Meridional mixing

Meridional mixing, which occurs most strongly in the fall and winter months, mixed the bulk of this injected 14C southward and into the southern hemisphere troposphere. Thus, each year from September through February the levels of 14C declined at more northerly latitudes while at more sourtherly latitudes the levels of 14C rose, until by about mid-1966 the entire troposphere became fairly homogeneous in 14C. 

If our database obtained so far is considered representative for middle, high and low northern latitudes, latitude-height cross-sections of halocarbons can be derived based on the assumption of smooth meridional mixing on sloped surfaces and zonal symmetry. By applying a spline fit to the data obtained at the 3 discrete latitudes, isolines of 90, 80, 70%, - with respect to tropospheric abundance for CFC-12, CFC-11 and CH3CCI3 are shown in figs. 14-16. 

There is evidence that polar air masses, one and half years after the eruption, carry a good deal less aerosols indicating that meridional mixing is incomplete. In an analysis of the SAM II data satellite extinction data for the Northern hemisphere winter of 1982, supplemented by airborne lidar observations, McCormick et al. (1983) found the polar vortex to be an area of substantially low aerosol content where the El Chichon cloud does not seem to have penetrated and that either an aerosol sink or a supply of clean air exists in the polar winter vortex. 

Figure 3.25. Schematic representation of the wave-driven transport circulation (solid lines with arrows) in the winter stratosphere. The shaded area represents the surf zone where meridional mixing associated with wavebreaking is taking place. Light dashed lines represent isentropes. The heavy dashed line shows a constant mixing ratio surface of a long-lived tracer. The dotted line represents the tropopause. Adapted from Holton and Alexander (2000).

Bolin, B. and Keeling, C. D. (1963). Large-scale atmospheric mixing as deduced from the seasonal and meridional variations of carbon dioxide, /. Geophys. Res. 68,3899-3920. 

The localized-valence halogen-bridged platinum(II)/platinum(IV) complexes (175) are of interest because of their highly anisotropic electrical and optical properties. The complexes are characterized by broad and intense intervalence bands in their electronic spectra.542 Partial oxidation of [PtCl(dien)]Cl with iodine yields the mixed valence species [PtI(dien)][PtI3(dien)]I2,543 but when 4Me-dien is used, the mixed valence compound is only obtained if it is trapped quickly, before isomerization of the meridional platinum(IV) complex to a facial form.544 Although these species nominally have localized valences, the extent of delocalization increases as the bridging halide... 

Great care has to be given to the physics of rotation and to the treatment of its interaction with mass loss. For differentially rotating stars, the structure equations need to be written differently [9] than for solid body rotation. For the transport of the chemical elements and angular momentum, we consider the effects of shear mixing, meridional circulation, horizontal turbulence and in the advanced stages the dynamical shear is also included. Caution has to be given that advection and diffusion are not the same physical effect. 

Fig. 1. Cross-/] structure of amyloid fibrils. (A) Cartoon representation of a cross-/] X-ray diffraction pattern. The defining features are a meridional reflection at 4.7 A and an equatorial reflection on the order of 10 A. The 4.7-A reflection is generally much brighter and sharper than the reflection at 10 A. (B) The cross-/] core structure of amyloid fibrils. Parallel /(-sheets are depicted, but the structure could equivalendy be composed of antiparallel /(-sheets or a mix of parallel and antiparallel. The 4.7-A spacing of /(-strands within each /(-sheet is parallel to the long fibril axis. The depicted 10-A sheet-to-sheet spacing actually ranges from about 5 to 14 A (Fandrich and Dobson, 2002), depending on the size and packing of amino acid side chains. Amyloid fibrils have diameters on the order of 100 A.

In the open ocean, the major advective water motion is associated with the surfece-water geostrophic currents and meridional overturning circulation. These flow paths are shown in Figures 4.4b and 4.6. Advection is much fester than molecular diffusion and turbulence. This enables water masses to retain their original temperatures and salinities as they are advected away from their sites of formation. Slow turbulent mixing with adjacent water masses eventually alters this temperatme and salinity signal beyond... 

The initial decrease in ocean uptake rate will eventually be reversed once enough time has passed (millennia) for meridional overturning circulation to recycle the subsurface waters. This will serve to inject CO2 below the mixed layer. Once the surface waters have been sufficiently acidified and are transported into the deep sea, they will eventually start dissolving sedimentary calcium carbonate. The resupply of alkalinity via this route will provide sufficient enhancement to ocean carbon uptake capacity to... 

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