Boundar Layer Meteorology Lecture 2 Review chapter 1

Boundar Layer Meteorology Lecture 2 • • Review chapter 1 of Garratt Terminology and Notation Review Some non-dimensional numbers Reynolds Averaging

Review chapter 1 of Garratt • Inner and outer layers (what’s with this, is the outer layer really part of the boundary layer? ) • Seasonal and geographic variations of the boundary layer’s character.

Modeled Boundary Layer Depth

Observed Boundary Layer Depth

Terminology • Boundary Layer Regions: • Surface Layer • Mixed Layer • Residual Layer • Stable (Nocturnal Boundary) Layer • Entrainment Zone • Ekman Layer (Outer Layer) • Surface Layer

Boundary Layer Regions

Notation • Variables: T, Tv , , v , , q, x, y, z, • Viscosity: = du/dy ; �� T�� kg/(m s)=Pa/s� – Kinetmatic viscosity: m 2/s • Summation (Einstein) notation: see Stull handout (pp. 57 -74). Note definitions of the Kronecker delta (and distinction between it and the unit vector), and the alternating unit tensor (Levi-Civita symbol) used to express the cross product.

Some Non-Dimensional Numbers • Reynolds number: Re = VL/ – Reynolds number is ratio of acceleration (or “inertial force”) to friction force. It governs transition to turbulence (at high Reynolds numbers , e. g. about 2300 for pipes; highly variable!). • Richardson numbers: ratio of – Flux – Gradient: Ri = (g/ d dz)/(du/dz)2 – Bulk

Reynolds averaging and Reynolds Stresses t 1 should be enough larger than t 2 so that the average is independent of time.

Reynolds averaging and Reynolds Stresses

Understanding Reynolds Stress