First ISCCP Regional Experiment (FIRE) Atlantic Stratocumulus Transition Experiment (ASTEX) University of Washington C-131A Aircraft Data

The Atlantic Stratocumulus Transition EXperiment (ASTEX) was designed to address key issues related to stratocumulus to trade cumulus transition and mode selection. ASTEX involved intensive measurements from several platforms operating from 1-28 June 1992 in the area of the Azores and Madeira Islands. The purpose was to study how the transition and mode selection are effected by 1) cloud-top entrainment instability, 2) diurnal decoupling and clearing due to solar absorption, 3) patchy drizzle and a transition to horizontally inhomogeneous clouds through decoupling, 4) mesoscale variability in cloud thickness and associated mesoscale circulations, and 5) episodic strong subsidence lowering the inversion below the LCL.

Detailed descriptions of the scientific goals of ASTEX are in the FIRE Phase II: Research plan (1989) and in the ASTEX Operations Plan (1992). The University of Washington Convair data are best considered raw at this point and should be validated by comparing with data collected from other platforms where possible if high accuracy is desired. Of the three measures of liquid water content available from the Convair, the Johnson-Williams (JW) hot-wire probe is considered the most readily usable, although there is a significant drift in the output that should be accounted for.

The Forward Scattering Spectrometer Probe (FSSP) measured the liquid water content using optical scattering principles.