University of Washington
North Atlantic PALACE Floats

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Table of Contents

1. Introduction
2. Automatic data processing & web-page generation
3. Deployment locations for the Atlantic PALACE floats
4. Deployments from Voluntary Observing Ships (VOS)
5. Reliability Statistics
   • Heterogeneous Reliability Statistics
   • Homogeneous Reliability Statistics
6. Argos Data Telemetry
7. Sea-Bird CTD module
   • Stability of salinity measurements for float 063
   • Stability of salinity measurements for float 125
   • Stability of salinity measurements for float 126
   • Salinity Measurements from the Atlantic Trials of the APEX-SBE Float
     • Stability of salinity measurements for float 215
     • Stability of salinity measurements for float 216
     • Stability of salinity measurements for float 220
     • Stability of salinity measurements for float 221
8. GTS publication of float profiles
9. Contact Information

Introduction

This project, sponsored by the US National Science Foundation, is designed to examine the formation and circulation of the so-called "18-degree water" of the North Atlantic, using the technique of profiling ALACE (PALACE) floats. Components for these instruments are purchased from Webb Research, Inc., of Falmouth, MA, USA, and final assembly, calibration, and ballasting operations are carried out at the University of Washington in Seattle. In all, approximately 72 PALACEs have been deployed as part of this project. Other NSF-sponsored projects in the N. Atlantic using PALACE floats are also underway, in both the subarctic gyre and in the subtropical gyre, under the direction of scientists from other institutions, including Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, the University of Miami, and the NOAA/AOML Laboratory. All of these projects are part of the Atlantic Climate Change Experiment (ACCE), a 5-year program sponsored by NSF to examine ocean-atmosphere interaction in the N. Atlantic region and the ocean's effect on climate change.

Our goal here is to provide nearly real-time information on PALACE floats that have been launched in the 18° C water region (20°-40° N, 40°-80° W). Trajectories and profiles appear here as soon the data are received from the Argos system, normally within a day of data collection. Using this web page it is possible to view individual trajectories and temperature profiles along those trajectories, and to see a spaghetti plot of all trajectories. In addition, by clicking a mouse in any figure, it is possible to download a postscript file of the figure. As time goes on, new features will be added.

The first PALACEs were launched in July and August of 1997 from the R/V Knorr. Beginning in November of 1997, most floats were deployed from Voluntary Observing Ships (VOS). Between November, 1997 and March, 1998 a total of 43 VOS deployments of PALACE floats were successfully executed.

Automatic data processing, data distribution, & web-pages generation

Reliability Statistics

• Profiles Executed: For the purpose of computing these statistics, both complete and incomplete profiles are counted. For information about the cause of incomplete profiles, see the section entitled: Argos Data Telemetry.

• Profiles Expected: Each float is programmed to profile at regular intervals (nominally 10 days per profile). The number of profiles expected is determined by counting the number of profile intervals during the specified period.

Heterogeneous Reliability Statistics

The R1 PALACE Float: The R1 model of PALACE has reached a mature phase of the development cycle and has proven its reliability. A total of 41 of the R1 floats in the table were deployed using the VOS method. The remaining 22 R1 floats were deployed from research vessels. The R1 model of PALACE is manufactured by Webb Research Corporation (WRC).

The APEX Float: The APEX is a newer model of profiling float that has been tested in the subtropical North Atlantic since 1997. Seven Atlantic VOS deployments of APEX instruments equipped with Sea-Bird CTD modules were conducted between September, 1998 and February, 1999. These trials were designed to test the APEX in preparation for the Japan/East Sea experiment. The APEX is also manufactured by WRC.

Homogeneous Reliability Statistics

Argos Data Telemetry

• Float Id: A unique 3 digit identifier assigned to each float.

• Number of Profiles: The number of profiles the float has executed so far.

• Incomplete Profiles: The number of profiles that have an incomplete Argos message set. This condition results in a missing segment of data in the profile plots. The accompanying percentage gives the ratio of the Incomplete Profiles to the Number of Profiles.

• Satellite Passes: The average number of times that a satellite passed overhead while the float was on the surface.

• Messages Expected: This is the average number of messages that should have been received when satellites were overhead. If two or more satellites are overhead simultaneously then each transmission was multiply-counted. The number of messages expected for a given satellite pass is determined from the Argos data stream by counting the number of messages received and adding the number of messages missing. Due to averaging and rounding effects, these entries in the table below may not add up exactly.

• Messages Received: This is the average number of messages that were actually received by satellites (without regard to the CRC check). The accompanying percentage gives the average ratio of the messages received to the messages expected.

• Messages Missing: This is the average number of messages that were transmitted while a given satellite was overhead but that were not received by the satellite. These are detected in the Argos data stream by gaps in time and message number. The accompanying percentage gives the average ratio of the messages missing to the messages expected.

• Good Messages: This is the average number of messages received that passed the CRC check. The accompanying percentage gives the average ratio of the good messages to the messages received.

• Bad Messages: This is the average number of messages received that failed the CRC check. The accompanying percentage gives the average ratio of the bad messages to the messages received.

• Telemetric Efficiency: This measures the average rate of successful transmission when satellites are overhead. It is the average ratio of the number of good messages to the number of messages expected.

Publication of Profiles to the Global Telecommunications System (GTS)

Quality control of profile data is managed automatically by a QC module that is integrated into the GTS publication software. Each profile must pass a number of quality control criteria in order to be published via GTS. If even a single observation in the profile violates any of the criteria then publication of the entire profile is inhibited. For the Atlantic Ocean, the following criteria are used to inhibit publication of rejected profiles.

1. A profile that is older than 30 days will be rejected as required for GTS publication.

2. A profile that does not have a valid location fix will be rejected as required for GTS publication. This might happen if ARGOS reception is poor.

3. A profile with a gap between adjacent observations that exceeds 300 decibars will be rejected. A profile with the shallowest observation deeper than 300 decibars will also be rejected. This is to maintain reasonable accuracy in the pressure to depth conversion calculation as required for GTS publication. This might happen if ARGOS reception is poor.

4. A profile with an observation where the pressure is reported to be less than zero or greater than 3000 decibars will be rejected as indicative of a pressure sensor problem or malfunction.

5. A profile with deepest observation less than 50 decibars is rejected. For example, this might happen if the float drifts into shallow water or becomes entangled in mats of surface-drifting seaweed.

6. A profile with pressures that are not monotonic will be rejected. This is intended as a general criterion that a properly collected profile should satisfy.

7. A profile with fewer than 5 observations will be rejected. This is intended as a general criterion that a properly collected profile should satisfy.

This web site was developed and is maintained by Dana Swift (email: swift@ocean.washington.edu).

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