Variable transforms

Introduction

This section describes the various variable transforms (or conversions) available within UFO.

All variable transforms are performed using a unique filter (Observation Filters) called Variable Transforms, as shown in the example below:

window begin: 2018-04-14T21:00:00Z
window end: 2018-04-15T03:00:00Z

observations:
- obs space:
   name: test_relative_humidity1
   obsdatain:
      obsfile: Data/ioda/testinput_tier_1/sfc_obs_2018041500_metars_small.nc
   simulated variables: [specific_humidity, air_temperature, surface_pressure]
obs filters:
- filter: Variable Transforms
   Transform: ["RelativeHumidity"]
   Method: UKMO
   Formulation: Sonntag
The Variable Transforms filter has the following available yaml settings:

  • Transform: name of the variable transform that need to be performed. (see Variable transforms).

  • Method: [Optional] Method used during the variable transformation. This usually refers to the different Met Center. (See individual Variable transforms for possible choices and definitions)

  • Formulation: [Optional] Name of a specific formulation used during the variable transformation. (See individual Variable transforms for possible choices and definitions)

  • UseValidDataOnly: [Optional | default = true] Should the variable transform be applied only to valid data?

    Warning

    If UseValidDataOnly=true, the variable transform is not applied to observations that have a QCflag equal to either missing or bounds.

The new variable derived by the filter is then stored in the observation space with the @DerivedValue tag.

Warning

Each variable transforms requerest a specific set of variable (as specify in the documentation). If any compulsory variable is missig, the code will raise an exception and stop.

Variable transforms

The variable transforms available are:

Humidity

Pressure

Wind

Formulations

The formuations available are:

Table listing all the symbol used