Abstract
Column aerosol optical properties were derived from multifilter rotating shadowing radiometer (MFRSR) observations carried out at Girona (northeast Spain) from June 2012 to June 2014. We used a technique that allows estimating simultaneously aerosol optical depth (AOD) and Ångström exponent (AE) at high time-resolution. For the period studied, mean AOD at 500nm was 0.14, with a noticeable seasonal pattern, i.e. maximum in summer and minimum in winter. Mean AE from 500 to 870nm was 1.2 with a strong day-to-day variation and slightly higher values in summer. So, the summer increase in AOD seems to be linked with an enhancement in the number of fine particles. A radiative closure experiment, using the SMARTS2 model, was performed to confirm that the MFRSR-retrieved aerosol optical properties appropriately represent the continuously varying atmospheric conditions in Girona. Thus, the calculated broadband values of the direct flux show a mean absolute difference of less than 5.9Wm−2 (0.77%) and R=0.99 when compared to the observed fluxes. The sensitivity of the achieved closure to uncertainties in AOD and AE was also examined. We use this MFRSR-based dataset as a reference for other ground-based and satellite measurements that might be used to assess the aerosol properties at this site. First, we used observations obtained from a 100km away AERONET station; despite a general similar behavior when compared with the in-situ MFRSR observations, certain discrepancies for AOD estimates in the different channels (R<0.84 and slope<1) appear. Second, AOD products from MISR and MODIS satellite observations were compared with our ground-based retrievals. Reasonable agreements are found for the MISR product (R=0.92), with somewhat poorer agreement for the MODIS product (R=0.70). Finally, we apply all these methods to study in detail the aerosol properties during two singular aerosol events related to a forest fire and a desert dust intrusion.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.