Steven Platnick

A Validation of a Satellite Cloud Retrieval during ASTEX

Abstract An algorithm using NOAA-12 AVHRR (Advanced Very High Resolution Radiometer) solar reflectance measurements for retrieving cloud droplet size and optical thickness has been applied to a boundary layer stratocumulus cloud in the vicinity of the Azores on 12 June 1992 during the Atlantic Stratocumulus Transition Experiment (ASTEX). This day was particularly advantageous for validations because of the absence of cirrus or other higher-level clouds during the satellite overpass and the existence of a large relatively uniform stratus cloud dock. Uncertainty estimates for the retrievals are presented along with a discussion of the algorithm. An in-flight absolute calibration of AVHRR channel 1, necessary for accurate optical thickness retrievals, was done concurrently with the retrievals through comparison with a visible radiometer flown on the National Aeronautics and Space Administrations ER-2 and using the stratus cloud as the common reflectance target. Results are compared with in situ microphysica...

Airborne brightness temperature measurements of the polar winter troposphere as part of the airborne arctic stratosphere experiment II and the effect of brightness temperature variations on the diabatic heating in the lower stratosphere

In this paper the authors report radiometric measurements of tropospheric brightness temperatures obtained during the AASE II experiment. These measurements represent the first attempt to characterize effective radiative temperatures as seen from above the troposphere during the Arctic winter. The reported measurements include brightness temperatures at 6.7 and 10.5[mu]m as seen from the NASA DC-8 aircraft flying at about 11 km altitude. The authors present radiative transfer calculations to estimate the effect of tropospheric brightness temperature on the lower stratospheric heating rates. Because of the recent massive eruption of the Pinatubo volcano, the authors also discuss the effects of a volcanic aerosol layer. It is concluded that small particles like the volcanic aerosol or PSCs type 1 do not affect stratospheric heating rates by much; on the other hand, larger particles, PSCs types 2 and 3, may have significant effects on heating rates and consequently on dynamics of the lower stratosphere. The dynamical effects of local stratospheric temperature variations are briefly discussed. 14 refs., 7 figs., 2 tabs.

The MODIS Cloud Optical and Microphysical Product: An Evaluation of Effective Radius Retrieval Statistics and Model Simulations

Retrieved cloud optical and microphysical global statistics from the MODIS Collection 5 processing stream will be discussed. Evaluation includes algorithm sensitivities, aggregation sensitivities, and retrievals run on cloud resolving models of marine boundary layer clouds.