Research Review. The Atmospheric Boundary Layer (ABL) over Mesoscale Surface Heterogeneity. 25 June 2009 Song- Lak Kang. The ABL … . typically 1-2 km high. the lowest 10-20 % of the troposphere. directly influenced by the earth’s surface. Convective Boundary Layer.
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The Atmospheric Boundary Layer (ABL) over Mesoscale Surface Heterogeneity
25 June 2009
1700 MST ON 17 JUNE 2009
The sun’s ray heats the earth’s surface, which then heats and moistens the air above it.
From Wyngaard (1990)
Mesoscale and turbulent fluctuations coexist in the CBL
Aircraft Observation at 33 m AGL
From Mahrt et al. (1994)
Aircraft Observation at various levels
From LeMone et al. (2002)
Assumption of mesoscale modeling
High-amplitude surface heat flux variation
Low-amplitude surface heat flux variation
Why do the horizontal flows oscillate?Divergence of vertical heat flux .vs. Temperature advection
Temperature gradient increased
by divergence of vertical heat flux
Temperature gradient reduced
by temperature advection
The Ramp Event
One of the most difficult issues that wind power forecasting system has encountered is a so-called ramp event. An unforeseen ramp event may be costly to balance the supply and demand of power and affect power system security (Cutler et al. 2007) .
The red solid lines represent observed wind speed and the blue solid lines wind power produced. From Cutler et al. (2007)
The diurnal cycle of surface heat flux variation
Multi-scale surface heat flux variation