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Over 8500 rawinsonde soundings within 8° radius of tropical cyclones in the northwest Pacific and West Indies regions are statistically analyzed to determine occurrence frequencies of 15 m s−1 (30 kt) winds at the sea surface. At any radius the likelihood of encountering winds >15 m s−1 is found to increase with increasing central wind speed and with increasing radius of the highest closed isobar. There are significant right-side wind maxima and left-side minima with respect to the direction of storm motion. This reflects the natural storm asymmetry. Much variability is found in the radius of 15 m s−1 winds between cyclones of similar inner core intensity.

Ten years of rawinsonde data for 30 stations in the western North Pacific have been composited relative to tropical cyclone center positions. This is the same data set described in a previous paper by the same authors. These data were used to study prior (12–72 h) differences in surrounding environmental fields between tropical cyclones which recurved and those which did not. Differences in the wind, height and temperature fields out to 21° radius to the north between these two classes of storms are presented. A strong recurvature correlation is found in the 200 mb wind and height fields at large radii to the north. It is suggested that an operational long-range (2–3 days) tropical cyclone recurvature forecast scheme can be developed using upper tropospheric wind-height data.

Ten years of rawinsonde data for 30 stations in the western North Pacific have been composited relative to tropical cyclone center positions. This information is used to study tropical cyclone motion and surrounding parameter relationships. Tropical cyclone motion and lower troposphere surrounding actual and geostrophic flow fields from 1°–7° radius are very well correlated. This general correlation of surrounding flow features applies equally well for cyclones with different directions of motion, speeds of propagation, intensities and intensity changes. The 700 mb level best specifies cyclone speed. The 500 mb level best specifies cyclone direction. The steering flow concept of cyclone motion appears to be quite valid in the statistical sense. These results may be useful to tropical cyclone forecasters.

Growing global population pressures and predicted future food and energy shortages dictate that man fully explore his potential use of solar energy. This paper investigates the possibility of beneficial weather modification through artificial solar energy absorption. A variety of physical ideas related to artificial heat sources on different scales of motion are considered. Interest is concentrated on the feasibility of mesoscale (∼100–300 km) weather modification through solar energy absorption by carbon aerosol particles of size ∼0.1 μm or less. Particles of this size maximize solar energy absorption per unit mass. It is hypothesized that significant beneficial influences can be derived through judicious exploitation of the solar absorption potential of carbon black dust. There is an especially high potential for this in the boundary layer over tropical oceans and in the formation of cirrus clouds and the consequent alteration of the tropospheric IR energy budget. If dispersed in sizes ≤0.1 μm,...

In cumulus convective atmospheres the most significant length scale of vertical motion is of cumulus draft size—of horizontal lengths two to four orders of magnitude less than the synoptic scale and of magnitude one to three orders greater. This draft motion on scales between the gust and synoptic motion has been least investigated. The purpose of this paper is to propose a new method of calculating draft velocities from aircraft and present results of calculations with this method in hurricanes. An aircraft Doppler radio navigation instrument which is capable of measuring horizontal wind variations to a space resolution of a fraction of a nautical mile can be employed with other instruments to measure an aircraft's pitch angle changes. From this determination, along with other standard aircraft measurements such as radar and pressure altitude, power setting, etc., it is possible to make determinations of average vertical air motion to space resolutions of 0.4 to 0.7 nautical miles. Calculations ...