DISTRIBUTIONS AND CHARACTERISTICS OF VARIOUS BROADSCALE AND SPECIAL CLOUD SYSTEMS

Cloud cover--as shown by various types of data such as surface observations, satellite photographs, U-2 photographs, and vertically pointing radar--was analyzed to provide information on clouds as an obstacle to vision through the atmosphere. In these studies the photographic data were used to assess the extent to which significant operational knowledge can be derived from surface cloud observations. Comparison of surface observations with U-2 and TIROS photographs shows that surface observations are frequently not representative of cloud cover over even a small fraction of the distance between adjacent stations. Time changes in cloud cover were determined from hourly cloud observations and were summarized to show the probability of extended periods of various amounts of cloud cover. Comparison of probabilities for different seasons and different geographic locations is included. The probabilities of seeing specific locations along latitudes 15, 30, and 45 degrees N were determined from nephanalyses of TIROS photographs and surface synoptic reports. These probabilities are given for the four seasons, and the effects of synoptic features on these probabilities are discussed. The report also contains cloud top altitudes measured from U-2 photographs and thicknesses of cloud layers with bases at various heights as shown by a vertically pointing radar. (Author) Available copy will not permit fully legible reproduction. Reproduction will be made if requested by users of DDC. Copy is available for public sale.