The theory of radiative transfer is used to explain how a stratospheric aerosol layermay, for large solar zenith angles, increase the flux of UV-B light at the ground. Asprevious explanations are heuristic and incomplete, I first provide a rigorous and completeexplanation of how this occurs. I show that an aerosol layer lying above Antarctica duringspring will decrease the integrated daily dose of biologically weighted irradiance, weightedby the erythema action spectrum, by only up to 5%. Thus after a volcanic eruption, life inAntarctica during spring will suffer the combined effects of the spring ozone hole andozone destruction induced by volcanic aerosols, with the latter effect only slightly offset by aerosol scattering.
I extend subsurface radar imaging by considering the additional information thatmay be derived from radar interferometry. I show that, under the conditions that temporaland spatial decorrelation between observations is small so that the effects of thesedecorrelations do not swamp the signature expected from a subsurface layer, the depth ofburial of the lower surface may be derived. Also, the echoes from the lower and uppersurfaces may be separated. The method is tested with images acquired by SIR-C of the areaon the Egypt/Sudan border where buried river channels were first observed by SIR-A.Temporal decorrelation between the images, due to some combination of physical changesin the scene, changes in the spacecraft attitude and errors in the processing by NASA of theraw radar echoes into the synthetic aperture radar images, swamps the expected signaturefor a layer up to 40 meters thick. I propose a test to determine whether or not simultaneousobservations are required, and then detail the radar system requirements for successfulapplication of the method for both possible outcomes of the test. I also describe in detail the possible applications of the method. These include measuring the depth of burial of ice in the polar regions of Mars, enhancing the visibility of buried features and, most importantly, the ability to map soil moisture in arid regions of the earth at high spatial resolution.
