 |
| Titel |
New NDACC recommendations for the retrieval of stratospheric NO2 columns |
| VerfasserIn |
F. Hendrick, D. Ionov, F. Goutail, A. Pazmino, U. Frieß, M. Gil, J.-C. Lambert, M. Navarro, M. Pastel, J.-P. Pommereau, A. Richter, T. Wagner, F. Wittrock, M. Van Roozendael |
| Konferenz |
EGU General Assembly 2012
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062900
|
|
|
|
|
|
| Zusammenfassung |
| Stratospheric nitrogen dioxide (NO2) column measurements are daily performed at sunrise
and sunset using ground-based zenith-sky UV-visible spectrometers deployed all over the
world in about 35 stations, most of them belonging to the Network for the Detection of
Atmospheric Composition Change (NDACC). Despite several cross evaluation exercises, it
has been recognized that the NO2 data records still suffer from residual inconsistencies
mainly due to (1) differences in the DOAS settings, in particular the temperature dependence
of the NO2 absorption cross sections and (2) a lack of homogeneity in the air mass factors
(AMFs) applied to the measured NO2 slant columns for their conversion into vertical
columns.
Recently, the NDACC UV-visible Working Group has formulated new recommendations
aiming at improving the homogeneity of the stratospheric NO2 column measurements.
Regarding the spectral analysis, a list of recommended settings has been established
including fitting intervals, absorption cross sections data sets and temperature dependence, as
well as methods for wavelength calibration and residual amount in the reference spectrum
determination. In case of AMFs, look-up tables (LUTs) have been built from NO2 profile
climatologies based on the harmonic decomposition of the HALOE, SAGE-II and
POAM-III data records for the stratosphere and on SAOZ balloon observations for the
UTLS, allowing accounting for the dependence of the AMF on the latitudinal and
seasonal variations of the NO2 vertical profile at sunrise and sunset. The calculated
LUTs, only suitable for background aerosols conditions, depend on latitude, day
of year, wavelength, SZA, surface albedo, and station altitude. The error budget
on the AMFs as well as on the spectral analysis is evaluated. The impact of those
recommendations is investigated through their application to measurements from a selection
of stations of the NDACC UV-visible network. The consistency of the new NDACC
stratospheric NO2 data sets with correlative observations from the ERS-2/GOME,
ENVISAT/SCIAMACHY, and EOS-AURA/OMI satellite nadir instruments is also discussed. |
|
|
|
|
|
|