Stewart. Introduction to physical oceanography (2001)(T)(117s).djvu: eKnigu

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Stewart. Introduction to physical oceanography (2001)(T)(117s).djvu

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Date Jul 4, 2004

Wideband radiometers sensitive to radiation from 0.3 /im to
50 /xm can measure incoming solar and infrared radiation with an accuracy of
around 3% provided they are well calibrated and maintained...
Insolation is calculated
from cloud data (which also includes reflection from aerosols) collected from
instruments such as the AVHRR on meteorological satellites...
It can be calculated by numerical
weather-prediction models or from observations of the vertical structure of the
atmosphere from atmospheric sounders...
The most useful maps are those made by combining level 3 and 4 satellite
data sets with observations from ships, using numerical weather models...
The clouds were observed with visible-light instruments on polar-orbiting and
geostationary satellites...
The atmospheric models do not require that the net heat fiux averaged
over time and Earth's surface be zero...
Rain releases the latent heat
evaporated from the sea, and it heats the air in cumulus rain clouds by as much
as 125 W/m2 averaged over a year (See figure 14.1)...
First average the
satellite observations in the zonal direction, to obtain a zonal average of the heat
flux at the top of the atmosphere...
Also shown are direct measurements at 24°N by Hall and Bryden A982)
and 11°N by Friedrichs and Hall A993)...
If water from the surface sinks
into the deeper ocean, it retains a distinctive relationship between temperature
and salinity which helps oceanographers track the movement of deep water...
For
example, how do we measure volatile material like gasses? Nor can we evapo-
rate sea-water to dryness because chlorides are lost in the last stages of drying
(Sverdrup, Johnson, and Fleming, 1942: 50)...
Millero A996) points
out that F.3) is not a new definition of salinity, it merely gives chlorinity as a
function of conductivity of seawater relative to standard seawater...
The result is based on Dittmar's A884) chemical
analysis of 77 samples of sea water collected by the Challenger Expedition and
further studies by Carritt and Carpenter A958)...
The anomalies of sea-surface temperature, the deviation from a long term
average, are small, less than 1.5°C except in the equatorial Pacific where the
deviations can be 3°C (figure 6.3: top)...
As a result, two water samples having the same
density but different temperature and salinity at a depth of four kilometers can
have noticeably different potential density...
The International Equation of State A980) published by the Joint
Panel on Oceanographic Tables and Standards A981) is now used...
A pair of protected and
unprotected thermometers gives temperature and pressure of the water at the
depth the thermometer was reversed...
Clouds smaller in diameter than 1 km, such as trade-wind cumuli,
are also difficult to detect...
Sea water forms one
side of a transformer, and the current induced in the transformer coils depends
on conductivity of sea water (figure 6.13)...
Expendable Bathythermograph (XBT) is an electronic device that mea-
sures temperature vs depth using a thermistor on a free-falling streamlined
weight...
The measurements are recorded in digital
form either within the instrument as it is lowered from a ship or on the ship...
Thus the strong current which flows northward offshore of Japan carrying
very clear water from the central Pacific into higher latitudes is known as the
Black Current, or Kuroshio in Japanese...
To compare temperature and density of water masses at different depths in
the ocean, oceanographers use potential temperature and potential density
which remove most of the influence of pressure on density...