1. Mars Aerodynamic Roughness Maps and Their Effects on Boundary Layer Properties in A GCM Nicholas Heavens (with Mark Richardson and Anthony Toigo) 9 May 2007 Nicholas Heavens (with Mark Richardson and Anthony Toigo) 9 May 2007

2. The Roughness Parameter (z 0 )  Arises from the need to treat Heat and Momentum Transfer Between Atmosphere and Surface  In a neutrally stratified near- surface layer:  Arises from the need to treat Heat and Momentum Transfer Between Atmosphere and Surface  In a neutrally stratified near- surface layer:

3. The influence of z 0  Z 0 primarily influence GCMs through u*, controlling: Surface Heat and Tracer Diffusion, Stress Partitioning to the Surface (dust/sand particle transport), often used in routines to simulate dry convection  Z 0 primarily influence GCMs through u*, controlling: Surface Heat and Tracer Diffusion, Stress Partitioning to the Surface (dust/sand particle transport), often used in routines to simulate dry convection

4. Z 0 and Geometric Roughness (1-D) Z 0 =h triangle /30 Z 0 =h triangle /8 Z 0 =h triangle /30 |dh/dx|=low |dh/dx|=high |dh/dx|=low Idealized after Greeley and Iversen (1985)

5. Z 0 and geometric roughness (2.5-D)  Imagine a Chessboard (nxn) with pieces of uniform height, H, distributed randomly with a Fractional occupation F  Then the variance (  h 2 ) of the topography is equal to: H 2 (F-F 2 ) and  h =H(F-F 2 ) 1/2  Imagine a Chessboard (nxn) with pieces of uniform height, H, distributed randomly with a Fractional occupation F  Then the variance (  h 2 ) of the topography is equal to: H 2 (F-F 2 ) and  h =H(F-F 2 ) 1/2

6. Theory + Observations (Dong et al. 2002) (2.5 D) H=12 mm. H=31 mm. H=43 mm. Z 0 =H 2n (F-F 2 ) n ?, 1>n>0.5?

7. Two Different Maps of z 0  One is Based on MOLA Pulse Width Roughness (How Laser Scattered by Surface) z 0max =15 cm.  The Other is Based on Kreslavsky and Head’s (2001) Roughness Parameter C (relation with  H 2? ), which we Extrapolate to C(10 m.~|L| in Vigorous Dry Convection) using self-affinity assumption:  H 2 = AL 2J, 0<=J<=1 We calibrate using Pathfinder Estimate: z 0 =3 cm.  One is Based on MOLA Pulse Width Roughness (How Laser Scattered by Surface) z 0max =15 cm.  The Other is Based on Kreslavsky and Head’s (2001) Roughness Parameter C (relation with  H 2? ), which we Extrapolate to C(10 m.~|L| in Vigorous Dry Convection) using self-affinity assumption:  H 2 = AL 2J, 0<=J<=1 We calibrate using Pathfinder Estimate: z 0 =3 cm.

8. The Maps

9. MarsWRF Basics  Uses 36x64 grid (heavy interpolation of much higher resolution maps)  We compare here Year 8 of the Model forced by each model (Passive Dust Forcing makes interannual variability limited, only weather noise)  Uses 36x64 grid (heavy interpolation of much higher resolution maps)  We compare here Year 8 of the Model forced by each model (Passive Dust Forcing makes interannual variability limited, only weather noise)

10. 370 Pa Daytime Comparison Smith, 2004 C(10 m.)Pulse width C(10 m.)-Pulse width

11. Vertical T Comparisons C-PW Daytime C-PW Nighttime C-PW (day) (10 m. above sfc.)C-PW (day) (3500 m. above sfc.)

12. Implications for Dust Devil Activity  Kurgansky (2006) proposed that dust devil size distribution strong function of |l|  Hess and Spillane (1990) proposed that Dust Devil Activity in General, a strong function of 1/|L|.  Combination Could Result in High dust devil Density in High Lats, Large DDs at mid z 0 (Amazonis Planitia?) Alternate Explanations… Whelley et al. (2006)

13. Summary  We present two different possible aerodynamic roughness maps (both with different controversial assumptions)  Daytime summer temperatures in high latitudes very sensitive to z 0 change (reduced eddy diffusion wins over convection)  Smoothness of high latitudes may explain high dust devil activity (provided tracks are a Good Metric)  We present two different possible aerodynamic roughness maps (both with different controversial assumptions)  Daytime summer temperatures in high latitudes very sensitive to z 0 change (reduced eddy diffusion wins over convection)  Smoothness of high latitudes may explain high dust devil activity (provided tracks are a Good Metric)