Intercomparison of NO, NO sub(2), NO sub(y), O sub(3), and RO sub(x) measurements during the Oxidizing Capacity of the Tropospheric Atmosphere (OCTA) campaign 1993 at Izana

An informal comparison of NO, NO sub(2), NO sub(y), O sub(3), and RO sub(x) measurements obtained by different instruments and techniques at Izana in 1993 during the European Oxidizing Capacity of the Tropospheric Atmosphere (OCTA) campaign was performed. For O sub(3), two UV instruments agree within 7% (95% cl.) limited by a difference in response of 7.0% plus or minus 0.2% (95% cl.) which likely was caused by O sub(3) losses in one of the inlet lines. The NO mixing ratios obtained by two NO/O sub(3) Chemiluminescence (CL) instruments range between 0-200 parts per trillion by volume (pptv), except for short periods influenced by traffic pollution. The response of the two CL detectors agrees within 3% plus or minus 10% (95% cl.). The NO sub(y) data, ranging between 100 pptv and several ppbv in plumes, were obtained using two different gold-CO-converters and inlet designs with subsequent CL detection of NO. A systematic difference in the slope between the two data series of 1.44 plus or minus 0.05 (95% cl.) was likely caused by NO sub(y), losses in the inlet line of one of the instruments. Three different NO sub(2) data sets were obtained using Tunable Diode Laser Absorption Spectroscopy (TDLAS), a photolytic converter/CL technique (PLC/CL), and the Matrix Isolation Electron Spin Resonance (MIESR) technique. The linear slopes between the data sets of the three methods are consistent with unity at a 95% confidence level, 1.13 plus or minus 0.30 (TDL versus PLC/CL), 0.90 plus or minus 0.47 (TDL versus MIESR), and 1.04+0.34 (PLC/CL versus MIESR). RO sub(x) measurements were performed by three different chemical amplifier (CA) designs and the MIESR technique. Using 30-min averaged values between 13-65 pptv, two CA instruments agree within 25% (95% cl.) with the mean of MIESR (1.01+0.20 and 0.98 plus or minus 0.24, 95% cl.), while the third CA responded low (0.65 plus or minus 0.32, 95% cl.).