Graphical Determination of the Geostrophic Wind Over a Point or Small Area

1952 ◽  
Vol 33 (8) ◽  
pp. 326-328
Author(s):  
John E. Hovde ◽  
Carl M. Reber
Keyword(s):  
Pressure Gradient ◽  
Sea Level ◽  
Total Pressure ◽  
Small Area ◽  
Geostrophic Wind ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Sea Level Pressure ◽  
Level Pressure

Assuming straight, parallel, and equally-spaced contour heights or isobars over a small area, the total pressure-gradient force (and the geostrophic wind) may be determined graphically using the contour-height or sea-level pressure differences between 3 stations around the area. The method is objective and eliminates personal discrepancies in scaling geostrophic wind from pressure or contour-height analyses.

scholarly journals Decadal variability and trends of the Benguela Upwelling System as simulated in a high-resolution ocean simulation

2015 ◽  
Vol 12 (2) ◽  
pp. 403-447
Author(s):  
N. Tim ◽  
E. Zorita ◽  
B. Hünicke
Keyword(s):  
Statistical Analysis ◽  
Pressure Gradient ◽  
Sea Level ◽  
Wind Stress ◽  
Large Scale ◽  
Sea Level Pressure ◽  
Subtropical Anticyclone ◽  
Level Pressure ◽  
Benguela Upwelling ◽  
Atmospheric Variables

Abstract. Detecting the atmospheric drivers of the Benguela Upwelling Systems is essential to understand its present variability and its past and future changes. We present a statistical analysis of an ocean-only simulation driven by observed atmospheric fields over the last decades with the aim of identifying the large-scale atmospheric drivers of upwelling variability and trends. The simulation is found to reproduce well the seasonal cycle of upwelling intensity, with a maximum in the June-to-August season in North Benguela and in the December-to-February season in South Benguela. The statistical analysis of the interannual variability of upwelling focuses on its relationship to atmospheric variables (sea level pressure, 10 m-wind, wind stress). The relationship between upwelling and the atmospheric variables differ somewhat in the two regions, but generally, the correlation patterns reflect the common atmospheric pattern favoring upwelling: southerly wind/wind stress, strong subtropical anticyclone, and an ocean-land sea level pressure gradient. In addition, the statistical link between upwelling and large-scale climate variability modes was analyzed. The El Niño Southern Oscillation and the Antarctic Oscillation exert some influence on austral summer upwelling velocities in South Benguela. The decadal evolution and the long-term trends of upwelling and of ocean-minus-land air pressure gradient do not agree with Bakun's hypothesis that anthropogenic climate change should generally intensify coastal upwelling.

On the Determination of 500 mb Height Tendencies

1957 ◽  
Vol 38 (4) ◽  
pp. 221-225
Author(s):  
Lawrence A. Hughes
Keyword(s):  
Sea Level ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Upper Level

The methods for computing “instantaneous” upper-level pressure or height tendencies are revised to allow computation of the 500 mb height tendency using the observed surface (or sea-level) pressure tendency and an appropriate portion of the 1000–500 mb thickness advection. An evaluation is made as to what constitutes an appropriate portion of the thickness advection. Use of the method is discussed and an example is given.

scholarly journals A Cloud-Resolving Simulation Study on the Merging Processes and Effects of Topography and Environmental Winds

2012 ◽  
Vol 69 (4) ◽  
pp. 1232-1249 ◽  
Author(s):  
Danhong Fu ◽  
Xueliang Guo
Keyword(s):  
Water Vapor ◽  
Pressure Gradient ◽  
Large Scale ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Low Level ◽  
Level Pressure ◽  
Merging Process ◽  
Upper Level ◽  
Water Vapor Convergence

Abstract The cloud-resolving fifth-generation Pennsylvania State University–National Center for Atmospheric Research Mesoscale Model (MM5) was used to study the cloud interactions and merging processes in the real case that generated a mesoscale convective system (MCS) on 23 August 2001 in the Beijing region. The merging processes can be grouped into three classes for the studied case: isolated nonprecipitating and precipitating cell merging, cloud cluster merging, and echo core or updraft core merging within cloud systems. The mechanisms responsible for the multiscale merging processes were investigated. The merging process between nonprecipitating cells and precipitating cells and that between clusters is initiated by forming an upper-level cloud bridge between two adjacent clouds due to upper-level radial outflows in one vigorous cloud. The cloud bridge is further enhanced by a favorable middle- and upper-level pressure gradient force directed from one cloud to its adjacent cloud by accelerating cloud particles being horizontally transported from the cloud to its adjacent cloud and induce the redistribution of condensational heating, which destabilizes the air at and below the cloud bridge and forms a favorable low-level pressure structure for low-level water vapor convergence and merging process. The merging of echo cores within the mesoscale cloud happens because of the interactions between low-level cold outflows associated with the downdrafts formed by these cores. Further sensitivity studies on the effects of topography and large-scale environmental winds suggest that the favorable pressure gradient force from one cloud to its adjacent cloud and stronger low-level water vapor convergence produced by the topographic lifting of large-scale low-level airflow determine further cloud merging processes over the mountain region.

scholarly journals Decadal variability and trends of the Benguela upwelling system as simulated in a high-resolution ocean simulation

Ocean Science ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 483-502 ◽  
Author(s):  
N. Tim ◽  
E. Zorita ◽  
B. Hünicke
Keyword(s):  
Statistical Analysis ◽  
High Resolution ◽  
Pressure Gradient ◽  
Sea Level ◽  
Wind Stress ◽  
Large Scale ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Benguela Upwelling ◽  
Atmospheric Variables

Abstract. Detecting the atmospheric drivers of the Benguela upwelling systems is essential to understand its present variability and its past and future changes. We present a statistical analysis of a high-resolution (0.1°) ocean-only simulation driven by observed atmospheric fields over the last 60 years with the aim of identifying the large-scale atmospheric drivers of upwelling variability and trends. The simulation is found to reproduce well the seasonal cycle of upwelling intensity, with a maximum in the June–August season in North Benguela and in the December–February season in South Benguela. The statistical analysis of the interannual variability of upwelling focuses on its relationship to atmospheric variables (sea level pressure, 10 m wind, wind stress). The relationship between upwelling and the atmospheric variables differ somewhat in the two regions, but generally the correlation patterns reflect the common atmospheric pattern favouring upwelling: southerly wind/wind stress, strong subtropical anticyclone, and an ocean–land sea level pressure gradient. In addition, the statistical link between upwelling and large-scale climate variability modes was analysed. The El Niño–Southern Oscillation and the Antarctic Oscillation exert some influence on austral summer upwelling velocities in South Benguela. The decadal evolution and the long-term trends of simulated upwelling and of ocean-minus-land air pressure gradient do not agree with Bakun's hypothesis that anthropogenic climate change should generally intensify coastal upwelling.

scholarly journals Climatological Mean Circulation at the New England Shelf Break

2011 ◽  
Vol 41 (10) ◽  
pp. 1874-1893 ◽  
Author(s):  
Weifeng G. Zhang ◽  
Glen G. Gawarkiewicz ◽  
Dennis J. McGillicuddy ◽  
John L. Wilkin
Keyword(s):  
Seasonal Variation ◽  
Pressure Gradient ◽  
New England ◽  
Sea Level ◽  
Shelf Break ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Upwelled Water ◽  
Shelf Sea ◽  
Mean Circulation

Abstract A two-dimensional cross-shelf model of the New England continental shelf and slope is used to investigate the mean cross-shelf and vertical circulation at the shelf break and their seasonal variation. The model temperature and salinity fields are nudged toward climatology. Annual and seasonal mean wind stresses are applied on the surface in separate equilibrium simulations. The along-shelf pressure gradient force associated with the along-shelf sea level tilt is tuned to match the modeled and observed depth-averaged along-shelf velocity. Steady-state model solutions show strong seasonal variation in along-shelf and cross-shelf velocity, with the strongest along-shelf jet and interior onshore flow in winter, consistent with observations. Along-shelf sea level tilt associated with the tuned along-shelf pressure gradient increases shoreward because of decreasing water depth. The along-shelf sea level tilt varies seasonally with the wind and is the strongest in winter and weakest in summer. A persistent upwelling is generated at the shelf break with a maximum strength of 2 m day−1 at 50-m depth in winter. The modeled shelfbreak upwelling differs from the traditional view in that most of the upwelled water is from the upper continental slope instead of from the shelf in the form of a detached bottom boundary layer.

An Objective Method for Forecasting Winds at an Inter-Mountain Station

1957 ◽  
Vol 38 (8) ◽  
pp. 470-474
Author(s):  
C. L. Simpson ◽  
J. M. Thorp
Keyword(s):  
Wind Speed ◽  
Pressure Gradient ◽  
Sea Level ◽  
Empirical Method ◽  
Objective Method ◽  
Surface Winds ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Mountain Station ◽  
Conventional Methods

An empirical method for forecasting surface winds at an inter-mountain station, based on the differences in sea-level pressure between Hanford and five other stations, is developed. Nomograms relating the ten-hour velocity trend to the pressure gradient are presented. The method is discussed in relation to conventional methods of wind forecasting as pertaining to apparent counter-gradient winds, cyclic features of the surface winds, and variations in wind speed.

2. Note on the Determination of Heights, chiefly in the Interior of Continents, from Observations of Atmospheric Pressure

1869 ◽  
Vol 6 ◽  
pp. 465-472
Author(s):  
Alexander Buchan
Keyword(s):  
Sea Level ◽  
Atmospheric Pressure ◽  
Boiling Point ◽  
Great Distance ◽  
Close Approximation ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Meteorological Observations

The weight or pressure of the atmosphere is ascertained by the mercurial barometer, the aneroid, or from the temperature of the boiling point of water. The height of a hill is measured barometrically, from observations made simultaneously at its base and top, and the application of certain well-known formulæ. The height of a place at no great distance from another place whose height is known, and at which observations are made about the same time, may similarly be ascertained with a close approximation to the truth.But, with regard to places far from any place of known elevation, or from any place at which meteorological observations are made, it is plain that the height can only be computed by assuming a certain pressure as the sea-level pressure at that place.

scholarly journals Research Aircraft Determination of D-Value Cross Sections

2016 ◽  
Vol 33 (2) ◽  
pp. 391-396 ◽  
Author(s):  
Thomas R. Parish ◽  
David A. Rahn ◽  
Dave Leon
Keyword(s):  
Pressure Gradient ◽  
Cross Sections ◽  
Vertical Structure ◽  
Gradient Force ◽  
Pressure Gradient Force ◽  
Horizontal Pressure Gradient ◽  
Airborne Measurements ◽  
Horizontal Pressure ◽  
D Values

AbstractUse of an airborne platform to determine the dynamics of atmospheric motion has been ongoing for over three decades. Much of the effort has been centered on the determination of the horizontal pressure gradient force along an isobaric surface, and with wind measurements the nongeostrophic components of motion can be obtained. Recent advances using differential GPS-based altitude measurements allow accurate assessment of the geostrophic wind. Porpoise or sawtooth maneuvers are used to determine the vertical cross section of the horizontal pressure gradient force. D-values, the difference of the height of a given pressure level from that in a reference atmosphere, are used to isolate the vertical structure of the horizontal component of the pressure gradient force from the vastly larger hydrostatic pressure gradient. Comparison of measured D-value cross sections with airborne measurements of the horizontal pressure gradient is shown. Comparison of D-values with output from the WRF Model demonstrates that the airborne measurements are consistent with finescale numerical simulations. This technique provides a means of inferring the thermal wind, thereby enabling a detailed examination of the vertical structure of the forcing of mesoscale and synoptic-scale wind regimes.

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