Changes in storm tracks and energy transports in a warmer climate simulated by the GFDL CM2.1 model

Storm tracks play a major role in regulating the precipitation and hydrological cycle in midlatitudes. The changes in the location and amplitude of the storm tracks in response to global warming will have significant impacts on the poleward transport of heat, momentum and moisture and on the hydrological cycle. Recent studies have indicated a poleward shift of the storm tracks and the midlatitude precipitation zone in the warming world that will lead to subtropical drying and higher latitude moistening. This study agrees with this key feature for not only the annual mean but also different seasons and for the zonal mean as well as horizontal structures based on the analysis of Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 model simulations. Further analyses show that the meridional sensible and latent heat fluxes associated with the storm tracks shift poleward and intensify in both boreal summer and winter in the late twenty-first century (years 2081-2100) relative to the latter half of the twentieth century (years 1961-2000). The maximum dry Eady growth rate is examined to determine the effect of global warming on the time mean state and associated available potential energy for transient growth. The trend in maximum Eady growth rate is generally consistent with the poleward shift and intensification of the storm tracks in the middle latitudes of both hemispheres in both seasons. However, in the lower troposphere in northern winter, increased meridional eddy transfer within the storm tracks is more associated with increased eddy velocity, stronger correlation between eddy velocity and eddy moist static energy, and longer eddy length scale. The changing characteristics of baroclinic instability are, therefore, needed to explain the storm track response as climate warms. Diagnosis of the latitude-by-latitude energy budget for the current and future climate demonstrates how the coupling between radiative and surface heat fluxes and eddy heat and moisture transport influences the midlatitude storm track response to global warming. Through radiative forcing by increased atmospheric carbon dioxide and water vapor, more energy is gained within the tropics and subtropics, while in the middle and high latitudes energy is reduced through increased outgoing terrestrial radiation in the Northern Hemisphere and increased ocean heat uptake in the Southern Hemisphere. This enhanced energy imbalance in the future climate requires larger atmospheric energy transports in the midlatitudes which are partially accomplished by intensified storm tracks. Finally a sequence of cause and effect for the storm track response in the warming world is proposed that combines energy budget constraints with baroclinic instability theory

Changes in storm tracks and energy transports in a warmer climate simulated by the GFDL CM2.1 model

Storm tracks play a major role in regulating the precipitation and hydrological cycle in midlatitudes. The changes in the location and amplitude of the storm tracks in response to global warming will have significant impacts on the poleward transport of heat, momentum and moisture and on the hydrological cycle. Recent studies have indicated a poleward shift of the storm tracks and the midlatitude precipitation zone in the warming world that will lead to subtropical drying and higher latitude moistening. This study agrees with this key feature for not only the annual mean but also different seasons and for the zonal mean as well as horizontal structures based on the analysis of Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 model simulations. Further analyses show that the meridional sensible and latent heat fluxes associated with the storm tracks shift poleward and intensify in both boreal summer and winter in the late twenty-first century (years 2081-2100) relative to the latter half of the twentieth century (years 1961-2000). The maximum dry Eady growth rate is examined to determine the effect of global warming on the time mean state and associated available potential energy for transient growth. The trend in maximum Eady growth rate is generally consistent with the poleward shift and intensification of the storm tracks in the middle latitudes of both hemispheres in both seasons. However, in the lower troposphere in northern winter, increased meridional eddy transfer within the storm tracks is more associated with increased eddy velocity, stronger correlation between eddy velocity and eddy moist static energy, and longer eddy length scale. The changing characteristics of baroclinic instability are, therefore, needed to explain the storm track response as climate warms. Diagnosis of the latitude-by-latitude energy budget for the current and future climate demonstrates how the coupling between radiative and surface heat fluxes and eddy heat and moisture transport influences the midlatitude storm track response to global warming. Through radiative forcing by increased atmospheric carbon dioxide and water vapor, more energy is gained within the tropics and subtropics, while in the middle and high latitudes energy is reduced through increased outgoing terrestrial radiation in the Northern Hemisphere and increased ocean heat uptake in the Southern Hemisphere. This enhanced energy imbalance in the future climate requires larger atmospheric energy transports in the midlatitudes which are partially accomplished by intensified storm tracks. Finally a sequence of cause and effect for the storm track response in the warming world is proposed that combines energy budget constraints with baroclinic instability theory

Lower Vitamin D Levels are Associated with Higher Seroprevalence of Toxoplasma gondii —a US National Survey Study

Vitamin D deficiency is associated with high susceptibility to infections. The present study aimed at exploring the relationship between vitamin D levels and Toxoplasma gondii ( T. gondii ) infection, on the basis of a nationally representative database. The study data came from the National Health and Nutrition Examination Surveys (NHANES) 2001–2004. Participants underwent both Toxoplasma IgG antibody testing and serum vitamin D testing. Vitamin D deficiency was defined by a serum 25-hydroxyvitamin D level <20 ng/mL. Multivariate logistic regression and propensity score matching were used to adjust for potential confounders. All analyses were conducted in R software. A total of 10613 participants were included. Among these, 3973 (37.4%) were vitamin D deficient, and 2070 (19.5%) were seropositive for T. gondii IgG antibody. Vitamin D deficiency was found in 42.3% of the seropositive population, compared with 36.3% of the seronegative population ( P <0.001). After adjustment for sex, age, body mass index, smoking history, drinking history and testing season, vitamin D deficiency was associated with an elevated risk of T. gondii infection (OR=1.303, 95% CI=1.136–1.495, P <0.001). This effect persisted in the propensity matching cohort. Low vitamin D levels are associated with high seroprevalence of T. gondii

Mechanisms of ENSO-forcing of hemispherically symmetric precipitation variability

The patterns of precipitation anomalies forced by the El Nin ̃o–Southern Oscillation during northern hemisphere winter and spring are remarkably hemispherically symmetric and, in the midlatitudes, have a prominent zonally symmetric component. Observations of global precipitation variability and the moisture budget within atmospheric reanalyses are examined to argue that the zonally symmetric component is caused by interactions between transient eddies and tropically-forced changes in the subtropical jets. During El Nino events the jets strengthen in each hemisphere and shift equatorward. Changes in the subtropical jet influence the transient-eddy momentum fluxes and the eddy-driven mean meridional circulation. During El Nino events, eddy-driven ascent in the midlatitudes of each hemisphere is accompanied by low-level convergence and brings increased precipitation. These changes in the transient-eddy and stationary-eddy moisture fluxes almost exactly cancel each other and, in sum, do not contribute to the zonal-mean precipitation anomalies. Propagation of anomalous stationary waves disrupts the zonal symmetry. Flow around the deeper Aleutian Low and the eastward extension of the Pacific jet stream supply the moisture for increased precipitation over the eastern North Pacific and the western seaboard of the United States, while transient-eddy moisture convergence supplies the moisture for increased precipitation over the southern United States. In each case, increased precipitation is fundamentally caused by anomalous ascent forced by anomalous heat and vorticity fluxes

Static and dynamical properties of the spin-5/2 nearly ideal triangular lattice antiferromagnet Ba3MnSb2O9

We study the ground state and spin excitation in Ba3MnSb2O9, an easy-plane S = 5/2 triangular lattice antiferromagnet. By combining single-crystal neutron scattering, electric spin resonance (ESR), and spin wave calculations, we determine the frustrated quasi-two-dimensional spin Hamiltonian parameters describing the material. While the material has a slight monoclinic structural distortion, which could allow for isosceles triangular exchanges and biaxial anisotropy by symmetry, we observe no deviation from the behavior expected for spin waves in the in-plane 120o state. Even the easy-plane anisotropy is so small that it can only be detected by ESR in our study. In conjunction with the quasi-two-dimensionality, our study establishes that Ba3MnSb2O9 is a nearly ideal triangular lattice antiferromagnet with the quasi-classical spin S = 5/2, which suggests that it has the potential for an experimental study of Z- or Z2-vortex excitations

Model projections of an imminent transition to a more arid climate in southwestern North America

How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades

The strong chromatic index of (3,Δ)-bipartite graphs

A strong edge-coloring of a graph G=(V,E) is a partition of its edge set E into induced matchings. We study bipartite graphs with one part having maximum degree at most 3 and the other part having maximum degree Δ. We show that every such graph has a strong edge-coloring using at most 3Δ colors. Our result confirms a conjecture of Brualdi and Quinn Massey (1993) for this class of bipartite graphs

The strong chromatic index of (3,Δ)-bipartite graphs

A strong edge-coloring of a graph G=(V,E) is a partition of its edge set E into induced matchings. We study bipartite graphs with one part having maximum degree at most 3 and the other part having maximum degree Δ. We show that every such graph has a strong edge-coloring using at most 3Δ colors. Our result confirms a conjecture of Brualdi and Quinn Massey (1993) for this class of bipartite graphs

The strong edge-coloring for graphs with small edge weight

A strong edge-coloring of a graph G=(V,E) is a partition of its edge set E into induced matchings. The edge weight of a graph G is defined to be max{dG(u)+dG(v)|e=uv∈E(G)}. We study graphs with edge weight at most 7. We show that 1) every graph with edge weight at most 6 has a strong edge-coloring using at most 10 colors; and 2) every graph with edge weight at most 7 has a strong edge-coloring using at most 15 colors