Horizontal pressure gradient and Soret effects on the onset of thermosolutal porous convection

Heat Transfer ◽  
2021 ◽  
Author(s):  
C. Hemanthkumar ◽  
I. S. Shivakumara ◽  
B. M. Shankar ◽  
G. Pallavi
Keyword(s):  
Pressure Gradient ◽  
Horizontal Pressure Gradient ◽  
Horizontal Pressure ◽  
Porous Convection

The Relationships among Wind, Horizontal Pressure Gradient, and Turbulent Momentum Transport during CASES-99

2013 ◽  
Vol 70 (11) ◽  
pp. 3397-3414 ◽  
Author(s):  
Jielun Sun ◽  
Donald H. Lenschow ◽  
Larry Mahrt ◽  
Carmen Nappo
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Pressure Gradient ◽  
Coriolis Force ◽  
Wind Direction ◽  
Momentum Flux ◽  
Momentum Transport ◽  
Horizontal Pressure Gradient ◽  
Horizontal Pressure ◽  
Turbulent Momentum

Abstract Relationships among the horizontal pressure gradient, the Coriolis force, and the vertical momentum transport by turbulent fluxes are investigated using data collected from the 1999 Cooperative Atmosphere–Surface Exchange Study (CASES-99). Wind toward higher pressure (WTHP) adjacent to the ground occurred about 50% of the time. For wind speed at 5 m above the ground stronger than 5 m s−1, WTHP occurred about 20% of the time. Focusing on these moderate to strong wind cases only, relationships among horizontal pressure gradients, Coriolis force, and vertical turbulent transport in the momentum balance are investigated. The magnitude of the downward turbulent momentum flux consistently increases with height under moderate to strong winds, which results in the vertical convergence of the momentum flux and thus provides a momentum source and allows WTHP. In the along-wind direction, the horizontal pressure gradient is observed to be well correlated with the quadratic wind speed, which is demonstrated to be an approximate balance between the horizontal pressure gradient and the vertical convergence of the turbulent momentum flux. That is, antitriptic balance occurs in the along-wind direction when the wind is toward higher pressure. In the crosswind direction, the pressure gradient varies approximately linearly with wind speed and opposes the Coriolis force, suggesting the importance of the Coriolis force and approximate geotriptic balance of the airflow. A simple one-dimensional planetary boundary layer eddy diffusivity model demonstrates the possibility of wind directed toward higher pressure for a baroclinic boundary layer and the contribution of the vertical turbulent momentum flux to this phenomenon.

scholarly journals Aircraft Measurements and Numerical Simulations of an Expansion Fan off the California Coast

2016 ◽  
Vol 55 (9) ◽  
pp. 2053-2062 ◽  
Author(s):  
Thomas R. Parish ◽  
David A. Rahn ◽  
David C. Leon
Keyword(s):  
Pressure Gradient ◽  
Cross Sections ◽  
The United States ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Differential Gps ◽  
Horizontal Pressure Gradient ◽  
Point Conception ◽  
Expansion Fan ◽  
Horizontal Pressure

AbstractMountains along the California coastline play a critical role in the dynamics of marine atmospheric boundary layer (MBL) airflow in the vicinity of the shoreline. Large changes in the MBL topology have been known to occur downwind of points and capes along the western coast of the United States. Large spatial gradients in wind and temperature become established that can cause anomalous electromagnetic wave propagation. Detailed airborne measurements using the University of Wyoming King Air were conducted to study the adjustment of the MBL to the Point Arguello and Point Conception headlands. Pronounced thinning of the MBL consistent with an expansion fan occurred to the south of Point Conception on 13 June 2012. A sharp cloud edge was collocated with the near collapse of the MBL. D-value cross sections derived from differential GPS altitude measurements allow assessment of the vertical profile of the horizontal pressure gradient force and hence thermal wind forcing in response to the near collapse of the MBL. The Weather Research and Forecasting Model was run with a 1-km grid spacing to examine the atmospheric adjustment around Point Conception during this period. Results from the simulations including the vertical cross sections of the horizontal pressure gradient force were consistent with the aircraft observations. Model results suggest that divergence occurs as the flow rounds Point Conception, characteristic of an expansion fan. Wind speeds in the MBL increase coincident with the decrease in MBL thickness, and subsiding flow associated with the near collapse of the MBL is responsible for the sharp cloud edge.

scholarly journals Statistical Relationship between Atmospheric Rivers and Extratropical Cyclones and Anticyclones

2020 ◽  
Vol 33 (18) ◽  
pp. 7817-7834 ◽  
Author(s):  
Yanjuan Guo ◽  
Toshiaki Shinoda ◽  
Bin Guan ◽  
Duane E. Waliser ◽  
Edmund K. M. Chang
Keyword(s):  
Pressure Gradient ◽  
Global Scale ◽  
Extratropical Cyclones ◽  
Close Link ◽  
Atmospheric Rivers ◽  
Horizontal Pressure Gradient ◽  
Subtropical Highs ◽  
Horizontal Pressure ◽  
Key Features ◽  
Statistical Relationships

AbstractStatistical relationships between atmospheric rivers (ARs) and extratropical cyclones and anticyclones are investigated on a global scale using objectively identified ARs, cyclones, and anticyclones during 1979–2014. Composites of circulation and moisture fields around the ARs show that a strong cyclone is located poleward and westward of the AR centroid, which confirms the close link between the AR and extratropical cyclone. In addition, a pronounced anticyclone is found to be located equatorward and eastward of the AR, whose presence together with the cyclone leads to strong horizontal pressure gradient that forces moisture to be transported along a narrow corridor within the warm sector of the cyclone. This anticyclone located toward the downstream equatorward side of the cyclone is found to be missing for cyclones not associated with ARs. These key features are robust in composites performed in different hemispheres, over different ocean basins, and with respect to different AR intensities. Furthermore, correlation analysis shows that the AR intensity is much better correlated with the pressure gradient between the cyclone and anticyclone than with the cyclone/anticyclone intensity alone, although stronger cyclones favor the occurrence of AR. The importance of the horizontal pressure gradient in the formation of the AR is also consistent with the fact that climatologically ARs are frequently found over the region between the polar lows and subtropical highs in all seasons.

Pressure Perturbations and Upslope Flow over a Heated, Isolated Mountain

2008 ◽  
Vol 136 (11) ◽  
pp. 4272-4288 ◽  
Author(s):  
Bart Geerts ◽  
Qun Miao ◽  
J. Cory Demko
Keyword(s):  
Pressure Gradient ◽  
Diurnal Variation ◽  
Monsoon Season ◽  
Potential Temperature ◽  
Surface Flow ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Thermal Forcing ◽  
Horizontal Pressure Gradient ◽  
Horizontal Pressure

Abstract Surface and upper-air data, collected as part of the Cumulus Photogrammetric, In Situ, and Doppler Observations (CuPIDO) experiment during the 2006 monsoon season around the Santa Catalina Mountains in southeast Arizona, are used to study the diurnal variation of the mountain-scale surface convergence and its thermal forcing. The thermal forcing is examined in terms of a horizontal pressure gradient force, which is derived assuming hydrostatic balance. The mountain is ∼30 km in diameter, ∼2 km high, and relatively isolated. The environment is characterized by weak winds, a deep convective boundary layer in the afternoon, and sufficient low-level moisture for orographic cumulus convection on most days. The katabatic, divergent surface flow at night and anabatic, convergent flow during the day are in phase with the diurnal variation of the horizontal pressure gradient force, which points toward the mountain during the day and away from the mountain at night. The daytime pressure deficit over the mountain of 0.5–1.0 mb is hydrostatically consistent with the observed 1–2-K virtual potential temperature excess over the mountain. The interplay between surface convergence and orographic thunderstorms is examined, and the consequence of deep convection (outflow spreading) is more apparent than its possible trigger (enhanced convergence).

scholarly journals THE INFLUENCE OF DUNE AND FLOW PARAMETERS ON THE FRICTION FACTOR

1978 ◽  
Vol 1 (16) ◽  
pp. 108
Author(s):  
J. Sundermann ◽  
H. Vollmers ◽  
W. Puls
Keyword(s):  
Numerical Model ◽  
Pressure Gradient ◽  
Friction Factor ◽  
Experimental Results ◽  
Special Importance ◽  
Physical Reason ◽  
Horizontal Pressure Gradient ◽  
Flow Parameters ◽  
Horizontal Pressure

Taking for example the flow over a ripple, some results of a hydrodynamic numerical model are presented and compared with experimental results. Special importance is attached to the pressure. On the basis of the used equations the physical reason for the horizontal pressure gradient is investigated. The influence of some dune and flow parameters on the friction is examined.

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