SetSurfaceType¶

Determine and output surface type for use with observation operator (e.g. RTTOV) based on GeoVaLs, observation report type and AAPP (ATOVS and AVHRR Pre-processing Package) classification, where available. Based on UK Met Office Ops_SatRad_SetSurfaceType procedure.

Required input variables:¶

GeoVaLs: surface_altitude@GeoVaLs ice_area_fraction@GeoVaLs
ObsSpace: latitude@MetaData

Optional input variables:¶

ObsSpace: land_sea@MetaData (required if UseReportSurface is true)

surface_height@MetaData (required if UseReportElevation is true)

surface_class@MetaData (required if UseAAPPSurfaceClass is true)

water_area_fraction@MetaData (required if UseSurfaceWaterFraction is true)

Input parameters:¶

UseReportSurface: Use reported BUFR surface type. If the surface is classified as coast, the surface elevation and model orography are used to determine if it is most likely land or sea.

(default false)

UseReportElevation: Use reported surface elevation. Otherwise, model orography is used instead.

(default false)

UseAAPPSurfaceClass: Use additional surface type information derived by AAPP using radiances to reclassify surfaces.

(default false)

UseSurfaceWaterFraction: Use reported Surface Water Fraction.

(default false)
MinIceFrac: Minimum ice fraction required for assignment of sea-ice surface type.

(default 0.2)
MinWaterFrac: Minimum water fraction for assignment of sea surface type. Only used if UseSurfaceWaterFraction is set to true.

(default 0.99)
IceLimitHard: Latitude south of which sea-ice is assumed to be present regardless of model ice fraction. IceLimitHard is only specified for the Southern Hemisphere while IceLimitSoft is applied in both hemispheres.

(default 72 [degrees latitude south])
IceLimitSoft: Latitude past which sea-ice is assumed when AAPP surface classification is present and valid (assuming UseAAPPSurfaceClass is true).

(default 55 [degrees latitude])
HighlandHeight: Height below which surface may be reclassified by AAPP surface classification as sea.

(default 1000 [metres])
SurfaceTypeLand: Observation operator land surface type value to map to.

(default 0, RTTOV land surface value)
SurfaceTypeSea: Observation operator sea surface type value to map to.

(default 1, RTTOV sea surface value)
SurfaceTypeSeaIce: Observation operator sea-ice surface type value to map to.

(default 2, RTTOV sea-ice surface value)

Notes¶

Only sea spots may be reclassified as sea-ice. Land points that may be covered with ice are left as land. The assignment of sea-ice is determined using a threshold on the model seaice fraction.

Required yaml parameters¶

ATMS Example (atms_qc_filters.yaml):

- filter: Variable Assignment
  assignments:
  - name: surface_type@MetaData
    function:
      name: SetSurfaceType@ObsFunction
      options:
        UseReportSurface:        true  # non-default
        UseReportElevation:      true  # non-default
        UseAAPPSurfaceClass:     true  # non-default
        UseSurfaceWaterFraction: false # default
    type: int