Chapter 18
Physical Basis for Microwave Remote
Sensing of Sea Ice and Snow
Martti Hallikainen
Laboratory of Space Technology
Helsinki University of Technology
Otakaari 5 A, 02150 Espoo
Finland
18.1 Introduction
About 10% of the world Ocean is covered by sea ice during some portion of the year. Sea
ice participates in the key large-scale processes of the Earth's climate system, the absorption
and emission of radiant energy, and the poleward flux of heat (Carsey et al., 1992). This
participation comes about through processes involving the atmosphere, the ocean, and the
radiation field. Some of these are outlined below:
Radiative balance: The snow-covered sea ice has a very high albedo relative to that of the open
ocean. Therefore, changes in sea ice extent cause drastic changes in the surface albedo of the
high-latitude seas.
Surface heat: Although the fully developed ice cover is an effective insulator between the cold
air and the relatively warm ocean, areas of open water and thin ice lose heat rapidly during
the cold seasons (Maykut, 1986).
Ice margin processes: The abrupt transition to open water gives rise to unique processes, including water mass formation, oceanic upwelling, eddy formation, and generation of atmospheric
instability (Muench et aL, 1987).
Operations: Navigation and trafficability on and below the surface, drill ship operations in the
marginal seas and harbor operations are concerned with locating areas of thin ice, identifying
hazards such as very thick and deformed ice, and forecasting ice conditions.
Snow is an important component of the Earth's climate and it impacts significantly global
weather and is vital to the water supply in many areas. Snow serves as a water vapor input to
the atmosphere through the processes of sublimation and evaporation and as a source of water to
the soil and river system when melting occurs. It changes the albedo and the radiation balance
and may reduce the solar energy available to heat the surface and the lower atmosphere by more
than 50%. Therefore, snow cover represents a changing atmosphere output that is a function of
variability in the Earth's climate and is also a boundary condition that affects meteorology and
NATO ASI Series. Vol. 145
Radiation and Water in the Climate System:
Remote Measurements
Edited by Ehrhard Raschke
@ Springer-Verlag Berlin Heidelberg 1996
Physical Basis for Microwave Remote
Sensing of Sea Ice and Snow
Martti Hallikainen
Laboratory of Space Technology
Helsinki University of Technology
Otakaari 5 A, 02150 Espoo
Finland
18.1 Introduction
About 10% of the world Ocean is covered by sea ice during some portion of the year. Sea
ice participates in the key large-scale processes of the Earth's climate system, the absorption
and emission of radiant energy, and the poleward flux of heat (Carsey et al., 1992). This
participation comes about through processes involving the atmosphere, the ocean, and the
radiation field. Some of these are outlined below:
Radiative balance: The snow-covered sea ice has a very high albedo relative to that of the open
ocean. Therefore, changes in sea ice extent cause drastic changes in the surface albedo of the
high-latitude seas.
Surface heat: Although the fully developed ice cover is an effective insulator between the cold
air and the relatively warm ocean, areas of open water and thin ice lose heat rapidly during
the cold seasons (Maykut, 1986).
Ice margin processes: The abrupt transition to open water gives rise to unique processes, including water mass formation, oceanic upwelling, eddy formation, and generation of atmospheric
instability (Muench et aL, 1987).
Operations: Navigation and trafficability on and below the surface, drill ship operations in the
marginal seas and harbor operations are concerned with locating areas of thin ice, identifying
hazards such as very thick and deformed ice, and forecasting ice conditions.
Snow is an important component of the Earth's climate and it impacts significantly global
weather and is vital to the water supply in many areas. Snow serves as a water vapor input to
the atmosphere through the processes of sublimation and evaporation and as a source of water to
the soil and river system when melting occurs. It changes the albedo and the radiation balance
and may reduce the solar energy available to heat the surface and the lower atmosphere by more
than 50%. Therefore, snow cover represents a changing atmosphere output that is a function of
variability in the Earth's climate and is also a boundary condition that affects meteorology and
NATO ASI Series. Vol. 145
Radiation and Water in the Climate System:
Remote Measurements
Edited by Ehrhard Raschke
@ Springer-Verlag Berlin Heidelberg 1996