Error in Dasibi flight measurements of atmospheric ozone due to instrument wall‐loss

Abstract

Theory suggests that in laminar flow the percent loss of a trace constituent to the walls of a measuring instrument varies as P −2/3 , where P is the total gas pressure. Preliminary laboratory ozone wall‐loss measurements confirm this P −2/3 dependence. Accurate assessment of wall‐loss is thus of particular importance for those balloon‐borne instruments utilizing laminar flow at ambient pressure, since the ambient pressure decreases by a factor of 350 during ascent to 40 km. Measurements and extrapolations made for a Dasibi ozone monitor modified for balloon flight indicate that the wall‐loss error at 40 km was between 6 and 30 percent and that the wall‐loss error in the derived total ozone column‐content for the region from the surface to 40 km altitude was between 2 and 10 percent. At 1000 mb, turbulence caused an order of magnitude increase in the Dasibi wall‐loss.