POLIPHON conversion factors for retrieving dust-related cloud condensation nuclei and ice-nucleating particle concentration profiles at oceanic sites
<p>Aerosol–cloud interactions (ACIs) are the largest contributor to the uncertainty in the global radiation budget. To improve the current consideration of ACIs in global circulation models, it is necessary to characterize the 3-D distribution of dust-related cloud condensation nuclei concentr...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-04-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/16/1951/2023/amt-16-1951-2023.pdf |
| Summary: | <p>Aerosol–cloud interactions (ACIs) are the largest contributor to
the uncertainty in the global radiation budget. To improve the current
consideration of ACIs in global circulation models, it is necessary to
characterize the 3-D distribution of dust-related cloud condensation nuclei
concentration (CCNC) and ice-nucleating particle concentration (INPC)
globally. This can potentially be realized using the POlarization
LIdar PHOtometer Networking (POLIPHON) method together with spaceborne lidar
observations. However, dust-related conversion factors that convert bulk
aerosol optical properties from lidar measurements to aerosol microphysical
properties are still less constrained in many regions, which limits the
applications of the POLIPHON method. Here we retrieve the essential
dust-related conversion factors at remote oceanic and coastal sites using the
historical AErosol RObotic NETwork (AERONET) database.
Depolarization-ratio-based dust ratios <span class="inline-formula"><i>R</i><sub>d</sub></span> at 1020 nm are
applied to identify the dust-occurring cases, thus enabling us to contain
fine-mode dust-dominated cases (after the preferential removal of large-sized dust particles during transport), study the evolution of dust microphysical properties along the transoceanic pathway, and mitigate occasional interference of large-sized marine aerosols. The newly proposed scheme is proven to be valid and feasible by intercomparisons with previous studies at
nine sites in/near deserts. The dust-related conversion factors are
calculated at 20 oceanic and coastal sites using both pure dust (PD) and PD plus dust-dominated mixture (PD+DDM)
datasets. At nearly half of the sites, the
conversion factors are solely calculated using the PD datasets, while at the remaining sites, the participation of DDM datasets is required to ensure a sufficient number of data for the calculation. Evident variation trends in conversion factors are found for <span class="inline-formula"><i>c</i><sub>v,d</sub></span> (extinction-to-volume concentration, gradually decreasing), <span class="inline-formula"><i>c</i><sub>250,d</sub></span> (extinction-to-particle (with a radius <span class="inline-formula">></span> 250 nm) number concentration, gradually increasing), and <span class="inline-formula"><i>c</i><sub>s,d</sub></span> (extinction-to-surface-area concentration, gradually
decreasing) along both the transpacific and transatlantic dust transport
pathways. The retrieved dust-related conversion factors are anticipated to
inverse 3-D dust-related CCNC and INPC distributions globally, thereby
improving the understanding of ACIs in atmospheric circulation models.</p> |
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| ISSN: | 1867-1381 1867-8548 |