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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 medium i.


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 equilibrium line.


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 vegetation. See Kagan (1995).


soil horizon
A layer of soil distinguishable from adjacent layers by characteristic physical properties such as structure, color, texture, and chemical composition.


An easterly wind that brings rain to the southeast coast of Spain and the Straits of Gibraltar. This is another name for the levanter.


solar constant
The energy flux density of the solar luminosity 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
Variations in 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 Endal (1981). 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. See the 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 SURFRAD. 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. See the 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 process. 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 separates the Antarctic Zone (AZ) to the north from the 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 Antarctic Circumpolar Current (ACC), the others being (to the north) 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 equator.


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. See the 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 force.


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 expressed as

where the second through seventh terms on the right-hand-side are called the specific volume anomaly and the second through fourth terms the thermosteric anomaly.


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 interglacial and interstadial periods. 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 polar coordinates. Gravitational acceleration is also assumed constant in this approximation. See Stommel and Moore (1989) and Muller (1995).


Spilhaus, Athelstan
More later.


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 Levitus climatology) 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 neap tide.


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 convective region. 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.


Abbreviation for 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 instrument package.


Abbreviation for 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 boundary features. See Molinari (1989).


A relatively cold period during an interglacial stage of insufficient duration or magnitude to be or cause a . Contrast with interstadial.


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 Henry's law, 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 boundary stratotypes. 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 IHDP/IGBP/WCRP 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. See the START Web site.


static pressure
The weight of the fluid (air or sea water) in an atmosphere or ocean at rest. See hydrostatic equation.


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 grounds.


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. See CTD.


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 jet stream.


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 interaction.


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, the 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 poles.


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 realizations, selected.


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 itself). See Dutton (1986).


Stokes velocity
A velocity in fluids that derives from the wave Reynolds stresses. Compare to Lagrangian velocity and Eulerian velocity. 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
More later.


Stommel-Arons thermohaline circulation
To be completed.


Acronym for Stormscale Operational and Research Climatology Program.


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 biostratigraphy and 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 stratosphere below.


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 low altitudes.


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. See the 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 Antarctic Circumpolar 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 Winter Water. 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 Southern Ocean 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 Sub-Boreal period and followed by the Little Climatic Optimum. See Lamb (1985), p. 373.


Subarctic Intermediate Water
In physical oceanography, this is a water mass 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 lignite 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 Sub-Atlantic period. 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 thermocline. 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 Central Water.

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 reliable indicator. 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. See the 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 of ``dead'' carbon dioxide into the atmosphere by fossil fuel combustion since the Industrial Revolution. See Suess (1955).


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 more. 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 waves. 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
More later.


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 climate. See the 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 energy.


Sverdrup, Harald
More later.


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 modeling. 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 Langmuir circulation. 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 in them.


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
Stable 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 Meehl (1992).


The branch of biology dealing with the interrelationships of different species and their classification.

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Next: Ta-Tm Up: Glossary of OceanographyClimatology Previous: Sa-Sm

Steve Baum
Mon Sep 2 11:24:01 CDT 1996