HCFC-22 flux estimates over East Asia by inverse modeling from hourly observations at Hateruma monitoring station

A series of high-frequency observations of chlorodifluoromethane (HCFC-22) at Hateruma Island (latitude 24.1 degrees N, longitude 123.8 degrees E) was used to evaluate the strength of various sources in East Asia by a tracer transport inversion. The forward calculation was conducted with a regional meteorological model using an online tracer transport scheme, and the inversion calculation used a Bayesian approach. On the basis of winter observations during 2005-2007, we estimated the annual HCFC-22 emission from China to be 32 Gg, which is nine times current estimates. The total uncertainty of the Chinese emission was reduced from 50% (a priori) to 15% (a posteriori) by the inversion calculation. A sensitivity study showed that the a posteriori values for China showed little dependency on the a priori values, whereas those for Japan, Korea, and Taiwan were considerably affected by the a priori values used. This can be explained by the more frequent high-concentration events from China observed at the Hateruma site. The a posteriori emission estimates from central China accounted for half of the total emissions from China.