| P. Heck, R. Palikonda, and D.F. Young Lockheed Engineering and Sciences Company Hampton, VA 23666; 804-766-9674 heck@blitz.larc.nasa.gov |
P. Minnis Atmospheric Sciences Division NASA Langley Research Center Hampton, VA 23681 804-864-5671 |
The Atlantic Stratocumulus Transition Experiment (ASTEX) performed during June
1992 measured boundary layer cloud characteristics from the surface, aircraft,
balloons, and satellites. The latter measurements are critical to the
verification and assessment of mesoscale and GCM models of marine stratus.
Comparisons of the satellite results with other measurements are essential for
improvement and validation of satellite cloud retrieval schemes. Cloud
properties and their variations during ASTEX are examined using hybrid
bispectral threshold analyses of Meteosat visible and infrared data. CIoud
amount, height, thickness, and visible optical depth are determined for 0.5deg.
and 2.5deg. grids. Detailed results are presented for the instrumented islands
of Santa Maria, Azores and Porto Santo, Madieras. Diurnal variations in each
parameter are also presented. Radiative fluxes at the top of the atmosphere
are estimated for the larger grids using empirical spectral conversion
techniques. These flux values provide a boundary for radiation convergence
calculations for the grid. The ASTEX was executed in an area dominated by
stratocumulus. A Meteosat-derived cloud climatology is used to examine how
typical the weather conditions were during ASTEX.