Temperature and Humidity Structure in the Lower Atmosphere

Webb, E. K.

doi:10.1007/978-3-642-45583-4_6

Cited by 10 publications

(7 citation statements)

References 219 publications

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“…Observed dust devils in orbiter images can be several hundred meters to over a kilometer in diameter [Malin and Edgett, 2001;Fisher et al, submitted manuscript, 2002]. Extrapolating from terrestrial observations and modeling of convective cells [Willis and Deardorff, 1979;Webb, 1984;Young et al, 2002], the horizontal diameter of cells was expected to be from 1 to 1.5 times the depth of the convectively mixed layer, which was expected to be roughly 4 to 5 km. Combined, these constraints suggested an initial model domain size of roughly 10 km, with horizontal resolution of 100 m. The vertical resolution was set to vary from a few tens of meters in the lower part of the domain (with the lowest level being approximately 10 m thick), to about 100 m near the top, with 57 vertical levels.…”

Section: Methodsmentioning

confidence: 99%

Numerical simulation of Martian dust devils

et al. 2003

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[1] Large eddy simulations of vertical convective vortices and dust devils in the Martian convective boundary layer are presented, employing a version of the Mars MM5 mesoscale model, adapted to use periodic boundary conditions and run at resolutions of 10 to 100 m. The effects of background horizontal wind speed and shear on dust devil development are studied in four simulations, each extending over the daytime portion of one Martian day. The general vorticity development in all cases is similar, with roughly equal positive and negative vorticity extrema. Two dust devils were found to develop in the highest wind speed case and in a case run without background wind. The dust devil structures were found to agree well qualitatively with terrestrial dust devil observations, including the prediction of greatly diminished vertical velocities in the vortex core. Thermodynamic scaling theory of dust devils was found to provide good prediction of the relationship between central pressure and temperature in the modeled vortices. Examination of the turbulent kinetic energy budgets suggests balance between buoyancy generation and loss through dissipation and transport. The vorticity for the dust devils is provided by twisting of horizontal vorticity into the vertical. The horizontal vorticity originates from horizontal variations in temperature at the lower boundary (thermal buoyancy). While the horizontal winds generated by the modeled dust devils were likely insufficient to lift dust, this study provides a solid starting point for dynamic modeling of what may be an important component of the Martian dust cycle.

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Section: Methodsmentioning

confidence: 99%

Numerical simulation of Martian dust devils

et al. 2003

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“…Kiikkamaki [1938] developed corrections for leveling observations under the dual assumptions that isothermal surfaces within the lowest 3 m of the atmosphere align parallel to the ground surface and that the dependence of temperature on height within this thermal boundary layer can be represented by the power law (1), with c = -1/3. Angus-Leppan [1979,1984] also constrained c = -1/3, under the free convection approximation [Webb, 1984]. Convection of the unstable boundary layer causes variations of the instantaneous temperature and its gradient; thus (1) can hold only for time-averaged and spatially averaged observations of temperature.…”

Section: Refraction Modelsmentioning

confidence: 99%

Saugus‐Palmdale, California, field test for refraction error in historical leveling surveys

Stein¹,

Whalen²,

Holdahl³

et al. 1986

J. Geophys. Res.

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A field test designed to measure atmospheric refraction error in historical and modern leveling was conducted in May–June 1981 on a 50‐km‐long grade from Saugus to Palmdale, California. During 1955–1971, the length of sights made between the level instrument and rods systematically decreased from 60 m to 26 m. The difference in height near Palmdale measured by single‐run long‐sight (42‐m) and short‐sight (22‐m) leveling during the test was 6 times larger than expected random error. Correction for refraction by using either the observed or modeled vertical temperature gradient in Kükkamaki's balanced sight equation reduced the height difference to the level of random error uncertainty. The observed temperature gradient obeyed a power law relation, T = a + bzc, where z is the height and a, b, and c are constants that depended on atmospheric conditions and the ground surface beneath the line of sight. The refraction‐corrected leveling satisfies the specifications and meets all standards of first‐order control surveys. The six historical surveys of the Saugus‐Palmdale grade were corrected for refraction error using the results of the experiment and for rod scale errors and nontectonic subsidence considered in previous investigations. The corrected uplift near Palmdale reached 56 ± 16 mm with respect to Saugus during the period 1955–1965. This amount of uplift is about one third that obtained before removal of refraction error. The corrected displacement profiles also reveal previously unrecognized deformation in the epicentral region of the 1971 San Fernando ML = 6.4 earthquake during the decade before the main shock.

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“…The long primacy of ensemble statistics generated through experiment and observation testifies to the impact of the Russian school that included A. N. Kolmogorov. Numerical simulation has fundamentally changed our approach to turbulence, however; today, for better and for worse, the turbulence community is substantially if not predominantly numerical Adding to the foundations laid by Gossard and Strauch [1983] and Webb [1984], we shall discuss the underlying concepts of refractive index turbulence in the lower atmosphere, observations of its structure, and its coupling to the larger-scale meteorology. We stress the differences between statistical and instantaneous properties.…”

Section: Introductionmentioning

confidence: 99%

Concepts, observations, and simulation of refractive index turbulence in the lower atmosphere

Wyngaard¹,

Seaman²,

Kimmel³

et al. 2001

Radio Science

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Abstract. Advances in computers and in computational techniques now allow the calculation of electromagnetic (EM) wave propagation through simulated refractive index turbulence in the lower atmosphere. Such applications call for instantaneous turbulence fields, not turbulence statistics, the traditional focus of the turbulence community. We clarify their important differences and review what is known about key statistics of refractive index turbulence. We discuss the calculation of EM propagation with a parabolic equation model that uses composite refractive index fields, the larger scales being calculated with a dynamical mesoscale model and the smaller scales being calculated through large-eddy simulation. The locally, instantaneously sharp top of the atmospheric boundary layer can have a profound effect on forward scatter of EM waves. This top appears to be even sharper than is revealed by conventional measurements, particularly in the convective boundary layer. IntroductionThree parallel developments over the past few decades now allow a new approach to the calculation of electromagnetic (EM) wave propagation in environmental flows, one that does not require inventing your own refractive index fields. They are (1) is similar to the most advanced operational forecast 643

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Temperature and Humidity Structure in the Lower Atmosphere

Cited by 10 publications

References 219 publications

Numerical simulation of Martian dust devils

Numerical simulation of Martian dust devils

Saugus‐Palmdale, California, field test for refraction error in historical leveling surveys

Concepts, observations, and simulation of refractive index turbulence in the lower atmosphere

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