Showing papers in "Journal of the Atmospheric Sciences in 1978"
TL;DR: In this paper, a trigonometrical formula for the Earth's orbital elements is presented, which allows direct spectral analysis and the computation of those long-term variations of the orbital elements which are of primary interest for the calculation of the insolation.
Abstract: Provides all trigonometrical formulas which allow the direct spectral analysis and the computation of those long-term variations of the Earth's orbital elements which are of primary interest for the computation of the insolation. The elements are the eccentricity, the longitude of the perihelion, the precessional parameter and the obliquity. This new formulary is much more simple to use than the ones previously designed and still provides excellent accuracy, mainly because it takes into account the influence of the most important higher order terms in the series expansions. The daily insolation both for calendar and solar dates is computed.
2,146 citations
TL;DR: In this article, a new three-dimensional cloud model was developed for investigating the dynamic character of convective storms, which solved the compressible equations of motion using a splitting procedure which provided numerical efficiency by treating the sound wave modes separately.
Abstract: A new three-dimensional cloud model has been developed for investigating the dynamic character of convective storms. This model solves the compressible equations of motion using a splitting procedure which provides numerical efficiency by treating the sound wave modes separately. For the subgrid turbulence processes, a time-dependent turbulence energy equation is solved which depends on local buoyancy, shear and dissipation. First-order closure is applied to nearly conservative variables with eddy coefficients based on the computed turbulence energy. Open lateral boundaries are incorporated in the model that respond to internal forcing and permit gravity waves to propagate out of the integration domain with little apparent reflection. Microphysical processes are included in the model using a Kessler-type parameterization. Simulations conducted for an unsheared environment reveal that the updraft temperatures follow a moist adiabatic lapse rate and that the convection is dissipated by water loadin...
1,453 citations
TL;DR: In this paper, the effect of the electrical field on charge separation during riming and the freezing potential of drops of rime was examined in cold room experiments simulating thunderstorm conditions.
Abstract: Riming electrification was studied in cold room experiments simulating thunderstorm conditions. When both ice crystals and supercooled droplets coexist in the experimental chamber, high electric charge occurs on the riming probes. Both the sign and magnitude of riming electrification are highly dependent on the temperature and cloud water content. Electric charge of the order of 10−4 esu (33 fC) is separated on riming with each ice crystal collision under conditions typical of the in-cloud environment of continental thunderstorms. This amount of charge is sufficient to produce the high electrification required for lightning discharge within reasonably short periods of time. The effect of the electrical field on charge separation during the riming and effect of the freezing potential of drops of rime also were examined. It appears that these effects play only a secondary role for charge separation in thunderstorms. Three different physical mechanisms of charge separation during riming are proposed...
826 citations
TL;DR: In this paper, the shortwave absorption, albedo and longwave emissivity of water clouds are parameterized for use in operational and climatic models of the atmosphere.
Abstract: The shortwave absorption, albedo and longwave emissivity of water clouds are parameterized for use in operational and climatic models of the atmosphere. The parameterization also provides the shortwave heating and longwave cooling rates within the cloud. The scheme presented in this paper assumes a prior knowledge of the broadband spectral fluxes incident on the cloud and further assumes that the atmospheric models will provide the surface albedo, solar zenith angle, cloud temperature and total vertical liquid water path. The last parameter was chosen because it likely to be available in atmospheric circulation models and both observational and theoretical evidence suggest that it is strongly related to the radiative properties of clouds (Paltridge, 1974; Platt, 1976). The parameterization of shortwave radiation resembles a two-stream approximation which has been “tuned” to match the results from a detailed theoretical model. The longwave scheme simply involves the parameterization of effective e...
689 citations
TL;DR: In this paper, an inversion formula which explicitly includes the magnitude of the measurement variances is derived and applied to optical depth measurements obtained in Tucson with a solar radiometer, and it is found that the individual size distributions of the aerosol particles (assumed spherical), at least for radii greater than or approximately equal to 0.1 micron, fall into one of three distinctly different categories.
Abstract: Columnar aerosol size distributions have been inferred by numerically inverting particulate optical depth measurements as a function of wavelength. An inversion formula which explicitly includes the magnitude of the measurement variances is derived and applied to optical depth measurements obtained in Tucson with a solar radiometer. It is found that the individual size distributions of the aerosol particles (assumed spherical), at least for radii greater than or approximately equal to 0.1 micron, fall into one of three distinctly different categories. Approximately 50% of all distributions examined thus far can best be represented as a composite of a Junge distribution plus a distribution of relatively monodispersed larger particles centered at a radius of about 0.5 micron. Scarcely 20% of the distributions yielded Junge size distributions, while 30% yielded relatively monodispersed distributions of the log-normal or gamma distribution types. A representative selection of each of these types will be presented and discussed. The sensitivity of spectral attenuation measurements to the radii limits and refractive index assumed in the numerical inversion will also be addressed.
484 citations
TL;DR: In this article, the nonlinear behavior of mid-latitude baroclinic waves is investigated by means of a series of integrations of the primitive equations with spherical geometry, each integration has as initial conditions a balanced zonal flow perturbed by a small amplitude disturbance of normal-mode form.
Abstract: Some aspects of the nonlinear behavior of mid-latitude baroclinic waves are investigated by means of a series of integrations of the primitive equations with spherical geometry. Each integration has as initial conditions a balanced zonal flow perturbed by a small-amplitude disturbance of normal-mode form. Results are presented in detail for several zonal flows and perturbations which are confined initially to either zonal wavenumber 6 or zonal wavenumber 9. In each case a disturbance grows by baroclinic instability and develops a structure in some agreement with the usual synoptic picture of an occluding system. Its growth rate at low levels decreases more rapidly than that at higher levels, as found by Gall using a more severely truncated model, and upper-level amplitudes become larger relative to surface values than in the initial linear mode. This is more marked for wavenumber 6 than for wavenumber 9, and differences in linear structure are thus enhanced in the nonlinear regime. Barotropic pro...
447 citations
TL;DR: In this paper, a detailed multiple-scattering model was employed to investigate the sensitivity of radiation profiles and flux divergences to changes in macrostructure and microstructure of basic water cloud types.
Abstract: A detailed multiple-scattering model has been employed to investigate the sensitivity of radiation profiles and flux divergences to changes in macrostructure and microstructure of basic water cloud types. The study has been performed on a range of cloud types including variable distributions of liquid water content (LWC) and drop-size distributions. Total shortwave heating rates vary from 1 to 5°C h−1 and are larger in higher clouds. IR cooling rates in the upper regions of cloud also increase with increasing elevation and are dominated by the atmospheric window contribution. Thus the typical instrument discriminating the IR radiation between 7 and 14,μm will measure almost the entire IR radiative cooling or heating of low-level water clouds. Both shortwave heating and IR cooling within cloud layers are primarily dependent on LWC and its vertical distribution and are more or less independent of drop-size distribution. Cloud albedo does vary with drop-size distribution but is virtually independent...
434 citations
TL;DR: In this article, a high-order model is proposed for the study of the 24-hour evolution of clear planetary boundary layers, which includes the rate equations of correlations up to the third order, but it also takes into account interactions between radiative transfer and turbulence in order to achieve a physically reasonable description of the nocturnal structure of the boundary layer.
Abstract: A high-order model is proposed for the study of the 24 h evolution of clear planetary boundary layers. The model includes the rate equations of correlations up to the third order, as required for an accurate description of daytime convective phenomena, but it also takes into account interactions between radiative transfer and turbulence in order to achieve a physically reasonable description of the nocturnal structure of the boundary layer. This numerical model is tested against the Wangara boundary layer data of Day 33 and Night 33–34 (Clarke et al., 197l). The computed daytime mean structure of the boundary layer compares favorably with the Wangara data, while the daytime turbulent structure, expressed in the framework of the convective similarity theory, is in particularly good quantitative agreement with a number of experimental and numerical data concerning convection in the boundary layer, with particular concern to the production of turbulence at the top of the mixed layer. The computed no...
384 citations
TL;DR: In this paper, a second-order turbulence model is used to study the stable boundary layer (SBL) over a horizontal surface, a constant surface cooling rate drives the SBL to a steady state within a few hours.
Abstract: A second-order turbulence model is used to study the stable boundary layer (SBL). Over a horizontal surface, a constant surface cooling rate drives the SBL to a steady state within a few hours. Parameterizations are developed for eddy diffusivities, the kinetic energy dissipation rate and the geostrophic drag law in this idealized case. Over a sloped surface, a constant cooling rate produces a quasi-steady-state SBL in which some flow properties continue to vary but h(|f|/u*L)½ becomes constant; however, this constant is a function of the wind direction relative to the slope and the baroclinity, as measured by the cooling rate times the slope. Calculated eddy diffusivity profiles in the baroclinic (sloping terrain) case compare well with recent data from Antarctica. If a surface energy budget is used rather than a constant cooling rate, the SBL does not reach a steady state even over a horizontal surface; the nondimensional height slowly decays. We conclude that equilibrium models of the SBL are ...
370 citations
TL;DR: In this paper, a numerical model for simulating the flow of stably stratified nonrotating air over finite-amplitude, two-dimensional mountain ranges is developed for accurate treatment of internal dissipation and formulation of an upper boundary region and lateral boundary conditions which allow upward and lateral propagation of wave energy out of the model.
Abstract: A numerical model is developed for simulating the flow of stably stratified nonrotating air over finite-amplitude, two-dimensional mountain ranges. Special attention is paid to accurate treatment of internal dissipation and to formulation of an upper boundary region and lateral boundary conditions which allow upward and lateral propagation of wave energy out of the model. The model is hydrostatic and uses potential temperature for the vertical coordinate. A local adjustment procedure is derived to parameterize low Richardson number instability. The model behavior is tested against analytic theory and then applied to a variety of idealized and real flow situations, leading to some new insights and new questions on the nature of large-amplitude mountain waves. The model proves to be effective in simulating the structure of two observed cases of strong mountain waves with very different characteristics.
369 citations
TL;DR: In this article, the mean meridional mass circulation of the stratosphere and mesosphere is discussed under solstice conditions, and it is shown that this Lagrangian-mean circulation may be inferred, as a first approximation, from the Eulerian-means diabatic heating.
Abstract: Using a simplified, approximate 'Lagrangian-mean' dynamical formulation, the mean meridional mass circulation of the stratosphere and mesosphere is discussed. Under solstice conditions, it is shown that this Lagrangian-mean circulation may be inferred, as a first approximation, from the Eulerian-mean diabatic heating. Diabatic heating rates for the solstices, originally derived by Murgatroyd and Goody (1958), result in Lagrangian-mean rising motion at the tropical tropopause, subsidence across the extra-tropical tropopause, and a very strong summer-to-winter pole flow in the mesosphere. This circulation is exactly that obtained by Murgatroyd and Singleton (1961) for the solstices. Those authors, however, attempted to identify this circulation as the Eulerian-mean motion, and were later criticized for their neglect of the meridional eddy heat flux in the calculation, which proved to be extremely important in the winter hemisphere. The present study, nevertheless, indicates that Murgatroyd and Singleton's circulation may in fact be representative of actual air parcel motions in the stratosphere and mesosphere.
TL;DR: In this article, the formative processes of the planetary circulations of Jupiter and Saturn were studied and it was shown that a strong affinity exists between the Jovian and terrestrial circulations.
Abstract: We seek the formative processes of the planetary circulations of Jupiter and Saturn. The study concentrates on examining whether processes known to control the terrestrial circulation, namely, two-dimensional turbulence and baroclinic instability, can produce Jovian circulations under Jovian conditions. The first numerical model involves a spherical barotropic vorticity equation subjected to a stochastic representation of baroclinic processes. The resulting solutions suggest that a strong affinity exists between the Jovian and terrestrial circulations. This leads to a reevaluation of terrestrial circulation theory from the broader perspective of parameter space. The solutions in the Jovian regime support the hypothesis that a variation of the Rhines effect—an interaction of the two-dimensional turbulence cascade and Rossby wave propagation—creates the pseudoaxisymmetry and scale Lβ=π(2U/β)½ of the bands (U is the rms zonal velocity, and β the northward gradient of the Coriolis force). The anisotr...
TL;DR: In this article, it was shown that the eddy viscosity for very stable conditions does not take the infinitesimally small value predicted from extrapolation of the so-called log-linear profile, and that the flux Richardson number has a limit in the range of 0.1-0.4, although the gradient Richardson number can become indefinitely large.
Abstract: Transfers of heat and momentum under strongly stable conditions in the atmospheric boundary layer have been studied through measurements of the turbulent fluctuations and vertical mean profiles of wind velocity and air temperature. As the local gradient Richardson number increases, intermittent turbulence appears, especially in temperature fluctuations. The ratio of the eddy conductivity to the eddy viscosity decreases with increasing Richardson number and tends to zero at high stabilities. The local value of the dimensionless shear function for wind velocity does not exceed a limit of about six. These results imply that the eddy viscosity for very stable conditions does not take the infinitesimally small value predicted from extrapolation of the so-called log-linear profile, and that the flux Richardson number has a limit in the range of 0.1–0.4, although the gradient Richardson number can become indefinitely large. It is also shown that the divergences of both the radiative and turbulent heat f...
TL;DR: Andrews and Mclntyre as mentioned in this paper showed that no approximation beyond axisymmetry of the mean flow is necessary for the case of sinusoidal, hydrostatic waves with exponentially growing or decaying amplitude.
Abstract: The theorems, which exhibit the role of wave dissipation, excitation and transience in the forcing of mean flow changes of second order in wave amplitude by arbitrary, small-amplitude disturbances, are obtained 1) for the primitive equations in pressure coordinates on a sphere, and 2) in a more general form (applicable for instance to nonhydrostatic disturbances in tornadoes or hurricanes) establishing that no approximations beyond axisymmetry of the mean flow are necessary It is shown how the results reduce to those found by Boyd (1976) for the case of sinusoidal, hydrostatic waves with exponentially growing or decaying amplitude, and it is explained why the approximation used by Boyd in the thermodynamic equation is not needed The reduction to Boyd's results entails the use of a virial theorem This theorem amounts to a generalization of the “equipartition” law derived in an earlier paper (Andrews and Mclntyre, 1976) That derivation appeared to rely on an assumption about relative phases of
TL;DR: In this article, self-sustaining right and left-moving storms are simulated which arise through splitting of the original storm, and the right-moving storm develops a structure which bears strong resemblance to Browning's (1964) conceptual model, while the left moving storm has mirror image characteristics.
Abstract: Using a three-dimensional numerical cloud model, self-sustaining right- and left-moving storms are simulated which arise through splitting of the original storm. The right-moving storm develops a structure which bears strong resemblance to Browning's (1964) conceptual model, while the left-moving storm has mirror image characteristics. By altering the direction of the environmental shear at low and middle levels, either the right- or the left-moving storm can be selectively enhanced. Specifically, if the wind hodograph turns clockwise with height, a single right-moving storm envolves from the splitting process. Conversely, counterclockwise turning of the hodograph favors development of the left-moving storm.
TL;DR: In this paper, an analysis is made of equatorial wave disturbances in the upper stratosphere and mesosphere by the use of meteorological rocket and satellite observations, to clarify their structure and behavior in relation to the semiannual oscillation of the mean zonal wind.
Abstract: An analysis is made of equatorial wave disturbances in the upper stratosphere and mesosphere by the use of meteorological rocket and satellite observations, to clarify their structure and behavior in relation to the semiannual oscillation of the mean zonal wind. From a power spectral analysis of wind and temperature over Ascension Island during the four years from 1969 to 1972, it is found that in the height region between 25 and 60 km there exists a wave disturbance with a characteristic vertical scale of 15–20 km; the wave is more active in the easterlies than in the westerlies, showing marked semiannual variation. Compared with the well-known characteristics of equatorial waves in the lower stratosphere, this wave is likely to he identified as a Kelvin wave with a period of about 10 days. It is suggested that this wave plays an essential role in producing the semiannual reversal of the mean zonal wind by supplying the westerly momentum to the equatorial mesospheric levels. Further discussions ...
TL;DR: A detailed analysis of the large-scale, mesoscale and turbulent-scale features of a major downslope windstorm event in central Colorado on 11 January 1972 is presented in this article.
Abstract: A detailed analysis is presented of the large-scale, mesoscale and turbulent-scale features of a major downslope windstorm event in central Colorado on 11 January 1972. The storm is found to be associated with a moderate amplitude baroclinic disturbance moving across the northwestern United States within an intense zonal current. Optimal conditions for strong mountain wave generation are detectable from sounding data 12–24 h in advance and about 1000 km upstream. The mesoscale structure is dominated by a single quasi-hydrostatic wave of extreme amplitude and variable location, with corresponding variations in the windstorm structure. Severe to extreme aircraft turbulence is observed in a deep boundary layer over the region of strong surface winds and also in a separate mid-tropospheric turbulence zone. Analysis of the latter shows that it originates in a region of intense wave-generated shear and is then carried downstream by the mean flow and upward by the wave motion. Energy generation and diss...
TL;DR: In this paper, the Eady problem instability is associated with energy transfer both up and down the vertical wavenumber spectrum although energy transfer from small to large three-dimensional wavenumbers may occur over a finite range of the spectrum.
Abstract: Uniform potential vorticity flows are examined. In the quasi-geostrophic system, conservation of total energy and conservation of available potential energy on plane rigid horizontal boundaries imply a restriction on energy exchanges as a result of scale interactions. It is shown that for the Eady problem instability is always associated with energy transfer both up and down the vertical wavenumber spectrum although energy transfer from small to large three-dimensional wavenumbers may occur over a finite range of the spectrum. An inertial theory of two-dimensional turbulence is also presented. The formal analysis, based on Leith's diffusion approximation, predicts two inertial subranges: −5/3 and −1 power dependences on the horizontal wavenumber for available potential energy on horizontal boundaries. In the former range, available potential energy on horizontal boundaries cascades at a constant rate toward higher wavenumbers; in the latter range, the depth-integrated total energy cascades at a c...
TL;DR: In this paper, a theoretical model is described which determines the efficiency E with which aerosol particles of radius r are collected by water drops of radius a due to the combined action of Brownian diffusion, thermo- and diffusiophoresis and electric forces, in the absence of inertial impaction effects.
Abstract: A theoretical model is described which determines the efficiency E with which aerosol particles of radius r are collected by water drops of radius a due to the combined action of Brownian diffusion, thermo- and diffusiophoresis and electric forces, in the absence of inertial impaction effects. The results of this model are combined with the results of our earlier model which determines the collection efficiency of drops for particles due to the combined action of inertial impaction, thermo- and diffusiophoresis and electric forces, in the absence of effects due to Brownian diffusion. Both models combined quantitatively determine the variation of E vs r for 0.001≤r≤10 μm, and 42≤a≤310 μm, for relative humidities up to and including 100%, and for electric charges on drops and aerosol particles ranging in magnitude up to that found under thunder-storm conditions. In particular, a combination of both models allows a quantitative description of the particle size range where the collection efficiency o...
TL;DR: In this paper, an 11-level general circulation model with seasonal variation is used to perform an experiment on the dispersion of passive tracers, where the tracer is assumed to have no sources or sinks in the stratosphere, but is subject to removal processes in the lower troposphere.
Abstract: An 11-level general circulation model with seasonal variation is used to perform an experiment on the dispersion of passive tracers. Specially constructed time-dependent winds from this model are used as input to a separate tracer model. The methodologies employed to construct the tracer model are described. The experiment presented is the evolution of a hypothetical instantaneous source of tracer on 1 January with maximum initial concentration at 65 mb, 36°N, 180°E. The tracer is assumed to have no sources or sinks in the stratosphere, but is subject to removal processes in the lower troposphere. The experimental results reveal a number of similarities to observed tracer behavior, including the average poleward-downward slope of mixing ratio isopleths, strong tracer gradients across the tropopause, intrusion of tracer into the Southern Hemisphere lower stratosphere, and the long-term interhemispheric exchange rate. The model residence times show behavior intermediate to those exhibited for parti...
TL;DR: In this article, an experiment is described in which a standing internal wave is forced at the lower boundary of an annulus of salt-stratified water, and the wave motion generates a strong mean azimuthal circulation which itself exhibits a long-period oscillation.
Abstract: An experiment is described in which a standing internal wave is forced at the lower boundary of an annulus of salt-stratified water. At sufficiently large forcing amplitudes, the wave motion generates a strong mean azimuthal circulation which itself exhibits a long-period oscillation. Theoretical calculations, based on the wave-driven theory of the quasi-biennial oscillation of the tropical stratosphere (with suitable modifications), are performed and compared with the experimental results. Agreement is good and the study thus provides substantial confirmation of the fundamental principles of the theory.
TL;DR: In this article, the vertical turbulent diffusion coefficient in a stably stratified fluid is derived analytically, without requiring that the flux Richardson number be known or specified, and the resulting expression for the diffusion coefficient is compared with the previous stratospheric results of Lilly et al.
Abstract: The vertical turbulent diffusion coefficient in a stably stratified fluid is derived analytically. This derivation does not require that the flux Richardson number be known or specified. The resulting expression for the diffusion coefficient is compared with the previous stratospheric results of Lilly et al. (1974) and its applicability to atmospheric diffusion and clear air turbulence is discussed.
TL;DR: In this paper, large-scale departure maps of sea level pressure and sea surface temperature (SST) are presented for the tropical Atlantic and eastern Pacific Oceans, as obtained by stratification with respect to extreme climatic events in key regions of the tropical Americas.
Abstract: Large-scale departure maps of sea level pressure (SLP) and sea surface temperature (SST) are presented for the tropical Atlantic and eastern Pacific Oceans, as obtained by stratification with respect to extreme climatic events in key regions of the tropical Americas. Drought in the Central American-Caribbean region is characterized by an equatorward expansion of the North Atlantic high, a band of anomalously cold water extending across the North Atlantic and a positive SST anomaly in the eastern Pacific. Drought in northeast Brazil is associated with high SLP over the South Atlantic and low SLP over the North Atlantic, cold water in the South Atlantic, a band of positive SST anomalies across the North Atlantic, and positive SST departures in the eastern Pacific. During the Ecuador/Peru El Nino, SLP in the eastern Pacific is low and SST high, and positive SLP departures dominate the tropical Atlantic. Independently, preferred modes of departure configurations are identified from principal compone...
TL;DR: In this article, the behavior of the temperature-humidity covariance (θq) budget in the convectively driven boundary layer is determined through analysis of data from AMTEX and (to a lesser extent) Kansas and Minnesota.
Abstract: The behavior of the temperature-humidity covariance (θq) budget in the convectively driven boundary layer is determined through analysis of data from AMTEX and (to a lesser extent) Kansas and Minnesota. In the near-neutral surface layer a balance is found between production and molecular destruction; in the mixed layer, transport is also important. We extend the Corrsin theory for inertial subrange scalar spectral behavior to the temperature-humidity cospectrum, and thus relate the molecular destruction rate of θq to its inertial range level. Destruction rates inferred from AMTEX cospectra agree with those found from the imbalance of production and transport terms. The budgets within the surface layer and the mixed layer are parameterized separately with appropriate scales. Both temperature and humidity fluctuations contribute to the small-scale refractive index variations which affect acoustic and electromagnetic wave propagation in the atmosphere. Our results indicate that their joint contribut...
TL;DR: In this article, six case studies of planetary boundary layer clouds are reported where the solar and infrared radiation fields, liquid water content, drop-size distributions and temperature and humidity profiles were measured simultaneously.
Abstract: Six case studies of “uniform” planetary boundary layer clouds are reported where the solar and infrared radiation fields, liquid water content, drop-size distributions and temperature and humidity profiles were measured simultaneously. The measurements are compared with theoretical prediction from a detailed radiative transfer model in an attempt to verify the performance of the model and its associated parameterization schemes (Parts 1 and 2). The measurements support the parameterization of both shortwave and longwave radiative characteristics in terms of vertical liquid water path (LWP) i.e., without the need to define cloud drop-size distributions. Within experimental error, there are no significant discrepancies between theory and measurement. However, there is some evidence in the present study, supported by measurements of others in (generally) thicker and denser clouds that solar absorption is in excess of theoretical prediction.
TL;DR: In this article, a boundary-layer experiment conducted over a flat, uniform site in Minnesota provided a clue to the behavior of the low-frequency peak in surface-layer horizontal velocity spectra.
Abstract: Data from a boundary-layer experiment conducted over a flat, uniform site in Minnesota provide a clue to the behavior of the low-frequency peak in surface-layer horizontal velocity spectra This portion of the spectra shows systematic behavior only when plotted in dimensionless coordinates appropriate to the mixed layer, whereas the inertial subrange frequencies follow Monin-Obukhov similarity Based on this observation, interpolation formulas for both the longitudinal and the lateral velocity components, are derived The expressions involve the boundary-layer depth in addition to the usual surface-layer parameters
TL;DR: In this paper, wind speed, ambient and surface temperatures from both Viking Landers have been used to compute bulk Richardson numbers and Monin-Obukhov lengths during the earliest phase of the Mars missions.
Abstract: Wind speed, ambient and surface temperatures from both Viking Landers have been used to compute bulk Richardson numbers and Monin-Obukhov lengths during the earliest phase of the Mars missions. These parameters are used to estimate drag and heat transfer coefficients, friction velocities and surface heat fluxes at the two sites. The principal uncertainty is in the specification of the roughness length. Maximum heat fluxes occur near local noon at both sites, and are estimated to be in the range 15-20 W/sq m at the Viking 1 site and 10-15 W/sq m at the Viking 2 site. Maximum values of friction velocity occur in late morning at Viking 1 and are estimated to be 0.4-0.6 m/s. They occur shortly after dawn at the Viking 2 site where peak values are estimated to be in the range 0.25-0.35 m/s. Extension of these calculations to later times during the mission will require allowance for dust opacity effects in the estimation of surface temperature and in the correction of radiation errors of the Viking 2 temperature sensor.
TL;DR: In this article, the number of fragments in a collision was found as a function of the change in momentum on impact with a fixed plate, and the crystal type and degree of rime.
Abstract: The number of fragments generated by crystal collisions in a cloud is a product of the number of fragments produced per collision and the collision frequency. The first term, called the fragment generation function, was obtained experimentally by taking high-speed photographs of collisions of natural ice crystals with a fixed plate. The number of fragments in a collision was found as a function of the change in momentum on impact with a fixed plate and as a function of crystal type and degree of rime. The difference in the change in momentum for collisions in a cloud compared to the fixed plate is treated theoretically and developed into a mathematical model. The collision frequency is incorporated into the model and rates of fragment generation studied for different crystal combinations, sizes and concentrations. The generation of secondary particles by mechanical fracturing does not explain the presence of large concentrations of ice crystals in relatively warm clouds. The additional crystals g...
TL;DR: In this article, the authors show that the time averaged, vertically integrated, poleward eddy heat flux is proportional to the fifth power of the meridional temperature gradient when h 0 is much less than the scale height of the atmosphere.
Abstract: Linear, quasi-geostrophic waves destabilized by a surface temperature gradient produce eddy potential vorticity fluxes which characteristically extend above the surface to a height where the vertical shear ∂u¯/∂z, static stability N2 and potential vorticity gradient ∂q/∂y of the zonal flow are evaluated at the surface. Utilizing this result and a simple scaling analysis, we argue that the time averaged, vertically integrated, poleward eddy heat flux is proportional to the fifth power of the meridional temperature gradient when h0 is much less than the scale height of the atmosphere.
TL;DR: In this paper, a Monte Carlo model applied to a wide range of cloud widths and heights, and for an analytical model restricted in its application to cuboidally shaped clouds whose length, breadth, and depth may be varied independently; the clouds must be internally homogeneous with respect to their intrinsic radiative properties.
Abstract: Results are presented for a Monte Carlo model applied to a wide range of cloud widths and heights, and for an analytical model restricted in its application to cuboidally shaped clouds whose length, breadth, and depth may be varied independently; the clouds must be internally homogeneous with respect to their intrinsic radiative properties. Comparative results from the Monte Carlo method and the derived analytical model are presented for a wide range of cloud sizes, with special emphasis on the effects of varying the single scatter albedo, the solar zenith angle, and the scattering phase angle.