Improved Depth and Temperature Conversion Equations for Sippican AXBTs (Air-Deployed Expendable Bathythermographs)

摘要

In October 1985, in a region of large-scale thermohaline staircases off the northeast coast of South America, five shallow and seven deep Sippican AXBTs (air-deployed expendable bathythermographs) were hand-deployed from the USNS Bartlett during times when CTD (conductivity, temperature, and depth) cast were being conducted. AXBT temperature and depth values calculated from several standard conversion equations were compared with the CTD values, and improved conversion equations were derived. Two different elapsed fall-time-to depth conversion equations were found for the shallow and deep AXBTs, but only one frequency-to-temperature conversion equation. The depth equations, accurate to + or - 5 m over the range 0-700 m, were z = 1.5573t - 0.000301 t sq for shallow AXBTs and z = 1.6325t - 0.000215 t sq for deep, with z the depth in meters and t the elapsed fall time of the probe in seconds. The temperature equation, accurate to + or - 0.2 C between 6 and 28 C, was T = -38.6045 + 0.0271075, with T the temperature in degrees centigrade and F the transmitted frequency in hertz.