ObsErrorFactorSfcPressure

This obsfunction was designed to mimic the GSI Observer code (i.e., setupps.f90) to inflate the observation error for surface pressure. The purpose of the function is to inflate the observational error from its initial value to a larger value based on large discrepancies between model and observations that would be expected when the model terrain (pressure) differs from the observed terrain, which is likely in coarse resolution model simulations. The filter variable must be stationPressure since this function is designed solely to affect the assignment of ObsError on this variable alone.

The following observed variables are required inside the code: stationElevation, stationPressure, and airTemperature, although this may contain missing data at some locations. In addition, the required model GeoVaLs variables are: surface_altitude, surface_pressure, and vertical profiles of air_pressure and air_temperature. Since some model interfaces may supply different variable names for surface_altitude or temperature, there are yaml parameters to override the defaults.

Required Parameters

error_min and error_max

specify the min and max ObsError which will be used within the function as limits on the output.

Optional Parameters

geovar_sfc_geomz

an optional variable name to override the default of surface_altitude in the event the model variable name is different (example would be surface_geopotential_height).

geovar_temp

an optional variable name to override the default of virtual_temperature in the event the model variable name is different (example would be air_temperature).

original_obserr

an optional group name to override the default of ObsErrorData in the event the input dataset already has a pre-determined value of ObsError.

Example

- filter: Perform Action
  filter variables:
  - name: stationPressure
  action:
    name: inflate error
    inflation variable:
      name: ObsFunction/ObsErrorFactorSfcPressure
      options:
        error_min: 100         # 1 mb
        error_max: 300         # 3 mb
        geovar_sfc_geomz: surface_geopotential_height   # Optional, default is surface_altitude
        geovar_temp: air_temperature                    # Optional, default is virtual_temperature
        original_obserr: ObsError                       # Optional, default is ObsErrorData