Land Hydrosphere Products

Documenting the global water and energy cycle through modeling and observations is fundamental to achieve the goals of NASA’s Earth Science Research Strategy. Such documentation is needed to enable NASA and its supported investigators to acquire enhanced knowledge of Earth’s climate, including characterizing the memories, pathways and feedbacks between key water, energy and biogeochemical cycles. With this enhanced knowledge, there is the potential for NASA to resolve its overarching scientific goal: How is the Earth changing and what are the consequences for life on Earth?, which the Earth Science Research Strategy further delineates into five areas related to variability, forcings, response, consequences, and predictions.

Snow Cover

Satellites are well suited to the measurement of snow cover because the high albedo of snow presents a high contrast with most other natural surfaces except clouds. Spectral reflectivity of snow depends on grain size and shape, impurity content, liquid water content, depth, surface roughness, and solar elevation angle (Hall and Martinec 1985). Reflectance of fresh snow is very high in the visible wavelengths, but decreases in the near-infrared wavelengths especially as grain size increases. Because of natural aging and other factors such as soot or volcanic ash deposition, reflectance of snow decreases over time. Fresh snow can have a reflectance up to about 80 percent, but its reflectance may decrease to below 40 percent after snow crystals metamorphose (Hall et al. 1998).

More information can be found in the Snow Cover ESDR white paper.

Sea Ice

Sea ice is defined as any form of ice found at sea which has originated from the freezing of sea water. Satellites can easily measure sea ice in the visible, infrared, and microwave regions of the electromagnetic spectrum. However, there are advantages and disadvantages to each type of radiation because no one spectral region allows an optimal view of sea ice in all conditions (from NSIDC).

Surface Hydrology

The surface hydrology suite encompasses several products including, but not limited to evapotranspiration (ET). ET is the sum of water lost to the atmosphere from the soil surface through evaporation and from plant tissues via transpiration, is a vital component of the water cycle, which includes precipitation, runoff, stream flow, soil water storage and ET (Mu et al. 2007).

More information can be found in the Surface Hydrology ESDR white paper.