Near-Real-Time Meteorological and Hydrodynamic Monitoring:
Concept, Fabrication, and Data Processing
Both the hardware and software were designed and fabricated
at the Coastal Studies Institute (CSI) at Louisiana State University (LSU).
The hardware comprising the monitoring station consists of three components;
power supply, measurement module, and communication module. The software includes the remote control
and communication module as well as the data processing module.
The hardware package was designed and assembled by the Field
Support Group at the Coastal Studies Institute, at Louisiana State University.
1. Power Supply: The ventilation fans and computer monitor,
the ADCP Rio Grand Workhorse (1200Khz) and the Belfort Visibility Sensor
(Model 6100) are each powered by a deep cycle lead/acid marine battery of 115
ampere-hour capacity. The batteries are charged by a Newmar 12Vdc (Model RM-2033) battery
charger capable of charging 3 isolated battery banks. The measurement module
(CR23X4M) is powered by two internal 6 ampere/hour sealed lead
acid batteries charged by a 120 VAC/18VAC plug-in transformer. The CR23X provides the
power needed for the operation of most of the sensors, and the storage
and transmission of data. The On-Site Computer is powered by a 24Vdc power
system consisting of 2 115 Amp/Hour batteries connected in series. The computer has
a special ATX power supply designed to run off of 24Vdc. These batteries
are charged by a Newmar 24Vdc battery charger (Model RM-2415). The present
power supply system for the station was designed to run the entire station for
24 hours. The actual time is closer to 36 hours as proven during Hurricane
Lili when the oil platform’s generator shut down about 12 hours before the storm
actual passage over the station. The present power supply has proven
to be adequate
for the designed hourly sampling and data transmission. The system
has not experienced a power shortage since going on line in 2000.
2. Sensor Package and Data Storage: The sensor package includes
above water meteorological sensors and underwater hydrodynamic sensors. The
meteorological sensors,including a windbird, a barometer, and an electronic thermometer,
provide measurements of wind speed, wind direction, air temperature, humidity,
visibility and barometric pressure.
The hydrodynamic sensors, including a digiquartz pressure transducer and an electronic
thermometer, provide measurements of waves, water level, and near-surface
The on-site data are stored in a Campbell CR23X Data-Logger. The CR23X also functions
as the central control of the remote station. The entire automated
operation is executed by the software developed by Coastal Studies Institute
personnel upon the operation-platform and interface-drivers provided by Campbell
Scientific Inc and the Field Support Group. The user-developed software controls
the sampling scheme and the operational control of all of the sensors
and the computer.
3. Communication Package: Retrieval of the
data is done through a dedicated telephone line at the receiving station. The
is controlled by Symantic’s PC Anywhere software with the capability of regular
data downloading and remote control from the Coastal Studies Institute.
The sampling and communication schemes can be modified remotely from
Coastal Studies Institute. The remote control also allows quality checks of
the sensors and power supply.
The entire hardware is mounted on a Chevron/Texaco manned oil platform (TS-217A).
LSU and Coastal Studies Institute sincerely thank Chevron/Texaco
for providing the facilities and support necessary to make this vital and important
program a success. The wind speed and direction, and air temperature are
measured at approximately 20 m above mean water level. The barometric pressure
is measured at approximately 12 m above mean water level. The near-surface
water temperature and water-level fluctuation are measured at approximately
2 m below mean water level to minimize the depth-attenuation of strength
of the high-frequency wave signal.
The software package includes a communication control module,
an automated data processing module, and an automated online database.
1. Communication Control: Symantic’s PC Anywhere communications software allows
for the hourly transfer of the Campbell data and the ADCP data. This software
also allows us to remotely access both the ADCP and the CR23X directly so
that troubleshooting and changes can be made in real time to one or both systems.
The communications with the CR23X was developed on the platform of Campbell
PC208 software. PC208W initiates the automated data downloading every hour and
also allows irregular manual data downloading. It also controls when the ADCP
data is taken. Remote modification of the on-site operation can be executed from
a Coastal Studies Institute laboratory via PC Anywhere.
2. Sampling Scheme and Data Processing: The meteorological parameters,
including wind speed and direction, barometric pressure, air temperature, and
water temperature are sampled at 1 Hz for a 10-min period beginning 10 minutes
before the top of every hour. The hydrodynamic parameters, including water depth and
current velocity, are sampled at 2 Hz for approximately 17 minute period at
the beginning of every hour. Two thousand and forty-eight samples are collected during each
wave burst. The high-frequency sampling was designed to ensure reliable measurements
of locally wind-generated waves in the sound, which have peak periods typically
ranging from 2 to 4 seconds.
The data processing, including data averaging and directional spectral analysis,
is initiated automatically immediately after each data downloading.
The posted wind speed and direction, barometric pressure, air temperature,
and near-surfacewater temperature represent averages over the 10 minute period at the
beginning of the hour. Wind gust, the highest 5-s average during the sampling
period, is calculated on site. Water depth, current velocity, and current direction
are averaged over the 8.5-min sampling interval.
Directional wave spectra are calculated following the procedure described by
the US Army Corps of Engineers (USACE) Field Wave Gaging Program (FWGP).
The automated directional wave spectra analysis software was mostly developed
at the Coastal Studies Institute. Two central functions, the fast-Fourier
transformation and computation of cross-spectral density, were included from
the Wave Data Analysis Standard Spectral Analysis Program (WDASSAP) developed by USACE. Wave
parameters posted on the Internet include significant wave height, maximum
wave height,dominant wave direction, peak wave period, and average wave period.
Detailed directional wave spectra are archived for future analysis.
The RD Instrument’s ADCP is controlled and initiated by the computer via the
PC208 Software. The wavesmon program controls the ADCP and provides for the
storage of the raw data as well as the processing of the data. Water currents
and the water current direction are provided from near the bottom to near the surface
in 35cm bins. Significant wave height, peak wave height, average period,
peak period, peak wave direction and the directional wave spectra are the parameters
that are separate from the CR23X data but included in separate files that
are transferred to Coastal Studies Institute via the PC Anywhere program.
3. Online Information: The data are processed automatically following
successive data downloading every hour. The information is archived in a relational
database, and posted to the web page simultaneously. The interactive
web page is designed not only for users to acquire the latest updated information, but
also to provide an interface for users to access our online database. All information
in the database can be retrieved, queried, and graphically viewed on the
The Raw ADCP data is retrieved periodically from the site and archived.
This data can be obtained by contacting Dr. Changxing Li. Arrangements can then
be made on how to best transfer the data set that you are interested in.
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