The Fall Rate of the T-7 XBT
NAVAL OCEANOGRAPHIC AND ATMOSPHERIC RESEARCH LAB STENNIS SPACE CENTER MS
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A theoretical model of expendable bathythermograph XBT fall rate is reviewed, and a new form of fall-rate equation is proposed to include near-surface transient effects. Comparisons are made of T-7 XBT and CTD conductivity, temperature, and depth depths of thermohaline features off Barbados. Fall-rate equation coefficients are derived and compared with the manufacturer-supplied coefficients. As other investigators have found, the Sippican equation consistently underestimates probe depth by as much as 35 m at 760 m. Analysis yields a new equation, Z 6.798t-0.002383t sq. - 4.01, for depths greater than about 10 m. Considerable probe-to-probe variability is noted and is found to be primarily the result of differences in the linear term or terminal velocity of the probes variation in effective drag resulting from probe irregularities is the likely cause. Recommendations for additional work are made.
- Physical and Dynamic Oceanography