One key component of the UFO for GSI will be the interpolation of model fields to observation locations to provide inputs to the observation operator itself. The main objective of this task is to encapsulate the interpolations and interface them with the UFO abstract implementation. The interpolations to observations locations will be implemented using the NEMS/ESMF existing tools. Because the FV3 grid is available in ESMF, the GSI observation operator will be available for use with FV3 model fields.
As work progresses, all inputs and outputs of the interpolations will be identified and passed by argument (as opposed to global variables) through newly defined classes.