ObsErrorFactorTopoRad¶
This obsfunction was designed to mimic GSI-Observer method of observation Error Inflation Factor (EIF).
Error Inflation Factor (EIF) as a function of terrain height, channel, and surface-to-space transmittance.
H = surface height [m]
X = surface-to-space transmittance
IASI, CrIS, AIRS and AVHRR3:
\(factor = (2000/H)^4\)
\(EIF = SQRT \{ 1 / [ 1 - (1 -factor ) * X] \}\) if \(H > 2000\), for all the input channels
AMSU-A:
\(EIF = SQRT [ 1 / ( 2000 / H ) ]\) if \(2000 < H < 4000\), for Channels 1-6,15
\(EIF = SQRT [ 1 / ( 4000 / H ) ]\) if \(H > 4000\), for Channel 7
ATMS:
\(EIF = SQRT [ 1 / ( 2000 / H ) ]\) if \(2000 < H < 4000\), for Channels 1-7,16
\(EIF = SQRT [ 1 / ( 4000 / H ) ]\) if \(H > 4000\), for Channel 8
Required input parameters:¶
- Sensor
Sensor name: currently only works for these sensors
iasi
,cris-fsr
,airs
,avhrr3
,amsua
,atms
- Channels
Used channels
Output parameters:¶
Error Inflation Factor (EIF) for each input channel of the input sensor at each location.
Required fields from obs/geoval:¶
- geovals
GeoVaLs/surface_geopotential_height
- obsDiag
ObsDiag/transmittances_of_atmosphere_layer
Example configurations:¶
- filter: BlackList
filter variables:
- name: brightnessTemperature
channels: 1-15
action:
name: inflate error
inflation variable:
name: ObsFunction/ObsErrorFactorTopoRad
channels: 1-15
options:
sensor: amsua_n19
channels: 1-15
In this example, the observation errors of NOAA-19 AMSU-A are inflated according to the algorithm.