
VLIDORT History In 2004, the vector code VLIDORT for polarized light was created for Stokes vector output in the pseudospherical approximation. Profile linearization was completed in 2005. In 2006, VLIDORT was given the bulkproperty linearization, and the BRDF surface capability was installed; thermal emission and exact singlescatter calculations were introduced in 2007 (Version 2.0). The capabilities for VLIDORT were then brought up to the same level as those for the scalar code LIDORT; this effort culminated in Version 2.4 (2009). In recent years, the VLIDORT code has been upgraded to Fortran 90 (2011, Version 2.5), and the surfaceleaving, external SS and observational geometry options introduced (2013, Version 2.6). In 2015, the code was made threadsafe for use in parallelcomputing environments. VLIDORT is currently at Version 2.7, and an upgrade to Version 2.8 is expected in 2017.
VLIDORT Capabilities VLIDORT generates Stokes vector output [I, Q, U, V]. It has all the above capabilities as LIDORT  general output, the full atmospheric/surface linearization facility, the BRDF and other supplements, the exact single scatter treatments, the performance enhancements. The option to output the linearly polarized field (V component absent) exists. Neglecting polarization altogether in VLIDORT gives identical results to LIDORT. VLIDORT does not use the Green's function method to solve the RTE  instead, solutions are obtained using the classical substitution method to solve coupled linear differential equations. VLIDORT uses the same total optical property inputs as LIDORT, with one exception. Instead of Legendre expansion coefficients, VLIDORT requires a 4x4 matrix of expansion coefficients appropriate for scatteringmatrix expansions in terms of generalized spherical functions. Thermal emission inputs are the same as those in LIDORT. VLIDORT is available in Fortran 90 (Version 2.7) and Fortran 77 (version 2.5).



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