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  • 1
    Online Resource
    Online Resource
    American Meteorological Society ; 2012
    In:  Journal of Applied Meteorology and Climatology Vol. 51, No. 6 ( 2012-06), p. 1010-1025
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 51, No. 6 ( 2012-06), p. 1010-1025
    Abstract: Episodic nighttime intrusions of warm air, accompanied by strong winds, enter the enclosed near-circular Meteor Crater basin on clear, synoptically undisturbed nights. Data analysis is used to document these events and to determine their spatial and temporal characteristics, their effects on the atmospheric structure inside the crater, and their relationship to larger-scale flows and atmospheric stability. A conceptual model that is based on hydraulic flow theory is offered to explain warm-air-intrusion events at the crater. The intermittent warm-air-intrusion events were closely related to a stable surface layer and a mesoscale (~50 km) drainage flow on the inclined plain outside the crater and to a continuous shallow cold-air inflow that came over the upstream crater rim. Depending on the upstream conditions, the cold-air inflow at the crater rim deepened temporarily and warmer air from above the stable surface layer on the surrounding plain descended into the crater, as part of the flowing layer. The flow descended up to 140 m into the 170-m-deep crater and did not penetrate the approximately 30-m-deep crater-floor inversion. The intruding air, which was up to 5 K warmer than the crater atmosphere, did not extend into the center of the crater, where the nighttime near-isothermal layer in the ambient crater atmosphere remained largely undisturbed. New investigations are suggested to test the hypothesis that the warm-air intrusions are associated with hydraulic jumps.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2012
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 2
    In: Journal of Applied Meteorology and Climatology, American Meteorological Society, Vol. 57, No. 4 ( 2018-04), p. 969-989
    Abstract: The successive stages of nocturnal atmospheric structure inside a small isolated basin are investigated when a katabatically driven flow on an adjacent tilted plain advects cold air over the basin rim. Data came from Arizona’s Meteor Crater during intensive observing period 4 of the Second Meteor Crater Experiment (METCRAX II) when a mesoscale flow above the plain was superimposed on the katabatic flow leading to a flow acceleration and then deceleration over the course of the night. Following an overflow-initiation phase, the basin atmosphere over the upwind inner sidewall progressed through three stages as the katabatic flow accelerated: 1) a cold-air-intrusion phase in which the overflowing cold air accelerated down the upwind inner sidewall, 2) a bifurcation phase in which the katabatic stable layer lifted over the rim included both a nonnegatively buoyant upper layer that flowed horizontally over the basin and a negatively buoyant lower layer (the cold-air intrusion) that continued on the slope below to create a hydraulic jump at the foot of the sidewall, and 3) a final warm-air-intrusion phase in which shear instability in the upper overflowing layer produced a lee wave that brought warm air from the elevated residual layer downward into the basin. Strong winds during the third phase penetrated to the basin floor, stirring the preexisting, intensely stable, cold pool. Later in the night a wind direction change aloft decelerated the katabatic wind and the atmosphere progressed back through the bifurcation and cold-air-intrusion phases. A conceptual diagram illustrates the first four evolutionary phases.
    Type of Medium: Online Resource
    ISSN: 1558-8424 , 1558-8432
    RVK:
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2018
    detail.hit.zdb_id: 2227779-1
    detail.hit.zdb_id: 2227759-6
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  • 3
    Online Resource
    Online Resource
    American Meteorological Society ; 2016
    In:  Journal of the Atmospheric Sciences Vol. 73, No. 10 ( 2016-10-01), p. 4065-4076
    In: Journal of the Atmospheric Sciences, American Meteorological Society, Vol. 73, No. 10 ( 2016-10-01), p. 4065-4076
    Abstract: Observations and models of nocturnal katabatic winds indicate strong low-level stability with much weaker stability aloft. When such winds encounter an embedded depression in an otherwise smooth sloping plane, the flow responds in a manner that is largely describable by the inviscid fluid dynamics of stratified flow. Building on earlier work, the present study presents a series of numerical simulations based on the simplest nontrivial idealization relevant to the observations: the height-independent flow of a two-layer stratified fluid past a two-dimensional valley. Stratified flow past a valley has received much less attention than the related problem of stratified flow past a hill. Hence, the present paper gives a detailed review of existing theory and fills a few gaps along the way. The theory is used as an interpretive guide to an extensive set of numerical simulations. The solutions exhibit a variety of behaviors that depend on the nondimensional input parameters. These behaviors range from complete flow through the valley to valley-flow stagnation to situations involving internal wave breaking, lee waves, and quasi-stationary waves in the valley. A diagram is presented that organizes the solutions into flow regimes as a function of the nondimensional input parameters.
    Type of Medium: Online Resource
    ISSN: 0022-4928 , 1520-0469
    RVK:
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2016
    detail.hit.zdb_id: 218351-1
    detail.hit.zdb_id: 2025890-2
    SSG: 16,13
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  • 4
    In: Bulletin of the American Meteorological Society, American Meteorological Society, Vol. 102, No. 7 ( 2021-07), p. 659-666
    Type of Medium: Online Resource
    ISSN: 0003-0007 , 1520-0477
    Language: Unknown
    Publisher: American Meteorological Society
    Publication Date: 2021
    detail.hit.zdb_id: 2029396-3
    detail.hit.zdb_id: 419957-1
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2023
    In:  International Journal of Climatology Vol. 43, No. 1 ( 2023-01), p. 456-479
    In: International Journal of Climatology, Wiley, Vol. 43, No. 1 ( 2023-01), p. 456-479
    Abstract: A 25‐year set of daily radiosonde data was used to investigate temperature and humidity inversions at Neumayer Station, coastal Dronning Maud Land, Antarctica. For the first time, inversions were studied differentiating between different synoptic conditions and different height levels. It was shown that, generally, inversions occurred on the majority (78%) of the days, with simultaneous occurrence of humidity and temperature inversions being observed on approximately two thirds of all days. Multiple inversions are common in all seasons for cyclonic and noncyclonic conditions, however, typically occur more frequently under cyclonic conditions. The seasonality of inversion occurrence and features, that is, inversion strength, depth and vertical gradients, was analysed statistically. Different formation mechanisms depending on inversion levels and prevailing weather situations are related to typical annual courses of certain inversion features. Winter maxima were found for the features that are mostly connected to the temperature close to the surface, which is mainly a result of the negative energy balance, thus influencing surface‐based inversions. At the second level, both temperature and humidity inversions are often caused by advection of comparably warm and moist air masses related to the passage of cyclones and their frontal systems. Hence, maxima in several inversion features are found in spring and fall, when cyclonic activity is strongest. Monthly mean profiles of humidity and temperature inversions reveal that elevated inversions are often obscured in average profiles due to large variations in inversion height and depth.
    Type of Medium: Online Resource
    ISSN: 0899-8418 , 1097-0088
    URL: Issue
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1491204-1
    SSG: 14
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  • 6
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2019
    In:  Boundary-Layer Meteorology Vol. 173, No. 3 ( 2019-12), p. 435-450
    In: Boundary-Layer Meteorology, Springer Science and Business Media LLC, Vol. 173, No. 3 ( 2019-12), p. 435-450
    Type of Medium: Online Resource
    ISSN: 0006-8314 , 1573-1472
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 242879-9
    detail.hit.zdb_id: 1477639-X
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2018
    In:  Boundary-Layer Meteorology Vol. 169, No. 1 ( 2018-10), p. 11-46
    In: Boundary-Layer Meteorology, Springer Science and Business Media LLC, Vol. 169, No. 1 ( 2018-10), p. 11-46
    Type of Medium: Online Resource
    ISSN: 0006-8314 , 1573-1472
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 242879-9
    detail.hit.zdb_id: 1477639-X
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Wiley ; 2020
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 146, No. 728 ( 2020-04), p. 1206-1231
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 146, No. 728 ( 2020-04), p. 1206-1231
    Abstract: A comprehensive analysis of the turbulence structure of relatively deep midlatitude katabatic flows (with jet maxima between 20 and 50 m) developing over a gentle (1°) mesoscale slope with a long fetch upstream of the Meteor Crater in Arizona is presented. The turbulence structure of flow below the katabatic jet maximum shows many similarities with the turbulence structure of shallower katabatic flows, with decreasing turbulence fluxes with height and almost constant turbulent Prandtl number. Still stark differences occur above the jet maximum where turbulence is suppressed by strong stability, is anisotropic and there is a large sub‐mesoscale contribution to the flux. Detecting the stable boundary‐layer top depends on the method used (flux‐ vs. anisotropy‐profiles) but both methods are highly correlated. The top of the stable boundary layer, however, mostly deviates from the jet maximum height or the top of the near‐surface inversion. The flat‐terrain formulations for the boundary‐layer height correlate well with the detected top of the stable boundary layer if the near‐surface and not the background stratification is used in their formulations; however, they mostly largely overestimate this boundary‐layer height. The difference from flat‐terrain boundary layers is also shown through the dependence of size of the dominant eddy with height. In katabatic flows the eddy size is semi‐constant with height throughout the stable boundary‐layer depth, whereas in flat terrain, eddy size varies significantly with height. Flux‐gradient and flux‐variance relationships show that turbulence data from different stable boundary‐layer scaling regimes collapse on top of each other showing that the dominant dependence is not on the scaling regime but on the local stability.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    RVK:
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 147, No. 740 ( 2021-10), p. 3835-3861
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 147, No. 740 ( 2021-10), p. 3835-3861
    Abstract: Exchange of momentum and scalars in the mountain boundary layer is achieved through an interaction of meso‐to‐microscale motions, occurring to varying extents depending on the combined effect of thermally driven as well as dynamically driven forcings. One such motion, known as a secondary circulation, results from a horizontal force imbalance across a curved valley segment, wherein the centrifugal force towards the outside of the valley bend can create a pressure gradient force in the opposite direction. The lack of adequate measurement strategies capable of sampling such motions in curved mountain valleys explains the near‐absence of any observational evidence of secondary circulations there. The goal of the CROSSINN (Cross‐valley flow in the Inn valley investigated by dual‐Doppler lidar measurements) campaign, conducted in a curved segment of the Inn valley, Austria, was to determine the character of the cross‐valley flow by means of a coplanar retrieval applied to a multi‐Doppler wind lidar configuration. A signature of a secondary circulation, hereafter referred to as a cross‐valley vortex, stood out particularly during intense daytime upvalley flow episodes. Vortices were detected on 23 upvalley wind days, with a declining frequency of occurrence from August to October. Nearly all identified vortices were marked by a low‐level upvalley jet, a clockwise wind direction turning with height, and a cessation of upvalley flow at the local ridgeline level. The routinely sampled coplanar‐retrieved cross‐valley wind field enabled the quantification of more advanced parameters based on vorticity, revealing a faster spin rate of the vortex around its streamwise axis given a stronger upvalley flow, and a period of revolution on the order of several tens of minutes. A detailed inspection of the lateral momentum budget and associated uncertainties confirmed the importance of the relationship between the centrifugal and the pressure gradient force for the cross‐valley vortex occurrence in a curved valley.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    RVK:
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
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  • 10
    Online Resource
    Online Resource
    Wiley ; 2021
    In:  Quarterly Journal of the Royal Meteorological Society Vol. 147, No. 737 ( 2021-04), p. 2173-2196
    In: Quarterly Journal of the Royal Meteorological Society, Wiley, Vol. 147, No. 737 ( 2021-04), p. 2173-2196
    Abstract: Diurnal cycles of turbulent sensible and latent heat fluxes are typically closely related to the diurnal cycles of solar irradiation under synoptically undisturbed and clear‐sky conditions. In mountainous terrain, large variations can occur in the topographic and surface properties, which modify the local radiation budget and thus turbulent energy fluxes and the surface energy balance. Another characteristic of mountainous terrain is local, thermally driven circulation systems, such as the slope‐ and valley‐wind system, which can equally affect turbulent exchange. Observations of near‐surface radiative and turbulent fluxes are presented from six eddy‐covariance stations in an approximately east–west‐oriented major Alpine valley for undisturbed and clear‐sky conditions. Median diurnal cycles over the whole year are compared at the six sites and related to local terrain characteristics and the thermally driven wind systems. At a scale that is smaller than grid cells in current operational global forecast models, heat, moisture, and momentum fluxes show a large spatial variability in the magnitudes and their diurnal cycles. Lowest heat fluxes are observed on the north‐facing sidewall, where solar irradiation and thus available energy are reduced compared with the valley floor and south‐facing sidewall. Differences in the land surface characteristics further affect the partitioning of the available energy into sensible and latent heat fluxes. The median sensible heat flux reaches its daily peak already before solar noon at several sites, which appears to be related to the transition from down‐valley to up‐valley winds. In contrast to flat and homogeneous terrain, horizontal heat fluxes and lateral momentum fluxes can reach magnitudes that are similar to the magnitudes of vertical heat fluxes and longitudinal momentum fluxes, respectively.
    Type of Medium: Online Resource
    ISSN: 0035-9009 , 1477-870X
    URL: Issue
    RVK:
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 3142-2
    detail.hit.zdb_id: 2089168-4
    SSG: 14
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