Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements
Here we present new results comparing aerosol optical depth (AOD), aerosol absorption optical depth (AAOD) and column single scattering albedo (SSA) obtained from in situ vertical profile measurements with AERONET ground-based remote sensing from two rural, continental sites in the US. The profiles...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/17/6041/2017/acp-17-6041-2017.pdf |
| _version_ | 1818131039027986432 |
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| author | E. Andrews J. A. Ogren S. Kinne B. Samset |
| author_facet | E. Andrews J. A. Ogren S. Kinne B. Samset |
| author_sort | E. Andrews |
| collection | DOAJ |
| description | Here we present new results comparing aerosol optical depth (AOD), aerosol
absorption optical depth (AAOD) and column single scattering albedo (SSA)
obtained from in situ vertical profile measurements with AERONET ground-based
remote sensing from two rural, continental sites in the US. The profiles are
closely matched in time (within ±3 h) and space (within 15 km) with the
AERONET retrievals. We have used Level 1.5 inversion retrievals when there
was a valid Level 2 almucantar retrieval in order to be able to compare AAOD
and column SSA below AERONET's recommended loading constraint
(AOD > 0.4 at 440 nm). While there is reasonable agreement for
the AOD comparisons, the direct comparisons of in situ-derived to
AERONET-retrieved AAOD (or SSA) reveal that AERONET retrievals yield higher
aerosol absorption than obtained from the in situ profiles for the low
aerosol optical depth conditions prevalent at the two study sites. However,
it should be noted that the majority of SSA comparisons for
AOD<sub>440</sub> > 0.2 are, nonetheless, within the reported SSA
uncertainty bounds. The observation that, relative to in situ measurements,
AERONET inversions exhibit increased absorption potential at low AOD values
is generally consistent with other published AERONET–in situ comparisons
across a range of locations, atmospheric conditions and AOD values. This
systematic difference in the comparisons suggests a bias in one or both of
the methods, but we cannot assess whether the AERONET retrievals are biased
towards high absorption or the in situ measurements are biased low. Based on
the discrepancy between the AERONET and in situ values, we conclude that
scaling modeled black carbon concentrations upwards to match AERONET
retrievals of AAOD should be approached with caution as it may lead to
aerosol absorption overestimates in regions of low AOD. Both AERONET
retrievals and in situ measurements suggest there is a systematic
relationship between SSA and aerosol amount (AOD or aerosol light scattering)
– specifically that SSA decreases at lower aerosol loading. This implies
that the fairly common assumption that AERONET SSA values retrieved at
high-AOD conditions can be used to obtain AAOD at low-AOD conditions may not
be valid. |
| first_indexed | 2024-12-11T08:14:35Z |
| format | Article |
| id | doaj.art-53456da9cbd2498f9ddcb19a514fddfb |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-11T08:14:35Z |
| publishDate | 2017-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-53456da9cbd2498f9ddcb19a514fddfb2022-12-22T01:14:47ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-05-011796041607210.5194/acp-17-6041-2017Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurementsE. Andrews0J. A. Ogren1S. Kinne2B. Samset3CIRES, University of Colorado, Boulder, CO 80309, USANOAA/ESRL/GMD, Boulder, CO 80305, USAMax Planck Institute for Meteorology, 20146 Hamburg, GermanyCenter for International Climate and Environmental Research – Oslo (CICERO), 0349 Oslo, NorwayHere we present new results comparing aerosol optical depth (AOD), aerosol absorption optical depth (AAOD) and column single scattering albedo (SSA) obtained from in situ vertical profile measurements with AERONET ground-based remote sensing from two rural, continental sites in the US. The profiles are closely matched in time (within ±3 h) and space (within 15 km) with the AERONET retrievals. We have used Level 1.5 inversion retrievals when there was a valid Level 2 almucantar retrieval in order to be able to compare AAOD and column SSA below AERONET's recommended loading constraint (AOD > 0.4 at 440 nm). While there is reasonable agreement for the AOD comparisons, the direct comparisons of in situ-derived to AERONET-retrieved AAOD (or SSA) reveal that AERONET retrievals yield higher aerosol absorption than obtained from the in situ profiles for the low aerosol optical depth conditions prevalent at the two study sites. However, it should be noted that the majority of SSA comparisons for AOD<sub>440</sub> > 0.2 are, nonetheless, within the reported SSA uncertainty bounds. The observation that, relative to in situ measurements, AERONET inversions exhibit increased absorption potential at low AOD values is generally consistent with other published AERONET–in situ comparisons across a range of locations, atmospheric conditions and AOD values. This systematic difference in the comparisons suggests a bias in one or both of the methods, but we cannot assess whether the AERONET retrievals are biased towards high absorption or the in situ measurements are biased low. Based on the discrepancy between the AERONET and in situ values, we conclude that scaling modeled black carbon concentrations upwards to match AERONET retrievals of AAOD should be approached with caution as it may lead to aerosol absorption overestimates in regions of low AOD. Both AERONET retrievals and in situ measurements suggest there is a systematic relationship between SSA and aerosol amount (AOD or aerosol light scattering) – specifically that SSA decreases at lower aerosol loading. This implies that the fairly common assumption that AERONET SSA values retrieved at high-AOD conditions can be used to obtain AAOD at low-AOD conditions may not be valid.http://www.atmos-chem-phys.net/17/6041/2017/acp-17-6041-2017.pdf |
| spellingShingle | E. Andrews J. A. Ogren S. Kinne B. Samset Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements Atmospheric Chemistry and Physics |
| title | Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements |
| title_full | Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements |
| title_fullStr | Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements |
| title_full_unstemmed | Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements |
| title_short | Comparison of AOD, AAOD and column single scattering albedo from AERONET retrievals and in situ profiling measurements |
| title_sort | comparison of aod aaod and column single scattering albedo from aeronet retrievals and in situ profiling measurements |
| url | http://www.atmos-chem-phys.net/17/6041/2017/acp-17-6041-2017.pdf |
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