ObsErrorBoundMW¶
The observation error bounds for microwave are obtained through the ObsErrorBoundMW
function. This function determines the observation error bounds (\(\text{Residual Threshold}\)) for gross check as a function of transmittance at model top, latitude, and terrain height. This function filters out data if \(|obs-h(x)| > \text{Residual Threshold}\). Currently, this function is implemented for AMSU-A and ATMS platforms, and the \(\text{Residual Threshold}\) is obtained differently for each instrument and, furthermore, depends on the channel of the instrument and if it’s over water surface. For both instruments with observations over non-water surfaces, the \(\text{Residual Threshold}\) is obtained following:
where \(ErrobsMax\) represents the maximum observation error bound, \(Errflat\) the error factor as a function of latitude, \(Errftaotop\) the error factor as a function of transmittance at model top, and \(Errftopo\) the error factor as a function of terrain height.
Over water surfaces, the \(\text{Residual Threshold}\) depends on the instrument and its channels. For AMSU-A channels 5 and 15, the \(\text{Residual Threshold}\) is obtained following:
while for the other channels, it’s obtained following the same relationship over non-water surfaces. For ATMS channels 6 and 16, the \(\text{Residual Threshold}\) is obtained considering \(ErrobsMax=10.0\), while for other channels follow the same relationship over non-water surfaces.
Required input parameters:¶
- channels
List of channels available for assimilation.
- sensor
Name of the sensor for which the observation error factor applies.
- obserr_bound_max
The maximum value of the observation error bound for each channel in
channels
.- obserr_bound_latitude
Function to set the observation bound based on latitude.
- obserr_bound_transmittop
Function to set the observation bound based on transmittance at model top.
- obserr_bound_topo
Function to set the observation bound based on terrain height.
- obserr_function
Function to estimate observation error based on symmetric cloud amount.
Optional Input parameters:¶
- test_obserr
Name of the data group to which the observation error is applied (default: ObsErrorData).
- test_qcflag
Name of the data group to which the QC flag is applied (default is QCflagsData).
Example configuration:¶
- filter: Background Check
filter variables:
- name: brightnessTemperature
channels: 1-15
function absolute threshold:
- name: ObsFunction/ObsErrorBoundMW
channels: 1-15
options:
sensor: amsua_n19
channels: 1-15
obserr_bound_latitude:
name: ObsFunction/ObsErrorFactorLatRad
options:
latitude_parameters: [25.0, 0.25, 0.04, 3.0]
obserr_bound_transmittop:
name: ObsFunction/ObsErrorFactorTransmitTopRad
channels: 1-15
options:
channels: 1-15
obserr_bound_topo:
name: ObsFunction/ObsErrorFactorTopoRad
channels: 1-15
options:
channels: 1-15
sensor: amsua_n19
obserr_function:
name: ObsFunction/ObsErrorModelRamp
channels: 1-15
options:
channels: 1-15
xvar:
name: ObsFunction/CLWRetSymmetricMW
options:
clwret_ch238: 1
clwret_ch314: 2
clwret_types: [ObsValue, HofX]
bias_application: HofX
x0: [ 0.050, 0.030, 0.030, 0.020, 0.000,
0.100, 0.000, 0.000, 0.000, 0.000,
0.000, 0.000, 0.000, 0.000, 0.030 ]
x1: [ 0.600, 0.450, 0.400, 0.450, 1.000,
1.500, 0.000, 0.000, 0.000, 0.000,
0.000, 0.000, 0.000, 0.000, 0.200 ]
err0: [ 2.500, 2.200, 2.000, 0.550, 0.300,
0.230, 0.230, 0.250, 0.250, 0.350,
0.400, 0.550, 0.800, 3.000, 3.500 ]
err1: [20.000, 18.000, 12.000, 3.000, 0.500,
0.300, 0.230, 0.250, 0.250, 0.350,
0.400, 0.550, 0.800, 3.000, 18.000 ]
obserr_bound_max: [4.5, 4.5, 4.5, 2.5, 2.0,
2.0, 2.0, 2.0, 2.0, 2.0,
2.5, 3.5, 4.5, 4.5, 4.5]
action:
name: reject
The above example is for AMSU-A N19 (amsua_n19
), and the filter checks the brightness temperature for channels 1-15 that fails the background check according to its observation error bounds. These bounds are obtained using the ObsErrorBoundMW
function, considering observation error factors provided by other functions. See specific documentation for ObsErrorFactorLatRad, ObsErrorFactorTransmitTopRad, ObsErrorFactorTopoRad, ObsErrorModelRamp, and CLWRetSymmetricMW functions for more details.