DUGi

Common summertime total cloud cover and aerosol optical depth weekly variabilities over Europe: Sign of the aerosol indirect effects?

http://dugi.udg.edu/item/http:@@@@hdl.handle.net@@10256@@11845

In this study, the summer total cloud cover (TCC) weekly cycle over Europe is investigated using MODIS and ISCCP satellite data in conjunction with aerosol optical depth (AOD) MODIS data. Spatial weekly patterns are examined at a 1° × 1° (MODIS) and 250 × 250 km2 (ISCCP) resolution. Despite the noise in the TCC weekly cycle patterns, their large-scale features show similarities with the AOD550 patterns. Regions with a positive (higher values during midweek) weekly cycle appear over Central Europe, while a strong negative (higher values during weekend) weekly plume appears over the Iberian Peninsula and the North-Eastern Europe. The TCC weekly variability exhibits a very good agreement with the AOD550 weekly variability over Central, South-Western Europe and North-Eastern Europe and a moderate agreement for Central Mediterranean. The MODIS derived TCC weekly variability shows reasonable agreement with the independent ISCCP observations, thus supporting the credibility of the results. TCC and AOD550 correlations exhibit a strong slope for the total of the 6 regions investigated in this work with the slopes being higher for regions with common TCC-AOD550 weekly variabilities. The slope is much stronger for AOD550 values less than 0.2 for Central and South-Western Europe, in line with previous studies around the world. Possible scenarios that could explain the common weekly variability of aerosols and cloud cover through the aerosol indirect effects are discussed here also taking into account the weekly variability appearing in ECA&D E-OBS rainfall data

The authors would like to thank NASA Goddard Space Flight Center (GSFC) Level 1 and Atmosphere Archive and Distribution System (LAADS) (http://ladsweb.nascom.nasa.gov) for making available the MODIS TERRA and AQUA C005 Level 3 aerosol and cloud data and acknowledge the ISCCP (D1) cloud product from ISCCP’s website (http://isccp.giss.nasa.gov/), the E-OBS dataset from the EU-FP6 project ENSEMBLES (http:// ensembles-eu.metoffice.com) and the data providers in the ECA&D project (http://www.ecad.eu). A. Sanchez-Lorenzo was supported by a postdoctoral fellowship from the "Departament d’Innovacio, Universitats i Empresa de la Generalitat de Catalunya" (2011 BP-B 00078), the project NUCLIERSOL (CGL2010-18546), and the postdoctoral fellowship no. JCI-2012-12508. A. K. Georgoulias acknowledges the support from the QUADIEEMS project which is co-financed by the European Social Fund (ESF) and national resources under the operational program Education and Lifelong Learning (EdLL) within the framework of the Action "Supporting Postdoctoral Researchers" for part of his work

Elsevier