The meteorology is controlled by interacting circulations and dynamical instabilities from the planetary scale down to the microscale.
The northern winter season is unique; the air mass in the crater mixes with external crater air due to the breaking of large amplitude mountain waves.
At other seasons, the mixing between the air in the floor of Gale Crater and air external to the crater may be more limited.
It is difficult to reconcile the putative methane detection with the Gale Crater circulation.