Simultaneous in situ measurements and diurnal variations of NO, NO₂, O₃, jNO₂, CH₄, H₂O, and CO₂ in the 40‐ to 26‐km region using an open path tunable diode laser spectrometer

Simultaneous in situ measurements of [NO], [NO 2 ], [O 3 ], j NO 2 , [CH 4 ], [H 2 O], [CO 2 ], pressure, and temperature in the 40 to 26‐km region of the stratosphere were made from Palestine, Texas (32°N), on October 16, 1986, using the Jet Propulsion Laboratory (JPL) Balloon‐borne Laser In Situ Sensor (BLISS) instrument, carrying a University of Denver j NO 2 instrument piggyback. Using tunable diode laser absorption spectroscopy over a long path length, measurements were made as follows during a 21‐hour flight: daytime [NO], [NO 2 ], [O 3 ], and NO 2 near 40 km; [NO], [NO 2 ], and NO 2 through the sunset transition near 40 km; postsunset measurements of the rate of decay of [NO 2 ] into the night over the 35 to 29‐km range; nighttime measurements of [NO 2 ], [O 3 ], [CH 4 ], [H 2 O], and [CO 2 ] at 27 km; and [NO] after sunrise. The NO, NO 2 , O 3 , CH 4 , H 2 O, and CO 2 concentration measurements generally show good agreement with previous observations, with a tendency for somewhat lower NO 2 amounts. Measured O 3 concentrations at 38 km agree well with comparable measurements from in situ UV photometers, but at 28 km they are lower by about 10% and agree more closely with solar backscattered ultraviolet data at this altitude. The observed change in [NO 2 ] during the night over a 5‐km altitude range implies either lower [NO 2 ] postsunset profiles, or significantly faster [NO 2 ] decay than current model predictions using N 2 O 5 chemistry. Measurements of [NO], [NO 2 ], [H 2 O], and [CO 2 ] from an October 1985 flight are included for comparison.