Cloudless aerosol forcing efficiency in the UV region from AERONET and WOUDC databases

Aerosol Robotic Network (AERONET) and World Ozone and Ultraviolet Data Center (WOUDC) combined information have been used to calculate the aerosol forcing efficiency under cloud‐free conditions, ΔF e , in the ultraviolet region (290–325 nm) at surface. The stations of these global networks have been collocated spatial and temporarily, resulting three common stations: two in Canada, representative of background conditions (Bratt's Lake and Saturna Island) and one in Italy, characterized by rural and industrial aerosols (Ispra). The monthly ΔF e was calculated during spring and summer time in the common period, 1999 to 2004, and for the Cimel wavelengths 500, 440, 380 and 340 nm. The ΔF e values range from −0.65 ± 0.07 Wm −2 / τ 500 to −0.36 ± 0.03 Wm −2 / τ 340 for Ispra, whereas for the Canadian observatories the interval varies from −2.07 ± 0.62 Wm −2 / τ 500 to −0.16 ± 0.23 Wm −2 / τ 340 . No significant annual or seasonal trends for the ΔF e were found in any station.