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Boundary Layer Physics 14 May 2007

Boundary Layer Physics 14 May 2007. Claudia.Kubatzki@awi.de Literature: R.B. Stull (1988, new edition 1999): An Introduction into Boundary Layer Meteorology . Kluwer Academic Publishers, Dordrecht, Netherlands. Atmospheric Layers. z [m]. ~10 4. Free Atmosphere. ~10 3. Ekman Layer.

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Boundary Layer Physics 14 May 2007

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  1. Boundary Layer Physics14 May 2007 Claudia.Kubatzki@awi.de Literature: R.B. Stull (1988, new edition 1999): An Introduction into Boundary Layer Meteorology. Kluwer Academic Publishers, Dordrecht, Netherlands.

  2. Atmospheric Layers z [m] ~104 Free Atmosphere ~103 Ekman Layer Troposphere ~102 Planetary Boundary Layer Surface Layer Prandtl Layer ~10-2 Microlayer 0

  3. Dynamical Equationscartesian system Momentum budget For a fluid, Isaac Newton's second law „mass times acceleration equals the sum of forces“ is better stated per unit volume with density replacing mass. In the absence of rotation, the resulting equations are called the Navier-Stokes equations. real forces and apparent forces (Dynamics I)

  4. Eddy mixing Stull, 1988

  5. Prandtl - mixing length theory Stull, 1988

  6. Typical values for the roughness length (table see exercises) Stull, 1988

  7. Wind profiles for different surface types Emeis, 2000

  8. … ZRTOT(i,n,ntp)=ZRSUR(ntp)+ZRORO(i,n) endif C...2) Drag coefficient for neutral stratification if (ntp.eq.1) then C...2.1) Drag coefficent over ocean CDRGN(i,n,1)=1.5E-3 else C...2.2) Drag coefficient over sea ice and land CDRGN(i,n,ntp)=(CKARM/LOG(ZSURF/ZRTOT(i,n,ntp)))**2 endif CDM(i,n,ntp)=CDRGN(i,n,ntp) CHM(i,n,ntp)=1.3*CDRGN(i,n,ntp) C...3) Effective wind speed for transpiration if (ntp.ge.3. and .ntp.le.4) then … x x x (CLIMBER-2a)

  9. Displacement height Stull, 1988

  10. … C...3) Sensible heat flux CH =CHM(i,n,ntp) FH1=CH*USUR(i,n)*RA*CAV*(T1-T_air) if (FH1.lt.0.) FH1=0.1*FH1 C...4) Evaporation c...4.1) Evaporation from snow rp_S=EXP(-ZTS(i,n)/HATM) T_SNOW=AMIN1(TSUR(i,n,ntp),T0) FSUBL=1.E-3*USUR(i,n)*RA*(FQSATI(T_SNOW)-rp_S*QAM(i,n)) EVPSNST(i,n,ntp)=AMAX1(0.,FSUBL) c...4.2) evaporation from soil if (ntp.ge.3.and.ntp.le.5) then QSUR=FQSAT(T1) EVP1=0.1* > CH*USUR(i,n)*RA*(QSUR-QAMSUR(i,n,ntp))*RWSOIL(i,n,ntp,1)**2 EVP1=AMAX1(EVP1,0.) endif … x (CLIMBER-2a)

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