Evidence of a threshold wind speed in tower-mounted scatterometer data

The practical geological indicators of palaeowind are several scalar properties (bed thickness, grain size and sorting, mineral proportions) and directional structures (dune forms, yardangs and wind furrows, dune cross-bedding, windblow n trees, wind ripples, adhesion ripples, flutes and grooves). These indicators ideally should be sampled so as to minimize geographical bias, and the data assessed so as to afford smoothed paths of sand and dust flow. Because most geological wind-related processes involve a threshold wind speed and proceed nonlinearly, inferred patterns of sand and dust flow may not exactly match patterns of the time-averaged wind direction. The use and potential of palaeowind indicators are well illustrated by w indblown trees (mid Flandrian, southwest Britain) and by dune cross-bedding (Palaeozoic-Mesozoic, U.S.A.).

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A METHOD FOR ESTIMATING THRESHOLD WIND SPEED OF DUST EMISSION USING THERMAL INERTIA OVER A NON-VEGETATED SURFACE

Journal of Japan Society of Civil Engineers Ser B1 (Hydraulic Engineering) ◽

10.2208/jscejhe.68.i_1789 ◽

2012 ◽

Vol 68 (4) ◽

pp. I_1789-I_1794

Author(s):

Dai MATSUSHIMA ◽

Reiji KIMURA ◽

Masato SHINODA

Keyword(s):

Wind Speed ◽

Dust Emission ◽

Thermal Inertia ◽

Threshold Wind Speed

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Estimating the maritime component of aerosol optical depth and its dependency on surface wind speed using MODIS and QuikSCAT data

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-10-1983-2010 ◽

2010 ◽

Vol 10 (1) ◽

pp. 1983-2003 ◽

Cited By ~ 5

Author(s):

Y. Lehahn ◽

I. Koren ◽

E. Boss ◽

Y. Ben-Ami ◽

O. Altaratz

Keyword(s):

Wind Speed ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Surface Wind ◽

World Ocean ◽

Surface Wind Speed ◽

Marine Aerosol ◽

Coarse Mode ◽

Wind Intensity ◽

Threshold Wind Speed

Abstract. Seven years (2002–2008) of satellite measurements from SeaWinds aboard Quick Scatterometer (QuikSCAT) and Moderate Resolution Imaging Spectroradiometer (MODIS) aboard Terra are used for providing a global view on the link between surface wind speed and marine aerosol optical depth. This study shows that away form the continents the correlation time between the surface winds and the marine aerosol exceeds 4 h and therefore the two measurements can be linked. A systematic comparison between the satellite derived fields at different locations over the World Ocean allows to: (i) separate the relative contribution of wind-induced marine aerosol to the aerosol optical depth (ii) identify a threshold wind speed for triggering maritime contribution to aerosol optical depth; and (iii) extract an empirical linear equation linking marine aerosol optical depth and wind intensity. Wind induced marine aerosol contribution to aerosol optical depth is found to be dominated by the coarse mode elements. The threshold wind speed for triggering emission of coarse maritime aerosol is remarkably consistent with an average value of 4.1±0.1 m/s. When wind intensity exceeds the threshold value, coarse mode marine aerosol optical depth is linearly correlated to the surface wind speed, with a consistent slope of 0.0082±0.0004 s/m. The background aerosol optical depth, associated with aerosols that are not produced in-situ through wind driven processes, shows relatively large seasonal and geographical variability, and can be used for estimating the contribution of terrestrial aerosols to the aerosol optical depth over the ocean.

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Characterizing the convective heat exchange with plastic shading nets under natural arid conditions

International Journal of Energy Technology ◽

10.32438//ijet.11415 ◽

2019 ◽

pp. 11-20

Author(s):

Ahmed M Abdel-Ghanya ◽

Ibrahim M Al-Helal

Keyword(s):

Wind Speed ◽

Thermal Radiation ◽

Convective Heat ◽

Convective Heat Transfer Coefficient ◽

Convective Heat Exchange ◽

Radiative Properties ◽

Wooden Frame ◽

Arid Conditions ◽

Air Temperatures ◽

Radiation Fluxes

Plastic nets are extensively used for shading purposes in arid regions such as in the Arabian Peninsula. Quantifying the convection exchange with shading net and understanding the mechanisms (free, mixed and forced) of convection are essential for analyzing energy exchange with shading nets. Unlike solar and thermal radiation, the convective energy, convective heat transfer coefficient and the nature of convection have never been theoretically estimated or experimentally measured for plastic nets under arid conditions. In this study, the convected heat exchanges with different plastic nets were quantified based on an energy balance applied to the nets under outdoor natural conditions. Therefore, each net was tacked onto a wooden frame, fixed horizontally at 1.5-m height over the floor. The downward and upward solar and thermal radiation fluxes were measured below and above each net on sunny days; also the wind speed over the net, and the net and air temperatures were measured, simultaneously. Nets with different porosities, colors and texture structures were used for the study. The short and long wave’s radiative properties of the nets were pre-determined in previous studies to be used. Re and Gr numbers were determined and used to characterize the convection mechanism over each net. The results showed that forced and mixed convection are the dominant modes existing over the nets during most of the day and night times. The nature of convection over nets depends mainly on the wind speed, net-air temperature difference and texture shape of the net rather than its color and its porosity.

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