 |
| Titel |
Global Trends of Tropospheric NO2 Observed From Space |
| VerfasserIn |
P. Schneider, R. J. van der A |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250059799
|
|
|
|
|
|
| Zusammenfassung |
| Nitrogen Dioxide (NO2) is one of the major atmospheric pollutants and is primarily emitted
by industrial activity and transport. While observations of NO2 are frequently being carried
out at air quality stations, such measurements are not able to provide a global perspective of
spatial patterns in NO2 concentrations and their associated trends due to the stations’ limited
spatial representativity and an extremely sparse and often completely non-existent station
coverage in developing countries. Satellite observations of tropospheric NO2 are
able to overcome this issue and provide an unprecedented global view of spatial
patterns in NO2 levels and due to their homogeneity are well suited for studying
trends.
Here we present results of a global trend analysis from nearly a decade of NO2
observations made by the SCIAMACHY (SCanning Imaging Absorption spectroMeter
for Atmospheric CartograpHY) instrument onboard the Envisat satellite platform.
Using only SCIAMACHY data allows for mapping global and regional trends at an
unprecedented spatial resolution since no aggregation to the coarser resolution of
other sensors is necessary. Monthly average tropospheric NO2 column data was
acquired for the period between August 2002 and August 2011. A trend analysis was
subsequently performed by fitting a statistical model including a seasonal cycle and
linear trend to the time series extracted at each grid cell. The linear trend component
and the trend uncertainty were then mapped spatially at both regional and global
scales.
The results show that spatially contiguous areas of significantly increasing NO2 levels are
found primarily in Eastern China, with absolute trends of up to 4.05 (± 0.41) Ã 1015
molecules cm-2 yr-1 at the gridcell level and large areas showing rapid relative increases of
10-20 percent per year. In addition, many urban agglomerations in Asia and the Middle East
similarly exhibit significantly increasing trends, with Dhaka in Bangladesh being the
megacity with the most rapid relative increase during the study period (9.5 ± 1.7 percent per
year). In contrast, significantly decreasing trends in NO2 levels exist over large parts of
Europe and the Eastern United States, with average rates of decrease in the range of 0 to
-10 percent per year. The satellite-derived time series were further analysed with
respect to identification of the impact of the 2008/2009 economic crisis. European
trends obtained from the satellite analysis are also compared with corresponding
trends computed using data of the Co-operative Programme for Monitoring and
Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP)
model, as well as with NO2 trends calculated from station observations throughout
Europe. |
|
|
|
|
|
|