In April 2002, we installed two through-the-hull instrument ports on the R/V Ronald H.Brown at depths of 2 m and 3 m below the mean still water line. The ports are located in the bow thruster room on the starboard side directly above the ship's existing 5 m intake. In May 2003, the ports were instrumented with two SeaBird model SBE-39 Temperature sensors to provide temperature at depths intermediate between the CIRIMS skin SST and the ship's standard thermosalinograph depth of 5 m. The recent measurements from the Brown shown in the figure below demonstrate our ability to make underway measurements of the diurnal warm layer that occurs under conditions of low wind speed and high solar insolation. An identical through-hull installation on the UW R/V Thomas G. Thompson is planned for late 2003.
A diagram showing the placement of the through-the-hull ports located at 2 m and 3 m depth in relation to the ship's standard intake at 5 m. The ports incorporate a ball valve that allows the port to be closed off when the sensor is removed. The sensor housing has two O-ring seals that permit it to be installed and removed from inside the ship while it is in the water. The ports were designed by APL Mechanical Engineer Mike Welch. The engineering drawings were done by the naval architecture firm of The Glosten Associates of Seattle, Washington and approved by the Bureau of Ships. The ports were fabricated at the Applied Physics Laboratory and installed when the Brown was in dry dock for routine maintenance.
Diagram of the through-hull installation showing the ball valve, in orange, attached to the ship's hull on the right and the inboard casing on the left. The sensor casing is in grey with the SBE 39 shown within it. The probe tip, in red, extends through the ship's hull. The sensor casing is pushed into place by the removable rod shown in yellow and extending out of the inboard casing.
View of the completed 2 meter installation showing the end cap and the external wiring.
The completed SBE 39 through-hull installation. The 2 meter intake valve is in the foreground and the 3 meter intake is below it.
This time series illustrates the ability to measure the near-surface warm layer caused by diurnal warming due to low wind speed and high solar insolation. A subsurface temperature gradient is apparent between 2 m and 5 m. The skin temperature rises above the bulk temperature measured at 2 m near the time of maximum solar insolation. Note also that the bulk temperature at 5 m shows a jump that is correlated with the ship's speed. This example demonstrates the importance of understanding the effect of the ship's speed on the underway bulk temperature measurements.
Step-by-step Installation
APL mechanical engineer Mike Welch attaches the inboard casing to the ball valve.
Mike prepares to put the O-rings on the sensor cartridge, the SBE 39 is visible just behind the cartridge.
The sensor cartridge is inserted into the inboard casing. When a seal has been established, the ball valve is opened and the sensor casing is pushed into position.
The SBE 39 is fully in position and the sensor wiring will be attached to the plug on the inside of the end cap.