Air Mass Factor Calculations Based on Support Vector Regression Machine

Nitrogen dioxide (NO2) plays a key role in the chemistry of the atmosphere. Based on the space borne measurements, the Differential Optical Absorption Spectroscopy (DOAS) method determines the NO2 slant column density (SCD) along the light path through the atmosphere in a given spectral window between 405 and 465 nm. Based on radiative transfer model, a Look-Up-Table (LUT) of Air Mass Factor (AMF) is derived. The look-up parameters of the LUT are the solar zenith angles (SZA) and the detector viewing zenith angles (VZA), azimuth angles (AA), the surface albedo, the aerosol loading, the cloud parameters and the profiles of pressure and temperature. Conventionally, the MF values are derived using interpolation from LUT, which leads to bias. The accuracy can be improved by the application of Support Vector Machine (SVM). The AMF of the LUT is used to be samples of SVM. By training the samples and predicting, the appropriate AMF values are derived. For comparison, the interpolation AMF values are also calculated. The intercomparison result shows the accuracy of SVM method is comparable to that of interpolation approach.

[1]  Vladimir Vapnik,et al.  Statistical learning theory , 1998 .

[2]  Robert J. D. Spurr,et al.  Air-mass factor formulation for spectroscopic measurements from satellites: application to formaldeh , 2001 .

[3]  Korris Fu-Lai Chung,et al.  Theoretically Optimal Parameter Choices for Support Vector Regression Machines with Noisy Input , 2005, Soft Comput..

[4]  S. Smyth,et al.  Observed distributions of nitrogen oxides in the remote free troposphere from the Nasa Global Tropospheric Experiment Programs , 2000 .

[5]  K. Chance,et al.  Ring effect studies: Rayleigh scattering, including molecular parameters for rotational Raman scattering, and the Fraunhofer spectrum. , 1997, Applied optics.

[6]  Stanley C. Solomon,et al.  On the interpretation of zenith sky absorption measurements , 1987 .

[7]  A. Kokhanovsky,et al.  SCIATRAN 2.0 – A new radiative transfer model for geophysical applications in the 175–2400 nm spectral region , 2004 .

[8]  Stanley C. Solomon,et al.  On the evaluation of air mass factors for atmospheric near‐ultraviolet and visible absorption spectroscopy , 1993 .

[9]  J. Noxon,et al.  Stratospheric NO2: 2. Global behavior , 1979 .

[10]  D. Byun.  Science algorithms of the EPA Models-3 community multi-scale air quality (CMAQ) modeling system , 1999 .

[11]  Michael Buchwitz,et al.  The Global Ozone Monitoring Experiment (Gome) : Mission, instrument concept, and first scientific results , 1997 .

[12]  U. Platt,et al.  Simultaneous measurement of atmospheric CH2O, O3, and NO2 by differential optical absorption , 1979 .

[13]  Robert Sausen,et al.  Estimations of global no, emissions and their uncertainties , 1997 .