The Shipboard Use of a Low-Level Atmospheric Thermograph in Fog and Stratus Investigations

Abstract

A Low-Level Atmospheric Thermograph (LLAT) to obtain fine-scaled and detailed vertical temperature profiles to an altitude of 1000 m has been developed through a simple modification of the Sippican Expendable Bathythermograph (XBT) system. Only minutes are required for converting the system from one mode to the other, so taking atmospheric soundings does not prevent the use of the same system for oceanic soundings. Changes in temperature gradient occurring within 3 m altitude intervals are detected, thus detail previously unavailable in low-level soundings is obtained routinely. The acoustic sounder and LLAT are complementary instruments for investigating marine layer dynamics. LLAT temperature profiles allow accurate interpretation of layer backscattering detected by the acoustic sounder. The acoustic sounder allows precise height calibration for the LLAT. Because the LLAT is readily available and simple to use, temperature profiles may be obtained opportunistically at sea as various marine layer events are encountered. Profiles obtained in this manner under conditions of fog and stratus formation and persistence are presented.