Radiative transfer acceleration based on the principal component analysis and lookup table of corrections: optimization and application to UV ozone profile retrievals

Abstract. In this work, we apply a principal component analysis (PCA)-based approach combined with lookup tables (LUTs) of corrections to accelerate the Vector Linearized Discrete Ordinate Radiative Transfer (VLIDORT) model used in retrieval ozone profiles from backscattered ultraviolet (UV) measurements by Ozone Monitoring Instrument (OMI). The spectral binning scheme, which determines accuracy and efficiency PCA-RT performance, is thoroughly optimized over range 265 360 nm assumption Rayleigh-scattering atmosphere above Lambertian surface. high level (∼ 0.03 %) achieved fast-PCA calculations full radiances. approach, computationally expensive multiple scattering (MS) are limited small set PCA-derived optical states, while fast single two-stream MS performed, for every point. number calls only 51 application OMI profile retrievals fitting window 270–330 where RT should be called at fine intervals ∼ 2000 wavelengths) simulate (spectral resolution: 0.4–0.6 nm). LUT implemented online due reduction streams (discrete ordinates) 8 4, improving attainable simulations using vector 12 72 layers. Overall, speed up our factor 3.3 previous version, has already been significantly sped line-by-line various approximations. Improved treatments approximation errors improve (2 %–5 hence errors, especially tropospheric 10 %; remaining forward within 5 % troposphere 3 stratosphere.