Level-crossing statistics of the horizontal wind speed in the planetary surface boundary layer

2001 ◽  
Vol 11 (3) ◽  
pp. 611-618 ◽  
Author(s):  
Paul J. Edwards ◽  
Robert B. Hurst
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Horizontal Wind ◽  
Surface Boundary ◽  
Planetary Surface ◽  
Level Crossing ◽  
Horizontal Wind Speed ◽  
Surface Boundary Layer

Prediction of Atmospheric Turbulence Characteristics for Surface Boundary Layer using Empirical Spectral Methods

2020 ◽  
Author(s):  
Yagya Dutta Dwivedi ◽  
Vasishta Bhargava Nukala ◽  
Satya Prasad Maddula ◽  
Kiran Nair
Keyword(s):  
Boundary Layer ◽  
Time Series ◽  
Surface Roughness ◽  
Wind Speed ◽  
Atmospheric Turbulence ◽  
Surface Boundary ◽  
Low Frequencies ◽  
Surface Boundary Layer ◽  
Power Spectral ◽  
Mean Wind Speed

Abstract Atmospheric turbulence is an unsteady phenomenon found in nature and plays significance role in predicting natural events and life prediction of structures. In this work, turbulence in surface boundary layer has been studied through empirical methods. Computer simulation of Von Karman, Kaimal methods were evaluated for different surface roughness and for low (1%), medium (10%) and high (50%) turbulence intensities. Instantaneous values of one minute time series for longitudinal turbulent wind at mean wind speed of 12 m/s using both spectra showed strong correlation in validation trends. Influence of integral length scales on turbulence kinetic energy production at different heights is illustrated. Time series for mean wind speed of 12 m/s with surface roughness value of 0.05 m have shown that variance for longitudinal, lateral and vertical velocity components were different and found to be anisotropic. Wind speed power spectral density from Davenport and Simiu profiles have also been calculated at surface roughness of 0.05 m and compared with k−1 and k−3 slopes for Kolmogorov k−5/3 law in inertial sub-range and k−7 in viscous dissipation range. At high frequencies, logarithmic slope of Kolmogorov −5/3rd law agreed well with Davenport, Harris, Simiu and Solari spectra than at low frequencies.

scholarly journals Comparison of Large Eddy Simulations of a convective boundary layer with wind LIDAR measurements

2012 ◽  
Vol 8 (1) ◽  
pp. 83-86 ◽  
Author(s):  
J. G. Pedersen ◽  
M. Kelly ◽  
S.-E. Gryning ◽  
R. Floors ◽  
E. Batchvarova ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Geostrophic Wind ◽  
Large Eddy Simulations ◽  
Horizontal Wind ◽  
Convective Boundary ◽  
Horizontal Wind Speed ◽  
Large Eddy ◽  
Lidar Measurements ◽  
Wind Lidar

Abstract. Vertical profiles of the horizontal wind speed and of the standard deviation of vertical wind speed from Large Eddy Simulations of a convective atmospheric boundary layer are compared to wind LIDAR measurements up to 1400 m. Fair agreement regarding both types of profiles is observed only when the simulated flow is driven by a both time- and height-dependent geostrophic wind and a time-dependent surface heat flux. This underlines the importance of mesoscale effects when the flow above the atmospheric surface layer is simulated with a computational fluid dynamics model.

scholarly journals Short-term variation in near-highway air pollutant gradients on a winter morning

2010 ◽  
Vol 10 (17) ◽  
pp. 8341-8352 ◽  
Author(s):  
J. L. Durant ◽  
C. A. Ash ◽  
E. C. Wood ◽  
S. C. Herndon ◽  
J. T. Jayne ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Temporal Variation ◽  
Traffic Flow ◽  
Organic Compounds ◽  
Temporal Variations ◽  
Surface Boundary ◽  
Short Term ◽  
Surface Boundary Layer ◽  
Near Highway

Abstract. Quantification of exposure to traffic-related air pollutants near highways is hampered by incomplete knowledge of the scales of temporal variation of pollutant gradients. The goal of this study was to characterize short-term temporal variation of vehicular pollutant gradients within 200–400 m of a major highway (>150 000 vehicles/d). Monitoring was done near Interstate 93 in Somerville (Massachusetts) from 06:00 to 11:00 on 16 January 2008 using a mobile monitoring platform equipped with instruments that measured ultrafine and fine particles (6–1000 nm, particle number concentration (PNC)); particle-phase (>30 nm) NO3−, SO42−, and organic compounds; volatile organic compounds (VOCs); and CO2, NO, NO2, and O3. We observed rapid changes in pollutant gradients due to variations in highway traffic flow rate, wind speed, and surface boundary layer height. Before sunrise and peak traffic flow rates, downwind concentrations of particles, CO2, NO, and NO2 were highest within 100–250 m of the highway. After sunrise pollutant levels declined sharply (e.g., PNC and NO were more than halved) and the gradients became less pronounced as wind speed increased and the surface boundary layer rose allowing mixing with cleaner air aloft. The levels of aromatic VOCs and NO3−, SO42− and organic aerosols were generally low throughout the morning, and their spatial and temporal variations were less pronounced compared to PNC and NO. O3 levels increased throughout the morning due to mixing with O3-enriched air aloft and were generally lowest near the highway reflecting reaction with NO. There was little if any evolution in the size distribution of 6–225 nm particles with distance from the highway. These results suggest that to improve the accuracy of exposure estimates to near-highway pollutants, short-term (e.g., hourly) temporal variations in pollutant gradients must be measured to reflect changes in traffic patterns and local meteorology.

scholarly journals The dynamics of surface boundary layer during total Solar eclipse 1995

MAUSAM ◽  
2021 ◽  
Vol 49 (4) ◽  
pp. 475-480
Author(s):  
S. ARULRAJ ◽  
T. DHARMARAJ ◽  
S. B. DEBAJE ◽  
A. BAGAVATH SINGH ◽  
K. G. VERNEKAR
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Soil Temperature ◽  
Solar Eclipse ◽  
Total Solar Eclipse ◽  
Surface Boundary ◽  
Data Logger ◽  
Surface Boundary Layer ◽  
Set Up ◽  
Period Decrease

A microclimatological tower of 1.6 m height with six instrumented booms at different heights carrying wind speed, temperature and humidity sensors was set up at Robertsgun 24° 42'N, 83°4'E, 3l2m amsl) to study the implication of the total Solar eclipse on the dynamics of Atmospheric Boundary Layer (ABL). Apart from this, the soil temperature and heat flux were also measured during the same time. The observations were taken with a one minute average interval and recorded continuously with the data logger and then transferred to a PC for later use. The data were collected during 2l –26 October 1995. During the eclipse period decrease of surface temperature and soil temperature by 6.2°C and 3.5°C respectively and increase of humidity by nearly 60% were observed. Due to the decrease in velocity fluctuations, the mean wind speed showed the sharp increase compared to other days. The setting of stable atmosphere before the total solar eclipse was observed.

scholarly journals Dust aerosol radiative effect and influence on urban atmospheric boundary layer

2007 ◽  
Vol 7 (6) ◽  
pp. 15565-15580 ◽  
Author(s):  
L. Zhang ◽  
M. Chen ◽  
L. Li
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Atmospheric Boundary Layer ◽  
Dust Aerosol ◽  
Horizontal Wind ◽  
Transfer Model ◽  
Radiative Effect ◽  
Horizontal Wind Speed ◽  
The Mean ◽  
Aerosol Radiative

Abstract. An 1.5-level-closure and 3-D non-stationary atmospheric boundary layer (ABL) model and a radiation transfer model with the output of Weather Research and Forecast (WRF) Model and lidar AML-1 are employed to simulate the dust aerosol radiative effect and its influence on ABL in Beijing for the period of 23–26 January 2002 when a dust storm occurred. The simulation shows that daytime dust aerosol radiative effect heats up the ABL at the mean rate of about 0.68 K/h. The horizontal wind speed from ground to 900 m layer is also overall increased, and the value changes about 0.01 m/s at 14:00 LT near the ground. At night, the dust aerosol radiative effect cools the ABL at the mean rate of −0.21 K/h and the wind speed lowers down at about −0.19 m/s at 02:00 LT near the ground.

scholarly journals Tornado Vortex Structure, Intensity, and Surface Wind Gusts in Large-Eddy Simulations with Fully Developed Turbulence

2017 ◽  
Vol 74 (5) ◽  
pp. 1573-1597 ◽  
Author(s):  
David S. Nolan ◽  
Nathan A. Dahl ◽  
George H. Bryan ◽  
Richard Rotunno
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Vortex Structure ◽  
Surface Wind ◽  
Horizontal Wind ◽  
Injection Technique ◽  
Surface Boundary ◽  
Wind Gusts ◽  
Maximum Time ◽  
Large Eddy

Abstract A large-eddy simulation (LES) framework with an “eddy injection” technique has been developed that ensures a majority of turbulent kinetic energy in numerically simulated tornado-like vortices is represented by resolved eddies. This framework is used to explore the relationships between environmental forcing mechanisms, surface boundary conditions, and tornado vortex structure, intensity, and wind gusts. Similar to previous LES studies, results show that the maximum time- and azimuthal-mean tangential winds {V}max can be well in excess of the “thermodynamic speed limit,” which is 66 m s−1 for most of the simulations. Specifically, {V}max exceeds this speed by values ranging from 21% for a large, high-swirl vortex to 59% for a small, low-swirl vortex. Budgets of mean and eddy angular and radial momentum are used to show that resolved eddies in the tornado core act to reduce the wind speed at the location of {V}max, although they do transport angular momentum downward into the lowest levels of the boundary layer, increasing low-level swirl. Three measures of tornado intensity are introduced: maximum time–azimuthal-mean surface (10 m) horizontal wind speed ({S10}max), maximum 3-s gusts of S10 (S10-3s), and maximum vertical 3-s gusts at 10 m (W10-3s). While {S10}max is considerably less than {V}max, transient features in the boundary layer can generate S10-3s in excess of 150 m s−1, and W10-3s in excess of 100 m s−1. For high-swirl vortices, the extreme gusts are confined closer to the center, well inside the radius of maximum azimuthal-mean surface winds. For the low-swirl vortex, both the strongest mean winds and the extreme gusts are restricted to a very narrow core.

scholarly journals Short-term variation in near-highway air pollutant gradients on a winter morning

2010 ◽  
Vol 10 (2) ◽  
pp. 5599-5626 ◽  
Author(s):  
J. L. Durant ◽  
C. A. Ash ◽  
E. C. Wood ◽  
S. C. Herndon ◽  
J. T. Jayne ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Temporal Variation ◽  
Traffic Flow ◽  
Organic Compounds ◽  
Temporal Variations ◽  
Surface Boundary ◽  
Short Term ◽  
Surface Boundary Layer ◽  
Near Highway

Abstract. Quantification of exposure to traffic-related air pollutants near highways is hampered by incomplete knowledge of the scales of temporal variation of pollutant gradients. The goal of this study was to characterize short-term temporal variation of vehicular pollutant gradients within 200–400 m of a major highway (>150 000 vehicles/d). Monitoring was done near Interstate 93 in Somerville (Massachusetts) from 06:00 to 11:00 on 16 January 2008 using a mobile monitoring platform equipped with instruments that measured ultrafine and fine particles (6–1000 nm, particle number concentration (PNC)); particle-phase (>30 nm) NO3−, SO42−, and organic compounds; volatile organic compounds (VOCs); and CO2, NO, NO2, and O3. We observed rapid changes in pollutant gradients due to variations in highway traffic flow rate, wind speed, and surface boundary layer height. Before sunrise and peak traffic flow rates, downwind concentrations of particles, CO2, NO, and NO2 were highest within 100-250 m of the highway. After sunrise pollutant levels declined sharply (e.g., PNC and NO were more than halved) and the gradients became less pronounced as wind speed increased and the surface boundary layer rose allowing mixing with cleaner air aloft. The levels of aromatic VOCs and NO3−, SO42− and organic aerosols were generally low throughout the morning, and their spatial and temporal variations were less pronounced compared to PNC and NO. O3 levels increased throughout the morning due to mixing with O3-enriched air aloft and were generally lowest near the highway reflecting reaction with NO. There was little if any evolution in the size distribution of 6–225 nm particles with distance from the highway. These results suggest that to improve the accuracy of exposure estimates to near-highway pollutants, short-term (e.g., hourly) temporal variations in pollutant gradients must be measured to reflect changes in traffic patterns and local meteorology.

scholarly journals Distribution of horizontal wind components in the Surface Boundary Layer (SBL) over Sriharikota

MAUSAM ◽  
2021 ◽  
Vol 57 (2) ◽  
pp. 301-306
Author(s):  
K. V. S. NAMBOODIRI ◽  
G. V. RAMA ◽  
K. MOHAN KUMAR
Keyword(s):  
Boundary Layer ◽  
Horizontal Wind ◽  
Surface Boundary ◽  
Surface Boundary Layer

Reduction of horizontal wind speed in a boundary layer with obstacles

1993 ◽  
Vol 64 (3) ◽  
pp. 297-305 ◽  
Author(s):  
Stefan Emeis ◽  
Sten Frandsen
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Horizontal Wind ◽  
Horizontal Wind Speed
Sign in / Sign up

Export Citation Format

Share Document