442 DANIELSEN BOISE i LANDER DENVER | AMARILLO !MIDLAND see _ 100 — 150 ALTITUDE, 1000 FT 200 300 400 = 500 600 700 800 900 op 681 576 469 363 |__—J 1000 265 Fig. 4—Vertical cross section for Apr. 19, 1963,at 00Z. Continuous lines are © isotherms at 2°K intervals. Dashed lines are isotachs at l0-knot intervals. Total beta activities are plotted at sampling sites in disintegrations per minute per standard cubic foot. 161, and 180 dis/min per standard cubic foot. All these large values were obtained where ¢, is positive. At higher values of 6, the values increase to 498 and 620 dis/min per standard cubic foot. In addition to the filter samples, the WB50 obtained a continuous record of accumulated radioactivity. Also, while in flight, a meteorol- ogist recorded the temperature, relative humidity, and wind every 10 min. These recordings are presented in Fig. 5. As the plane entered the stratospheric air at 1920Z, the radioactivity accumulation rate in-creased. The temperature and wind traces do not show a corresponding increase because a cumulonimbus cloud penetrating the layer forced the plane to ascend to 27,000 ft. The initial temperature and wind changes are therefore due to altitude changes and are not representative of horizontal flight. After 1940Z a constant altitude, 27,000 ft, was maintained. Note that the rapid increase in temperature, wind speed, and accumulation rate all coincide. The changes of 14°C, 75 knots and 3500 counts/min are all dramatic. After the stratospheric layer was passed, the temperature dropped 4°C, the wind speed dropped 15 knots and the radioactivity accumulated remained essentially constant. On the return flight similar changes in all three variables were recorded.