CLWRetSymmetricMW

This function estimates the Cloud Liquid Water (CLW) content at the observation location from both the model background \(CLW_m\) and the observation derived \(CLW_o\). \(CLW\) is used in radiance assimilation as an indication of the presence of cloud.

The estimate is the mean of the model and observed content: \(CLW_{sym} = 0.5 * (CLW_m + CLW_o)\).

The mean is used so that the \(CLW\) is a symmetric function of \(CLW_o\) and \(CLW_m\). Since the observation error for radiances is inflated in presence of cloud, as indicated by \(CLW\), the symmetrical dependence on the model and observations better deals with situations when \(CLW_m\) and \(CLW_o\) are very different.

References

Geer A. J. and P Bauer, 2010: Enhanced use of all-sky microwave observations sensitive to water vapour, cloud and precipitation. ECMWF Technical Memoranda 620. http://dx.doi.org/10.21957/mi79jebka

Geer A. J. and P Bauer, 2011: Observation errors in all-sky data assimilation. https://doi.org/10.1002/qj.830

Required yaml parameters

Requires CLWRetMW inputs, and clwret_types of ObsValue (observations) TBs, and simulated bias-corrected TBs GsiHofXBc.

Returns clw_symmetric_amount.

Example configuration

AMSU-A Example (function_clwretmean.yaml), see “obs function” section below:

observations:
  observers:
  - obs space:
      name: amsua_n19
      obsdatain:
        engine:
          type: H5File
          obsfile: Data/ufo/testinput_tier_1/amsua_n19_obs_2018041500_m_qc.nc4
      simulated variables: [brightnessTemperature]
      channels: 1, 2
    geovals:
      filename: Data/ufo/testinput_tier_1/amsua_n19_geoval_2018041500_m_qc.nc4
    obs function:
      name: ObsFunction/CLWRetSymmetricMW
      options:
        clwret_ch238: 1
        clwret_ch314: 2
        clwret_types: [ObsValue, GsiHofXBc]
      variables: [clw_symmetric_amount]
      tolerance: 1.0e-8