V2.2_i6 L2AS Detailed Release Description
November 27, 2002

Algorithm Changes

  • During aerosol retrievals, eliminate optical depth values for which the optical depth exceeds a fraction of the optical depth upper bound and for which the optical depth uncertainty exceeds a threshold.
  • During aerosol retrievals, reject aerosol mixtures based on optical depth constraints and optical depth uncertainty constraints.
  • Enable the use of all four bands in aerosol retrievals over dark water, weighted as a function of optical depth.
  • Make configurable the eigenvector to start with in the determination of the number of eigenvectors to use in aerosol retrievals over heterogeneous land.
  • In aerosol retrieval, update AlgTypeFlag, RegBestFit* and Reg*OpticalDepth fields to include results of retrievals from homogeneous surface algorithm.
  • Increase the valid range of BHR and DHR from 1.0 to 1.05. This affects the scaling factors which are used to unscale the data.
  • Report all chi-square values over water, regardless of whether the chisquare_abs test succeeded or failed.
  • Refine optical depth upper bound calculation by linearly interpolating between grid points in optical depth grid.
  • Modify optical depth upper bound determination by using a minimum surface reflectance criterion.
  • Modify the aerosol retrieval over homogeneous surfaces to downgrade the weight of any spectral camera-averaged HDRF which is very different than the median.
  • In the aerosol retrieval, add penalization of the chi-square for heterogeneous surfaces to give a larger residual if (rho_misr - rho_model) becomes negative.
  • In the land surface retrieval, use geometric parameters computed at regional resolution (17.6km x 17.6km) instead of at domain resolution (70.4km x 70.4km).
  • Limit the value of optical depth for which surface retrievals are permitted.
  • Modify the iteration algorithm for HDRF retrieval to avoid numerical instability.

Bug Fixes

  • Fix bug so that the number of eigenvectors to use is always less than the number of cameras with valid data.
  • In aerosol retrieval, add rho_bias to rho_model instead of subtracting it.
  • Fix HDRF and BHR calculations to eliminate banding problem which occurs under poor MISR/sun geometry viewing conditions.

Product Changes

  • Add new flag value to AlgTypeFlag field in aerosol product. The new value is 8, to be interpreted as "homogeneous land retrieval".
  • Add field RegBestFitCombinedResidual to aerosol product.
  • Add fields RegSfcRetrOptDepth, RegSfcRetrOptDepthunc, RegSfcRetrMixture, RegSfcRetrAlgTypeFlag, to land surface product.
  • Change valid range and scaling of BHR and DHR in land product, so that maximum allowed value is 1.05 instead of 1.0.

Science Config File Changes

  • Remove obsolete field brf_tau_refinement_thresh.
  • Change values of existing fields:
    min_dw_subr_thresh: 16 -> 32
    dw_band_mask: F F T T -> T T T T
    het_band_mask: T T T F -> T T T T
    homog_band_mask: T T T F -> T T T T
    max_chisq_abs_dw_thresh: 4 -> 2
    max_chisq_geom_dw_thresh: 16 -> 3
    max_chisq_spec_dw_thresh: 4 -> 3
    max_chisq_maxdev_dw_thresh: 16 -> 5
    max_chisq_abs_ota_thresh: 3 -> 2
    max_chisq_maxdev_ota_thresh: 3 -> 5
    max_chisq_het_thresh: 3 -> 4
    hdrf_conv_iter: 2 -> 0
    max_bhr: 1.0 -> 1.05
    max_brf: 3.0 -> 5.0
    max_dhr: 1.0 -> 1.05
    max_hdrf: 2.0 -> 5.0
  • Add new fields:
    do_homog_retrieval = F
    homog_min_cam_thresh = 6
    homog_min_subr_thresh = 8
    first_eigenvalue_for_eofs = 1
    het_tau_upperbnd_fraction = 0.99
    max_het_tau_thresh = 3.0
    max_accept_tau_unc_per_het_case = 3.0
    max_chisq_homog_thresh = 500.
    num_tau_extra = 2
    cam_weight_oblique_flag = T
    cam_weight_nadir_flag = F
    band_weight_short_flag = T
    band_weight_long_flag = F
    homog_tau_upperbnd_fraction = 0.99
    max_tau_unc_homog_thresh = 0.1
    frac_bias_regmean = 0.0
    frac_geom_spec_mix = 0.5
    frac_geom_spec_tau = 0.5
    hdrf_thresh_factor_mix = 500.0
    hdrf_thresh_factor_tau = 500.0
    abs_tau_upperbnd_fraction = 0.99
    max_tau_unc_abs_thresh = 0.1
    dw_tau_min_for_weights(1) = 0.75
    dw_tau_min_for_weights(2) = 0.50
    dw_tau_min_for_weights(3) = 0.0
    dw_tau_min_for_weights(4) = 0.0
    dw_tau_max_for_weights(1) = 1.5
    dw_tau_max_for_weights(2) = 1.0
    dw_tau_max_for_weights(3) = 0.0
    dw_tau_max_for_weights(4) = 0.0
    low_tau_default_thresh = 0.1
    prev_region_default_thresh = 0.95
    albedo_thresh_land = 0.01
    albedo_thresh_water = 0.0
    chisq_het_normalize_flag = F
    use_dynamic_band_weights = F
    hdrf_green_tau_thresh = 1.0
    hdrf_iteration_weight = 1.0