On the Misclassification of Suspended Dust at an AERONET Site in the Sonoran Desert
Abstract
The Salton Basin is an arid, closed basin in southeastern California that experiences dust storms throughout the year. In order to better understand the dynamics of dust storms in this region, starting in 2020 a new research site was constructed within this basin and downwind of its main dust source region, the Anza Desert. Among other instruments, this site is equipped with a NASA Aerosol Robotic Network (AERONET) Cimel Electronique Sun-sky radiometer (CIMEL), in order to retrieve aerosol optical depth (AOD) of dust outbreaks there, along with other aerosol microphysical parameters. Here we report that cloud screening by the AERONET Version 3, level 1.5 algorithm oftentimes misclassifies dust storms advected over the site as cloud-contaminated or erroneous measurements. This misclassification is verified by simultaneous measurements with a Vaisala CL51 ceilometer and observations from a RoundShot 360-degree camera located to the west of the site. An analysis of the Version 3 processing algorithm demonstrates that dust misclassification regularly occurs because of the so-called "triplet criterion" test; where measurements are rejected if the 1-minute variability in the retrieved AOD at some wavelength is larger than 1.5% of the retrieved AOD. We also find that other spectral tests designed to discriminate clouds from aerosols result in the misclassification of dust, although less frequently, and that high-AOD restoring tests within the level 1.5 algorithm do not correct this misclassification. Correcting the misclassification of dusty measurements results in an increase in the daily averaged AOD during dusty days by a factor of two. Additionally, analogous recorded inaccuracies in the classification of advected Saharan dust following the level 1.5 algorithm are analyzed. These findings may be relevant to AOD measurements at other AERONET sites close to dust sources.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA019...05W
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 3322 Land/atmosphere interactions;
- ATMOSPHERIC PROCESSES;
- 1622 Earth system modeling;
- GLOBAL CHANGE