UTLS water vapour from SCIAMACHY limb measurementsV3.01 (2002–2012)
The SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) aboard the Envisat satellite provided measurements from August 2002 until April 2012. SCIAMACHY measured the scattered or direct sunlight using different observation geometries. The limb viewing geometry allows the...
| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/9/133/2016/amt-9-133-2016.pdf |
| Summary: | The SCanning Imaging Absorption spectroMeter for Atmospheric
CHartographY (SCIAMACHY) aboard the Envisat satellite provided
measurements from August 2002 until April 2012. SCIAMACHY measured
the scattered or direct sunlight using different observation
geometries. The limb viewing geometry allows the retrieval of water
vapour at about 10–25 km height from the near-infrared
spectral range (1353–1410 nm). These data cover the upper
troposphere and lower stratosphere (UTLS), a region in the
atmosphere which is of special interest for a variety of dynamical
and chemical processes as well as for the radiative forcing. Here,
the latest data version of water vapour (V3.01) from SCIAMACHY limb
measurements is presented and validated by comparisons with data
sets from other satellite and in situ measurements. Considering
retrieval tests and the results of these comparisons, the V3.01 data
are reliable from about 11 to 23 km and the best results are found
in the middle of the profiles between about 14 and 20 km. Above
20 km in the extra tropics V3.01 is drier than all other data
sets. Additionally, for altitudes above about 19 km, the vertical
resolution of the retrieved profile is not sufficient to resolve
signals with a short vertical structure like the tape recorder.
Below 14 km, SCIAMACHY water vapour V3.01 is wetter than most
collocated data sets, but the high variability of water vapour in
the troposphere complicates the comparison. For 14–20 km
height, the expected errors from the retrieval and simulations and
the mean differences to collocated data sets are usually smaller
than 10 % when the resolution of the SCIAMACHY data is taken
into account. In general, the temporal changes agree well with
collocated data sets except for the Northern Hemisphere
extratropical stratosphere, where larger differences are observed.
This indicates a possible drift in V3.01 most probably caused by the
incomplete treatment of volcanic aerosols in the retrieval. In all
other regions a good temporal stability is shown. In the tropical
stratosphere an increase in water vapour is found between 2002 and
2012, which is in agreement with other satellite data sets for
overlapping time periods. |
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| ISSN: | 1867-1381 1867-8548 |