Axisymmetric Hadley Cell Theory with a Fixed Tropopause Temperature Rather than Height

Axisymmetric Hadley cell theory has traditionally assumed that the tropopause height (H_t) is uniform and unchanged from its radiative–convective equilibrium (RCE) value by the cells’ emergence. Recent studies suggest that the tropopause temperature (T_t), not height, is nearly invariant in RCE, which would require appreciable meridional variations in H_t. Here, we derive modified expressions of axisymmetric theory by assuming a fixed T_t and compare the results to their fixed-H_t counterparts. If T_t and the depth-averaged lapse rate are meridionally uniform, then at each latitude H_t varies linearly with the local surface temperature, altering the diagnosed gradient-balanced zonal wind at the tropopause appreciably (up to tens of meters per second) but the minimal Hadley cell extent predicted by Hide’s theorem only weakly (≲1°) under standard annual-mean and solsticial forcings. A uniform T_t alters the thermal field required to generate an angular-momentum-conserving Hadley circulation, but these changes and the resulting changes to the equal-area model solutions for the cell edges again are modest (<10%). In numerical simulations of latitude-by-latitude RCE under annual-mean forcing using a single-column model, assuming a uniform T_t is reasonably accurate up to the midlatitudes, and the Hide’s theorem metrics are again qualitatively insensitive to the tropopause definition. However imperfectly axisymmetric theory portrays the Hadley cells in Earth’s macroturbulent atmosphere, evidently its treatment of the tropopause is not an important error source

Algebraic-matrix calculation of vibrational levels of triatomic molecules

We introduce an accurate and efficient algebraic technique for the computation of the vibrational spectra of triatomic molecules, of both linear and bent equilibrium geometry. The full three-dimensional potential energy surface (PES), which can be based on entirely {\it ab initio} data, is parameterized as a product Morse-cosine expansion, expressed in bond-angle internal coordinates, and includes explicit interactions among the local modes. We describe the stretching degrees of freedom in the framework of a Morse-type expansion on a suitable algebraic basis, which provides exact analytical expressions for the elements of a sparse Hamiltonian matrix. Likewise, we use a cosine power expansion on a spherical harmonics basis for the bending degree of freedom. The resulting matrix representation in the product space is very sparse and vibrational levels and eigenfunctions can be obtained by efficient diagonalization techniques. We apply this method to carbonyl sulfide OCS, hydrogen cyanide HCN, water H$_2$O, and nitrogen dioxide NO$_2$. When we base our calculations on high-quality PESs tuned to the experimental data, the computed spectra are in very good agreement with the observed band origins.Comment: 11 pages, 2 figures, containg additional supporting information in epaps.ps (results in tables, which are useful but not too important for the paper

The effects of orbital precession on tropical precipitation: Mechanisms controlling precipitation changes over land and ocean

The tropical precipitation response to precessional forcing is investigated using idealized precession experiments from the Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1 and mid-Holocene experiments from ten general circulation models participating in the Paleoclimate Modeling Intercomparison Project Phase III. Both sets of experiments show a seasonal land-ocean asymmetry in the tropical precipitation response: precipitation increases over land and decreases over ocean in the season with increased insolation and the opposite is true in the season with decreased insolation. This response is examined using a framework that describes how changes in net top-of-atmosphere radiation affect the atmosphere and surface energy balances. Over land, surface energy storage is small and changes in precipitation are balanced by changes in moist static energy flux divergence. Over ocean, surface energy storage is large, moist static energy flux divergence is small, and changes in precipitation are ultimately driven by changes in circulation and atmospheric stability

Low-energy excitations of a linearly Jahn-Teller coupled orbital quintet

The low-energy spectra of the single-mode h x (G+H) linear Jahn-Teller model is studied by means of exact diagonalization. Both eigenenergies and photoemission spectral intensities are computed. These spectra are useful to understand the vibronic dynamics of icosahedral clusters with partly filled orbital quintet molecular shells, for example C60 positive ions.Comment: 14 pages revte

Issues in Choosing the References to Use for Spectral Ratios from Observations and Modeling at Cavola Landslide in Northern Italy

A reference site has to be free of amplification or de-amplification effects, namely with no troughs and peaks in its Fourier amplitude spectrum. At the Cavola landslide we show that this spectrum is dependent on the direction of propagation of wave fronts for incidence angles in the range 30° to 90°. Our study is based on comparison of spectral ratios from observations and 2D numerical simulations. We have modeled propagation in a 2D profile for SH and SV waves with several incidence angles in the 0° ±90° range, where 0° and 90° are respectively vertical and horizontal incidence, except that ±90° denotes Rayleigh waves in the P-SV. We discuss in detail the result for angles of incidence of 0, ±20°, ±60°, ±90°. We have obtained observed horizontal-to-horizontal earthquakes spectral ratios using three reference sites. Two of these have matching receivers in the model, located at the opposite ends of the 2D profile. Overall observations are matched best when the reference site is located on the same side of the landslide as the incoming wave front. We also find general agreement of the observed H/H spectral ratios from earthquakes with H/V and H/H spectral ratios from noise, and the match between H/V values from noise and synthetic spectral ratios using an absolute, flat half-space reference is very good. On the other hand, 1D modeling performs poorly in comparison with 2D modeling in our case, for which the shape ratio h/D = 0.2 is intermediate between primarily-1D and strongly-2D wave propagation according to the classification of Bard and Bouchon (1985)

Detailed site distribution of melanoma and sunlight exposure: aetiological patterns from a Swiss series

Background: The relation between detailed cutaneous distribution of melanoma and indicators of sun exposure patterns has scantily been explored in moderately sun-sensitive populations. Patients and methods: The precise site of 1658 primary malignant melanoma, registered from 1995 to 2002, in Switzerland were retrieved and clinically validated. Relative melanoma density (RMD) was computed by the ratio of observed to expected number of melanoma allowing for body site surface areas, and further adjusted for site-specific melanocyte density. Results: Sites of highest risks were the face, shoulder and upper arm for both sexes, the back for men, and leg for women. Major features of this series were: (i) an unexpectedly high RMD for the face in women (5.6 versus 3.7 in men), (ii) the absence of a male predominance for melanoma on the ears and (iii) for the upper limbs, a steady gradient of increasing melanoma density with increasing proximity to the trunk, regardless of sex. Age and sex patterns of RMD parallelled general indicators of sun exposure and behaviour, except for the hand (RMD = 0.2). Conclusion: RMD increased with (cumulative) site sun exposure, but a few notable exceptions support the impact of intermittent exposure in melanoma ris