ae G aoa ithe ‘ . pA tldRtead aedaLs RkHe Sb ws . das wi a a Nad eee eo te A a medMe an deka on 140 4000 -——- 7 I LE | L _ 2 3000h— ° °o ~ _ — o (99° 2 . ae Q 2000-- 2 — e 4 FE as _] 16° 177-1 ——l7° BP geeeo— — 1000}— q ee: geooOCS ee a | 22° — T r t ARGONNE 7 28° ——_——_s ge. MIDWAY 25° — _| a LL SOLDIER'S FIELD (MEIGS) Fig. i102—Vertical temperature cross section over Chicago, December 16, 1968 limit mixing. Profiles at the other airports were simi- lar. (The SOz2 sensor on the flight package uses the David conductivity method. It is unable to distin- guish between SOz and COs; a scrubber is used to eliminate the SOz before the conductivity is measured. The CO. contribution is then subtracted from the COz plus SO» reading. In Figure 101, the periods when the scrubber was in operation are shown.) Several other flights have also been made using a very simple thermistor bridge combination furnished by the National Air Pollution Control Administration. This package has been flown both on a helicopter and on a light airplane. The thermistor, inside an aluminum radiator shield, was mounted at the forward end of the landing skid of the helicopter or on a strut of the airplane. The thermistor resistance was measured by manually nulling a Wheatstone bridge having the thermistor as one resistance element and a 10-turn potentiometer as another. Temperatures were then determined from a resistance vs. temperature calibration chart. Heights were taken directly from the aircraft altimeter. The first of these flights was made on December 16, 1968, when vertical temperature profiles were observed over Meigs (lakefront) and Midway (urban) Airports in Chicago and over Argonne(rural), using a Chicago Fire Department helicopter. Figure 102 shows the variation of temperature with height between Meigs Airport on the lakefront and Argonne. The three profiles are very similar, showing adiabatic lapse rates up to a strong inversion layer at about 2000 ft. Some of the horizontal differences may be due to the fact that the sounding at Meigs was made at 1000 CST, at Midway at 1015, and at 1100