Emission Factors from the satellite measurements?
Iryna Khlystova(1) and John. P. Burrows(1)
(1) IUP-Bremen, Otto-Hahn Al.,1, 28359 Bremen, Germany
Traditional methods for the quantification of emissions of atmospheric pollutants rely on local measurements or on statistical methods. These measurements and statistical results are usually only available for rather rare periods of time, e.g., only for one particular event or for a selected period in the past. Natural phenomena, however, are usually very complex and the amounts of emissions could be still different from the ones predicted by traditional quantification methods. This lack of information could be compensated by additionally applying simultaneous measurements from satellites.
The ability to measure several atmospheric components simultaneously is an important feature of modern environmental satellite instruments. The SCIAMACHY instrument on board ENVISAT is such a versatile device. Since 2002, it has been measuring several atmospheric trace gases with nearly identical sensitivity to all atmospheric layers including the boundary layer where the most important sources of pollution are located. Due to the continuous sampling and the global coverage, such simultaneous measurements can provide useful information about large and hardly predictable atmospheric processes, such as biomass burning, which is difficult to study solely with the help of local measurements.
However, the traditional methods can be used along with the available satellite measurements. Just as local measurements, satellite measurements can be applied in the scope of the well-established bottom-up method, which was developed by Seiler and Crutzen in 1980. In the past, this method has been widely applied to airborne measurements for the quantitative analysis of emissions. In contrast to the other quantification methods, this method does not rely on models and is not constrained by local measurements. For the first time, this method is considered here in connection with satellite measurements. Similar to the airborne measurements, the source and background regions must be selected. The background concentration is subtracted from the concentration in the source region to get the excess emission ratio of a particular component with respect to the one of the major carbon components CO or CO2 (here CO). However, due to the large uncertainty of satellite measurements, and due to the uncertainty of the biomass burning events as a natural phenomenon, several assumptions need to be made in order to calculate the background and source concentrations of the satellite measured trace gases.
In this work, the bottom-up method is applied to the SCIAMACHY measurements of CO, NO2, and HCHO. It is shown that the values of the excess ratios calculated from SCIAMACHY measurements agree well with the previously calculated values available from a number of airborne campaigns over the same burning area, e.g., for the campaign SAFARI2000. Detailed comparisons with available literature values will be presented for the values of ΔHCHO/ΔCO and ΔNO2/ΔCO. A comprehensive discussion will be conducted on the sources and magnitude of the uncertainty of the satellite measurements, on the assumptions required, as well as on potential future applications of the method of excess ratios and emission factors to the satellite measurements. This approach has the potential to become a useful compliment in addition to the existing emission quantification methods.