Microwave and IR Radiometry for Estimation of Atmospheric Radiation Balance and Sea Ice Formation

It is well known that space-born microwave and infrared (IR) polarization measurements allow the development of advanced technologies for permanent snow and ice pack monitoring in the Arctic region. But the interpretation of these data are complicated because variations of atmospheric radiation start to be close to the brightness contrasts of different types of ice. On the other hand, the same absorbing/scattering properties of the atmosphere play a key role in the shortwave radiation balance and therefore make a big impact in sea ice formation (freezing/melting). One of the first attempts to investigate sea ice formation using satellite-born IR and microwave instruments was made with the USSR “Meteor-18” satellite by Gorelik et al. (1978). Several statistically valuable data for determining the periods of sea ice melting in the Laptev Sea and Okhotsk Sea were obtained as well as mapping the sea ice structure. The comparison demonstrates that there is not a bad qualitative correspondence of the retrieved and observed data, but unfortunately, as shown in more recent works, it is the qualitative mapping. Retrieving the quantitative parameters, such as sea ice depth or melting of the ice under snow coverage, is a much more complicated task that needs detailed knowledge about transformation of the radiation received by space-born instruments. Although different atmosphere components take part in the formation of its absorbing/scattering properties (water vapor, aerosols, fogs, and so on), the importance of clouds is well recognized. The problem of accounting for the impact of clouds on the short radiation fluxes is enforced because of high temporary and spatial variability of cloud parameters. The parameterization of cloud properties using some integrative parameters has been proposed and been widely used recently. It is considered now that the main parameters of clouds that influence the radiation balance are (1) space structure, (2) height of clouds (cloud top and base in case of deep clouds), (3) average temperature of clouds, (4) integral liquid water content (LWC), and (5) integral ice water content. Some of the above-mentioned parameters are measured now by using regular meteorological satellites. However, retrieving the cloud base from satellite measurements is still a problem at least over the land surface as well as the average temperature of the clouds. The accuracy of retrieving the integral liquid/ice water content on the basis of satellite measurements is much less than that of ground-based instruments. Thus, the development of the ground-based validation measurements of different cloud parameters is the problem discussed in the presented work.