Columnar aerosol properties from sun-and-star photometry: statistical comparisons and day-to-night dynamic

Abstract

Abstract. This work presents the first analysis of longterm correlative day-to-night columnar aerosol optical properties. The aim is to better understand columnar aerosol dynamic from ground-based observations, which are poorly studied until now. To this end we have used a combination of sun-and-star photometry measurements acquired in the city of Granada (37.16 • N, 3.60 • W, 680 m a.s.l.; South-East of Spain) from 2007 to 2010. For the whole study period, mean aerosol optical depth (AOD) around 440 nm (±standard deviation) is 0.18 ± 0.10 and 0.19 ± 0.11 for daytime and nighttime, respectively, while the mean Angström exponent (α) is 1.0 ± 0.4 and 0.9 ± 0.4 for daytime and nighttime. The ANOVA statistical tests reveal that there are no significant differences between AOD and α obtained at daytime and those at nighttime. Additionally, the mean daytime values of AOD and α obtained during this study period are coherent with the values obtained in the surrounding AERONET stations. On the other hand, AOD around 440 nm present evident seasonal patterns characterised by large values in summer (mean value of 0.20 ± 0.10 both at daytime and nighttime) and low values in winter (mean value of 0.15 ± 0.09 at daytime and 0.17 ± 0.10 at nighttime). The Angström exponents also present seasonal patterns, but with low values in summer (mean values of 0.8 ± 0.4 and 0.9 ± 0.4 at dayand night-time) and relatively large values in winter (mean values of 1.2 ± 0.4 and 1.0 ± 0.3 at daytime and nighttime). These seasonal patterns are explained by the differences in the meteorological conditions and by the differences in the strength of the aerosol sources. To take more insight about the changes in aerosol particles between day and night, the spectral differences of the Angström exponent as function of the Angström exponent are also studied. These analyses reveal increases of the fine mode radius and of the fine mode contribution to AOD during nighttime, being more remarkable in the summer seasons. These variations are explained by the changes of the local aerosol sources and by the meteorological conditions between daytime and nighttime, as well as aerosol aging processes. Case studies during summer and winter for different aerosol loads and types are also presented to clearly illustrate these findings.

High temporal resolution estimates of columnar aerosol microphysical parameters from spectrum of aerosol optical depth by linear estimation: application to long-term AERONET and star-photometry measurements

“…20-21 and 25-27 July) possess relatively low values of AODs (∼ 0.15) and V (∼ 0.10 µm 3 µ −2 ), and medium values of α(440-870) (∼ 1.0). The Iberian Peninsula and the study area are important sources of anthropogenic pollution (Lyamani et al, 2010(Lyamani et al, , 2012, but during the summer season a significant amount of coarse particles from the ground are also injected into the atmosphere (Alados- Pérez-Ramírez et al, 2012a). This effect explains the relatively large values of r eff (0.30-0.55 µm) compared to those obtained in polluted areas (Dubovik et al, 2002b).…”

“…Alexandrov et al, 2008). Another motivation for developing such inversions algorithms is the development of star photometers (Herber et al, 2002;Perez-Ramirez et al, 2008a, 2012aBaibakov et al, 2015) and moon photometers (Esposito et al, 1998;Berkoff et al, 2011;Barreto et al, 2013) that can be used to fill the night-time gaps in the aerosol time series. However, the information content of retrievals based on AOD(λ) only is lower compared to those based on combined direct-sun and sky-radiance measurements.…”

Aerosol properties over the western Mediterranean basin: temporal and spatial variability

“…To date, a large number of studies has been done focusing on the eastern and central regions (e.g., Formenti et al, 1998;Gerasopoulos et al, 2003;Di Iorio et al, 2003;Kubilay et al, 2003;Pace et al, 2005Pace et al, , 2006Fotiadi et al, 2006;Meloni et al, 2007Meloni et al, , 2008Di Sarra et al, 2008;Di Biagio et al, 2010;Boselli et al, 2012). However, few studies have been done in the western Mediterranean Basin (Horvath et al, 2002;Alados-Arboledas et al, 2003;Mallet et al, 2003;Estellés et al, 2007;Saha et al, 2008;Pérez-Ramírez et al, 2012, Foyo-Moreno et al, 2014. The majority of these studies have been performed in coastal Mediterranean urban sites largely influenced by local pollution emissions, except those carried out at Crete and Lampedusa islands in the eastern and central Mediterranean Sea regions.…”

Effects of systematic and random errors on the retrieval of particle microphysical properties from multiwavelength lidar measurements using inversion with regularization

“…3040 D. Pérez-Ramírez et al: Errors of microphysical particle retrievals from 3β + 2α lidar measurements occurring in the atmosphere (Eck et al, 2010) and aerosol dynamics (e.g., Pérez-Ramírez et al, 2012).…”