Camella Nasr
7th Mars Atmosphere Modeling And Observations Workshop Abstract

Mach And Froude Numbers On Mars
Mars Atmospheric Global Circulation Models Exhibit Transonic Jet Streaks During Northern
Winter, Which Motivates This Study Of The Mach Number, Ma (The Ratio Of Flow Speed To
The Speed Of Sound), And Froude Number, Fr (The Ratio Of Flow Speed To The Speed Of
Buoyancy Waves), As A Function Of Season And Location. Two Global Reanalyses Spanning
Mars Years (My) 24 To 32 Are Used As Input, Emars And Openmars. Area-Weighted
Global Means And Standard Deviations, And 5-Year Temporal Means Using The Complete
Years My 25, 26, 29, 30, 31, Are Compared. Emars And Openmars Show General
Agreement Below Z ~ 50 Km, Where The Observational Constraints Are Strongest, But Can
Vary Significantly At Higher Levels. Both Reanalyses Contain Transonic Jet Streaks In Every
Northern Winter Sampled. The Fr Signal Is Roughly Twice The Ma Number Signal, As
Expected Where The Temperature Lapse Rate Is Small Compared To The Dry Adiabatic Lapse
Rate. Mach Numbers Are Similar In Both Reanalyses But Show Larger Year-To-Year Variability
In Openmars. Maps Of Standard Deviations Indicate A Depression Between The Main
Peaks In Tharsis, And Higher Variability In Mare Boreum Than Mare Australe. The Main
Conclusion Is That The Atmosphere Of Mars Routinely Operates In The Compressible Regime
(0.3 < Ma < 0.8), Unlike Earth. Preliminary Results On Mach And Froude Numbers In The