TRACE GAS MEASUREMENTS DURING THE OXIDIZING CAPACITY OF THE TROPOSPHERIC ATMOSPHERE CAMPAIGN 1993 AT IZANA

As part of the Oxidizing Capacity of the Tropospheric Atmosphere (OCTA ) project, an intensive measurement campaign was conducted in July/Aug ust 1993 at the high-altitude observatory Izana, Tenerife. Measurement s of NO, NO2, NOy, PAN, J(NO2), CO, VOC, HCHO, H2O2, O-3, and ROx were made to study the photochemical processes which control the oxidizing capacity of the remote troposphere. Special attention was paid to the processes controlling the budget of ozone. Diurnal changes in the con centration of the species resulted primarily from the transition betwe en downslope flow (usually free tropospheric air) and upslope flow (a mixture of marine boundary layer air and free tropospheric air modifie d by island emissions). Median concentrations for downslope and upslop e conditions were NOx (47/76 parts per trillion by volume (pptv)), NOy (392/519 pptv), peroxyacetylnitrate (PAN) (10/23 pptv), CO (89/92 par ts per billion by volume (ppbv), ethane (499/486 pptv), propane (35/40 pptv), ethene (25/31 pptv), isoprene (0/60 pptv), HCHO (1.1/1.4 ppbv) , H2O2 (2.4/2.1 ppbv), and O-3 (40/38 ppbv). Maximum amounts of ROx we re measured around noon and reached Values up to 70 pptv with no obser vable signal in the night during downslope conditions.