方法，方法是分别分析不同风向条件下的二氧化氮（NO(2)）下风模式。在低纬度和中纬度地区，白天的寿命约为 4 小时，但在莫斯科冬季约为 8 小时。得出的 NO(x)排放量与现有排放清单基本一致，但沙特阿拉伯首都利雅得的排放量高出 3 倍。
