SLIDE 1
Annual mean 10 m wind speed trend 1991 - 2008
+1.5 % +1.0 % +0.5 % 0 %
- 0.5 %
- 1.0 %
- 1.5 %
Young et al. (Nature, 2011)
Satellite radar altimeter Wave height 10 m wind speed
Observed and Projected Ocean Wind Speed Trends and Marine Boundary - - PowerPoint PPT Presentation
Observed and Projected Ocean Wind Speed Trends and Marine Boundary - - PowerPoint PPT Presentation
Observed and Projected Ocean Wind Speed Trends and Marine Boundary Layer Clouds Jan Kazil and Graham Feingold Annual mean 10 m wind speed trend 1991 - 2008 +1.5 % +1.0 % +0.5 % 0 % -0.5 % -1.0 % -1.5 % Young et al. (Nature, 2011)
SLIDE 2
SLIDE 3
JJA 10 m wind speed in 2081–2100 relative to 1981–2000
- 10%
- 5%
0% 5% 10%
McInnes et al. (Atm. Sci. Lett., 2011)
WCRP CMIP3 model mean 19 coupled climate models A1B emission scenario
SLIDE 4
Wind speed
Latent heat Horizontal momentum Sensible heat Sea spray
Moistens the boundary layer Warms the boundary layer Increases CCN number Drives non-thermal turbulence, shear
SLIDE 5
Simulations – WRF
North-east Pacific
DYCOMS II RF02 Different domain sizes and
resolutions
Geostrophic wind speed:
Fast (average + 25 %) Average (observations) Slow (average – 25 %)
South-east Pacific
VOCALS RF14 Different domain sizes and
resolutions
All else equal
SLIDE 6
Cloud field
DYCOMS II (after 6 h) VOCALS (after 12 h)
Response?
+18 %
- 18 %
SLIDE 7
Net down-welling radiation
+6.3 W m-2
- 0.99 W m-2
Faster wind Slower wind
DYCOMS II RF02 VOCALS RF14
+4.83 W m-2
- 5.83 W m-2
SLIDE 8
Decoupling due to wind shear?
u resolved (m s-1)
Less latent heat More entrainment Shear
Water vapor gradient
Θl (K) Cloud water (g kg-1) Water vapor (g kg-1)
SLIDE 9
Two different decoupling mechanisms at play?
DYCOMS II RF02 VOCALS RF14
SLIDE 10
Wind speed effects on non-precipitating Sc
Faster wind speed → higher radiative forcing Slower wind speed → reduced radiative
forcing Different decoupling mechanisms depending on boundary layer depth?
- Faster wind speed → Stronger wind shear at
inversion → more entrainment → decoupling
- Faster wind speed → Stronger latent heat flux
→ stronger drizzle → humidification of sub- cloud layer → decoupling
SLIDE 11
Path forward
- Simulations with higher resolution
- Isolate effect of different mechanisms
- Analyze observations for wind speed effects:
MAGIC!
SLIDE 12
Response to wind speed (VOCALS RF14)
SLIDE 13
Response to wind speed (DYCOMS II RF02)
SLIDE 14
Asymmetric response due to solar heating
Faster wind speed
→ more decoupling
Slower wind speed
→ less decoupling
Solar heating adds to
decoupling in both cases