Contents: A comparison of altitudes of the lower cloud boundaries determined by an instrument and from an aircraft; Frontal cloud systems as observed from aircraft.

Anyone who has experienced turbulence in flight knows that it is usually not pleasant, and may wonder why this is so difficult to avoid. The book includes papers by various aviation turbulence researchers and provides background into the nature and causes of atmospheric turbulence that affect aircraft motion, and contains surveys of the latest techniques for remote and in situ sensing and forecasting of the turbulence phenomenon. It provides updates on the state-of-the-art research since earlier studies in the 1960s on clear-air turbulence, explains recent new understanding into turbulence generation by thunderstorms, and summarizes future challenges in turbulence prediction and avoidance.

This topical volume of the Journal of Pure and Applied Geophysics utilizes new information not previously accessible for fog related research. It focuses on surface and remote sensing observations of fog, various numerical model applications using new parameterizations, fog climatology, and new statistical methods. The results presented in this special issue come from research efforts in North America and Europe.

Clear air turbulence data were collected from two of the four world-wide reporting periods set up by the International Civil Aviation Organization (ICAO). The occurrences and non-occurrences of turbulence were summarized with respect to time periods, altitudes, and geographical locations. These data were analyzed in relation to associated meteorological parameters and large-scale synoptic patterns. Special attention was given to areas with at least 25 percent probability of moderate or greater turbulence. Vertical wind shear appeared to be an important parameter along with 12-hour changes in wind speed, vertical wind shear, and horizontal wind shear. The synoptic patterns on the mean 300-mb charts and the individual 300-mb charts were discussed in relation to the probabilities of moderate or greater turbulence. The following forecast criteria were suggested: moderate or greater turbulence will be found (1) within 150 miles of a jet stream with at least a 100-knot maximum wind speed if the vertical wind shear is at least 4 knots per 1000 feet, or (2) within 150 miles of a sharp trough line with a marked horizontal wind shear across the trough line. (Author).