The Uncertainty of Tropospheric Observations Using Dropsondes

Dropsondes are small sensor packages, measuring pressure, temperature, water vapor and winds. These instruments are deployed from aircraft and other platforms and are capable of measuring atmospheric profiles in remote locations. The interpretation of the observations is fundamentally limited by the uncertainty of each measured parameter. Here we discuss the current status of the dropsonde technology, which has been developed at NCAR. The calibration uncertainty is the largest contribution in the uncertainty of the temperature and pressure measurement with only few external influences increasing this uncertainty. Radiation errors impacting temperature measurements on radiosondes do not play a role in dropsonde measurements due to the significantly faster vertical speed. On the other hand humidity measurements are strongly impacted by the fast vertical speed and suffer from time lag and larger calibration errors due to different operating procedures compared to the radiosondes using the same sensors. The uncertainty for wind and GPS altitude measurements is controlled by the uncertainty of the GPS technology, with the possibility for some artifacts near the ocean surface.