15-year variability of desert dust optical depth on global and regional scales

<p>This study aims to investigate global, regional and seasonal temporal dust changes as well as the effect of dust particles on total aerosol loading using the ModIs Dust AeroSol (MIDAS) fine-resolution dataset. MIDAS delivers dust optical depth (DOD) at fine spatial resolution (<span clas...

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Autores principales: S.-A. Logothetis, V. Salamalikis, A. Gkikas, S. Kazadzis, V. Amiridis, A. Kazantzidis
Formato: article
Lenguaje:EN
Publicado: Copernicus Publications 2021
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Acceso en línea:https://doaj.org/article/f45c2195c9cd4fcfb8084830529a174d
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Sumario:<p>This study aims to investigate global, regional and seasonal temporal dust changes as well as the effect of dust particles on total aerosol loading using the ModIs Dust AeroSol (MIDAS) fine-resolution dataset. MIDAS delivers dust optical depth (DOD) at fine spatial resolution (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M1" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">0.1</mn><msup><mi/><mo>∘</mo></msup><mo>×</mo><mn mathvariant="normal">0.1</mn><msup><mi/><mo>∘</mo></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="11pt" class="svg-formula" dspmath="mathimg" md5hash="9ff7f6b7ad74ef28cb0ca0c82ba5867a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-16499-2021-ie00001.svg" width="52pt" height="11pt" src="acp-21-16499-2021-ie00001.png"/></svg:svg></span></span>) spanning from 2003 to 2017. Within this study period, the dust burden increased across the central Sahara (up to 0.023 yr<span class="inline-formula"><sup>−1</sup></span>) and Arabian Peninsula (up to 0.024 yr<span class="inline-formula"><sup>−1</sup></span>). Both regions observed their highest seasonal trends in summer (up to 0.031 yr<span class="inline-formula"><sup>−1</sup></span>). On the other hand, declining DOD trends are encountered in the western (down to <span class="inline-formula">−0.015</span> yr<span class="inline-formula"><sup>−1</sup></span>) and eastern (down to <span class="inline-formula">−0.023</span> yr<span class="inline-formula"><sup>−1</sup></span>) Sahara, the Bodélé Depression (down to <span class="inline-formula">−0.021</span> yr<span class="inline-formula"><sup>−1</sup></span>), the Thar (down to <span class="inline-formula">−0.017</span> yr<span class="inline-formula"><sup>−1</sup></span>) and Gobi (down to <span class="inline-formula">−0.011</span> yr<span class="inline-formula"><sup>−1</sup></span>) deserts, and the Mediterranean Basin (down to <span class="inline-formula">−0.009</span> yr<span class="inline-formula"><sup>−1</sup></span>). In spring, the most negative seasonal trends are recorded in the Bodélé Depression (down to <span class="inline-formula">−0.038</span> yr<span class="inline-formula"><sup>−1</sup></span>) and Gobi Desert (down to <span class="inline-formula">−0.023</span> yr<span class="inline-formula"><sup>−1</sup></span>), whereas they are in the western (down to <span class="inline-formula">−0.028</span> yr<span class="inline-formula"><sup>−1</sup></span>) and the eastern Sahara (down to <span class="inline-formula">−0.020</span> yr<span class="inline-formula"><sup>−1</sup></span>) and the Thar Desert (down to <span class="inline-formula">−0.047</span> yr<span class="inline-formula"><sup>−1</sup></span>) in summer. Over the western and eastern sector of the Mediterranean Basin, the most negative seasonal trends are computed at summer (down to <span class="inline-formula">−0.010</span> yr<span class="inline-formula"><sup>−1</sup></span>) and spring (down to <span class="inline-formula">−0.006</span> yr<span class="inline-formula"><sup>−1</sup></span>), respectively. The effect of DOD on the total aerosol optical depth (AOD) change is determined by calculating the DOD-to-AOD trend ratio. Over the Sahara the median ratio values range from 0.83 to 0.95, whereas in other dust-affected areas (Arabian Peninsula, southern Mediterranean, Thar and Gobi deserts) the ratio value is approximately 0.6. In addition, a comprehensive analysis of the factors affecting the sign, the magnitude and the statistical significance of the calculated trends is conducted. Firstly, the implications of the implementation of the geometric mean instead of the arithmetic mean for trend calculations are discussed, revealing that the arithmetic-based trends tend to overestimate compared to the geometric-based trends over both land and ocean. Secondly, an analysis interpreting the differences in trend calculations under different spatial resolutions (fine and coarse) and time intervals is conducted.</p>