Ground-Level Turbulence Characteristics of Hurricane Wind Measured from Mobile Towers

2013 ◽  
Author(s):  
Sungmoon Jung ◽  
Forrest J. Masters
Keyword(s):  
Ground Level ◽  
Turbulence Characteristics ◽  
Hurricane Wind

scholarly journals Mean flow and turbulence characteristics of a nocturnal downburst recorded on a 213 m tall meteorological tower

2021 ◽  
Author(s):  
Djordje Romanic
Keyword(s):  
Surface Roughness ◽  
Wind Direction ◽  
Friction Velocity ◽  
Similarity Theory ◽  
Ground Level ◽  
Velocity Profiles ◽  
Secondary Vortex ◽  
Mean Flow ◽  
Measured Velocity ◽  
Turbulence Characteristics

AbstractThis study presents rare measurements and analysis of a nocturnal thunderstorm downburst on the 213 m tall Cabauw tower in The Netherlands. The event occurred on 12 March 2008 between 02:00 and 03:00 UTC and was measured using four ultrasonic 10-Hz anemometers positioned at 3, 60, 100, and 180 m above ground level. 1-second gusts in the outflow exceeded 30 m s−1 at 60 m and above. This wind event was accompanied by an abrupt change of wind direction from southwest to west. While the shift in wind direction corresponded with the change of upwind surface roughness, the time series of turbulence intensity and other turbulence characteristics were not affected. The statistical properties of this event were compared against the largest European database of thunderstorm winds measured in the Mediterranean. The study also demonstrated that primary and secondary vortex structures—secondary vortex being rarely observed in actual downbursts—developed at the forward edge of the cold outflow. The estimated diameter of the downdraft was 1200 m at 70 m above ground. The measured velocity profiles and friction velocity were compared against theoretical predictions of the Monin-Obukhov Similarity Theory (MOST). MOST without stratification adjustment overestimated measured friction velocity twofold. Alternative values for surface roughness during the outflow were derived based on the measured friction velocity and MOST-based fit of measured velocity profiles. Ceilometer and radar measurements were supplementary data in this analysis.

Effects of Vibration on the Preparation of Ultrathin Sections

1973 ◽  
Vol 31 ◽  
pp. 358-359
Author(s):  
Joseph M. Blum ◽  
Edward P. Gargiulo ◽  
J. R. Sawers
Keyword(s):  
Cutting Speed ◽  
Ground Level ◽  
Environmental Vibration ◽  
Block Face ◽  
Ultrathin Sections ◽  
Embedding Medium ◽  
Thickness Variations ◽  
Building Walls ◽  
Cutting Direction ◽  
Diamond Knife

It is now well-known that chatter (Figure 1) is caused by vibration between the microtome arm and the diamond knife. It is usually observed as a cyclical variation in “optical” density of an electron micrograph due to sample thickness variations perpendicular to the cutting direction. This vibration might be induced by using too large a block face, too large a clearance angle, excessive cutting speed, non-uniform embedding medium or microtome vibration. Another prominent cause is environmental vibration caused by inadequate building construction. Microtomes should be installed on firm, solid floors. The best floors are thick, ground-level concrete pads poured over a sand bed and isolated from the building walls. Even when these precautions are followed, we recommend an additional isolation pad placed on the top of a sturdy table.

A global perspective of ground level, 'ambient' carbon dioxide for assessing the response of plants to atmospheric CO2

2001 ◽  
Vol 7 (7) ◽  
pp. 789-796 ◽  
Author(s):  
L. H. Ziska ◽  
O. Ghannoum ◽  
J. T. Baker ◽  
J. Conroy ◽  
J. A. Bunce ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Ground Level ◽  
Global Perspective ◽  
Atmospheric Co2

The Sovereign States of Vietnam, 1945–1955

2016 ◽  
Vol 11 (3-4) ◽  
pp. 103-139 ◽  
Author(s):  
Brett Reilly
Keyword(s):  
Ground Level ◽  
Indochina War

This paper revisits the “bricolage” State of Vietnam and the fractured system of sovereignty that characterized its halting practice of sovereignty at the ground level during the First Indochina War. In addition, it examines how the French Union’s concept of shared external sovereignty became discredited by the end of the war.

Bones at ground level

2015 ◽  
Author(s):  
Elaine Walker
Keyword(s):  
Ground Level
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