The impact of aerosol fluorescence on long-term water vapor monitoring by Raman lidar and evaluation of a potential correction method
<p>The impact of aerosol fluorescence on the measurement of water vapor by UV (355 nm emission) Raman lidar in the upper troposphere and lower stratosphere (UTLS) is investigated using the long-term records of three high-performance Raman lidars contributing to the Network for the Detection of...
| Main Authors: | , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-07-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/15/4241/2022/amt-15-4241-2022.pdf |
| Summary: | <p>The impact of aerosol fluorescence on the measurement of water vapor by UV (355 nm emission) Raman lidar in the upper troposphere and
lower stratosphere (UTLS) is investigated using the long-term records of
three high-performance Raman lidars contributing to the Network for the
Detection of Atmospheric Composition Change (NDACC). Comparisons with
co-located radiosondes and aerosol backscatter profiles indicate that
laser-induced aerosol fluorescence in smoke layers injected into the
stratosphere by pyrocumulus events can introduce very large and chronic wet
biases above 15 km, thus impacting on the ability of these systems to
accurately estimate long-term water vapor trends in the UTLS.</p>
<p>In order to mitigate the fluorescence contamination, a correction method
based on the addition of an aerosol fluorescence channel was developed and
tested on the water vapor Raman lidar TMWAL located at the JPL Table Mountain Facility in California. The results of this experiment, conducted
between 27 August and 4 November 2021 and involving 22 co-located lidar and
radiosonde profiles, suggest that the proposed correction method is able to
effectively reduce the fluorescence-induced wet bias. After correction, the average difference between the lidar and co-located radiosonde water vapor measurements was reduced to 5 %, consistent with the difference observed during periods of negligible aerosol fluorescence interference.</p>
<p>The present results provide confidence that after a correction is applied,
long-term water vapor trends can be reasonably well estimated in the upper
troposphere, but they also call for further refinements or use of
alternate Raman lidar approaches (e.g., 308 nm or 532 nm emission) to
confidently detect long-term trends in the lower stratosphere. These
findings may have important implications for NDACC's water vapor measurement strategy in the years to come.</p> |
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| ISSN: | 1867-1381 1867-8548 |