BennartzScatIndex¶
This ObsFunction calculates a scattering index based on observations from two satellite microwave channels.
An offset is computed which varies with satellite zenith angle as
A scattering index is then computed as the difference between two channel brightness temperatures (BTs) minus the offset:
Typically channels such as 89 GHz and 150 GHz are chosen where the sensitivity to scattering by ice particles increases with frequency.
Required parameters:¶
- channel_89ghz
Channel number corresponding to 89 GHz (or nearby frequency depending on sensor channel specification) e.g. MHS channel 1 at 89 GHz.
- channel_150ghz
Channel number corresponding to 150 GHz (or nearby frequency depending on sensor channel specification) e.g. MHS channel 2 at 157 GHz.
- bennartz_coeff_1
First coefficient used to compute scattering index offset
- bennartz_coeff_2
Second coefficient used to compute scattering index offset
Optional parameters:¶
- apply_bias
Name of the bias correction group used to apply correction to ObsValue
Default (missing optional parameter) applies no bias correction
Reference:¶
R. Bennartz. Precipitation analysis using the Advanced Microwave Sounding Unit in support of nowcasting applications. Meteorol. Appl. 9, 177-189 (2002). DOI:10.1017/S1350482702002037
Example yaml:¶
Here is an example using this ObsFunction inside the Bounds Check filter for ATMS. The brightness_temperature filter variables are rejected if the output value of this ObsFunction is larger than the example maxvalue = -1.0.
- filter: Bounds Check
filter variables:
- name: brightness_temperature
channels: 1-7, 16-22
where:
- variable:
name: land_sea@MetaData
is_in: 0 # land=0, sea=1, ice=2
test variables:
- name: BennartzScatIndex@ObsFunction
options:
channel_89ghz: 16 # ATMS 89.5 GHz channel
channel_150ghz: 17 # ATMS 165.5 GHz channel
bennartz_coeff_1: 0.158
bennartz_coeff_2: 0.0163
apply_bias: ObsBias
maxvalue: -1.0
action:
name: reject