Measurements of NO2, and O3 on the P3-B during Pem Tropics-B

B. Ridley and J. Walega

National Center for Atmospheric Research

Boulder, CO

The four channel instrument was recently constructed and uses standard principles of NO/O3 chemiluminescence as the detection scheme. Three of the channels will be used during the PEM mission, one for meaurement of NO, one for measurement of NO2 using a broad-band (325-450 nm) photolysis converter, and one for measurement of O3 using pure NO rather than excess O3 as the reagent gas. The gas residence time in the cooled (5 °C) photolysis cell will be 1-2 sec and the photolytic efficiency for NO2 will be 50-60%. The NO and NO2 channels have sensitivities to NO of 6-7 cps/pptv at a reaction cell presssure of 7 torr. Photon counts will be recorded at 1-sec intervals but, except for O3, the data will have to be averaged over 1-min intervals to meet the required detection limits of 3 pptv for NO and yy for NO2. Ozone data will be available for 1-sec accumulations with a precision better than 0.5 ppbv and an estimated accuracy of 5% or 2-3 ppbv whichever is larger. The NO and NO2 channels are calibrated in-flight while the O3 instrument is calibrated before flight using a comercial calibrator.

References:

Distributions of NO, NOx, NOy, and O3 to 12 km altitude during the summer monsoon season over New Mexico, B. A. Ridley et al., J. Geophys. Res., 99, 25,529-25,534, 1994.

A small, high-sensitivity, medium-response ozone detector suitable for measurements from light aircraft, B. A. Ridley, F. E. Grahek, and J. G. Walega, J. Atmospheric and Oceanic Technology, 9, 142-148, 1992.