Thermal infrared dust optical depth and coarse-mode effective diameter over oceans retrieved from collocated MODIS and CALIOP observations

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Zheng, Jianyu, Zhang, Zhibo, Yu, Hongbin, Garnier, Anne, Song, Qianqian, Wang, Chenxi, Biagio, Claudia, Kok, Jasper F., Derimian, Yevgeny, Ryder, Claire
• Format: Text
• Language: English
• Published: 2023
• Subjects: Indian; Pacific; North Atlantic
• Online Access: https://doi.org/10.5194/acp-23-8271-2023; https://acp.copernicus.org/articles/23/8271/2023/

In this study, we developed a novel algorithm based on the collocated Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared (TIR) observations and dust vertical profiles from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) to simultaneously retrieve dust aerosol optical depth at 10 µ m (DAOD 10 µm ) and the coarse-mode dust effective diameter ( D eff ) over global oceans. The accuracy of the D eff retrieval is assessed by comparing the dust lognormal volume particle size distribution (PSD) corresponding to retrieved D eff with the in situ-measured dust PSDs from the AERosol Properties – Dust (AER-D), Saharan Mineral Dust Experiment (SAMUM-2), and Saharan Aerosol Long-Range Transport and Aerosol–Cloud-Interaction Experiment (SALTRACE) field campaigns through case studies. The new DAOD 10 µm retrievals were evaluated first through comparisons with the collocated DAOD 10.6 µm retrieved from the combined Imaging Infrared Radiometer (IIR) and CALIOP observations from our previous study (Zheng et al., 2022). The pixel-to-pixel comparison of the two DAOD retrievals indicates a good agreement ( R ∼0.7 ) and a significant reduction in ( ∼50 %) retrieval uncertainties largely thanks to the better constraint on dust size. In a climatological comparison, the seasonal and regional ( 2 ∘ × 5 ∘ <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="34pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="8a76e0febdc6ccff4a2b5651953fe28a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-8271-2023-ie00001.svg" width="34pt" height="11pt" src="acp-23-8271-2023-ie00001.png"/></svg:svg> ) mean DAOD 10 µm retrievals based on our combined MODIS and CALIOP method are in good agreement with the two independent Infrared Atmospheric Sounding Interferometer (IASI) products over three dust transport regions (i.e., North Atlantic (NA; R =0.9 ), Indian Ocean (IO; R =0.8 ) and North Pacific (NP; R =0.7 )). Using the new retrievals from 2013 to 2017, we performed ...