Sasktran Version 3 3.0
The model is intended for optically thin media on a spherical body. The model is well suited for applications in the stratosphere and mesosphere. The model is not well suited for ray tracing in optically thick media, such as dense clouds. The model explicitly assumes all rays are traced in a spherical atmosphere. Thus the model is most appropriate for conditions where unit optical depth along one ray occurs on a scale size where the curvature of the atmosphere is important. In Earth's atmosphere for example, atmospheric curvature is important on scale sizes of tens and hundreds of kilometers.
Components The model, from a programming perspective, has the following components
#- the ray geometry used by the model. This is implemented in a class derived from #SKTRAN_GridSpecifications_V2 #- the optical properties of the atmosphere. This is implemented in class #SKTRAN_AtmosphericState #- the ground albedo defined by a class derived from class #SKTRAN_RTAlbedo #- The Sasktran engine, implmented in class #SKTRAN_EngineInterface_V2
(often only one) and the accuracy of these terms depends mostly upon the validity of the coarse interpolation. execution and are sufficiently accurate for calculate the radiance coming into a single point at a single instant in time from several directions at several wavelengths. The single point represents an observer who may be below, in or above the atmosphere. The model was built to analyze radiances collected from limb viewing spacecraft but can be applied to nadir viewing geometries. Solar occultation geometries are not yet fully supported (2009-03-31) as we do not include the direct "no scatter" signal from the sun to the observer (this will change).
\Memory Usage This radiative transfer model typically consumes between several hundred of megabytes of memory to a few tens of gigabytes. This is a heavy burden on any operating system and can quickly exhaust system memory through memory fragmentation. The best strategy to avoid memory allocation failure is to use one instance of #SKTRAN_EngineInterface_V2 and keep it alive for the length of the process. This is especially useful if the ray geometry configuration is not changing the nature of the ray tracing (eg the number of heights is the same).