- Snell's law
A law that gives the relationship between the incident and
refracted angles at an interface between two media.
It is expressed as
where and are the incident and
reflected angles, respectively, the speed of light
through medium i, and the
refractive index for
See Southern Oscillation.
- soaked zone
One of five glacier zones
classified according to ice temperature and the amount of
melting. At the end of the summer in the zone all the snow
deposited since the end of the previous summer has been raised
to 0 deg. C and has melted, with some meltwater percolating
into the deeper layers deposited in previous years. The level
at which this percolation process begins is significant in that
mass balance calculations can no longer be restricted to the
current year's layer when percolation occurs. This zone is
sometimes divided into two parts separated by the slush limit,
the highest point on the glacier at which any material is lost
by runoff, often in the form of slush avalanches, whence the
name. This zone is separated from the higher
percolation zone by the
saturation line and from the lower
ablation zone by the
Acronym for the School of Ocean and Earth Science and Technology
at the University of Hawai'i at Manoa.
See the SOEST Web site.
Acronym for SOund Fixing And Ranging floats.
- soft tissue pump
See organic matter pump.
See Southern Oscillation Index.
- soil breathing
The emission of carbon dioxide by soil as the result of the oxidation
of soil organics by microorganisms and respiration of the roots of
See Kagan (1995).
- soil horizon
A layer of soil distinguishable from adjacent layers by characteristic
physical properties such as structure, color, texture, and chemical
An easterly wind that brings rain to the southeast coast of Spain and
the Straits of Gibraltar. This is another name for
- solar constant
The energy flux density of the
at a given distance from the Sun. At the mean distance of the Earth
from the Sun the most probable value of this flux is in the
range from 1368 to 1377 .
See Kagan (1995).
- solar declination angle
The angle between the ecliptic and the plane
of the earth's equator. This varies from
+23.45 on June 22 to -23.45 on Dec. 22 corresponding
to, respectively, summer and winter solstice
in the northern hemisphere. The solar declination angle for
any day of the year is given by
where is the tilt of the earth's axis relative to the
ecliptic, d is the
Julian Day of the year,
is the Julian Day of the summer solstice (i.e. 173),
is the number of days per year, and C is the circle
circumference (i.e. 360 ).
- solar insolation
The distribution of solar fluxes averaged over a certain period
of time, e.g. a solar day. This is a function of latitude and
the characteristics of the Earth's orbit around the Sun.
See Liou (1992).
- solar luminosity
The flux of energy emitted by the Sun. This is at present
approximately 3.9 x Watts.
- solar variability
the amount of solar radiation (insolation) reaching the earth.
This is one of the main external forcing processes for the climate
system, and varies on several time scales. The longest scale of
variability is a long-term increase in solar output due to the
evolution of the sun (an increase of approximately 1100 million years; see Newman and Rood (1977) and
Variations on shorter time scales of
days, months, years, decades, etc. (and their possible effects on
the climate) are less well understood, e.g. see
Sofia and Fox (1994) and Schonwiese et al. (1994).
Acronym for Stratospheric Ozone Law, Information and Science,
a site devoted to information and pointers to information relevant
in some way to the ozone layer, including the topic of
anthropogenic ozone depletion.
SOLIS Web site.
To be completed.
Acronym for NOAA's U.S. surface solar radiation network. A network
of instruments used to measure solar radiation at the Earth's surface
from about 1975 to 1995. The data from this system was often
beset with unwanted drift and poor data continuity. Starting in the
early 1990s, SOLRAD was replaced by
See Karl et al. (1995).
Acronym for Solar Stellar Irradiance Comparison Experiment, a project
intended to provide long-term measurements of solar Ultraviolet
and Far Ultraviolet radiation at the top of the Earth's atmosphere
with high absolute and relative accuracy.
SOLSTICE Web site.
- solubility pump
The process by which the ocean maintains a vertical gradient in
DIC as a result of gas exchange.
Surface water at equilibrium with a given CO2 concentration
will increase its DIC concentration (uptake CO2) when the
water temperature decreases since the solubility and
dissociation of CO2 increase in cold water. The regions
of deep water formation are located in high latitudes so
the deep ocean is filled with cold water with relatively
high DIC concentration. It is estimate that about 50% of
the vertical DIC gradient can be accounted for by this
See Najjar (1991).
- solution drift
See climate drift.
Abbreviation for soil organic matter.
- Soret effect
In fluid mechanics, mass diffusion caused by a temperature gradient.
See Hurle and Jakeman (1971).
- source water type
In physical oceanography, a point on a T-S diagram
indicative of a water mass. In practice, few
if any water masses have T-S values identical to that of their source
water types due to transformation by atmosphere-ocean interface processes and/
mixing, but they are almost inevitably within the theoretical standard
deviation and as such readily identifiable as to their origin.
See Tomczak and Godfrey (1994).
- South Equatorial Countercurrent
An eastward current in the Atlantic and Pacific that flows
between 5 and 10 deg. S., the limited evidence for which shows
it to be much less well developed than the
NECC. In the Indian Ocean this is almost
totally confined between the equator and the northern boundary
of the SEC at 4 deg. S.
See Leetmaa et al. (1981),
- South Equatorial Current
A westward flow in the Atlantic and Pacific located south of the
below 5 deg. N. The SEC is strongest during
July and August and usually vanishes during the northern winter
and spring. This is also seen in the Indian Ocean south of
4 deg. S.
See Leetmaa et al. (1981),
- South Equatorial Undercurrent
An eastward flow in the Atlantic Ocean whose core is located near
200 m depth a few degrees south of the Equator. A satisfactory
dynamical explanation for this is as yet nonexistent.
See Tomczak and Godfrey (1994), p. 260.
- South Subsurface Countercurrent
An eastward flow in the Pacific Ocean whose core is located near
600 m depth a few degrees south of the Equator. A satisfactory
dynamical explanation for this is as yet nonexistent.
See Tomczak and Godfrey (1994), p. 128.
- Southern ACC Front
A front in the
Southern Ocean that
Antarctic Zone (AZ) to the north
Continental Zone (CZ) to the south.
The position of the SACCF is usually indicated by a distinct
temperature gradient along the -maximum of the
Upper Circumpolar Deep Water
(UCDW) as it shoals southward to near 500 m.
The property indicators of the SACCF are
> 1.8 along -maximum at Z > 500 m,
< 0 along -minimum at Z < 150 m,
S > 34.73 along S-maximum at Z > 800 m, and O < 4.2 ml/l
along O minimum at Z > 500 m.
The SACCF is one of three fronts found in the
Current (ACC), the others being (to the
Polar Front (PF) and the
Subantarctic Front (SAF).
See Orsi et al. (1995).
- Southern Ocean
In oceanography, an unofficial term used to describe the oceans
surrounding the continent of Antarctica. The northern limit
is the broad zone of transition where the permanent thermocline
reaches the surface at the
Subtropical Convergence (STC).
The southern limit is similarly
demarcated by the Subtropical Front.
It is distinguished from the other oceans by the relative uniformity
of its characteristics of hydrography and circulation and that it
influences more than it is influenced by the others.
The Southern Ocean bathymetry consists of three major basins where the depth
exceeds 4000 m separated by three major ridges that reach at least
to the 3000 m level. These are (proceeding
from the Pacific sector west): (1) the Amundsen, Bellingshausen, and
Mornington Abyssal Plains, sometimes called the Pacific-Antarctic
Basin, (2) the Macquarie, Pacific-Antarctic, and Southeast Indian
Ridge sytem, (3) the Australian-Antarctic Basin, (4) the Kerguelan
Plateau, (5) the Ender and Weddell Abyssal Plains, also known as
the Atlantic-Indian Basin, and (6) the Scotia Ridge.
- Southern Oscillation
The name given to the atmospheric component of the
El Nino/Southern Oscillation
(or ENSO) phenomenon. The SO is a large-scale shift in atmospheric
mass between the western and eastern Pacific, monitored by computing
the SOI. An SOI indicating El Nino conditions means
that there is reduced rainfall over the Indonesian region and that
the west Pacific convective center is displaced eastward along the
- Southern Oscillation Index
An index that is calculated to monitor the ENSO phenomenon. It is
defined as the pressure anomaly at Tahiti minus the pressure
anomaly at Darwin, Australia. Anomalously high pressure at Darwin
and low pressure at Tahiti are indicative of El Nino conditions.
- South Pacific Equatorial Water
In physical oceanography, a water mass partly
formed by convective sinking of surface water at SSTs of 26 deg. C
and above in the tropics in the area
of Polynesia. It is identified at temperatures greater than 20 deg. C
by a higher salinity than WSPCW, although
below 20 deg. C it seems to be a mixture of
WSPCW and ESPCW.
See Tomczak and Godfrey (1994), p. 166.
- South Trench Current
See North Sea.
- Soya Current
An extension of the
Tsushima Current that
flows northward from the Japan Sea
into the Okhotsk Sea via the
Soya Strait. It is a fairly rapid curent with velocities
reaching 1 m/s and traveles close to the coast with the character
of a boundary current.
- Soya Strait
See Okhotsk Sea.
Acronym for Space Physics Analysis Network.
Acronym for the Stratospheric Processes and their Role in
Climate study of the WCRP, a project
whose main components for study are the influence of the
stratosphere on climate, the physics and chemistry associated
with stratospheric ozone decrease, stratospheric variability
and monitoring, and UV irradiation changes.
SPARC Web site.
Abbreviation for South Pacific Convergence Zone, an atmospheric
convergence zone in the southwestern Pacific Ocean that is
characterized more by a convergence in wind direction than as
a wind speed minimum. It extends from east of Papua New
Guinea in a southeastward direction towards 120 deg. E and
30 deg. S.
See Philander and Rasmusson (1985).
- species-energy theory
A hypothesis set down by David Hamilton Wright in 1983 to explain
species richness in terms of energy. It states that, subject to water
supply and other factors being not limiting, diversity within
terrestrial habitats is to a great extent controlled by the amount
of solar energy available, declining with latitude in accordance with
the polewards decrease of solar radiation receipt.
- specific force
Force per unit mass. When working with the equations of motion in
oceanography or meteorology it is customary to divide both sides
of the equation by the mass so that each term refers to the
- specific heat
The heat required to raise the temperature of a unit mass of a given
substance by one degree. It is normally expressed in units of
calories/gm deg. K. The specific heat of water is 1.00
cal/gm deg. K (although this varies about 1% with temperature),
and the specific heat of dry air at constant pressure (C)
is 0.240 cal/gm deg. K and at constant volume (C )
0.171 cal/gm deg. K. For water vapor the constant pressure
(C) value is 0.441 and the constant volume (C )
value 0.331 cal/gm deg. K.
- specific humidity
The ratio of the mass ( ) of water vapor to the mass
( + ) of moist air in which is contained, where
is the mass of dry air, or
- specific volume
The reciprocal of density. In the determination of the specific
volume of sea water, the specific volume is
where the second through seventh terms on the right-hand-side are
specific volume anomaly
and the second through fourth terms the
- specific volume anomaly
A physical oceanographic term referring to that portion of the
specific volume differing from a
standard specific volume determined at a salinity of 35 ppt,
a temperature of 0 deg. C, and the pressure at the depth at which
the sample was taken.
- spectral element method
A method for approximating solutions to the governing equations
of fluid motion in the ocean. It was developed to combine the
geometrical flexibility of the traditional low-order finite element
methods with the accuracy and high convergence rates of spectral
methods. See Iskandarani et al. (1995).
- spectral nesting
See nested modeling.
- spectral signature
This refers to the particular form or shape evinced by the
power spectrum calculated from
the data comprising the time series of a process.
For example, if the spectrum shows peaks at around 20, 40 and
100 thousand years it might be said to have the spectral
signature of Milankovitch orbital variations.
A calcium carbonate rock deposited in limestone caves by dripping
water, e.g. stalactites and stalagmites. This occurs when
calcite is precipitated from water due to excess dissolved
carbon being diffused into the atmosphere. Speleothem growth
is dependent on groundwater recharge and on biogenic carbon
production in the soil, and as such is related to temperature
and water availability. Speleothem growth is a paleoclimate indicator
of warm and relatively wet climate conditions typical of
Speleothems are also known as dripstones or flowstones.
See South Pacific Equatorial Water.
- spherical approximation
The fundamental geometric approximation in oceanography. It maps
the approximate oblate spheroidal shape of the
geoid on a sphere and introduces spherical
is also assumed constant in this approximation.
See Stommel and Moore (1989) and Muller (1995).
- Spilhaus, Athelstan
- spin up
In numerical modeling, this refers to the transient initial
stages of a numerical ocean simulation when the various fields
are not yet in equilibrium with the boundary and forcing functions.
Three techniques are generally used to initialize and spin up
the ocean components
of coupled models: (1) initializing with climatological values of
temperature and salinity (typically using the
throughout the volume of the ocean; (2) start with the aforementioned
Levitus ocean and then spin it up for about 100 years using
surface climatological forcing; (3) run the ocean to equilibrium by
either combining surface forcing terms with atmospheric model fluxes or
just using the surface forcing (and perhaps using an
acceleration method with either option).
The entire ocean is not in equilibrium using the first two methods,
although the second method does allow the thermocline to adjust to
equilibrium. This is due to both
systematic errors and other
shortcomings in the Levitus data. The third method may produce
and ocean in equilibrium, but it may differ considerably from the
observed ocean and the circulation may be distorted. For example,
the deep ocean is often too warm using this method.
- Sporer Minimum
An extended period of limited
sunspot activity lasting from
around 1460 to 1550. It is named after the German scientists who
first noted it in 1887.
See Foukal (1990),
Wigley (1988) and Herman and Goldberg (1985).
Acronym for Satellite pour l'Observation de la Terre (France).
- spring tide
The high tides of greatest amplitude caused
by the Earth, Sun and Moon being almost co-linear. This causes
the gravitational pulls of both the Sun and Moon to reinforce
each other. The high tide is higher and low tide is lower than
the average, and spring tides occur twice a month at the times
of both new moon and
full moon. See also
A violent wind that begins suddenly, lasts for a short time,
and dies suddenly. It is sometimes associated with a
temporary change of direction.
- squall line
One of the most severe kinds of storms in the tropics.
The system is typically hundreds of miles long and consists of
a line of active thunderstorms. The cumulonimbus clouds
representing individual storms have lifetimes on the order of an
hour or less, but new ones replace dying cells allowing the
system as a whole to last from hours to days. They form
preferably over land and move with speeds from 10-20 m/s.
In a squall line warm moist air enters the base of the cloud
at its leading edge and rises in a convective updraft with
accompanying condensation. An extensive cloud anvil forms to
the rear of the convective tower with precipitation falling
from both the main cloud column and the anvil. The evaporation
of this precipitation into dry mid-tropospheric air leads to
cooling and downdrafts concentrated in the region of intensive
convection although extending to the rear of the squall line.
This downward rushing cold air causes a pseudo cold front or
gust front at the leading edge. This front undercuts the warm
moist air ahead, causing more convection and new cumuliform
clouds ahead of the line and fostering the propagation of the
See Hastenrath (1985).
Abbreviation for the Surface Radiation Budget Project, a
GEWEX project to produce and archive a global set
of shortwave (SW) and longwave (LW) surface parameters for the
12-year period from July 1983 through June 1995 using
ISCCP and ERBE data. See the
SRB Web site.
See Singular Spectrum Analysis.
Abbreviation for Shuttle Solar Backscatter Ultraviolet instrument,
developed to measure ozone concentrations by comparing solar
ultraviolet radiation with radiation scattered back from the
Earth's atmosphere. SSBUV data are used to calibrate the
instruments on NOAA satellites, e.g. NOAA-9, NOAA-11 and
UARS. The amount and height distribution of ozone in the upper
atmosphere are measured in 12 discrete wavelength channels
in the ultraviolet since ozone absorption is a strong function
of wavelength. See the
SSBUV Web site.
Abbreviation for the Space Science and Engineering Center at the
University of Wisconsin-Madisona, a research and development center
in the University's graduate school specializing in atmospheric
studies of Earth and the other planets, and interactive computing,
data access and image processing. See the
SSEC Web site
for further details.
Abbreviation for Special Sensor Microwave/Imager is an instrument
flow on the DMSP F-8 spacecraft that was
launched in June 1987. It measures earth emitted radiation at
four different frequencies.
This instrument allows the measurement of such geophysical
parameters as rain rate, snow depth, ice concentration,
and near-surface oceanic wind speed.
Abbreviation for Scanning Multi-channel Microwave Radiometer.
Abbreviation for Special Sensor Microwave/Thermal, a passive
step scanning microwave radiometer with seven channels in the
50 GHz to 60 GHz oxygen region.
Standard Stratigraphic Scale.
Abbreviation for sea surface temperature.
Abbreviation for Stratospheric Sounder Unit, a step scanned
far infrared spectrometer with 3 channels in the 15 micrometer
carbon dioxide region. The nadir resolution is 147.3 km. This
is part of the TOVS
Seismic Sea-Wave Warning System.
1. See numerical stability.
2. In physical oceanography, a measure of the tendency of a
water parcel or particle to move vertically in comparison with
its surroundings. Neglecting adiabatic
effects, the stability is defined (over short vertical distances) by
where is the density and z the vertical coordinate.
There is a correspondingly more complicated expression for the
stability when adiabatic effects are taken into account as is
usually necessary at great depths.
Typical values of E in the upper 1000 m range from
100 to 1000 x /m, with the largest values generally
occurring in the upper few hundred meters. Below 1000 m
values decrease to less than 100 x /m and can
get as small as a hundredth of that in deep trenches.
- stability frequency
See buoyancy frequency.
Acronym for Subtropical Atlantic Climate Study, a NOAA project
directed at increased understanding of the role of western boundary
currents of the Atlantic ocean in meridional heat flux and
development of strategies to monitor important western
See Molinari (1989).
A relatively cold period during an
of insufficient duration or magnitude to be or cause a
. Contrast with
- staggered grid
In numerical analysis this refers to a
computational grid in or on which
separate dependent variables are represented on alternate or staggered
grid points. For example, a 1-D equation set for pressure and velocity
would be solved on a grid where the pressure is represented at points
n, n+2, n+4, etc. while the velocity is represented at
n+1, n+3, n+5, etc. This procedure can confer numerical advantages
and is also used for problems with more than one spatial dimension.
See Kowalik and Murty (1993).
- stagnant film model
The simplest of several models developed to understand the
processes that determine the gas flux in and near the liquid
boundary layer that is the air-sea interface. It assumes that
the boundary layer is a discrete, stagnant layer in which only
molecular diffusion takes place. This stagnant layer sits on
top of a well-mixed, purely turbulent layer. The flux across
the interface is assumed to be equal to the flux in the stagnant
film which, using
Fick's law, gives a linear
concentration profile within the film. This leads, with the
additional use of
to an expression for the flux
involving the gas concentration at the base of the film ( ),
the partial pressure of the gas in the atmosphere ( ), the solubility
of the gas in seawater ( ), and the
piston velocity ( ), i.e.
See Najjar (1991).
- Standard Atmosphere
An idealized, dry, steady-state approximation of the atmospheric
state as a function of height that has been adopted as an engineering
reference. It was not computed as a true average but rather
approximates average atmospheric conditions.
The temperature and pressure are calculated below a
geopotential height of 32 km using:
The density if found from these using the
ideal gas law.
- standard density
A conventional value for the density of mercury, adopted for the
sake of uniformity in the conversion of pressure readings from
units of pressure to units of height (or the converse). The
value adopted by the WMO is the density at
0 deg. C, i.e. 13.5951 gm/cm .
- standard gravity
A conventional value for the acceleration due to gravity, adopted
for the sake of uniformity. The value adopted by the
WMO is 980.665 cm/sec .
- Standard Stratigraphic Scale
A proposed globally standardized stratigraphy
whose chronostratigraphic units will
eventually be delimited by
These stratotypes have as yet only been
agreed upon for parts of the scale and, as such, the
chronostratigraphic units within the Scale are presently
defined by biostratigraphic means.
Another such proposed standard is the UTS.
Acronym for Global Change System for Analysis, Research and
Training, a global system of fourteen
regional research networks for distributing scientific data
and information about global environmental change. This is a joint
program. The purpose of the network is to develop and coordinate
research on the specific regional origins and impacts of global
environmental change that contribute to the objectives of the
three aforementioned parent organizations.
START Web site.
- static pressure
The weight of the fluid (air or sea water) in an atmosphere or
ocean at rest. See
The property requiring that certain statistical properties of
a stochastic process be invariant
with respect to time. As some have noted, the strict satisfaction
of this requirement is impossible if one lends creedence to the
Big Bang theory of universal origin, although inroads can be
made towards satisfaction on less strict and more pragmatic
- stationary planetary wave
Departures of the time average of the atmospheric circulation
from zonal symmetry. They result from east-west variations in
surface elevation and temperature associated with the continents
and oceans. See Hartmann (1994).
- statistical downscaling
A procedure wherein local or regional climate characteristics
are inferred from the output of GCMs that
don't explicitly resolve such scales. Statistical relationships
between observed local climate variables, e.g. surface air temperature,
precipitation, etc., and observed large-scale predictors are
developed and then applied to the same large-scale predictors in
the GCM output to predict the local climate variables. This
method has been shown to produce local temperature and precipitation
change fields that were significantly different and had a finer
spatial scale structure than those generated by directly interpolating
large-scale GCM fields.
See Houghton and Filho (1995).
- statistically robust
Statistical results which are relatively insensitive to the presence of a
moderate amount of bad data or to inadequacies in the statistical model
being used, and that react gradually rather than abruptly to
perturbations of either. See Chave et al. (1987)
for a discussion of this in relation to geophysical data.
1. See Subtropical Convergence.
2. See South Trench Current.
Abbreviation for Salinity-Temperature-Depth.
Abbreviation for Stratosphere-Troposphere Exchange, a
SPARC project whose goal is to
identify a modeling and measurement strategy to produce the
needed understanding and quantification of
stratosphere-troposphere exchange. See the
STE Web site.
- steering wind
An upper atmosphere phenomenon more well known as the
Referring to organisms adapted to live within a limited temperature range.
Acronym for Stratosphere-Troposphere Exchange Program, an experiment
conducted to obtain high-level aircraft measurements of trace
chemicals, radiation and other quantities above tropical
convection with the aim of understanding tropospheric-stratospheric
- steric height
In oceanography, a quantity introduced to determine the distance
or depth difference between two surfaces of constant pressure.
The steric height h is defined by
where and are the depths of the pressure surfaces,
specific volume anomaly,
T the temperature, S the salinity, p the pressure, and
a reference density.
It has the dimension of height and is expressed in meters.
- stereographic projection
A zenithal projection of the perspective type, i.e. it is made
upon a plane tangent to the globe at one point by means of an
optical projection from the other end of the diameter through the
tangent point. The tangent point is typically one of the
See Subtropical Front.
Abbreviation for SubTropical Mode Water.
- stochastic process
A reasonably strict definition of this (also called a random process)
is a family of random variables indexed
by t, where t belongs to some index set T (which may denote time,
space, or whatever else one wishes). A more intuitive definition
might call this the set of all possible outcomes of an experiment
(this set also being called the ensemble)
inherently involving some degree of randomness along with the
mechanism by which individual outcomes, or
- Stokes' theorem
A theorem of geophysical importance in that it enables one to
calculate whether there is a tendency for a flow to be circulating
around a curve C, e.g. the Earth.
It is mathematically expressed as
where is the normal vector to a surface S, the
tangent vector to the curve C bounding S, and v the
velocity vector field.
This theorem, dealing with the integration of the curl
of the velocity field (or, equivalently, the
vorticity vector), allows us to evaluate
whether or not the fluid is circulating (as well as rotating or spinning
via the calculation of the vorticity vector
See Dutton (1986).
- Stokes velocity
A velocity in fluids that derives from the wave Reynolds stresses.
Lagrangian velocity and
See Wunsch (1981), p. 345.
- stomatal conductance
A proportionaly constant used when modeling land surface processes.
The movement of water from the inside of a leaf to the outside
is controlled by a constant called the stomatal conductance
(or its inverse the stomatal resistance).
The conductance varies with the age of the leaf, its position in
the canopy, and the availability of water in the soil. Leaves with
an adequate supply of water also have conductances that vary with
temperature and light levels, e.g. most leaves exhibit the
largest stomatal opening (conductance) in the presence of
full sunlight and close in the absence of sunlight.
See Dickinson (1992) and
Farquhar and Sharkey (1982).
- stomatal resistance
See stomatal conductance.
- Stommel, Henry
- Stommel-Arons thermohaline circulation
To be completed.
Acronym for Stormscale Operational and Research Climatology
- storm surge
A phenomena wherein sea level rises above the normal tide level
when hurricanes or tropical storms move from the ocean along
or across a coastal region.
This sea level rise can consists of three components, the
first of which results from low barometric pressure, i.e.
the so-called inverse barometer effect, where lower atmospheric
pressure on the surface of the water allows it to rise.
The second component is wind set-up where the winds drag
surface water to the shore where it piles up. The third
component of the rise is due to coupled long waves where the
peak of the wave coincides with the shoreline.
See Wiegel (1964).
- storm track
Paths over which vigorous midlatitude cyclones are most frequently
observed. These are defined by local maxima in the time-average
wind speed of the subtropical jet stream which have associated with
them maxima in the transient eddy activity and eddy fluxes of heat
and moisture. During the northern hemisphere winter there are two
of these, located downstream of the Tibetan Plateau and the Rocky
Mountains, over the Pacific and Atlantic Oceans, respectively.
The seasonal migration of these plays a key role in the annual
variation of precipitation.
See Hartmann (1994).
- straight line winds
The winds that follow the
gust front caused by
a downburst. These can reach
30 m/s as opposed to the gust front spreading at speeds
of from 5 to 15 m/s.
In oceanography, the vertical density structure resulting from
a balance among atmospheric heating, surface water exchange,
freezing, stirring and diffusion of heat, and the horizontal
and vertical motion (advection) of waters with different
temperature and salinity characteristics.
- stratified estuary
One of four principal types of estuaries
as distinguished by prevailing flow conditions.
This type is stratified with a
halocline between the upper and lower
portions of the water column of nearly constant salinity.
The James and Mersey estuaries are examples of this type.
- stratiform precipitation
One of the two clearly distinguishable types of precipitation,
the other being convective.
Stratiform precipitation falls from
nimbostratus clouds, and is defined as
a precipitation process in which the vertical air motion is small
compared to the fall velocity of ice crystals and snow.
The formation mechanism starts with the presence of ice crystals
in the upper layer of the nimbostratus cloud growing by the
process of vapor deposition, a process facilitated by an upward
air velocity sufficient to maintain supersaturation (yet still
small in the sense given above). Aggregation and riming then
occur when the growing ice crystals descend towards the
0 C level, after which further descent to warmer
levels melt the snowflakes thus created and the precipitation
falls as rain. The process takes on the order of 1-3 hrs.
See Houze (1993), pp. 197-200.
The science or study of rock strata, concerned with the original
succession and age relations of rock strata as well as their
form, distribution, lithologic composition, fossil content,
geophysical and geochemical properties, and just about any
attributes of rocks as strata. This also entails the interpretation
of the above in terms of environment or mode of origin and geologic
history. Three major branches of this are
lithostratigraphy (which deal with
relative time scales), and
chronostratigraphy (which deals with
an absolute time scale).
The atmospheric vertical boundary between the
ionosphere above and the
The portion of the atmosphere between an altitude of about 12 to 40
kilometers (10 to 30 miles)
where the temperature is approximately constant and there
is little or no vertical mixing. The temperature in this layer
rises from -65 deg. F at the lower boundary, the
tropopause to about 32 deg. F near the upper
boundary, the stratopause,
where a thin layer of ozone
absorbs ultra-violet radiation.
In geology, an actual rock succession at a particular location
that acts as the standard comparison type for other stratigraphic
types of similar age and/or composition. This is called the
holostratotype if it is the original succession to be designated
and described, the lectostratotype if another succession was chosen
due to the absence of a satisfactory original, the neostratotype
if the first has been demolished or invalidated, the parastratotype
if it's an additional section augmenting the definition given by
the holostratotype during that definition, and a hypostratotype
if it's an additional, subordinate stratotype in another region
selected after the establishment of the original. The stratocaster,
on the other hand, is one mean axe.
A layer-shaped type of cloud that forms dull, overcast skies at
This is a radiative transfer model that can be used for computing
either radiances (intensities) or irradiances (fluxes) for a wide
variety of atmospheric and surface conditions. See the
STREAMER Web site.
Acronym for Storm Transfer and Response EXperiment.
Abbreviation for Stratospheric Temperature Trends Assessment,
a SPARC project to assess stratospheric
temperature trends in the middle atmosphere using and
intercomparing all available sources of data.
STTA Web site.
- Subantarctic Front
In physical oceanography, a region of rapid transition in the
Southern Ocean between the
Polar Frontal Zone (PFZ) to the south and
the Subantarctic Zone (SAZ) to the north.
Its position is generally identified by the rapid northward sinking of the
salinity minimum associated with the
Antarctic Intermediate Water
(AAIW) from near the surface in the PFZ (S < 34) to depths greater
than 400 m in the SAZ (S < 34.30). The property indicators within
the front are S < 34.20 at Z < 300 m, >4-5 at
400 m, and O > 7 ml/l at Z < 200 m.
The SAF is one of three distinct fronts in the
Current (ACC), the others being
(to the south) the
Polar Front (PF) and the
Southern ACC Front (SACCF).
See Orsi et al. (1995).
- Subantarctic Mode Water
In physical oceanography, a type of water
in the Subantarctic Zone
of the Southern Ocean.
The SMW is the deep surface layer of water with uniform temperature
and salinity created by convective processes in the winter. It can
by identified by a temperature of around -1.8 deg. C and a salinity
of around 34.4 and is separated from the overlying surface water
by a halocline at around 50 m in the summer.
Although it is not considered to be a water mass,
it contributes to the Central Water
of the southern hemisphere, and is additionally responsible for the
formation of AAIW in the eastern part of the
south Pacific Ocean. This has also previously been called
See Tomczak and Godfrey (1994), p. 82.
- Subantarctic Upper Water
In physical oceanography, a water mass located in the
Subantarctic Zone of the
Southern Ocean. It is characterized
hydrographically by temperatures ranging from 4-10 deg. C in the
winter and 4-14 deg. C in summer, with salinities between 33.9 and
34.9 and reaching as low as 33.0 in the summer as the ice melts.
See Tomczak and Godfrey (1994), p. 82.
- Subantarctic Zone
The name given to the region in the
between the Subantarctic Front to
the south and
the Subtropical Front to the north.
This zone is characterized by the presence of
SAUW at and near the surface.
The SAZ is one of four distinct surface water mass regimes in the
Southern Ocean, the others being (to the south) the
Polar Frontal Zone (PFZ), the
Antarctic Zone (AZ) and the
Continental Zone (CZ).
See Tomczak and Godfrey (1994) and
Orsi et al. (1995).
- Sub-Atlantic period
A post-LGM European climate regime.
This refers to the period from about 1000-500 BC onwards when the
climate cooled considerably. It was a period of mild winters and
great windiness, with summer cooling one of the most notable
features. It was preceded by the
and followed by the
Little Climatic Optimum.
See Lamb (1985), p. 373.
- Subarctic Intermediate Water
In physical oceanography, this is a water
which originates from the Polar Front
formed between the Kuroshio
and the Oyashio in the western
North Pacific Ocean. It is formed chiefly by the process of mixing
of surface and deeper waters and subducted
into the subtropical gyre, filling
the northern Pacific south of 40 deg. N from the east. This is one
of the few water masses whose formation process has little to do
with atmosphere-ocean interaction. It is characterized by a salinity
minimum ranging from about 300-1000 m depth and a large east-west
salinity gradient in the South Pacific.
See Tomczak and Godfrey (1994), p. 161.
- Subarctic Upper Water
A surface water mass found in the
north Pacific Ocean characterized by low salinities in the
range 33-34 and temperatures from 3-4 deg. C. Some SUW is
carried toward the tropics in the eastern boundary currents
of the subtropical gyre and
mixes with Central Water.
- subbituminous coal
A black coal intermediate in classification between
and bituminous coals. It is distinguished from lignite by a higher
carbon and lower moisture content. Its presence is taken as an
indicator of terrestrial humidity (precipitation exceeding evaporation)
at the time of formation and deposition.
- Sub-Boreal period
A post-LGM European climate regime.
This refers to the period from about 3000 to 1000-500 BC when, after
the Piora oscillation, the forests
regained ground in Europe.
It was preceded by the Atlantic period and
followed by the
See Lamb (1985), p. 373.
In physical oceanography, a process whereby
Ekman pumping injects surface water
into intermediate depths along isopycnal
surfaces. This process is responsible for the formation of the
water masses in the permanent thermocline.
Although it is a permanent process, water mass formation occurs only
in late autumn and winter due to variations in the seasonal
See Tomczak and Godfrey (1994).
- subjective analysis
In meteorology, the name given to
synoptic weather charts prepared
by hand since the resulting diagnosis or analysis relied extensively
on the subjective judgment of the preparer.
Compare to objective analysis.
See Daley (1991).
Of the subtropics.
- Subtropical Convergence
The name given by Deacon (Deacon (1933), Deacon (1937))
to the hydrographic boundary between the
Southern Ocean and
subtropical waters to the north. This was replaced by the
term Subtropical Front (STF)
in the mid-1980s.
- Subtropical Countercurrent
An eastward flowing current found in the region from 20-26 deg. N.
In geostrophic current calculations
these currents extend to the bottom of the thermocline and occasionally
to 1500 m, while they've been identified in ship drift data with
speeds reaching 0.15 m/s. They do not exist east of Hawaii and,
given also the fact that they are in the middle of the subtropical gyre,
are thought to be caused by a modification of the Sverdrup
circulation by those islands. No satisfactory explanation has as
yet been advanced, though.
See Tomczak and Godfrey (1994).
- Subtropical Front
In physical oceanography, a region of pronounced meridional
gradients in surface properties that serves as the boundary between
the Southern Ocean and the waters of
the subtropical regime
to the north. This was originally called the
Subtropical Convergence (DTC)
by Deacon but the newer terminology arose in the mid-1980s.
This is generally a subduction
region for various types of
The STF separates the
Subantarctic Surface Water
(SASW) to the south from the
Subtropical Surface Water
to the north.
The surface hydrographic properties
of the STF include a rapid salinity change from 35.0 to 34.5 and
a strong temperature gradient (from 14-10 deg. C in winter and
18-14 deg. C in summer) as one crosses from north to south.
At 100 m its approximate location is within a band across which
temperatures increase northward from 10 to 12 deg. C and salinities
from 34.6 to 35.0, with the salinity gradient usually the more
The position as well as the intensity of sinking or rising motion in
the STF is more variable than in any other front or divergence in
the Southern Ocean.
See Tomczak and Godfrey (1994), Tchernia (1980) and
Orsi et al. (1995).
- subtropical gyre
A clockwise/counterclockwise circulation in the northern/southern
hemisphere that is forced by the wind and features western intensification
in the form of a western boundary current. In the northern
hemisphere the gyres span the width of the oceans and extend from about
10 to 40 N with the boundary currents in the Atlantic
and Pacific called, respectively, the Gulf Stream and the Kuroshio.
There are analogous features in the southern hemisphere.
The polar boundaries between these and the
subpolar gyres coincide with
the latitude at which the curl of the wind
stress vanishes, the latter being largely the mechanism of causation.
See Schmitz and McCartney (1993).
Generally the part of the Earth's surface between the tropics and
the temperate regions, or between about 40 deg. N and S.
Acronym for SUbsonic Contrails and Clouds Effects Special
Study, a NASA field program using instrumented aircraft and
ground-based measurements to investigate the effects of
subsonic aircraft on contrails, cirrus clouds and atmospheric
chemistry. Objectives include better determining the
radiative properties of cirrus clouds and contrails to
better determine their effect on Earth's radiation budget and
determining the formation processes of cirrus clouds.
SUCCESS Web site.
- sudden stratospheric warmings
A polar atmospheric phenomenon where, during winter, planetary
waves sporadically amplify and dramatically change the circulation
and distribution of ozone. These episodes are marked by an
abrupt increase of temperature over the polar cap, e.g. more than
50 K in a few days. The polar-night vortex is displaced and
distorted and the zonal-mean temperature gradient reverses direction
from poleward to equatorward. The latter is accompanied by a reversal
of the zonal-mean circulation as demanded by the thermal wind
balance. The overall structure of the motions is zonally
asymmetric and large quantities of air are exchanged between low
and high latitudes.
See Salby (1992).
- Suess effect
The phenomena where the activity of 20th century wood is around
2% lower than that of 19th century wood due to the introduction
carbon dioxide into the atmosphere by fossil fuel
combustion since the Industrial Revolution. See
- Sulawesi Sea
Part of the
Australasian Mediterranean Sea centered at approximately
122 deg. E and 3 deg. N. It is surrounded by the Sulu
Archipelago and Mindinao to the north, Kalimantan to the
west, the Makassar Strait
and Sulawesi to the south, and the north part of the
Moluccan Sea to the west.
It covers about 280,000 sq. km with the deepest part being
around 6200 m just southwest of Mindanao. The entire Sulawesi
is mostly a deep, flat (4600-5200 m deep)
plain with steep sides.
The deep water Pacific Ocean water that passes through
the northern Molucca Sea and
enters the Sulawesi over a 1400 m deep sill. This water
eventually passes through the Makassar Strait and on into
the Flores Sea to the south.
The surface temperatures range between 28 deg. C in
April and 27 deg. C in February, and the salinities range
through four patterns during the year (i.e. 31-34 from SW to NE during
Dec.-Feb., 32.8-33.9 from SW to NE during Mar.-May, 34 from
Jun.-Aug., and 33.5-34.1 from NW to SE during Sep.-Nov.).
The monsoon pattern dominates the wind forcing, with the
winds blowing from the north to northeast during the northern
winter and more weakly from the south and southwest during
the summer. This creates a surface current directed from
Mindanao towards the Makassar Strait during the summer.
This regime is largely maintained through the winter although
westward currents are additionally found along Sulawesi.
See Fairbridge (1966).
A squall that occurs in the Malacca Strait, blowing from between
southwest and northwest. These usually occur at night and are
most frequent between April and November. They are generally
accompanied by thunder and lightning and torrential rain, and
their arrival is accompanied by a sudden fall of temperature.
- Sun synchronous
A satellite orbit such that as the Earth rotates the new orbit is
over an area experiencing the same local time as the area viewed
on the previous orbit. Therefore, half of each orbit is over the
dark or night side of the planet.
A relatively dark, sharply defined region on the solar disk,
marked by an umbra about 2000 deg. K cooler than the effective
photospheric temperature. It is surrounded by a less dark but
also sharply defined penumbra. The average diameter is about
37,000 km with large spots occasionally reaching 245,000 km
across or more. Most sunspots are found in groups of two or
See Herman and Goldberg (1985).
- superimposed ice zone
One of five glacier zones defined
to classify glacier areas in terms of the ice temperature and
the amount of melting.
In this zone so much meltwater is produced that the ice
layers found in other zones merge to form a continuous mass
of ice called superimposed ice, although the superimposed
ice zone is restricted to the area in which there is an
annual increment of superimposed ice exposed at the surface.
Superimposed ice is also formed in the lower parts of the
soaked zone but is covered by
firn there. The boundary between the
soaked and superimposed ice zones is defined as the bounary
between firn and ice on the glacier surface at the end of
the melt season. This boundary is variously called the
firn line, the firn edge or the annual snow line.
- surf beat
The rising and falling of the water level in the surf zone
at intervals in the vicinity of 2 to 5 minutes, especially
noticeable on a flat beach. This is caused by the pattern
of incoming waves being such that groups of high waves and
low waves follow each other at the same intervals. This is
in turn due to the interaction of wave groups with slightly
different frequencies, a process that leads to a much longer
envelope or beat frequency modulated the short wavelength
See Wiegel (1964).
- surface energy balance
The balance of energy terms
at the ocean surface in a climate model. The terms are the
absorbed solar flux (S), the downward
infrared flux (Sd), the
upward infrared flux (Su), the
sensible heat flux (H), and the
latent heat flux (LE). The balance can
be expressed as
S + Sd - Su - H - HE = 0.
- surface Reynolds number
See Kagan (1995).
- surface tension
Acronym for the U.S. surface radiation network, a NOAA project to
monitor and measure the surface radiation budget. This has replaced
the SOLRAD project.
The long-term ground-based observations from SURFRAD are useful
for evaluating satellite-based estimates of surface radiation,
for validating hydrologic, weather, and climate prediction models,
and for monitoring trends in parameters that affect the Earth's
SURFRAD Web site.
See Subarctic Upper Water.
Abbreviation for Soil-Vegetation-Atmosphere Transfer models.
These are schemes used to represent land in climate models.
Model elements include storage reservoirs and mechanisms for
the exchange with the atmosphere of water and thermal
- Sverdrup, Harald
A unit of transport used in oceanography equivalent to
m s and abbreviated as Sv.
- Sverdrup balance
A vorticity balance in which meridional advection in the presence
of the planetary vorticity gradient is balanced by the stretching
of fluid columns. It is most simply stated as
where is the meridional gradient of
the Coriolis parameter f,
v the meridional velocity, and w the vertical velocity.
- Sverdrup transport
The net meridional flow of mass in the interior of the ocean
gyres away from the lateral boundaries.
- swamp ocean
The simplest ocean model used in coupled model
simulations. SSTs are computed but from
surface energy balance
(local effects) only, i.e. there is no accounting for
heat storage (temporal) or ocean current (nonlocal) effects.
Only mean annual forcing can be applied when a swamp ocean is
used since the lack of the capability to store heat in the
oceans would allow sea ice to freeze into the mid-latitudes
in the winter hemisphere. On the plus side, the dominant
equilibration time is that of the atmosphere since the ocean
surface response time is almost instantaneous.
Abbreviation for Soil-Vegetation-Atmosphere Transfer.
Acronym for Surface WAve Dynamics Experiment, an experiment
performed in the fall of 1990 off the coast of Virginia which
was primarily concerned with the evolution of the directional
wave spectrum, wind forcing and wave dissipation, the effect
of waves on air-sea coupling mechanisms, and the microwave radar
response of the ocean surface. The scientific goals were
to understand the dynamics of the evolution of the wave field
in the open ocean; to determine the effect of waves on the
air-sea transfers of momentum, heat and mass; to explore the
response of the upper mixed layer to atmospheric forcing;
to investigate the effect of waves on the response of various
airborne microwave systems; and to improve numerical wave
See Weller et al. (1991).
Acronym for Surface WAve Processes Program, an experiment
conducted off the coast of California in 1990 and concerned
with wave breaking and the interaction between surface waves
and upper ocean boundary layer dynamics. The scientific
goals were to improve the understanding of processes involved
in wave breaking (e.g. what determines the occurrence of breaking
in space and time, the processes of bubble and fluid injection,
the generation of turbulence in the upper layer of the ocean
by waves) and in determining the structure of the upper
ocean (e.g. the role of surface waves in air-sea transfers
and in mixed layer dynamics, with particular emphasis on the
structure and dynamics of
See Weller et al. (1991).
Acronym for Stratospheric Wind Infrared Limb Sounder.
Abbreviation for southern warm tongue, a tongue of relatively warm
water located at the eastern boundary of the
WPWP. It is located at around 10 S.
See Ho et al. (1995).
The anthropogenic processes of the replacement of the natural vegetation by
cultivated vegetation and the deterioration in the composition and
structure of flora.
See Kagan (1995).
The branch of ecology that
deals with whole communities and the interactions of the organisms
Descriptive of the period between successive
conjunctions of two objects. The
synodic period of a planet or a moon is the interval of time
between successive conjunctions of the body and the sun, as
viewed from the earth.
Acronym for the SYNoptic Ocean Prediction experiment, an experiment
taking place in the subtropics.
Descriptive of data simultaneously obtained over a large area.
- synoptic mean circulation
In oceanography, the time-averaged flow field obtained in a coordinate
system whose axes are parallel and perpendicular to the instantaneous
axis of a particular strong current such as the Gulf Stream. This
coordinate system can and does change with time.
Compare to Eulerian mean circulation.
See Schmitz and McCartney (1993).
- systematic errors
in model simulations that result from model deficiencies in the
component (e.g ocean and atmosphere) models alone, additive errors
from the component models after they are coupled, or errors that
are produced by the coupled interactions between imperfect
component models. Sometimes called climate drift. See
The branch of biology dealing with the interrelationships of
different species and their classification.