One method of estimating the longwave radiative heating of the atmosphere is to combine satellite observations of emitted radiances with those computed from synoptic temperature and humidity profiles. Modeled and observed radiances are brought into agreement by altering cloud properties or even by adjusting the temperature and water vapor profiles. Here this strategy is examined in an exploratory study using global meteorological data sets and a radiative transfer model typical of those found in general circulation models. Calculated radiances are compared to those observed by the Earth Radiation Budget Satellite (ERBS). Input for the model is obtained from the National Meteorological Center (NMC) in the form of vertical profiles of temperature and relative humidity. The comparisons are limited to clear sky as deduced by ERBE algorithms, and additional filtering which requires homogeneous surface type for a 3 x 3 array of ERBS scanner fields of view. Observations are obtained from 60° N to 60° S that lie within 30 minutes of the NMC analysis time. Following the work of Ramanathan and Downey (1986), comparisons are separated into climatologically distinct groups as well as by satellite viewing angle. This separation is an attempt to distinguish between biases in the radiation model and those in the NMC data set. Results are presented for the months of July 1985, and January 1986. A comparison of the present radiation model's output with that obtained from a Geophysical Fluid Dynamics Laboratory (GFDL) model shows a bias of nearly 3% in the present model for a standard mid-latitude summer profile. Global results show a negative bias in the modeled values for nearly all scenes, except for nighttime desert. The nighttime desert bias may be a result of a skin-air temperature difference not resolved by the NMC analyses. The overall negative bias may be a result of an overestimation of water vapor for regions with low relative humidity. / Graduation date: 1991

The dynamics of the atmospheric meteor region have been studied using the data obtained with - - the Grahamstown (33°16'S, 26<>:30'E) meteor radar between the years 1987 and 1993 inclusive. Harmonic analysis and the maximum entropy method (MEM) , were used for the spectral characterization ofthe wind above Grahamstown. The prevailing wind, tidal (periods 12- and 24- h) and other (periods 8- and 6-h) oscillations were extracted from the data using the guidelines agreed upon by the A TMAP community. Above Grahamstown the zonal and meridional prevailing winds were found to be predominantly eastward and equatorward respectively. Tidal amplitudes are comparable to the magnitude of the prevailing wind vector, with the diurnal tide being stronger than the semidiurnal tide. The phase differences between ,the zonal and meridional components of the semidiurnal and diurnal tides are - 2 hand - 5 h respectively, which is in reasonable agreement with the corresponding expected values of3 hand 6 h. The tidal wind vectors are on average elliptically polarized with anticlockwise rotation. Longitudinal and day-to-day tidal variations were studied. From the longitudinal study, the semidiurnal tide was found to be dominated by migrating modes, while the diurnal tidal behaviour suggests the presence of nonmigrating modes with zonal wavenumber s = 4. Tides were found to be variable from day to day with little apparent correlation between the zonal and meridional components of the respective tides.