751 articles
Shrinkage of Lake Chad
The shrinkage of Lake Chad is the loss of about 90 percent of the lake's surface area from the 1960s to the 1990s, with recent refilling since 2000.
Siboga Expedition
The Siboga Expedition was a Dutch oceanographic expedition aboard H.M. Siboga, led by Max Weber, that surveyed the seas of the Dutch East Indies in 1899 and 1900.
Side-scan sonar
Side-scan sonar is a sonar technique that transmits sound pulses sideways from a towed or vehicle-mounted device, building acoustic images of the seafloor rather than depth maps.
Significant wave height
Significant wave height (Hs, also SWH) is the mean height of the highest one third of waves, the standard measure of sea state in forecasts and offshore engineering.
Slack water
Slack water, also called slack tide, is when a tidal current's speed is near zero, occurring between the flood and ebb currents as the tide changes.
SNOTEL
SNOTEL (SNOwpack TELemetry) is a network of more than 900 automated stations measuring snowpack in the mountains of the western United States, operated by the USDA.
Snow course
A snow course is a permanent transect where snowpack depth and water content are measured at fixed points year after year to forecast seasonal water supply.
Snow sublimation
Snow sublimation is the direct transfer of water from snow to the atmosphere as vapor, without melting; it can remove 10 to 90% of snowfall.
Snow water equivalent
Snow water equivalent (SWE) is the depth of liquid water that would result if a column of snowpack melted completely. It predicts spring runoff in the western United States.
Snowmelt freshet
A snowmelt freshet is the pronounced rise in river flow, often the annual peak, caused when a basin's winter snowpack melts in spring or early summer.
Snowmelt runoff
Snowmelt runoff is the portion of melting snow that flows over the land surface into streams and rivers, supplying much of the springtime water in colder climates.
Snowmelt Runoff Model
The Snowmelt Runoff Model (SRM) is a degree-day-based, semi-distributed model that simulates and forecasts daily streamflow in mountain basins, developed by Jaroslav Martinec in 1975.
SOCCOM project
SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) is a National Science Foundation-funded US research program that has deployed biogeochemical profiling floats throughout the Southern Ocean since 2014.
Soil moisture
Soil moisture, also called soil water content, is the amount of water held in the soil, a driver of soil processes and a key variable in agriculture, hydrology, and meteorology.
Soil salinity
Soil salinity, or the accumulation of salts in saline soils, impairs plant growth on over 1,381 million hectares worldwide; irrigation without leaching and drainage is a leading cause.
Soil water retention curve
The soil water retention curve, or soil water characteristic curve, relates the water a soil holds to its matric potential, a key property for irrigation and drainage design.
Soluble reactive phosphorus
Soluble reactive phosphorus (SRP), also called molybdate reactive phosphorus or dissolved reactive phosphorus, is a filtered phosphorus measurement used in limnology as an estimate of phosphate available to algae.
Sound speed profile
A sound speed profile is a record of how the speed of sound in seawater varies with depth, used in hydrographic surveying to convert acoustic travel times into depths and positions.
Southern Ocean Carbon and Climate Observations and Modeling
SOCCOM, the Southern Ocean Carbon and Climate Observations and Modeling project, is a US research program launched in 2014 to observe the Southern Ocean's carbon cycle with profiling floats.
Southern Ocean Time Series
The Southern Ocean Time Series (SOTS) is an Australian ocean observatory of automated deep-water moorings southwest of Tasmania that has measured air-sea heat and carbon exchange since 1998.
Special flood hazard area
A special flood hazard area (SFHA) is land subject to the 1-percent-annual-chance base flood, designated by FEMA, where flood insurance is mandatory for federally backed mortgages.
Specific storage
Specific storage measures the volume of water a unit volume of confined aquifer releases per unit decline in hydraulic head, expressed in units of inverse length.
Specific yield
Specific yield is the ratio of water a saturated rock or soil releases by gravity drainage to its total volume, fundamental for modeling unconfined aquifers.
Spheroidal carbonaceous particles
Spheroidal carbonaceous particles are carbon-rich fly-ash particles produced only by industrial coal and oil combustion, which accumulate in sediments as unambiguous markers of fossil-fuel pollution.
Spring tide
A spring tide is the larger-than-average tide at new and full moon, when Earth, Moon, and Sun align and tidal forces add, producing higher highs and lower lows.
St. Lawrence River Divide
The St. Lawrence River Divide is a continental divide in central and eastern North America separating the Great Lakes–St. Lawrence basin from the Mississippi and Hudson Bay basins.
Stanford Watershed Model
The Stanford Watershed Model is a pioneering computer program developed at Stanford University by Norman Crawford and Ray Linsley that simulates streamflow from precipitation, becoming the ancestor of the EPA's HSPF model.
Stemflow
Stemflow is precipitation intercepted by a plant canopy that runs down stems, branches, and trunks to the soil, concentrating water and nutrients at the plant's base.
Stomatal conductance
Stomatal conductance measures how readily water vapor diffuses out of a leaf through stomatal pores, set by pore aperture and guard cell turgor, and is a key parameter in earth system models.
Storativity
Storativity, also called the storage coefficient, is a dimensionless measure of the water volume an aquifer releases or absorbs per unit surface area per unit change in hydraulic head.