On the aerosol weekly cycle spatiotemporal variability over Europe
In this work, we focus on the spatial and temporal variability of the aerosol weekly cycle over Europe as these were recorded from TERRA MODIS and AQUA MODIS satellite instruments. Aerosol optical properties retrieved from MODIS TERRA (February 5 2000–February 2009) and AQUA (July 2002–December 2008) were used to produce an aerosol weekly cycle index. First, the general aerosol optical depth (AOD550 nm) weekly patterns were deﬁned at a 1 ◦ × 1 ◦ resolution using the satellite-based index and six regions of interest were selected. To remove episodic dust transport events, two diﬀerent aerosol ﬂags, employing ﬁne mode ratio (FMR550 nm) and AOD550 nm data, 10 were applied diagnostically. A second spatial averaging method was then used for the investigation of the weekly variability and the statistical signiﬁcance of the weekly cycle over each of the previously selected regions. Three major weekly cycle plumes are observed over Europe. A strong positive (higher values during midweek) weekly cycle plume appears over Central Europe, while a strong negative (higher values during 15 weekend) weekly plume appears over the Iberian Peninsula and the North-eastern Europe. A weak but statistically signiﬁcant negative plume is apparent over the Eastern Mediterranean. The temporal examination of the weekly cycles shows that in some areas there are seasonal diﬀerences in the sign of the weekly cycle. The aerosol weekly variability over diﬀerent regions in Europe was examined in conjunction with 20 the dominating synoptic wind patterns from the NCEP/NCAR reanalysis, showing that the seasonal weekly cycle plumes over regions situated in the eastern Europe and the Mediterranean Sea could be partly attributed to the westerly transport of continental aerosols.