The Roswell Report: Fact vs. Fiction in the New Mexico Desert

However, when weather conditions indicated a markedly discontinuous variation of temperature (i.e. a "front"), appropriate subjective modification of the objective linear interpolation technique was applied.

The vertical distribution of wind was determined mainly from direct observations (pilot-balloon and radio wind-sounding measurements) of free-air winds at weather stations in the area of each experiment. However, actual measurements of winds in the upper half of the troposphere often are scarce or completely lacking, and it was frequently necessary to make use of an indirect method of estimating the wind at elevations greater than 5 km. Charts of the distribution of atmospheric pressure (as given by radiosonde observations) at selected levels between 5 km and 15 km were constructed, and the wind direction and speeds at these levels were computed from the well-known geostrophic wind equation, which relates the wind to the horizontal distribution of pressure.

For the experiments carried out off the east coast of the U.S.A. between 1 August 1946 and 1 August 1947, it seemed feasible to show the distributions of both temperature and wind in vertical cross-section. This was due to the fact that these experiments were made, and the results of same recorded, within a fairly narrow band centered close to a line between Lakehurst, N. J., and Nantucket, Mass., at which points radiosonde and upper-wind observations are taken regularly. However, vertical cross-sections of temperature and wind were abandoned as a method of representation of the distribution pertaining to all subsequent experiments.

There were several reasons for this decision. In the first place, the sites and character of later experiments did not fit into the existing weather-observing network in a manner favorable to cross-sectional representation. In the second place, experience brought about the conclusion that the horizontal gradient of temperature is usually so small that, within the area encompassed by an experiment, the difference in temperature at a given level between points at the ends of a cross-section is no greater than the average error of the radiosonde measurements. Thirdly, it was soon realized that the variability of the wind in space and time is such that an individual pilot-balloon or rawinsonde ascent is not representative of the average vertical distribution of velocity during the interval occupied by a single experiment. Furthermore, as mentioned above, the wind at high levels in the troposphere often had to be inferred by indirect means. Since the true wind usually deviates somewhat from the theoretical geostrophic wind (the latter being derived under certain simplifying assumptions) and since the geometry of the pressure field is subject to some uncertainty owing to inaccuracies in the radiosonde observations, it became apparent that the assignment of a single velocity value at any