The Acqua Alta Oceanographic Platform
The Acqua Alta platform of the Istituto per lo Studio della Dynamica
delle Grandi Masse of the Consilio Nationalle delle Richerche (ISDGM/CNR)
is located in the Adriatic Sea 16 km off the coast off Venice. It was used
as the calibration site for the ERS-1
radar altimeter calibration. Equiped
with a tide gauge and various meteorological instruments it provided
an independent measurement of the sea level to which the one measured by
the radar altimeter was compared.
Location
The tower is located in the Northern Adriatic Sea, East of Italy, 16 km off
the coastline of Venice, on 16 m of depth. The bottom is a mixture of sand
and mud, deepening gently towards the southeast with a 1/1000 slope.
In connection with the calibration of the ERS-1
altimeter, the reference
mark on board has been positioned at:
latitude: 45 deg 18 min 51 sec North
longitude: 12 deg 30 min 30 sec East
Structure
The tower was placed into position in March 1970. Its basic structure is a
four leg, framed template extending 4 m above the sea surface. The template
is firmly fixed on the bottom, the poles penetrating 22 m inside the
sediments. The housing structure (three floors plus the top terrace) is
firmly joined to the upper end of the template.
The submerged part is protected by zinc anodes. The splash zone (+3, -2 m)
is covered with a fully protective layer of epoxy resin.
The three floors are at 4.5, 6.7, 9.3 m above the mean sea level. The terrace
floor is at 12.3 m.
Starting from the second floor, a large platform extends horizontally 7 m
in the southeast direction. Two smaller platforms protrude towards the
southwest and northeast.
Logistics
The tower is equipped with 380, 220, 125 VAC 50 Hz, available when personnel
are on board. A large set of batteries provides 12 and 24 VDC for occasional
measurements and for some basic regular needs.
The tower is not continuously manned. People move on board either for specific
needs or for maintenance (if so, on a fortnight basis).
The living quarters are on the third floor. They include a 5x5 m living room,
a 1x2 m bath, a 2x3 m kitchen, and a 2x2 m room devoted to on board
instruments. Cooking and sleeping facilities, taken care by devoted
personnel, allow four persons on board for an unlimited period of time.
The connection with the institute is by motor-boat with cabin and by
pilot boat, both capable to stand stormy conditions. The travel time
between the institute and the tower is 80 minutes.
Instruments
The tower is equipped with a meteo-oceanographic station. The data are
recorded on board and also telemetered to land. The station includes
measurements of:
atmosphere:
wind (two levels), temperature, humidity, solar radiation, rain.
sea:
waves (directional), tide, temperature (two levels).
A number of host instrumental sets record and transmit various data to land.
On top of the regular activities, the tower is used for devoted time-limited
campaigns. These have included:
vertical profile of water characteristics,
water quality,
kinematics of water particles under stormy conditions,
Reynolds stresses within the water,
tidal high frequency spectrum,
currents,
waves breaking,
suspension of sediments by waves and current,
atmospheric turbulence,
vertical wind profile,
Reynolds stresses in the atmosphere,
surface ripples and wind by scatterometer,
sea truth for satellite radiometers,
sea truth for the calibration of the ERS-1
altimeter.
Situation
A recent survey has revealed the very good conditions of the submerged
structure, with no sign of evident deterioration. Our present expectations
are therefore for a long term use of the full facility.
The tower is available upon contract for external users, both on a daily
or short term basis, and for the installation of long term instruments.
More Information
For more information contact ISDGM:
ISDGM-CNR
S.Polo 1364
30125 Venezia, Italy
phone: +39 - 41 - 5216811
fax: +39 - 41 - 2602340
For any request please refer to:
Luigi Cavaleri (direct phone 5216810,
e-mail: gigi@ocean.isdgm.ve.cnr.it)
Silvestro Curiotto (direct phone 5216914)