Test of a GPS Radiosonde in Thunderstorm Electrical Environments

Abstract

Meteorological radiosondes that use navigation systems to determine winds (and horizontal location) can be susceptible to data loss in thunderstorm environments. This paper reports on tests of a radiosonde that uses the Global Positioning System (GPS) for windfinding. Tests were made by flying the GPS radiosonde into three thunderstorms on free balloons that also carried an electric field meter and a long-range navigation (loran) radiosonde of a type previously tested. The GPS radiosonde performed without any significant loss of wind or thermodynamic data in in-storm maximum electric fields of up to ?104 kV m?1. Also, no obvious deleterious effect on radiosonde data was found from the presence of nearby lightning. The radiosonde was further tested in a laboratory-produced electric field in an ambient atmospheric pressure of about 70 kPa, in which the radiosonde functioned normally in a vertical electric field up to 160 kV m?1 and in a horizontal electric field up to 100 kV m?1, the respective maximum applied. Radiosondes that were sprayed with water to simulate flight in rain performed correctly in an electric field of 135 kV m?1?the maximum that could be applied safely. The hypothesized reason for the excellent windfinding performance in high electric fields is partly the very short antenna length needed for GPS reception. Other factors, which could not be assessed in this study, may include the inherent low-noise susceptibility of the GPS signals and the processing circuitry. The tests showed that the GPS radiosonde obtains wind data in larger electric fields than does the loran radiosonde. It is concluded that GPS radiosondes will acquire windfinding data in most, if not all, thunderstorm and nonthunderstorm clouds that contain high electric fields. The thermodynamic data were also very good in the large electric fields.