Study of vertically resolved aerosol properties over an urban background site in Madrid (Spain)

Abstract

This work presents a comparison of aerosol properties measured by in situ and remotesensing

instrumentation over an urban background site in Madrid (Spain) in autumn

2010. Aerosol size distribution was characterized at ground level by the combined use

of two instruments and also in elevated layers by airborne in situ instrumentation.

Simultaneously, vertically resolved lidar profiles provided information about the optical

properties of aerosols present in the different layers observed. Backscatter-derived

Ångström exponent, calculated using Mie theory with volume size distribution

detected experimentally, yielded values lower than 0.5 near ground level, increasing

to over 1.5 in elevated layers. The same trend was observed for values obtained using

the lidar system. Size distribution measured at elevated layers indicated that the large

exponents observed there are associated with size distribution, with a negligible

contribution of coarse particles. The results are compromised by the major uncertainty

associated with the backscatter-derived Ångström exponents, due to the low aerosol

load detected in the elevated layers.