High Resolution Vertical Profiling of Temperature, Relative Humidity, Wind Speed, Wind Direction, and O3

D. Helmig

University of Colorado, Boulder

To gain a better understand of the unusually high, yet variable, NO concentrations measured at SP it is critical that one have an accurate assessment of the extent of vertical mixing in this environment. Based on observations recorded during project ISCAT, have shown that there is a strong anticorrelation between NO concentrations and the apparent mixing depth. Thus, the measurements proposed here are a critical part of the effort to address the major science objective 1.
To carry out this study Sky-Doc tethered balloons (Floatograph Technologies, Napa, CA) will be used for all vertical profiling. This balloon is a new development that combines properties of a kite and a helium-filled balloon. The Sky-Doc has a flattened, round shape. In addition, a sail at the back of the balloon’s disk causes the front of the balloon to face into the prevailing wind, and as the wind speed increases, lifts the nose of the balloon upwards. The net result of this is that of projecting an increased cross sectional area toward the wind. We have used a 18-foot Sky-Doc in three different experiments, including some that were under extreme conditions, e.g., at Summit, Greenland. For ANTCI we will acquire a somewhat smaller Sky-Doc (13-foot), which is more than sufficient to simultaneously deploy all required meteorological and chemical instruments under most weather conditions. The maximum profiling altitude will be 1 km. However, profiling heights will be adjusted according to observed boundary layer heights, which are expected to be significantly lower (50 – 500 m). Sampling will be conducted to heights of about 20 % above boundary layer heights. Ascent and descent rates will be on the order of 1 m s-1 resulting in flight times of 15 - 20 min for a 500 m profile. Profiles will be repeated hourly and will be coordinated with and interrupted during aircraft operations at South Pole Station.
Vaisala tethersondes (TSP-5A-SP) and Vaisala radiosondes (RS-80) will be used for the measurement of meteorological parameters along vertical profiles defined by the balloon. The tethersonde records pressure, temperature, relative humidity, wind speed and wind direction. The RS-80 radiosonde measures pressure, temperature and relative humidity. All sondes will be thoroughly intercompared and calibrated. Both instruments operate continuously and provide a steady data profile between the surface and the maximum flight altitude. The time resolution of these instruments (8 s for RS-80 and 1.2 s for TSP-5A-SP) will yield data resolution of ~ 8 and 1.2 m, respectively, at typical ascent and descent rates.
Two independent instruments will be deployed for ozone measurements. Ozone mixing ratios will be measured with a 2B Technologies UV ozonesonde, which records data every 10 seconds. For backup intercomparison purposes we will also employ an EN-SCI electrochemical concentration cell (ECC) ozonesondes. This system records data every 2 seconds. Vertical resolution of ozone data will be on the order of 10 m and 30 m for the 2B and EN-SCI instruments, respectively. The ozone data from both the ECC and UV instruments will be transmitted to a ground receiver by the Vaisala radiosonde.