内容简介: Nitrous oxide is an important greenhouse gas and is a major ozone‒depleting substance. To understand and quantify soil nitrous oxide emissions, we expanded the Community Land Model with coupled Carbon and Nitrogen cycles version 3.5 by inserting a module to estimate monthly varying nitrous oxide emissions between 1975 and 2008. We evaluate our soil N2O emission estimates against existing emissions inventories, other process‒based model estimates, and observations from sites in the Amazon, North America, Central America, Asia, Oceania, Africa, and in Europe. The model reproduces precipitation, soil temperature, and observations of N2O emissions well at some but not at all sites and especially not during winter in the higher latitudes. Applying this model to estimate the past 24 years of global soil N2O emissions, we find that there is a significant decrease (increase) in soil N2O emissions associated with El Niño (La Niña) events. We used this emissions estimate and combined with other existing emissions inventories to create globally-gridded a priori N2O emissions since 1975. With the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method, we then estimated global as well as regional annual emissions for five source sectors from 13 regions in the world. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in the recent years, most likely due to an increase in the use of nitrogenous fertilizers, as has been suggested by previous studies, and in Asian natural soil.