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 remote-sensing 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.

Acknowledgements

The work was supported by the European Union under the EARLINET-ASOS project (contract no. 025991 (RICA)) and by MICINN (Spanish Ministry of Science and Innovation) through projects CGL2010-17777 (PHAESIAN), CGL2010-09225-E (ISLIDAR), and CGL2010-10012-E (MISPA-LIDAR). The authors gratefully acknowledge the AEMET for the provision of the CIMEL data within the framework of collaboration agreement 10/161. The authors are grateful to INTA Aerial platforms of the Spanish ICTS programme, and the Spanish Air Force, via the CLAEX unit, for their efforts in maintaining and operating the aircraft. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model.