Testing of the non-local turbulent length-scale formulation within 3D COSMO-RU model, comparison

with profilers and radiosondes data

Veniamin Perov and Oleg Evteev

Hydrometcentre of Russia

z

TKE

Schematic view of a turbulent length scale (mixing length)scheme based on a parcel displacement (BL89) for a boundary layer scheme of the

COSMO model

)()()( '' zEdzzzg

vv

lz

z ref

up

)()()( '' zEdzzzg

vv

lz

z ref

up

,2/1downup llL Lkzl

111

Blackadar formula, local l

.m 200,76.0,40.0,111

2/1

lCeC

N

lzl NN

Turbulent length scale based on a parcel displacement scheme

Potential temperature profiles for local L (blue) and nonlocal L(red),Moscow 12h, 17.07.09

Difference of T2M fields (new – ref), COSMO-RU, 19.07.2009

Differences for T2M fields (nonlocal L minus local L), 12h, 170709,Full area

Differences for T2M fields (nonlocal L minus local L), 12h, 17072009,Moscow area

Differences for T2M fields (nonlocal L minus local L), left and total cloud cover,

right , Black Sea coastal region

Differences for TD2M fields (nonlocal L minus local L), 12h, 17072009,Moscow area

Differences for U10M fields (nonlocal L minus local L), 12h, 17072009,Moscow area

• Mesoscale modeling in mountain area should include simulations of main processes in this domain. These are formation of the regional slope winds, blocked flow, deviated flow, sheltering effect after obstacle, generation of turbulence by wind shear at the lower part of flow.

• In the upper part of flow it will be generation of turbulence by roughness, mountain waves and generation of turbulence by mountain wave breaking.

• For high mountains we need also to take into account a tropopause perturbation. All these processes require the use of three-dimensional turbulence and the non-use of simple diagnostic formulas for turbulence length scale (mixing length).

• In this case, together with the equation for the turbulent kinetic energy (TKE) will have to use the equation for mixing length or equation for the dissipation of TKE.

Mesoscale modeling in mountain region

Turbulence and convection in mountain region

Main results

• Algorithm for computing the nonlinear turbulence length scale based on displacement method of air parcel (BL89) was developed. A new algorithm for calculation turbulence length scale has a more rigorous physical basis in comparison with the algorithm currently used (Blackadar formulae).

• Algorithm was impact in module TUBDIFF of main COSMO program • Calculations were performed for convective situations (July 2009) by full

3-D COSMO model. Results showed differences in fields of temperature, humidity, clouds and wind between variants with local (reference) and nonlocal turbulence length scales.

• An article for publication is prepared base on the current work.