Geoscience Reference
In-Depth Information
Recommendation:
Two important concerns regarding the entire coastal sea level network
employed by the TWCs in their warning activities need to be addressed soon, as follows:
•
A priority list of the coastal sea level stations should be constructed, based at irst on
the experience of the TWC forecasters, and later updated from the results of the more
objective coverage analysis described in the previous section.
•
A risk assessment of the data low from the highest priority stations should be
performed.
U.S. or international stations deemed high priority with a high risk that the data low
could be interrupted for more than very short periods of time should thereafter be carefully
monitored and, if possible, upgraded by the appropriate authority (national or international) to
meet all requirements for a tsunami monitoring sea level station that are listed in the Tsunami
Warning Center Reference Guide (U.S. Indian Ocean Tsunami Warning System Program, 2007).
As an example of prioritization, note that as of June 26, 2009, all ive DART stations covering
the Aleutian Islands west of the Dateline, and the Kuril Islands to Hokkaido, had been inopera-
tive for nearly all of 2009. Such failures meant that the Midway Island coastal station at 28.2
o
N,
177.4
o
W, was the only sea level station that forecasters had available during the irst six
months of 2009 to evaluate whether a tsunami created in the Kuril Island, and directed toward
the southeast (e.g., Figure 4.3), was bearing down on Hawaii. Therefore, the Midway Island
station is a strong candidate for high-priority status.
Compliance with the Reference Guide's recommendations would be a good starting point
for assessing the risk in the data low from each high-priority sea level station. Much of the
needed information is now available at the IOC's SLSMF (http://www.vliz.be/gauges/) dis-
cussed previously. SLSMF also has the information needed to determine data stream reliability,
at least since 2007. SLSMF is actually a very appropriate place to obtain such reliability informa-
tion because it lists only data that was initially made available in near-real time over the Global
Telecommunications System, not what was eventually available after internal memory was
inally accessed during a maintenance operation.
Coastal Sea Level Data Processing
In January 2008, NTHMP issued a report (National Tsunami Hazard Mitigation Program,
2008) intended to identify vulnerabilities in the U.S. environmental data streams needed by the
TWCs to effectively detect tsunamis and make accurate tsunami forecasts. The data streams
under consideration included, among others, sea level data from DART buoys and from U.S.
coastal gauges. The committee identiied indings in NTHMP (2008) with respect to processing,
distribution, archiving, and long-term access to tsunami-relevant sea level data that remain
highly relevant today including the following issues:
•
There is currently no routine acquisition of the 15-second CO-OPS data, which are
most relevant for model validation, and there is no routine retention of these data.
•
Fifteen-second data are only collected on request and have no quality control or archive.
