Observations of wintertime clouds and precipitation were made from Nov, in 1979 to Jan. 1980 at Inuvik in Northwest Territories of Canada. Following conclusions about the charac-teristic features of clouds and precipitation were reached mainly by analysing the data of upper-air sounding and our radar observation. Three types of clouds were observed frequently during the observation period. In type I clouds the lapse rate of temperature is nearly moist-adiabatic, in type II clouds temperature hardly changes with height and in type III clouds it increases with height. In warm period types I and III clouds were observed and they often constituted a two-layers cloud system. In cold period type II clouds were often observed, and they tended to be more persistent and deeper than types I and III clouds. Most of type II clouds were detected by a vertically pointing radar of 8.6mm in wave-length, though they were not identified clearly by eye observation in many cases. They are inferred to have been composed of large ice particles whose number concentration was not high. During the obser-vation period precipitation originated from type II clouds occupied about 30% of the total period of precipitation and it contributed to about 20% of total precipitation amount.
One of the subprograms of the Polar-Experiment North (POLEX-North), "Observation of. Wintertime Clouds and Precipitation" was carried out at Inuvik (68°22'N, 133°42'W), Northwest Territories, Arctic Canada, from December 1, 1979 to January 5, 1980. When the warm air from the Pacific Ocean advected over the observation station, dendritic crystals were observed as rimed and snowflakes, and at times, graupel particles. Corresponding to these snow crystals, a PPI radar echo showed convective type. On the other hand, when the polar air masses covered over the observation station, as expected from the temperature condition, the prevailing shapes . of snow crystals were combination of bullets, columns and crossed plates. Corresponding to these air masses, a PPI radar echo was a stratiform type. The maximum precipitation intensities in a successive snowfall during the observation period were in the order of 10-3 to 100mm•hr-1. Calculating the mass using the number flux and the maximum precipitation intensity, they fell into the range between 1×10-3mg and 1×10-2mg. The equivalent diameters corresponding to these masses were from 0.12mm to 0.27mm. The Z-R relation, Z=13R1.2 and Z=9R1.1 were obtained for crossed plates and column type snow crystals, respectively. These relations were nearly equal to Z=10R1.0 for ice crystals introduced by Sato et al. (1981) for the light precipitation intensity during the summer season at the South Pole. About the relation between the maximum size and number flux, the increase in number flux increased the maximum size when the cloud thick-ness was thick and the increase in number flux decreased the maximum size when the cloud thickness was very thin. Based on the relation above described, a correlation between cloud thickness, maximum and minimum temperatures in clouds, weather conditions of synoptic scale and the shapes of snow crystals was summarized in Fig. 15.
Wintertime snow clouds were observed by a vertically pointing radar of 8.6mm in wavelength from Nov. 1979 to Jan. 1980 at Inuvik in the Arctic Canada. In most cases the level of the radar-echo top was nearly equal to or lower than that of the cloud top. Less frequently, however, it was higher than 4500m in altitude independently of the cloud top level. Air temperature was always higher than -40°C at the level of the radar-echo top. The radar-echo intensity near the ground surface tended to increase with an increase in the level of the radar-echo top. Typical types of snow crystals were the crossed plates, the bullet and the column. The type predominant over others in occurrence varied with the radar-echo intensity near the ground surface and the level of the radar-echo top. This predominance was discussed by taking into account a difference in the vertical profile of air temperature in cloud layers.
A theoretical assessment has been made on the relationship between the number of chan-nels used and the accuracy of remotely measured sea surface temperature (SST) by multi-channel radiance observations from satellite. It has been shown that the accuracy of SST continuously increases with the increase of the number of channels. The accuracy also depends on the accuracy of they clear radiance, accuracy of the initial guess of the SST and transmittance of the atmosphere. A procedure of the objective analysis for the SST has been developed and applied to the analysis of the SST that is obtained in Meteorological Satellite Center (MSC) on routine base from NOAA-6 meteorological satellite. The results has been compared with buoy and ship reports of SST and the GOSSTCOMP sea surface temperature made by NOAA/NESS. Root-mean-square deviation of satellite derived SST from ship reports is about 0.8°K.
Size distributions and optical thicknesses of aerosols were measured with the particle counter and the sunphotometer respectively on an aircraft and at the surface. The optical thickness was calculated from measured size distributions and compared with that observed with the sunphotometer. For the aircraft measurements, the optical thickness was determined for refractive indices 1.4, 1.5, 1.595 and 1.5-0.01i from the counter measurements and com-pared with the observed values. The result showed that the observed and the calculated optical thicknesses at 500nm were in fairly good agreement, even though it depended on the refractive index. A mixing layer was observed during the aircraft measurements and the aerosol optical thickness at the top of this layer decreased to about one tenth of that at the surface, so the aerosols in the mixing layer account for the greatest part of the contributions to the optical thickness at the surface. From the observed aerosol concentration at the surface and the aerosol vertical profile given by Elterman, the optical thickness at the surface was also determined and compared with the observed values. The ratio of the calculated optical thickness to the observed at the surface was close to unity for neutral conditions. But the calculated value was larger and smaller than the observed for stable and unstable conditions, respectively.
To estimate the complex refractive indices and the size distributions of aerosols and hydrosols from light scattering measurements, we present a data processing technique using both inversion and library methods. Extensive numerical simulations have shown that the true values of complex refractive index and size distribution are retrieved fairly well when this method is applied to measurements of polarization components of scattered radiation parallel and perpendicular to the scattering plane.
Ship-based measurements of wind profiles in the boundary layer were carried out suc-cessfully in the tropical western Pacific, as a part of the observational program of the MONEX in Japan. A wind-finding procedure by use of pilot-balloon observation on board a ship is developed for the present study. Observed wind field in the boundary layer shows the characteristics of the mixed layer, that is, the layer of uniform wind speed and direction in the vertical. The depth of the layer almost corresponds with that of the mixed layer deter-mined from the thermodynamical structure of the boundary layer. The results seem to be in contrast with the general feature in the undisturbed trade winds where there appears appreciable vertical shear of wind speed in the thermodynamically determined mixed layer. A few estimations of cross-isobar angle and ratio of actual to geostrophic wind speed of the boundary layer wind are made, though roughly, in good agreement with climatological value in lower latitudes. An evidence is obtained that the depth of "a density current" by downdraft in front of the squall cell is about two hundred meters above the sea surface.
Airborne measurements within an internal boundary layer were carried out above a coastal region. Here, the free convective internal boundary layer, IBLt, which develops along with the sea breeze is analyzed. Data are classified into several groups considering the horizontal and vertical variations of the potential temperature. When the airplane travels from the stable marine atmosphere into the IBLt, vigorous turbulence is measured earlier than potential temperature begins to increase. The IBLt determined from the turbulence level is about one and a half times higher than the IBLt determined from the temperature. Humidity begins to increase when vigorous turbulence takes place. This seems to be due to the entrainment effect of thermal plumes into the upper marine stable atmosphere. The lapse rate of the marine atmosphere plays an important role in determing the height of the IBLt and potential temperature increase within the layer.
The turbulent structure of the atmospheric boundary layer above the ocean was inves-tigated by experimental measurements of wind vectors and air temperature at several points around a marine observation tower, and the space correlation of turbulence is estimated from the behaviour of eddies with frequency under near neutral conditions in the surface layer. Coherences of wind vector and of air temperature are considered to be the unique func-tion of the frequency which is non-dimensionalized by the mean wind velocity and the height, and of the distance which is non-dimensionalized by the height. Phase spectra are also considered. Furthermore the coherence in three-dimensional space and the phase spec-trum in a vertical direction are formulated with the exponential and algebraic functions respectively. They are confirmed by the simultaneous measurement of turbulent air flow. However when the distance is very large, the lateral and vertical wind components do not always obey the present empirical forms. An integral scale of turbulent eddies with frequency is evaluated from the empirical formula of the coherence, and its relation to characteristics of the surface layer is discussed. Eddy slopes are estimated from the observed vertical phase spectrum and the integral scale.