Microwave Signatures Of Sea Ice Research Articles

Seasonal and Regional Variations of Active/Passive Microwave Signatures of Sea Ice

Ku-band (13.3 GHz) scatterometer and K-band (19.4 GHz) radiometer data acquired by the CCRS CV-580 aircraft over the period from 1979 to 1982 in Canadian and Danish (Greenland) coastal waters have been analyzed to determine the seasonal and regional variations of microwave sea-ice signatures. A clustering analysis of the like and cross-polarized scattering cross sections, ?HHo and ?HVo, and the H polarized emissivity ?H, has been used to identify distinct microwave sea-ice signatures for each ice type and to trace the evolution of these signatures with region and season. Ice-type signatures in the high Arctic under cold conditions are quite stable, and major ice classes are readily identified from microwave measurements. Under warmer conditions the signatures change with the structure, moisture content of the snow pack, and with the free water in the surface layers of the underlying ice. An attempt is made to create a consistent picture of the microwave signature transformation by grouping the data into seaice seasons (snow and ice surface transformation stages). The separation between microwave ice-class signatures reaches a minimum at the peak of the summer melt.

Temporal variations of the microwave signatures of sea ice during the late spring and early summer near Mould Bay NWT

A series of surface‐based measurements of microwave brightness temperatures and accompanying ice characteristics have been made on first‐year and multiyear sea ice in the Canadian archipelago and in the southeastern Beaufort Sea during the late spring and early summer of 1982. Radiometer data taken at frequencies of 10, 18.7, and 37 GHz show the transition from conditions of snow‐covered ice from the onset of snow melt through to full summer melt conditions. Initially, values of TB for multiyear ice were larger than for first‐year ice, but by the middle of the experiment this distinction disappeared. Drained surfaces often had emissivities above 0.95, but values dropped considerably lower during heavy melting events. The skewness of the distribution of TB appears to distinguish ice types further into the melt season. The standard deviation is not useful for ice type discrimination but is sensitive to the area covered by melt ponds. Microwave attenuation in various surface layers was found to range from 2 m−1 early in the experiment to >400 m−1 during full summer melt, indicating penetration depths from 250 to 2.5 mm, respectively.

Simultaneous scatterometer and radiometer measurements of sea-ice microwave signatures

This paper discusses a combined data set obtained in the Canadian Arctic which partially covers the variation with season of the microwave signatures of sea ice. Results draw together airborne collection periods which include: March 1979, April 1979, and June 1980. The data set consists of RC-10 aerial photograph; HH - and HV -polarized backscattering coefficients from a fanbeam scatterometer operating at 13.3 GHz over incidence angles extending from nadir to 60\deg ; 19.4 GHz, H -polarized radiometer brightness temperatures at a fixed incidence angle of 45\deg ; and overlapping X - and L -band SAR imagery. A precision radiation thermometer (PRT-5) was also included in the sensor complement in the 1980 missions. Accumulated statistics for each microwave measurement were determined by segmenting the time histories of the profiling sensors by (WMO) World Meteorological Organization sea-ice class and then recombining the information for each ice category. Eigenvector analysis was applied to specify the radiometer and scatterometer hyperspace boundaries of each sea-ice class and examine the classification utility of this microwave information.