Radiative transfer acceleration based on the principal component analysis and lookup table of corrections: optimization and application to UV ozone profile retrievals
Year: 2021
Type: article
Abstract: . In this work, we apply a principal component analysis (PCA)-based approach combined with look-up tables (LUTs) of corrections to accelerate the VLIDORT radiative transfer (RT) model used in the retrieval of ozone profiles from backscattered ultraviolet (UV) measurements by the Ozone Monitoring Instrument (OMI). The spectral binning scheme, which determines the accuracy and efficiency of the PCA–RT performance, is thoroughly optimized over the spectral range 265 to 360 nm with the assumption of a Rayleigh-scattering atmosphere above a Lambertian surface. The high level of accuracy (~ 0.03 %) is achieved from fast-PCA calculations of full radiances. In this approach, computationally expensive full multiple scattering (MS) calculations are limited to a small set of PCA-derived optical states, while fast single scattering and 2-stream multiple scattering calculations are performed, for every spectral point. The number of calls to the full MS model is only 51 in the application to OMI ozone profile retrievals with the fitting window of 270–330 nm where the RT model should be called at fine intervals (~ 0.03 nm with ~ 2000 wavelengths) to simulate OMI native measurements at 229 wavelengths (spectral resolution: 0.4–0.6 nm). We also developed a Look Up Table (LUT) to correct RT approximations performed using a scalar RT model with 4 streams (discrete ordinates) and 24 layers, thereby achieving the accuracy at the level attainable from simulations with a vector model with 12 streams and 72 layers; this speeds up the RT calculations by more than 2 orders of magnitude when ignoring other overhead. Overall, we speed up our OMI retrieval by a factor of 3.3 over the previous version, which has already been significantly sped up over line-by-line calculations due to various RT approximations. Improved treatments for RT approximation errors using LUT corrections improve spectral fitting (2–5 %) and hence retrieval errors, especially for tropospheric ozone by up to ~ 10 %; the remaining errors due to the forward model errors are within 5 % in the troposphere and 3 % in the stratosphere.
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,585
Awards: G4809145194, FROM PREVIOUS ROSES FUNDING WE HAVE PRODUCED FROM OMI RADIANCES AN OZONE PROFILE AND TROPOSPHERIC OZONE PRODUCT (PROFOZ) AVAILABLE ON AURA VALIDATION DATA CENTER (AVDC) FOR THE ENTIRE RECORD. OZONE PROFILES ARE RETRIEVED IN 24 LAYERS FROM THE SURFACE TO ABOUT 60 KM. THE RETRIEVED TROPOSPHERIC OZONE HAS SUFFICIENT ACCURACY TO SEE OZONE SIGNALS CAUSED BY CONVECTION EL NINO BIOMASS BURNING ANTHROPOGENIC POLLUTION AND STRATOSPHERIC INTRUSION AND TO TRACK THEIR TRANSPORT SPATIOTEMPORALLY. TROPOSPHERIC STRATOSPHERIC AND TOTAL OZONE COLUMNS CAN EACH BE ACCURATELY RETRIEVED TO TYPICALLY WITHIN THE FEW DOBSON UNIT RANGE. THIS ALGORITHM PRODUCES MORE ACCURATE OZONE PROFILES IN THE LOWER STRATOSPHERE AND TROPOSPHERE AND TOTAL OZONE THAN STANDARD ALGORITHMS. VALIDATION OF 10-YEAR PRODUCT (2004-2014) SHOWS VERY GOOD COMPARISON WITH OZONESONDE IN THE TROPICS AND MID-LATITUDE AND ABOVE ~20 KM AT HIGH LATITUDES AND WITH MICROWAVE LIMB SOUNDER (MLS) OZONE PROFILE (EXCEPT FOR ABOVE ~32 KM AFTER THE OCCURRENCE OF SERIOUS ROW ANOMALY IN 2009) AND STRATOSPHERIC OZONE COLUMN. HOWEVER THE RETRIEVAL EXHIBITS TEMPORAL DEPENDENT BIASES (ARTIFICIAL TREND) ESPECIALLY AFTER 2009 AS WELL AS SOME LATITUDINAL/SOLAR ZENITH ANGLE/CROSS-TRACK DEPENDENT BIASES. IN ADDITION RETRIEVAL SENSITIVITY TO TROPOSPHERIC OZONE AVAILABLE FROM THE OMI MEASUREMENTS IS NOT MAXIMIZED DUE TO INTERFERENCES FROM THE FITTED SURFACE ALBEDO PARAMETERS AND RETRIEVAL ACCURACY TO TROPOSPHERIC OZONE IS AFFECTED DUE TO THE LACK OF EXPLICIT CONSIDERATION OF THE EFFECTS OF AEROSOL AND SURFACE BIDIRECTIONAL REFLECTANCE DISTRIBUTION FUNCTIONS (BRDF). WE PROPOSE TO CONTINUE OUR INVOLVEMENT IN THE AURA SCIENCE TEAM AND ATMOSPHERIC COMPOSITION MODELING ANALYSIS PROGRAM WITH A THREE-YEAR STUDY TO: A. PRODUCE A SIGNIFICANTLY IMPROVED LONG-TERM AND SPATIAL CONSISTENT PRODUCT AT NATIVE OMI SPATIAL RESOLUTION (13 48 KM2 AT NADIR INCLUDING ZOOM-MODE) INCORPORATING RECENT DEVELOPMENTS OF TROPOPAUSE-BASED CLIMATOLOGY SIMULTANEOUS RETRIEVAL OF OPTICAL DEPTH OF POLAR MESOSPHERIC CLOUDS CLOUD AND SURFACE RETRIEVAL USING THE RING EFFECT AND O4 ABSORPTION IN ~340-365 NM ENHANCEMENT OF TROPOSPHERIC OZONE RETRIEVAL SENSITIVITY USING LONGER WAVELENGTHS TO DERIVE WAVELENGTH-DEPENDENCE IN SURFACE ALBEDO UPDATED CHARACTERIZATION OF SLIT FUNCTIONS AND PROPOSED UPDATES BELOW (I.E. B-E) AND PRODUCE A NEW L3 PRODUCT IN THE OMI SIPS. B. IMPROVE THE CHARACTERIZATION OF OMI MEASUREMENT ERRORS TO BETTER CONSTRAIN OMI RETRIEVALS AND FURTHER OPTIMIZE THE SPECTRAL FITTING. C. MAINTAIN THE SPATIOTEMPORAL CONSISTENCY PERFORMING TEMPORAL DEPENDENT EMPIRICAL RADIOMETRIC CALIBRATION AND BY FITTING STRAY-LIGHT SPECTRA AND SYSTEMATIC FITTING RESIDUALS. D. INVESTIGATE THE IMPACTS OF LACKING EXPLICIT AEROSOL AND SURFACE BRDF TREATMENTS ON RETRIEVALS AND THE USE OF OMI AEROSOL PRODUCT OR SIMULTANEOUS AEROSOL RETRIEVAL AND THE INCLUSION OF SURFACE BRDF TO IMPROVE THE RETRIEVAL ACCURACY TO TROPOSPHERIC OZONE. E. SPEED UP AND IMPROVE THE ACCURACY OF RADIATIVE TRANSFER CALCULATIONS BASED ON LOOK-UP TABLES TO CORRECT ERRORS DUE TO NEGLECTING POLARIZATION AND INADEQUATE NUMBER OF STREAMS/LAYERS OR USING THE PRINCIPAL COMPONENT ANALYSIS APPROACH AND IMPROVE FORWARD MODEL INPUTS WITH HIGH-RESOLUTION METEOROLOGICAL FIELDS AND SURFACE ALBEDO. F. COMBINE OUR RETRIEVALS WITH OTHER SATELLITE AND IN-SITU DATA AND DYNAMICS FIELDS TO INVESTIGATE THE IMPACT OF VARIOUS DYNAMICAL PROCESSES ON OZONE VARIABILITY INCLUDING ASIAN SUMMER MONSOON TRANSPORT FROM DEEP CONVECTION AND STRATOSPHERIC-TROPOSPHERIC EXCHANGE (STE) AND INVESTIGATE THE USE OF OUR RETRIEVALS TO MONITOR HIGH-O3 EVENTS OVER US INTERMOUNTAIN WEST. THIS PROPOSAL DIRECTLY RESPONDS TO 6 OUT OF 7 SPECIFIC GOALS OF THIS PROGRAM ELEMENT., G8975532903
OpenAlex ID: W3087035807