SOLAR ABSORPTION BY WINTER BOUNDARY-LAYER CLOUDS OVER THE SEA THROUGH COLLOCATED AIRCRAFT MEASUREMENTS: TWO CASE STUDIES OF CONTINENTAL-TYPE WATER AND MARITIME MIXED-PHASED STRATOCUMULI

摘要

By means of collocated and synchronized flights by two instrumented aircraft, flying respectively above and below the cloud layer, we have directly measured the solar radiation budgets for two cases of wintertime boundary-layer clouds over the sea: one is featuring a rather uniform, super-cooled water stratocumulus cloud polluted by continental aerosols observed on 21 January 1999, and the other is highly inhomogeneous, mixed-phased stratiform clouds on 30 January 1999. The former cloud layer with the mean thickness of 500m absorbed appreciable (7%) and reasonable amounts of solar radiation in the visible and near-IR bands, respectively. The detected visible solar absorption was estimated to be caused by dust particles from the desert area in the northwest part of China. For the latter mixed-phase clouds, on the other hand, the visible solar absorption was almost zero averaging over a long flight distance, and the averaged near-IR absorption was about 24% for the cloud layers with the mean thickness of 1.3km. For the both cloud cases, we have again found no evidence of the solar absorption anomaly.