Assimilating spacecraft observations into a Mars Global Circulation Model using LETKF: managing bias and ensemble spread

Temperature profiles retrieved from the Thermal Emission Spectrometer (TES) instrument on the Mars Global Surveyor spacecraft, as well as from the Mars Climate Sounder (MCS) aboard the Mars Reconnaissance Orbiter, are assimilated into a Mars Global Circulation Model (MGCM) using the Local Ensemble Transform Kalman Filter (LETKF). The latter instrument, a limb sounder, extends vertical observation coverage to more than 80 km in altitude. Bias between forecasts and observations is reduced through empirical bias correction methods and refinement of the MGCM physical parameterizations. Ensemble spread, representing forecast errors, is tuned using adaptive inflation techniques, as well as through the variation of dust in the ensemble. Performance metrics include the use of short term forecasts compared with observations, as well as a comparison to the freely running model without assimilation.