Weekly cycle of NO2 revisited
Steffen Beirle(1) and Thomas Wagner(1)
(1) MPI Chemistry Mainz, Becherweg 27, 55128 Mainz, Germany
Some years ago, we reported on a significant weekend reduction of NO2 column densities derived from the Global Ozone Monitoring Experiment (GOME) over the industrialized areas of the US, Europe, and Japan. Meanwhile, several years of data from further instruments (SCIAMACHY, OMI, and GOME-2) are available with improved spatial resolution that allows to investigate tropospheric NO2 levels on almost urban scale.
Here we present an update of the "weekend effect" from satellite observations of NO2. In particular, we investigate regional and seasonal differences of the strength as well as the shape of the weekly cycle. These characteristics allow to draw conclusions on the contribution of different NOx sources (mainly industry, power generation, and traffic), having different weekly (and possibly seasonal) patterns.
In addition, we estimate (regional and seasonal) tropospheric lifetimes (tau) of NO2 from the change of the weekly cycle pattern downwind from source regions: The longer tau, the longer the NO2 columns "remember" the (Sunday) reduction in the Monday (Tuesday…) levels.
Finally, we discuss the impact of the observed weekend reduction of NO2 on tropospheric chemistry.