The Mid-latitude Wave Activity of the LASG ModelXiaoyun Liang, Yimin Liu, Guoxiong WuState Key Laboratory of Numerical Modeling Atmospheric Sciences &Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences

OutlineContent:Total Fluxes in 8 experimentsContributions in Control run(Cases: uv, vT)ConclusionMotivation: to capture the contribution to the time averaged atmospheric flux of quantities by mid-latitude wave activity co-variance statistics are required.

The budget equation for the total zonally averaged covariance of the quantities and is Total fluxes. Contribution from the time mean meridional circulation. Contribution from the stationary eddies. Contribution from the transient mean meridional circulation. Contribution from the transient eddies.

Total Fluxes

Zonal wind variance (m2 s-2)The maxima of zonal wind variance lie near the westerly jet in upper troposphere.The baroclinicity of atmosphere is larger in winter hemisphere than in summer hemisphere.so the maximum of zonal wind variance lies in winter hemisphere.Zonal wind variance is sensitive to the latitudinal curvature of SST.

Meridional wind variance (m2 s-2)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The maxima of meridional wind variance also lie near the westerly jet in upper troposphere.The maximum of meridional wind variance lies in summer hemisphere.The sensitivity of it to the latitudinal curvature of SST is smaller than that of zonal wind variance.

Temperature variance (K2)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The temperature variance only in tropical boundary is sensitive to the latitudinal curvature of SST.

Omega variance (Pa s-1)peakedcontrol1keqcontrol 5nflatqobs3keq3kw1The omeg variance is more sensitive to the latitudinal curvature of SST.The ascent movement in tropic is strong in control and peaked.

Geopotential variance /1010 (m2 s-2)2peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The geopotential variance is insensitive to the latitudinal curvature of SST.

Specific humidity variance X105 (kg kg-1)2peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The specific humidity variance is little sensitive to the latitudinal curvature of SST.

Poleward zonal momentum flux (m2 s-2)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The distribution of poleward zonal momentum flux is complicated. It is more sensitive to the latitudinal curvature of SST.Poleward transfer of momentum flux weaken when the curvature of SST near equator decrease special in lower level.

Vertical zonal momentum flux (m Pa s-2)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1Vertical zonal momentum flux is very sensitive to the curvature of SST near equator.The larger the curvature of SST near equator is, the stronger the upward transfer of zonal wind momentum flux in tropic.

Vertical meridional momentum flux (m Pa s-2)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1Vertical meridional momentum flux is little sensitive to the latitudinal curvature of SST.

Poleward temperature flux (m s-1 K) peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The distribution of poleward temperature flux is also more sensitive to the latitudinal curvature of SST.Poleward transfer of heat flux in tropic upper troposphere and equator-ward transfer of heat flux in tropic lower level intensify when the curvature of SST near equator increase. Otherwise transfer of heat flux in mid-latitude lower level will not change.In summer time, because the baroclinicity of atmosphere are weak, the poleward transfer of heat flux reduce.

vertical temperature flux (Pa s-1 K) peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The transfer of heat flux in vertical is very sensitive to the latitudinal distribution of SST. The larger the curvature of SST near equator is, the stronger the vertical transfer of heat flux is.

Poleward moisture flux (m s-1Kg Kg-1)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1Moisture flux is to equator. The larger the curvature of SST near equator is, the stronger the transfer of moisture flux to equator is.

Vertical moisture flux X104 (Pa s-1Kg Kg-1)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The transfer of moisture flux in vertical is very very sensitive to the latitudinal distribution of SST.The width of the convective maxima appears to depend quite strongly on the near-equator curvature of SST.

Poleward geopotential flux /105 (m3 s-3)peakedcontrolflatqobs1keqcontrol 5n3keq3kw1The maxima of poleward geopotential flux lie in upper troposphere in tropic.The transfer of poleward geopotential flux is sensitive to the latitudinal curvature of SST.Since the baroclinicity of atmosphere is larger in winter hemisphere than in summer hemisphere, the transfer of poleward geopotential flux is larger in winter hemisphere than in summer hemisphere.

Contributions

Poleward zonal momentum flux Total flux.(TF) Contribution from the stationary mean meridional circulation (SM). Contribution from the stationary eddies (SE). Contribution from the transient mean meridional circulation (TM). Contribution from the transient eddies (TE).

Control runTFSESMTMTE

Poleward temperature flux Total flux (TF). Contribution from the stationary mean meridional circulation (SM). Contribution from the stationary eddies (SE). Contribution from the transient mean meridional circulation (TM). Contribution from the transient eddies (TE).

Control runSESMTMTETF

ConclusionExcept for the geopotential variance, all fluxes listed in table are sensitive to the latitudinal curvature of SST. But the temperature variance and poleward moisture flux are sensitive only in lower levels.

ConclusionThe transient eddy fluxes predominate in upper troposphere. Contribution from stationary mean meridional circulation to the total northward transfer of momentum is less than contribution from the transient eddy besides the surface boundary. The location of maximum transfer in upper troposphere is sensitive to latitudinal profile of SST. The larger the curvature of SST profile is, the nearer the maximum of transfer to equator.

Conclusion

The transfer of poleward heat flux mainly depends on stationary mean meridional circulation. The sensitivity of northward transfer of heat flux to the SST profile is less than that of northward transfer of momentum flux.

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