Whitecap coverage, which influences microwave and short wave radiation from the sea sur
face, is not only a non-linear function of the surface wind speed, but also is influenced by other
physical parameters. Dependence of whitecapping on the wind speed, sea surface temperature
(SST), surface air temperature (SAT), fetch and duration are discussed with data obtained by insitu
observation from a view point of atmospheric correction for ocean color sensors. The whitecap
coverage was estimated by photographs taken from high altitude platforms. Wind speed,
water and air temperature were measured synchronously with the photography, and their relation
ships with the coverage were analyzed, by principal component and multiple regression analyses.
The results show that the whitecap coverage depends on the wind speed as pointed out by previ
ous investigations but also varies with changes in SST, SAT, atmospheric stability and fetch. And
it is found that the factors of whitecapping can be expressed with following three components;
thermal stability of the sea surface, dynamic disturbance by the sea surface wind, development of
wind waves. Finally, an effective empirical model which can estimate whitecap coverage with
other ”surface parameters” , is proposed.
Ocean Acoustic Tomography (OAT) allows the oceanic mesoscale variability to be monitored
both widely and rapidly using sound propagation techniques. The systems of the OAT are classi
fied into two types by the horizontal OAT transceiver deployments [i.e., linear: two-dimensional
(2D) system; planar: three-dimensional (3-D) system]: however the difference between the per
formances of these two types of system has not been studied. Generally, the 3-D analyzing system
has been regarded as the composite system of the 2-D ones. We evaluated the difference using the
Geophysical Fluid Dynamics Laboratory (GFDL) model field as input. The simulations suggest
that the advantage of applying 3-D analyzing system in estimating temperature field because of a
high linear-independence of acoustic rays of the 3-D system.
Ecology of many species of whales are not knownbecauseof their wide scope of activities.We are
building a new system to reveal their migration pattern and living style in the sea. This system is
composed of three segments: a dedicated small satellite in a polar orbit of 1000km high, probes at
tached to many whales in various oceanic regions, and a ground station for tracking, telemetry and
command of the satellite.
In each probe a GPS receiver for obtaining the position on the sea surface, and several sensors
(pressure, temperature,geomagnetic field and acoustic signal) to detect the environment under the sea
are installed. When the whale surfaces these data are sent by UHF band telemetry transmitter to the
satellite. The satellite stores the data in a memory after the reception. When the satellite enters in the
visible rangeof the groundstation, it sendsout a command signalinVHFband, and the storeddata in
the satellite are transmitted to the ground station in L-band telemetry. The electric power needed for
the probeoperation will be generated by utilizing the motion of whale,in whichAGSsystem devel
opedby Seiko-Epson Co. for a wristwatch will be applied. Ecological data of whaleswith individual
identification code will be retrieved on the ground. This system is in a process of construction in the
Chiba Institute of Technology, expecting the launch of the satellite in 1998-1999.
To realize this system attachment of probes to whales is indispensable. Based on fundamental
studies on the attachment, application of a small harpoon shot by an airgun is most promising.To
achieve a long term (l-2years) observation, attachment to a livingbodyshouldbe as gentleas possile.
To attain tight fixing of the probe a set of barb plane strips madeof Ti-Ni shape memory alloy is
attached at the top of the harpoon, whose phase transition temperature is chosen to be30°C, and the
shape in the higher temperature is so designed as to bea quarter circle, by which the pressure of the
barbagainst the fascia is reduced andthis fact will beeffective to avoidthe necrosis. Usage of a kind
of medicineto avoid infection, and a proper surface treatmentof the harpoon material for improving
the affinity withliving tissues are alsoconsidered. Sincethe thermal timeresponse of thebarbis very
important fordefining the attachment procedure, thethermal time constant of barb plate is calculated
basedon the configuration underdesign, and a practical operational scheme is proposed.
A tidal-flat ecosystem model was developed and applied to a natural tidal flat area and an
artificial beach of Tokyo Bay. Based on those model results, the nitrogen cycle in thease areas
were evaluated. It was found that the purification ability on the natural tidal flat area is greater
than it is on the artificial beach. On the natural tidal flat area, about 60%of the imported organic
matter returns to the bay water as inorganic nutrient, and therefore 40%of it is removed from the
system. On the other hand, about 90% of the imported organic matter to artificial beach area
returns to bay water as inorganic nutrient, and thus only 10% of it is removed from the system.
The difference in purification ability between these two areas can be attributed to food web struc
tures. Benthic algae and macrobenthos dominated the natural tidal flat area resulting in forming
a complex food web structure which shows a high buffer ability. However, benthic bacteria
dominated the artificial beach area and thus has a simple food web structure which is not readily
able to absorb environmental change.
An ocean observation data management and providing system has been developed with the
Special Coordination Funds provided by the Science and Technology Agency of the Japanese
Government since FY 1993. This system enables to manage efficiently ocean observation data as
a database. User can easily search necessary data from the database, and display figures interactively.
We designed that the system will be managed by a system manager, and many users will
utilize this system for scientific purpose. The characteristics of the system are as follows: 1)
various kinds of data obtained with ocean observing instruments can be treated. 2) Various type
of oceanographic figures can be easily derived.
We plan to enhance the system for dealing the data obtained with new type of instruments
developed by other institutions with the same Special Coordination Funds. It will also be up
graded taking account of the concept of Geographic Information System (GIS).
Nitrogen cycle in a sediment and nitrogen budget between a sediment and an overlying water
were evaluated by benthic ecosystem model at Isshiki tidal flat that is the most largest one in
Mikawa bay. Model analysis was carried out in two cases of 1994 and 1984 to compare them by
the difference of benthic community. The result of the fluxes between sediment and the upper
water was in good agreement with that of the budget calculated from particulate organic nitrogen
and dissolved organic nitrogen distributions by box model method. Nitrogen cycle greatly change
in time and space by the difference of benthic community. Especially, nitrogen budget is influ
enced by the mass balance between suspension feeding type macrobenthos and benthic
microalgae and seagrass (including seaweed). From the view point of water purelify function of
tidal flat, the removal ability of particulate organic nitrogen increased 10% than that of 10 years
ago, but the removal ability of total nitrogen decreased to 5% of that of 10 years ago. From the
numerical simulation in the case supposing that the standing stock of seagrass (including sea -
weed) of 1984 applies to 1994's case, it was shown that uptake of particulate organic nitrogen
by suspension feeder increased 9% and that of total nitrogen changes from slight sink about 11mg
N・m^-2・d^-1 to large sink about 200mg N・m^-2・d^-1. Seagrass includingseaweed is very important
to increase the water purerify function.
Usinga numerical model,we reproduced an oxygen-depleted watermass that occurredduring
the summer in 1991, in Ise and Mikawa bay that comprise one of the most eutrophic estuaries in
Japan. The most severely oxygen-depleted water mass appeared in the middle-basin of Ise bay
and the inner-part of Atsumi bay, located in the east of Mikawa bay.
In these areas, particulate organic matter accumulated due to oceanographic features such as
horizontal circulation in the upper-layer and down-welling on the off-shore sides. The latter fea
ture ultimately obstructed the supply of dissolved oxygen to the inner-areas of the bays.
Carbon cycle and dissolved oxygen budgets for the bottom layer were calculated for these
oxygen depleted areas. We found that bottom mud consumed the most oxygen (45-66%), fol
lowed by the degradation of particulate organic matter from the upper-layer (21~35%).
Using this numericalmodel, we evaluated the feasibility of improvingtechnology to increase
the dissolved oxygen content of water mass for these two areas. The calculation was based on the
assumption that the upper water rich in dissolved oxygen was supplied to the bottom layer. The
calculations were conductedin these cases.A supplement at 100m^3/min, that was the most biggest
in realizablescale, slightly increasedthe dissolvedoxygenconcentration but was not sufficient to
a low recovery of the macrobenthos community.
Backed by the rapid increase of world population, a basis of the survival of mankind, espe
cially the shortage of food is presumed to become serious issues through the change of eco
system which caused by the global warming and climate changes.
In order to assure the practical prediction of climate changes and to take advanced countermeasures,
critical issues are the understanding of mechanism and process of the ocean variability
through global observation and study, and develop and improve the global simulation model of
the climate change which strongly affected by the ocean.
And also, the ocean is known to storage massive mineral, living things and energy resources,
and the sub-bottom is often become the origin of such natural disasters as earthquake, tsunami
and volcanic eruption.
In April 1991 and 1994, Nikkei Research Institute of Industry and Market (Nikkei RIM) es
tablished ”Research Committee on the Ocean Science and Technology for the Global Environ
ment” made up of university professors, engineers and journalists, and research and develop Sea-co
Program, and proposed to the political parties in Japn.
One of the highlight of this program is the application of small commercial aircraft for ocean
observation and these huge mother ship which also act as an ocean-going technopolis, and aim to
be the center of excellence opened to the world.
This program was proposed to be a measure of international contribution from Japan.