Flight-level thermodynamic instrument wetting errors in hurricanes. I - Observations

Flight-level thermodynamic errors caused by the wetting of temperature and moisture sensors immersed within the airstream are studied using data from 666 radial legs collected in 31 hurricanes at pressure levels ranging from 850 to 500 mb. Concurrent measurements from a modified Barnes radiometer and a Rosemount 102 immersion thermometer are compared to identify regions, called instrument wetting events (IWE), in which Rosemount temperatures are significantly cooler than radiometer-derived temperatures by a specified amount. A total of 420 IWE are identified in the dataset. Roughly 50 percent of the radial legs contain at least one instrument wetting event. More than 90 percent of IWE are associated with updrafts containing cloud water and are confined to scales less than 10 km. IWE are also found to be more frequent in eyewalls and intense hurricanes. Thermodynamic errors within IWE and convective updrafts and downdrafts are summarized as distributions of average temperature, specific humidity, virtual potential temperature, and equivalent potential temperature error. (Author)