Abstract: Satellite observations allowed obtaining data on the visible brightness of cumulus clouds over South Park, Colorado, while aircraft observations were made in cloud to obtain the drop size distributions and liquid water content of the cloud. Attention is focused on evaluating the relationship between cloud brightness, horizontal dimension, and internal microphysical structure. A Monte Carlo cloud model for finite clouds was run using different distributions of drop sizes and numbers, while varying the cloud depth and width to determine how theory would predict what the satellite would view from its given location in space. Comparison of these results to the satellite observed reflectances is presented. Theoretical results are found to be in good agreement with observations. For clouds of optical thickness between 20 and 60, monitoring cloud brightness changes in clouds of uniform depth and variable width gives adequate information about a cloud's liquid water content. A cloud having a 10:1 width to depth ratio is almost reaching its maximum brightness for a specified optical thickness.

Abstract: Stereographic pairs of SMS/GOES images, generated simultaneously by the spin-scan cameras of each of two geostationary satellites (SMS 1 and SMS 2, separated by 32 degrees of longitude on February 17, 1975), have been analyzed photogrammetrically to yield cloud heights with a two-sigma uncertainty of 500 meters. The 32-degree angle between the image plane of the two satellites, plus the distortions involved in transferring the image of a nearly full hemisphere of the earth onto a plane, required the development of a special instrument to permit stereographic compilation. Cloud heights measured stereographically compared favorably with heights of the same clouds measured by radar and IR methods. The same SMS image pairs were used to measure mountain-top heights with a mean deviation of 0.24 km from cartographic values.

Abstract: Monthly and zonally averaged surface cover climatology data are presented which are used to construct monthly and zonally averaged surface albedos. The albedo transformations are then applied to the surface albedos, using solar zenith angles characteristic of the Nimbus 6 satellite local sampling times, to obtain albedos at the top of clear and totally cloud covered atmospheres. These albedos are then combined with measured albedo data to solve for the monthly and zonally averaged fractional cloud cover. The measured albedo data were obtained from the wide field of view channels of the Nimbus 6 Earth Radiation Budget experiment, and consequently the fractional cloud cover results are representative of the local sampling times. These fractional cloud cover results are compared with recent studies. The cloud cover results not only show peaks near the intertropical convergence zone, but the monthly migration of the position of these peaks follows general predictions of atmospheric circulation studies.

Abstract: The pressure perturbation associated with a convective cell has been measured with an aircraft, at one level about 1500 m below cloud top. Agreement is found with Barnes' (1969) experimental data and with the results of the Wilhelmson's (1974) three-dimensional model of a convective cloud in a shared environment. The efficiency of the “pressure shield” against entrainment is examined.

Abstract: This study describes the design and construction of a 5 µm imaging system used at the Hale 5 m (200 inch) telescope to acquire high spatial resolution infrared images of Jupiter. These images, recorded in a spectral region clear of terrestrial and Jovian gaseous absorption, offer a unique look into the deep atmosphere and provide direct observational evidence for the existence of multiple layers of clouds in the Jovian atmosphere. Evidence of layering is provided by the observed trimodal nature and persistence of the 5 µm flux-frequency distribution of equal areas on the Jovian disk. This indicates that three distinct brightness temperatures have a higher probability of being observed than a continuum of temperatures, and that, despite significant observed variations in the lateral 5 µm cloud distribution, this phenomenon is a long term stable vertical cloud feature. Furthermore, the visible color differences correlate with areas of different 5 µm intensity, implying that the colors are due to reflection from areas of different chemistry or state at different levels in the atmosphere. Also, short time scales are observed for large 5 µm flux variations over extensive areas of the Jovian disk, supporting the concept that the redistribution of obscuring clouds accounts for the contrasts at 5 µm. Finally, the 5 µm limb-darkening and opacity models, derived from imaging and spectroscopic measurements, are consistent with multiple layering of clouds in the Jovian atmosphere. Further information about the Jovian clouds results from the combination of 5 µm spectroscopic and imaging data sets. From the shape of the 5 µm spectrum true maximum brightness temperatures are derived, corrected for the clearest regions in the Jovian atmosphere. Furthermore, from data on spectral line saturation, limits are placed on the 5 µm cloud reflectivity over the field of view of the spectrometer. With this information, combined with the knowledge of the spatial flux distribution from imaging, constraints are derived for the optical properties of the upper Jovian clouds. A three layer cloud model is developed which is consistent with all of the observational data at 5 µm. The three model cloud layers have cloud top temperatures of T_1 ≤ 190°K (presumably T_1 ≃ 140°K), T_2 = 228 ± 2°K and T_3 = 292 ± 8°K. The highest layer, found only over the white zones and red spots, has optical depth near unity and transmits radiation from deeper levels. This upper level has a mean 5 µm cloud reflectivity less than 0.4, while the whole central 25% of the disk has a mean reflectivity less than 0.1. The middle cloud deck is present under the upper level clouds and over the brown colored Jovian belts. This level is optically thick everywhere except in regions where blue-gray areas are visible. Here the middle level thins to a mean optical depth of about 2 and allows radiation from the deepest and hottest level to be detected.

Abstract: : Variations of thunderstorm cloud-top parameters are examined using high temporal frequency satellite digital data. The day chosen as a case study, 5 May 1977, featured an extensive severe weather outbreak and was part of the Research Rapid Scan Day program during which three-minute interval satellite data was collected from GOES-1. Overshooting top heights, measured by a shadow casting method, are added to infrared-determined heights and compared to radar echo top heights. Good agreement is noted between satellite-determined tops and radar echo tops. Overshooting tops are significantly higher just prior to hail occurrences than for tornado occurrences. Infrared imagery is found not to be adequate to reliably identify overshooting tops. Growth rate diagrams for five storms yield little in the way of signatures which would be an aid in prediction of severe weather events. An image differencing technique is demonstrated which may be of some aid in quantitatively measuring thunderstorm growth and advection. This study stresses the analysis of digital satellite data with a sophisticated video imaging system, the All Digital Video Imaging System for Atmospheric Research (ADVISAR) at Colorado State University. (Author)

Abstract: : A horizontal differencing bi-spectral technique has been developed which includes an iteration scheme for reducing errors in computed cloud amount. The technique requires that cloud surfaces over the area of application be horizontally homogeneous, and as developed, assumes that the observed maximum and minimum brightness counts represent cloud and clear filled resolution points respectively. These values are then used to normalize the data in computing total cloud amount. The computed results of the horizontal differencing bi-spectral method, as applied to real data sets, have been compared to the results obtained from a modified frequency distribution method and the general bi-spectral method. The results of this comparative analysis indicate that the computed cloud amounts of the horizontal differencing method are less variable than for the frequency distribution and general bi-spectral methods, and are thus better suited for objective analyses. The computed cloud temperatures of the horizontal differencing method were also shown to be more realistic than those computed by the general bi-spectral method.

Abstract: Cloud altitudes specified from the Infrared Temperature Profile Radiometer on the Nimbus 5 satellite are compared with simultaneous observations by radiosonde and ground-based ranging measurements conducted with the lidar system at CSIRO in Aspendale, Victoria, Australia, during September 1976. The results show that the cloud altitudes deduced by the CO2 channel absorption method are in general agreement with the lidar and radiosonde determinations, regardless of the cloud opacity and amount.