General circulation models are a useful tool in understanding the three dimensional structure of hot Jupiter and sub-Neptune
atmospheres; however, understanding the validity of the results from these simulations requires an understanding the artificial
dissipation required for numerical stability. In this paper, we investigate the ...
General circulation models are a useful tool in understanding the three dimensional structure of hot Jupiter and sub-Neptune
atmospheres; however, understanding the validity of the results from these simulations requires an understanding the artificial
dissipation required for numerical stability. In this paper, we investigate the impact of the longitudinal filter and vertical “sponge”
used in the Met Office’s Unified Model when simulating gaseous exoplanets. We demonstrate that excessive dissipation can
result in counter-rotating jets and a catastrophic failure to conserve angular momentum. Once the dissipation is reduced to a
level where a super-rotating jet forms, however, the jet and thermal structure are relatively insensitive to the dissipation, except
in the nightside gyres where temperatures can vary by ∼ 100 K. We do find, however, that flattening the latitudinal profile of
the longitudinal filtering alters the results more than a reduction in the strength of the filtering itself. We also show that even
in situations where the temperatures are relatively insensitive to the dissipation, the vertical velocities can still vary with the
dissipation, potentially impacting physical processes that depend on the local vertical transport.