A NEW INVERSE METHOD FOR TRACE GAS FLUX ESTIMATION - 2 - APPLICATION TO TROPOSPHERIC CFCL3 FLUXES

An initial application of a new inverse method for the estimation of f lux strengths of long-lived atmospheric trace gases is presented. CFCl 3 is studied using the Australian National University's Chemical Trans port Model. Unit-pulse responses are derived from the model, and used to identify a time-varying state-space model of tropospheric CFCl3. Th is in turn is used in a Kalman filter to perform two input-estimation studies. The first uses model generated measurements to estimate known flux strengths. This demonstrates the robustness of the method, altho ugh it is found that instantaneous stratospheric loss rates are not we ll-estimated using only surface concentration measurements. Emissions however, are robustly estimated. A time-averaged tropospheric lifetime can be estimated however, with an accuracy of +/-5 years. Thirteen ye ars of Atmospheric Lifetime Experiment/Global Atmospheric Gases Experi ment CFCl3 measurements are used in the second flux estimation experim ent. The estimated fluxes though are outside known physical limits for CFCl3, and it is concluded that either a more accurate/appropriate tr ansport model, or more measurement locations, are needed to obtain use ful information regarding regional tropospheric CFCl3 fluxes.