Horizontal variability of aerosol optical depth observed during the ARCTAS airborne experiment

摘要

We present statistics on the horizontal variability of aerosol optical depth(AOD) directly measured from the NASA P-3 aircraft. Our measurements duringtwo contrasting phases (in Alaska and Canada) of the ARCTAS mission arguablyconstrain the variability in most aerosol environments common over theglobe. In the Canada phase, which features local emissions, 499 nm AOD has amedian relative standard deviation (std_{rel, med}) of 19 % and 9 % andan autocorrelation (r) of 0.37 and 0.71 over 20 km and 6 km horizontalsegments, respectively. In the Alaska phase, which features long-rangetransport, the variability is considerably lower (std_{rel, med} = 3 %, r = 0.92 even over 35.2 km). Compared to the magnitude of AOD, its wavelengthdependence varies less in the Canada phase, more in the Alaska phase. Wetranslate these findings from straight-line flight tracks into grid boxesand points, to help interpretation and design of satellite remote sensing,suborbital observations and transport modeling.