Shadoz—a Tropical Ozonesonde–radiosonde Network for the Atmospheric Community

OCTOBER 2004 AMERICAN METEOROLOGICAL SOCIETY | BACKGROUND. The ozonesonde measurement. Although ozone-measuring satellites have been collecting data since 1970 (Heath et al. 1975), validation of profiles and total column measurements is still performed by relatively lowtechnology instruments. Total column ozone is verified with spectrophotometric data from a ground-based network (Bojkov et al. 1999). Profiles measured by balloon-borne ozonesondes are used to evaluate satellite retrievals (WMO 1998a). The ozonesonde is flown with a standard radiosonde. Designed to measure ozone concentrations from the surface to above the ozone concentration maximum, the combined ozonesonde–radiosonde package is flown with a 1200–1500-g balloon that usually bursts at 4–8 hPa. In an electrochemical concentration cell (ECC) ozonesonde, air pumped through a pair of cells containing a potassium iodide solution initiates an electric current proportional to the amount of ozone in the atmosphere. The ozone current is transmitted back to a ground receiver and the partial pressure of ozone is recorded with the pressure–temperature– humidity (PTU) readings of the radiosonde. Figure 1 shows an ozonesonde during its preflight testing (Fig. 1a) and its assembly with the radiosonde (Fig. 1b) prior to launch. Figure 2 shows the raw data (relative humidity, temperature, and ozone pressure; left panel) and ozone amount (right panel) in volume mixing ratio, the unit most commonly used by atmospheric chemists. Note that stratospheric ozone (the “good” ozone shielding the earth from ultraviolet radiation) is present at > 1 part per million by volume (ppmv), whereas tropospheric ozone (sometimes referred to as “bad” or “smog” ozone) is counted in parts per billion by volume (ppbv). Background surface ozone ranges from 10 to 40 ppbv, depending on geographiSHADOZ—A TROPICAL OZONESONDE–RADIOSONDE NETWORK FOR THE ATMOSPHERIC COMMUNITY