An Investigation of the Local Energetics of the Martian Atmosphere

The local energetics of the Martian Northern hemisphere atmosphere are investigated using the Mars Analysis Correction Data Assimilation (MACDA) dataset. The MACDA dataset is a reanalysis of Thermal Emission Spectrometer (TES) retrievals from the Mars Global Surveyor during Mars Year (MY) 24-27 (Montabone et al., 2011). The local energy conversion processes are diagnosed with the help of the eddy kinetic energy (EKE) equation. Implementing the EKE equation on the MACDA dataset required evaluation of the vorticity from the horizontal wind vector and the calculation of the vertical component of the wind vector from the quasi-geostrophic omega equation. The computation of the terms that include the horizontal divergence required special care due to the sensitivity of the calculation of the divergence by a numerical approximating scheme. Results are provided for the Ls = 200-230 early winter period that allows for direct comparison to results in Kavulich et al. (2013), which used the Mars global circulation model (MGCM) of the Geophysical Fluid Dynamics Laboratory (GFDL) for the investigation of the local energetics. Overall patterns are similar; however, there are important differences between the local energy conversion processes in the different MY's and in the MACDA and the MGCM datasets. Most importantly, the geopotential flux convergence, which serves as a trigger for EKE generation, is stronger in the MACDA dataset than the MGCM dataset. Additionally, the EKE and forcing terms are weaker in MY 26 than in MY 24/5. Kavulich, M. J., Szunyogh, I., Gyarmati, G., & Wilson, R. J. (2013). Local Dynamics of Baroclinic Waves in the Martian Atmosphere. Journal of the Atmospheric Sciences, 70(11), 3415-3447. doi:10.1175/JAS-D-12-0262.1. Montabone, L.; Lewis, S. R.; Read, P. L. (2011) Mars Analysis Correction Data Assimilation (MACDA): MGS/TES v1.0. NCAS British Atmospheric Data Centre, doi: 10.5285/78114093- E2BD-4601-8AE5-3551E62AEF2B.