Search Results

You are looking at 1 - 9 of 9 items for

  • Author or Editor: Yale Mintz x
  • All content x
Clear All Modify Search
Yale Mintz

The rule is formulated that in regions with horizontal temperature gradients tropical cyclones are eccentric on the warm air side and move along the mean free air isotherms keeping the warmer air to the right of the direction of motion.

Full access
Yale Mintz

Observational data from many sources are brought together to form a composite picture of the distribution, from pole to pole and from sea level to the 5-centibar level, of the normal summer and winter zonal winds averaged around the earth.

Full access
Daniel Rosenfeld and Yale Mintz

Abstract

The rainshafts of about 3000 summer afternoon convective rain cells in the semiarid region of central south Africa were tracked and measured with a volume scanning radar. The area and time integrated rain volume of each individual rain cell was obtained at the cloud base level and at a lower level, assuming a fixed radar reflectivity-rain intensity (Z-R) relationship.

The ratio of the rain volumes at the two levels arid, thereby, the cumulative fractional evaporation of the failing rain was found to depend on the rain intensity at the cloud base level and on the fall distance from the cloud base. With a small lifetime peak rain intensity at the cloud base (1.0 mm h−1), about 50% of the rain evaporated by 1 km below the cloud base and all of the rain evaporated by 1.6 km. With a medium rain intensity (10 mm h−1), about 25% evaporated by 1 km and 50% by 1.6 km. With very heavy rain intensity (80 mm h−1), about 15% evaporated by 1 km and 30% by 1.6 km below the cloud base level. These must be regarded as lower limits of the evaporation, because the more rapid evaporational depletion of the smaller drops with increasing fall distance causes a relative radar overestimate of the rain intensity at the lower level and, therefore, an underestimate of the evaporation, when using the vertically fixed Z-R relationship.

Full access
Conway Leovy and Yale Mintz

Abstract

The Mintz-Arakawa two-level model for planetary atmospheres has been adapted to simulate the atmospheric circulation and climate of Mars. The model uses the primitive equations of atmospheric motion, with heating and cooling by solar and infrared radiative transfer and by turbulent convection. Carbon dioxide is the principal atmospheric constituent and is allowed to condense on the planet's surface, releasing latent heat where the surface cools to the CO2 frost point. Two numerical experiments are made; one simulates orbital conditions at the southern summer (northern winter) solstice of Mars, and the other orbital conditions at the southern autumnal equinox.

The results of the solstice experiment show strong zonal mean west winds in the middle and high latitudes of the winter hemisphere produced by the net eastward Coriolis torque that accompanies the poleward mass transfer toward the condensing CO2 polar ice cap, wave cyclones in the winter hemisphere, a strong ther-mally-direct mean meridional circulation across the equator, with a strong east wind maximum near the equator, and weak east winds over most of the summer hemisphere.

The results of the equinox experiment are more like conditions in the earth's atmosphere. In both hemispheres there are zonal mean west winds in the middle latitudes with wave cyclones in the middle and higher latitudes and east winds in the tropics.

In both experiments there are large diurnal tidal components of the circulation.

Full access
Yale Mintz and Shih-Kung Kao

Abstract

An equation is derived relating the rate of change of the integrated zonal-index to the poleward angular-momentum flux convergence. The validity of the equation and its utility in forecasting the zonal-index change are checked against observed cases, with good results. For the simple harmonic case, the equation is integrated and the solution compared with an observed example.

Full access
Michael E. Schlesinger and Yale Mintz

Abstract

The production, transport and distribution of ozone are simulated for a January with a global atmospheric general circulation model. In this model the ozone influences the radiational heating as well as the photochemical ozone production and destruction, the radiational heating influences the atmospheric circulation, and the circulation redistributes the ozone.

The model has fairly successfully simulated the synoptic and time-averaged observed large-scale fields of temperature, mass, and velocity in the troposphere and stratosphere, although there are some deficiencies. In particular, the simulated temperatures are too cold in the lower and middle stratosphere in the polar regions, the sea level pressure is too high in the Arctic and in the Antarctic circumpolar trough, and the flow field in the middle-latitude troposphere does not show the observed wavenumber 3.

Despite these shortcomings, the model has simulated the observed high correlation of synoptic and time-averaged total ozone with the tropospheric height field in middle latitudes, with the ozone maxima and minima, respectively, located at the troughs and ridges of the tropospheric waves. The deficiencies which are seen in the time-averaged O3 distribution are attributable to recognized deficiencies of the general circulation model.

In the tropics there is a vertically integrated transport of 03, from the summer to the winter hemisphere which is almost entirely produced by the mean-meridional circulation. In the middle latitudes, in both hemispheres, 03 is transported toward the equator by the mean-meridional circulation and toward the poles by the zonal eddies; but the eddy transport dominates, so that the net 03, transport is poleward. In the high latitudes in both hemispheres, there is a reversal in the directions of the two components of the 03, transport; but here the transport by the mean-meridional circulation dominates, so that the net transport continues to be poleward.

In the individual latitudes, the zonally integrated vertical transport of ozone is dominated by the transport by the mean-meridional circulation; but integrated over the globe, the vertical O3 transport is dominated by the eddy transport. Between 20 and 31 km elevation, the globally integrated vertical 03, transport is a countergradient transport with respect to the globally integrated 03, mixing ratio.

The divergence of the 03 transport maintains the ozone below its photochemical equilibrium concentration in the tropics and subtropics, and the convergence of the 03 transport maintains the ozone above its photochemical equilibrium concentration in the middle and high latitudes of both hemispheres. In this way, both the atmospheric motions and the 03 photochemistry determine the 03, sources and sinks.

The globally integrated photochemical production of ozone exhibits variations with periods of a day and less. These high-frequency oscillations are due to the quasi-stationary longitudinal variation in the ozone that is produced by the 03 transports.

Full access
ROBERT SADOURNY, AKIO ARAKAWA, and YALE MINTZ

Abstract

A finite difference scheme is developed for numerical integration of the nondivergent barotropic vorticity equation with an icosahedral-hexagonal grid covering the sphere. The grid is made by dividing the 20 triangular faces of an icosahedron into smaller triangles, the vertices of which are the grid points. Each grid point is surrounded by six neighboring points, except the 12 vertices of the icosahedron which are surrounded by five points. The difference scheme for the advection of vorticity exactly conserves total vorticity, total square vorticity, and total kinetic energy. A numerical test is made, with a stationary Neamtan wave as the initial condition, by integrating over 8 days with 1-hr. time steps and a grid of 1002 points for the sphere. There is practically no distortion of the waves over the 8 days, but there is a phase displacement error of about 1° of long. per day toward the west.

Full access
Albert J. Semtner Jr. and Yale Mintz

Abstract

The circulation of the western North Atlantic is simulated with a primitive equation model that has 5 levels and a horizontal grid size of 37 km. The idealized model domain is a rectangular basin, 3000 km long, 2000 km wide and 4 km deep, which is oriented so that the long axis of the basin is parallel to the east coast of the United States. The nearshore side of the basin has a simple continental shelf and slope, whereas the other sides are bounded by vertical wills. The model ocean is driven by a 2½ gyre pattern of steady zonal wind stress and by a Newtonian-type surface heating. After initialization from a 15-year spin-up with a coarser grid, two experiments are carried out, each of several years duration: the first uses a Laplacian formulation for the subgrid-scale lateral diffusions of heat and momentum, the second uses a highly scale-selective biharmonic formulation for these diffusions. Bottom friction is present in each case.

In both experiments, a western boundary current forms which separates from the coast and continues eastward as an intense free jet, with surface velocities >1 m s−1 for almost 1000 km downstream. In the experiment with biharmonic closure, this simulated Gulf Stream develops large-amplitude transient meanders, some of which become cold-core cyclonic rings and warm-core anticyclonic rings that drift westward. In both experiments, transient mesoscale eddies also form in the broad westward-moving North Equatorial Current, where the simulated thermocline in the model ocean slopes downward toward the north. The remaining regions of the model ocean also contain transient mesoscale eddies, but they are of weaker intensity.

The dominant process of eddy kinetic energy production, in both experiments, is a baroclinic-barotropic instability which is concentrated in the part of the Gulf Stream that is over the continental slope. But where the Gulf Stream lies over the abyssal plains, there is a large reconversion of eddy kinetic energy into the kinetic energy of the time-averaged flow. Eddy kinetic energy is also produced by baroclinic instability in the North Equatorial Current, but at a much smaller rate. In the biharmonic experiment, the eddies transfer considerable kinetic energy downward, and bottom friction is the dominant process of eddy kinetic energy dissipation.

An analysis of the heat transports in the biharmonic experiment, shows that the horizontal transport of heat by eddies is much larger than the subgrid-scale horizontal heat diffusion. In the Gulf Stream region, the eddy heat transport is comparable to the effect of a lateral diffusion coefficient of 107 cm2 s−1.

Full access
James B. Pollack, Conway B. Leovy, Paul W. Greiman, and Yale Mintz

Abstract

A three-layer general circulation model, used to simulate the Martian atmosphere, is described and results are presented. The model assumes a dust-free pure C02 atmosphere and allows for a diurnally- varying convective boundary layer. Smoothed Martian topography and albedo variations are incorporated. The simulation described is for the period near southern winter solstice, season of the Viking landings. The zonally-averaged circulation, mass, heat and momentum balances, and properties of stationary and transient waves are described in some detail, and are compared with results of previous simulations of the Martian general circulation, with related features of the Earth's general circulation, and with observed characteristics of the Martian atmosphere.

The principal conclusions are the following: 1) The simulated zonally-averaged circulation is not very sensitive to differences between this model and the earlier general circulation model of Leovy and Mintz (1969), and compares reasonably well with observations, except for differences attributable to dust and season. 2) The meridional mass flow produced by the seasonal condensation of CO2, in the winter polar region has a major influence on the circulation, but, because of the weak influence of atmospheric heat transport, it is controlled almost entirely by radiation. 3) Quasi-barotropic stationary waves forced kinematically by the topography and resembling topographically-forced terrestrial planetary waves, are generated by the model in the winter hemisphere region of strong eastward flow, while baroclinic stationary waves are thermally forced by topography in the tropics and summer subtropics. 4) Transient baroclinically unstable waves, of somewhat lower dominant wavenumber than those found on the Earth, are generated in winter midlatitudes and their amplitudes, wavenumbers and phase speeds closely agree with what has been deduced from the Viking lander observations.

Full access