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Trends in tropospheric NO2 over megacities in the Mediterranean and Middle East from SCIAMACHY

Andreas Hilboll(1), Joana Leitão(1), Mihalis Vrekoussis(1), Andreas Richter(1) and John P. Burrows(1)

(1) University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany

Abstract

According to UN estimates, more than half of the Earth's population is living in cities. This phenomenon of urbanisation is especially pronounced in the so-called megacities. Due to high traffic, energy use and industrial production, these megacities form hot-spot areas in terms of pollution.

Currently, satellite instruments provide the only way to derive long and consistent time series of atmospheric trace gases with global coverage. Even though they do not provide vertical resolution, they prove a useful tool to study the temporal evolution of pollution proxies.

The improved spatial resolution of the SCIAMACHY on ENVISAT (as compared to the GOME instrument) allows for investigation of tropospheric NO2 as a proxy for pollution over megacities. With the onward availability of time series of measurements of atmospheric trace gases from the SCIAMACHY instrument spanning more than just a few years, it has recently become possible to derive consistent mid-term trends of tropospheric NO2.

In this study, we provide a first comparison of tropospheric NO2 trends over megacities of the Mediterranean and Middle East regions in the time period from August 2002 until now, making use of improved stratospheric and aerosol corrections. Across all cities considered, large increases in tropospheric NO2 concentrations can be found in this period, ranging up to more than 10% annually. Further consideration will be given to the seasonality of these increases as well as the possible correlations to population and economic growth.