Global 3-D distribution of aerosol composition by synergistic use of CALIOP and MODIS observations
<p>For the observation of the global three-dimensional distribution of aerosol composition and the evaluation of the shortwave direct radiative effect (SDRE) by aerosols, we developed a retrieval algorithm that uses observation data from the Cloud–Aerosol Lidar with Orthogonal Polarization (CA...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2023-08-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/16/3835/2023/amt-16-3835-2023.pdf |
| Summary: | <p>For the observation of the global three-dimensional distribution of aerosol composition and the evaluation of the shortwave direct radiative effect (SDRE) by aerosols, we developed a retrieval algorithm that uses observation data from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud–Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite and the Moderate Resolution Imaging Spectroradiometer (MODIS) on board Aqua. The CALIOP–MODIS retrieval optimizes the aerosol composition to both the CALIOP and MODIS observations in the daytime. Aerosols were assumed to be composed of four aerosol components: water-soluble (WS), light-absorbing (LA), dust (DS), and sea salt (SS) particles. The outputs of the CALIOP–MODIS retrieval are the vertical profiles of the extinction coefficient (<span class="inline-formula"><i>α</i><sub>a</sub></span>), single-scattering albedo (<span class="inline-formula"><i>ω</i><sub>0</sub></span>), asymmetry factor (<span class="inline-formula"><i>g</i></span>) of
total aerosols (WS<span class="inline-formula">+</span>LA<span class="inline-formula">+</span>DS<span class="inline-formula">+</span>SS), and <span class="inline-formula"><i>α</i><sub>a</sub></span> of WS, LA, DS, and SS. Daytime observations of CALIOP and MODIS in 2010 were analyzed by the CALIOP–MODIS retrieval. The global means of the aerosol optical depth (<span class="inline-formula"><i>τ</i><sub>a</sub></span>) at 532 nm were <span class="inline-formula">0.147±0.148</span> for total aerosols, <span class="inline-formula">0.072±0.085</span> for WS, <span class="inline-formula">0.027±0.035</span> for LA, <span class="inline-formula">0.025±0.054</span> for DS, and <span class="inline-formula">0.023±0.020</span> for SS. <span class="inline-formula"><i>τ</i><sub>a</sub></span> of the CALIOP–MODIS retrieval was
between those of the CALIPSO and MODIS standard products and was close to
the MODIS standard product. The global means of <span class="inline-formula"><i>ω</i><sub>0</sub></span> and <span class="inline-formula"><i>g</i></span> were
<span class="inline-formula">0.940±0.038</span> and <span class="inline-formula">0.718±0.037</span>; these values are in the range
of those reported by previous studies. The horizontal distribution of each
aerosol component was reasonable; for example, DS was large in desert
regions, and LA was large in the major regions of biomass burning and
anthropogenic aerosol emissions. The values of <span class="inline-formula"><i>τ</i><sub>a</sub></span>, <span class="inline-formula"><i>ω</i><sub>0</sub></span>, <span class="inline-formula"><i>g</i></span>, and fine and coarse median radii of the CALIOP–MODIS retrieval were compared with those of the AERONET products. <span class="inline-formula"><i>τ</i><sub>a</sub></span> at 532 and 1064 nm
of the CALIOP–MODIS retrieval agreed well with the AERONET products. The
<span class="inline-formula"><i>ω</i><sub>0</sub></span>, <span class="inline-formula"><i>g</i></span>, and fine and coarse median radii of the CALIOP–MODIS
retrieval were not far from those of the AERONET products, but the
variations were large, and the coefficients of determination for linear
regression between them were small. In the retrieval results for 2010, the
clear-sky SDRE values for total aerosols at the top and bottom of the
atmosphere were <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">4.99</mn><mo>±</mo><mn mathvariant="normal">3.42</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="e400f353e553e3d00dfc8e8beb553623"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-3835-2023-ie00001.svg" width="64pt" height="10pt" src="amt-16-3835-2023-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M26" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">13.10</mn><mo>±</mo><mn mathvariant="normal">9.93</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="70pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="3afa36f3598cd775cd5cd24385673b4f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="amt-16-3835-2023-ie00002.svg" width="70pt" height="10pt" src="amt-16-3835-2023-ie00002.png"/></svg:svg></span></span> W m<span class="inline-formula"><sup>−2</sup></span>,
respectively, and the impact of total aerosols on the heating rate was from
0.0 to 0.5 K d<span class="inline-formula"><sup>−1</sup></span>. These results are generally similar to those of
previous studies, but the SDRE at the bottom of the atmosphere is larger
than that reported previously. Consequently, comparison with previous
studies showed that the CALIOP–MODIS retrieval results were reasonable with
respect to aerosol composition, optical properties, and the SDRE.</p> |
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| ISSN: | 1867-1381 1867-8548 |