Ítem


Aerosol optical depth in a western Mediterranean site: An assessment of different methods

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 500 nm was 0.14, with a noticeable seasonal pattern, i.e. maximum in summer and minimum in winter. Mean AE from 500 to 870 nm 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 5.9 W m-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 100 km 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

This research was supported by the Spanish Ministry of Economy and Competitiveness projects NUCLIERSOL (CGL2010-18546) and NUBESOL (CGL2014-55976-R). The first author enjoys a grant by the FPU program (FPU AP2010-0917) of the SpanishMinistry of Education. The fourth author enjoys a grant fromthe SpanishMinistry of Economy and Competitiveness (JCI-2012-12508)

© Atmospheric Research, 2016, vol. 174-175, p. 70-84

Elsevier

Autor: Sánchez Romero, Alejandro
González Gutiérrez, Josep Abel
Calbó Angrill, Josep
Sánchez Lorenzo, Arturo
Michalsky, J.
Data: 15 juny 2016
Resum: 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 500 nm was 0.14, with a noticeable seasonal pattern, i.e. maximum in summer and minimum in winter. Mean AE from 500 to 870 nm 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 5.9 W m-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 100 km 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
This research was supported by the Spanish Ministry of Economy and Competitiveness projects NUCLIERSOL (CGL2010-18546) and NUBESOL (CGL2014-55976-R). The first author enjoys a grant by the FPU program (FPU AP2010-0917) of the SpanishMinistry of Education. The fourth author enjoys a grant fromthe SpanishMinistry of Economy and Competitiveness (JCI-2012-12508)
Format: application/pdf
ISSN: 0169-8095
Accés al document: http://hdl.handle.net/10256/13133
Llenguatge: eng
Editor: Elsevier
Col·lecció: MICINN/PN 2011-2014/CGL2010-18546
MINECO/PE 2015-2017/CGL2014-55976-R
Reproducció digital del document publicat a: http://dx.doi.org/10.1016/j.atmosres.2016.02.002
Articles publicats (D-F)
És part de: © Atmospheric Research, 2016, vol. 174-175, p. 70-84
Drets: Tots els drets reservats
Matèria: Radiació solar
Solar radiation
Aerosols
Títol: Aerosol optical depth in a western Mediterranean site: An assessment of different methods
Tipus: info:eu-repo/semantics/article
Repositori: DUGiDocs

Matèries

Autors