ISAR (Infrared Sea Surface Temperature Autonomous Radiometer)

Transcription

1 ISAR (Infrared Sea Surface Temperature Autonomous Radiometer) (1) Personnel R. Michael Reynolds (RMRCO) Principal Investigator Jeremiah Reynolds (RMRCO) Instrument Technician (2) Objective a. To provide high-quality sea surface skin temperature measurements, Tskin, with the ISAR (Infrared Sea Surface Temperature Autonomous Radiometer), for the MISMO cruise. b. To work with Mirai staff to assemble a quality meteorological data set and apply these to the COARE-3 flux algorithms. c. To work with and train Mirai staff on special data processing software. (3) Method The ISAR instrument was mounted on the ship foremast top on the starboard side and facing downward at 45 degrees from the horizontal (Figure 1). It sampled sea surface, sky, and tow internal black body temperatures with a narrow field-of-view IR radiometer. Individual samples were taken every 2-3 seconds and an entire sweep required about three minutes. Individual samples were processed to a standard 10-min averaging time. For quality assurance temperatures from the JAMSTEC seasnake and the Mirai intake port were compared (Figure 2). Meteorological data were produced by the SOJ system (2-sec samples), ZMET system (10- sec), PRP (2-min averages), Seasnake (5-sec), and ISAR (10-min averages). These data were all averaged, quality checked, and merged into a single best data set (Figure 3). This data set was used as input to the COARE-3 bulk flux software package to compute net ocean heat flux on a 10-min, daily, and full cruise averages (Figure 4). A special set of processing software to accomplish the above meteorological processing was developed. The software was demonstrated to Mirai staff. Then, it was applied to current and past data sets. Any software problems or operation questions were corrected over the remainder of the cruise. (4) Results Figure 1 shows (panel 1) the ISAR mounted on the foremast and (panel 2) the data acquisition system that was located in the meteorological data room. Figure 2 shows an example of temperature measured by various instruments. Air temperature at 25-m height (approx) was measured by the Zeno data logger, Water temperature was measured at the Mirai intake port at 5-m depth and was recorded on the SOJ data files. Tskin was measured by ISAR and recorded on its data acquisition. Finally two Seasnake probes recorded water temperature just a few cm below the water surface.

2 Figure 3 is a plot of the meteorological measurements and computed sea surface energy fluxes for one day during the cruise. Figure 4 shows the energy (heat) fluxes computed for one day. (5) Data Archive Data are stored on the Mac computer mike in the meteorological workroom. The computer is under the care and supervision of the Mirai technical staff. A data processing manual (draft) is available as part of the installation. Figure 1. The ISAR (Infrared Sea Surface Temperature Autonomous Radiometer) was mounted on the foremast, starboard side with a 45º view to the ocean.

3 Figure 2a. The cool skin (blue) is compared with the ship intake temperature at a depth of 5 m (red) and the two seasnake probes (green). On days with high insolation the seasnake and skin temperatures rise above the deeper water temperature. At night the skin and seasnake temperatures are cooler than the 5-m temperature. Figure 2b. This blowup of the water temperature results for one sunny day is an excellent example of the warm layer and cool skin temperature behavior.

4 Figure 3. Summary of meteorological observations during the intensive observation period. The SOJ (green) and Zeno (red) meteorological data are compared. All the data from all sources were pooled and a best data set was developed for application to the heat flux algorithm.

5 Figure 4. An example of energy flux computations for one day in the intensive observation period. Graphs on the left show the best data set and graphs on the right are the computed fluxes: radiation, latent, sensible, rain and the net flux into the ocean. The net flux is high during the day but is negative at night. On this day the daily mean was W/ m^2, strong heating.