scholarly journals Evaluation and Post-Processing of Reanalysis Wind Speeds for Renewable Energy Applications

2021 ◽  
Author(s):  
Sebastian Brune ◽  
Jan D. Keller ◽  
Sabrina Wahl
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Wind Turbine ◽  
Wind Field ◽  
Lower Boundary ◽  
Horizontal Resolution ◽  
Lower Atmosphere ◽  
Wind Fields ◽  
Wind Model ◽  
Lower Boundary Layer

<p>The correct spatio-temporal representation of wind speed is of large interest for the wind energy sector. Therefore, this study compares wind measurements in different heights from several locations in Central Europe with two global (ERA5, MERRA-2) and one regional reanalysis (COSMO-REA6). Employing a two-parameter Weibull distribution, the shape and scale parameters as well as mean, standard deviation and RMSE are investigated at and around common wind turbine hub height. We find that COSMO-REA6 best describes wind fields closer to the surface possibly due to its high horizontal resolution. Here, it also exhibits a good alignment with the diurnal cycle. However, for common wind turbine hub heights and above, ERA5 outperforms the other two reanalyses possibly due to its higher vertical resolution. MERRA-2 overestimates wind speed in the lower boundary layer at nearly all sites.</p><p>In the next step, a diagnostic and mass-consistent wind model is applied to the COSMO-REA6 wind field. The resolution of the wind field will be increased by a factor of 8 from originally 6 km to approximately 800 m. In addition to the vertical stability of the lower atmosphere, the orography on the finer grid and the corresponding effects are taken into account. We expect that especially in complex terrain the wind field will be corrected and thus should fit better to the observations. Channeling effects, shadowing and increased wind speed in exposed locations can be better represented. The new high-resolution wind field forms the basis for a statistical wind model to obtain post-processed wind estimates in the lower boundary layer. This approach will utilize generalized linear model and/or an artificial neural network techniques.</p>

scholarly journals Boundary layer structure and stability classification validated with CO<sub>2</sub> concentrations over the Northern Spanish Plateau

2009 ◽  
Vol 27 (1) ◽  
pp. 339-349 ◽  
Author(s):  
I. A. Pérez ◽  
M. L. Sánchez ◽  
M. Á. García ◽  
B. de Torre
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Layer Structure ◽  
Lower Boundary ◽  
Acoustic Sounding ◽  
Obukhov Length ◽  
Wind Speeds ◽  
Stability Classification ◽  
Sodar Measurements ◽  
Lower Boundary Layer

Abstract. A description of the lower boundary layer is vital to enhance our understanding of dispersion processes. In this paper, Radio Acoustic Sounding System sodar measurements obtained over three years were used to calculate the Brunt-Väisälä frequency and the Monin-Obukhov length. The Brunt-Väisälä frequency enabled investigation of the structure of this layer. At night, several layers were noticeable and the maximum was observed at the first level, 40 m, whereas during the day, it was present at about 320 m. The Monin-Obukhov length was calculated with the four first levels measured, 40–100 m, by an original iterative method and used to establish four stability classes: drainage, extremely stable, stable and unstable. Wind speed and temperature median profiles linked to these classes were also presented. Wind speeds were the lowest, but temperatures were the highest and inversions were intense at night in drainage situations. However, unstable situations were linked to high wind speeds and superadiabatic temperature profiles. Detrended CO2 concentrations were used to determine the goodness of the classification proposed evidencing values which under drainage at night in spring were nearly 28 ppm higher than those corresponding to unstable situations. Finally, atmosphere structure was presented for the proposed stability classes and related with wind speed profiles. Under extremely stable situations, low level jets were coupled to the surface, with median wind speeds below 8 m s−1 and cores occasionally at 120 m. However, jets were uncoupled in stable situations, wind speed medians were higher than 11 m s−1 and their core heights were around 200 m.

Wind speed measurements in upper and lower boundary layer to determine regional momentum fluxes

1999 ◽  
Vol 98-99 ◽  
pp. 145-158 ◽  
Author(s):  
Tetsuya Hiyama ◽  
Michiaki Sugita ◽  
Hans Bergström ◽  
Meelis Mölder
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Lower Boundary ◽  
Momentum Fluxes ◽  
Lower Boundary Layer

Simulation of the wind fields over complex terrain with coupling of CFD and WRF

2021 ◽  
pp. 1-12
Author(s):  
Xiaoyu Luo ◽  
Yiwen Cao
Keyword(s):  
Wind Speed ◽  
Wind Field ◽  
Complex Terrain ◽  
Civil Engineering ◽  
Meteorological Data ◽  
Mass Conservation ◽  
Coupling Method ◽  
Wind Fields ◽  
Civil Structures ◽  
Civil Engineers

In the field of civil engineering, the meteorological data available usually do not have the detailed information of the wind near a certain site. However, the detailed information of the wind field during typhoon is important for the wind-resistant design of civil structures. Furthermore, the resolution of the meteorological data available by the civil engineers is too coarse to be applicable. Therefore it is meaningful to obtain the detailed information of the wind fields based on the meteorological data provided by the meteorological department. Therefore, in the present study, a one-way coupling method between WRF and CFD is adopted and a method to keep the mass conservation during the simulation in CFD is proposed. It is found that using the proposed one-way coupling method, the predicted wind speed is closer to the measurement. And the curvature of the wind streamline during typhoon is successfully reproduced.

Hydrodynamics and behaviour of Simuliidae larvae (Diptera)

1986 ◽  
Vol 64 (6) ◽  
pp. 1295-1309 ◽  
Author(s):  
M. M. Chance ◽  
D. A. Craig
Keyword(s):  
Boundary Layer ◽  
Lower Boundary ◽  
The Body ◽  
The Other ◽  
Avoidance Reaction ◽  
Larval Body ◽  
Video Recordings ◽  
Von Karman ◽  
Von Kármán ◽  
Lower Boundary Layer

Detailed water flow around larvae of Simulium vittatum Zett. (sibling IS-7) was investigated using flow tanks, aluminium flakes, pigment, still photography, cinematography, and video recordings. Angle of deflection of a larva from the vertical has a hyperbolic relationship to water velocity. Velocity profiles around larvae show that the body is in the boundary layer. Frontal area of the body decreases as velocity increases. Disturbed larvae exhibit "avoidance reaction" and pull the body into the lower boundary layer. Longitudinal twisting and yawing of the larval body places one labral fan closer to the substrate, the other near the top of the boundary layer. Models and live larvae were used to demonstrate the basic hydrodynamic phenomenon of downstream paired vortices. Body shape and feeding stance result in one of the vortices remaining in the lower boundary layer. The other rises up the downstream side of the body, passes through the lower fan, then forms a von Karman trail of detaching vortices. This vortex entrains particulate matter from the substrate, which larvae then filter. Discharge of water into this upper vortex remains constant at various velocities and only water between the substrate and top of the posterior abdomen is incorporated into it. The upper fan filters water only from the top of the boundary layer. Formation of vortices probably influences larval microdistribution and filter feeding. Larvae positioned side by side across the flow mutually influence flow between them, thus enhancing feeding. Larvae downstream of one another may use information from the von Karman trail of vortices to position themselves advantageously.

scholarly journals Evaluation of simulated aerosol properties with the aerosol-climate model ECHAM5-HAM using observations from the IMPACT field campaign

2010 ◽  
Vol 10 (16) ◽  
pp. 7709-7722 ◽  
Author(s):  
G.-J. Roelofs ◽  
H. ten Brink ◽  
A. Kiendler-Scharr ◽  
G. de Leeuw ◽  
A. Mensah ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Climate Model ◽  
Lower Boundary ◽  
Synoptic Scale ◽  
Concentration Gradients ◽  
Cloud Properties ◽  
Dry Conditions ◽  
Strong Exchange ◽  
The Impact ◽  
Lower Boundary Layer

Abstract. In May 2008, the measurement campaign IMPACT for observation of atmospheric aerosol and cloud properties was conducted in Cabauw, The Netherlands. With a nudged version of the coupled aerosol-climate model ECHAM5-HAM we simulate the size distribution and chemical composition of the aerosol and the associated aerosol optical thickness (AOT) for the campaign period. Synoptic scale meteorology is represented realistically through nudging of the vorticity, the divergence, the temperature and the surface pressure. Simulated concentrations of aerosol sulfate and organics at the surface are generally within a factor of two from observed values. The monthly averaged AOT from the model is 0.33, about 20% larger than observed. For selected periods of the month with relatively dry and moist conditions discrepancies are approximately −30% and +15%, respectively. Discrepancies during the dry period are partly caused by inaccurate representation of boundary layer (BL) dynamics by the model affecting the simulated AOT. The model simulates too strong exchange between the BL and the free troposphere, resulting in weaker concentration gradients at the BL top than observed for aerosol and humidity, while upward mixing from the surface layers into the BL appears to be underestimated. The results indicate that beside aerosol sulfate and organics also aerosol ammonium and nitrate significantly contribute to aerosol water uptake. The simulated day-to-day variability of AOT follows synoptic scale advection of humidity rather than particle concentration. Even for relatively dry conditions AOT appears to be strongly influenced by the diurnal cycle of RH in the lower boundary layer, further enhanced by uptake and release of nitric acid and ammonia by aerosol water.

scholarly journals Wind Turbine Wake Modeling in Accelerating Wind Field: A Preliminary Study on a Two-Dimensional Hill

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 153 ◽  
Author(s):  
Omar M. A. M. Ibrahim ◽  
Shigeo Yoshida ◽  
Masahiro Hamasaki ◽  
Ao Takada
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Field ◽  
Complex Terrain ◽  
Wind Farm ◽  
Wind Tunnel Test ◽  
Two Dimensional ◽  
Preliminary Study ◽  
Wake Model

Complex terrain can influence wind turbine wakes and wind speed profiles in a wind farm. Consequently, predicting the performance of wind turbines and energy production over complex terrain is more difficult than it is over flat terrain. In this preliminary study, an engineering wake model, that considers acceleration on a two-dimensional hill, was developed based on the momentum theory. The model consists of the wake width and wake wind speed. The equation to calculate the rotor thrust, which is calculated by the wake wind speed profiles, was also formulated. Then, a wind-tunnel test was performed in simple flow conditions in order to investigate wake development over a two-dimensional hill. After this the wake model was compared with the wind-tunnel test, and the results obtained by using the new wake model were close to the wind-tunnel test results. Using the new wake model, it was possible to estimate the wake shrinkage in an accelerating two-dimensional wind field.

scholarly journals Resolution Dependence of Turbulent Structures in Convective Boundary Layer Simulations

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 986 ◽  
Author(s):  
Mary-Jane M. Bopape ◽  
Robert S. Plant ◽  
Omduth Coceal
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Convective Boundary Layer ◽  
Inversion Layer ◽  
Lower Boundary ◽  
Quadrant Analysis ◽  
Turbulent Structures ◽  
Convective Boundary ◽  
Large Eddy ◽  
Lower Boundary Layer

Large-eddy simulations are performed using the U.K. Met Office Large Eddy Model to study the effects of resolution on turbulent structures in a convective boundary layer. A standard Smagorinsky subgrid scheme is used. As the grid length is increased, the diagnosed height of the boundary layer increases, and the horizontally- and temporally-averaged temperature near the surface and in the inversion layer increase. At the highest resolution, quadrant analysis shows that the majority of events in the lower boundary layer are associated with cold descending air, followed by warm ascending air. The largest contribution to the total heat flux is made by warm ascending air, with associated strong thermals. At lower resolutions, the contribution to the heat flux from cold descending air is increased, and that from cold ascending air is reduced in the lower boundary layer; around the inversion layer, however, the contribution from cold ascending air is increased. Calculations of the heating rate show that the differences in cold ascending air are responsible for the warm bias below the boundary layer top in the low resolution simulations. Correlation length and time scales for coherent resolved structures increase with increasing grid coarseness. The results overall suggest that differences in the simulations are due to weaker mixing between thermals and their environment at lower resolutions. Some simple numerical experiments are performed to increase the mixing in the lower resolution simulations and to investigate backscatter. Such simulations are successful at reducing the contribution of cold ascending air to the heat flux just below the inversion, although the effects in the lower boundary layer are weaker.

Quantification of NOX Emissions Based on Car MAX-DOAS Measurements over Beijing and Impacts of Wind Field

2020 ◽  
Author(s):  
Xinghong Cheng
Keyword(s):  
Spatial Distribution ◽  
Wind Speed ◽  
Wind Field ◽  
Meteorological Condition ◽  
Emission Rates ◽  
Wind Fields ◽  
Vertical Column ◽  
Wind Speeds ◽  
South Central ◽  
The Mean

&lt;p&gt;We carried out 14 days of Car MAX-DOAS experiments on the 6th Ring Rd of Beijing in January, September and October, 2014. The tropospheric vertical column densities (VCD) of NO&lt;sub&gt;2&lt;/sub&gt; are retrieved and used to estimate the emissions of NO&lt;sub&gt;x&lt;/sub&gt;. The offline LAPS-WRF-CMAQ model system is used to simulate wind fields by assimilation of observational data and calculate the NO&lt;sub&gt;2&lt;/sub&gt; to NO&lt;sub&gt;x&lt;/sub&gt; concentration ratios. The NO&lt;sub&gt;X&lt;/sub&gt; emissions in Beijing for different seasons derived from Car MAX-DOAS measurements are compared with the multi-resolution emission inventory in China for 2012 (MEIC 2012), and impacts of wind field on estimated emissions and its uncertainties are also investigated. Results show that the NO&lt;sub&gt;2&lt;/sub&gt; VCD is higher in January than other two months and it is typically larger at the southern parts of the 6th Ring Road than the northern parts of it. Wind field has obvious impacts on the spatial distribution of NO&lt;sub&gt;2&lt;/sub&gt; VCD, and the mean NO&lt;sub&gt;2&lt;/sub&gt; VCD with south wind at most sampling points along the 6th Ring Rd is higher than north wind. The journey-to-journey variation pattern of estimated NO&lt;sub&gt;X&lt;/sub&gt; emissions rates (E&lt;sub&gt;NOX&lt;/sub&gt;) is consistent with that of the NO&lt;sub&gt;2&lt;/sub&gt; VCD, and E&lt;sub&gt;NOX &lt;/sub&gt;is mainly determined by the NO2 VCD. In addition, the journey-to-journey E&lt;sub&gt;NOX&lt;/sub&gt; in the same month is different and it is affected by wind speed, the ratio of NO&lt;sub&gt;2&lt;/sub&gt; and NOx concentration and the decay rate of NO&lt;sub&gt;X&lt;/sub&gt; from the emission sources to measured positions under different meteorological condition. The E&lt;sub&gt;NOX&lt;/sub&gt; ranges between 6.46&amp;#215;10&lt;sup&gt;25&lt;/sup&gt; and 50.05&amp;#215;10&lt;sup&gt;25&lt;/sup&gt; molec s&lt;sup&gt;-1&lt;/sup&gt;. The averaged E&lt;sub&gt;NOX&lt;/sub&gt; during every journey in January, September and October are respectively 35.87&amp;#215;10&lt;sup&gt;25&lt;/sup&gt;, 20.34&amp;#215;10&lt;sup&gt;25&lt;/sup&gt;, 8.96&amp;#215;10&lt;sup&gt;25&lt;/sup&gt; molec s&lt;sup&gt;-1&lt;/sup&gt;. The estimated E&lt;sub&gt;NOX&lt;/sub&gt; after removing the simulated error of wind speed and observed deviation of NO&lt;sub&gt;2&lt;/sub&gt; VCD are found to be mostly closer to the MEIC 2012, but sometimes E&lt;sub&gt;NOX &lt;/sub&gt;is lower or higher and it indicates that the MEIC 2012 might be overestimate or underestimate the true emissions. The estimated E&lt;sub&gt;NOX&lt;/sub&gt; on January 27 and September 19 are obviously higher than other journeys in the same month because the mean NO&lt;sub&gt;2&lt;/sub&gt; VCD and Leighton ratio during these two periods are larger, and corresponding wind speeds are smaller. Additionally, because south wind may affect the spatial distribution of mean NO&lt;sub&gt;2&lt;/sub&gt; VCD in Beijing which is downwind of south-central&amp;#160;regions of Hebei province with high source emission rates, the uncertainty of the estimated E&lt;sub&gt;NOX&lt;/sub&gt; with south wind will be increased.&lt;/p&gt;

scholarly journals Operational profiling of temperature using ground-based microwave radiometry at Payerne: prospects and challenges

2012 ◽  
Vol 5 (5) ◽  
pp. 1121-1134 ◽  
Author(s):  
U. Löhnert ◽  
O. Maier
Keyword(s):  
Boundary Layer ◽  
Data Quality ◽  
Microwave Radiometer ◽  
Lower Boundary ◽  
Weather Conditions ◽  
Atmospheric Temperature ◽  
Temperature Profiles ◽  
Data Quality Control ◽  
Time Period ◽  
Lower Boundary Layer

Abstract. The motivation of this study is to verify theoretical expectations placed on ground-based microwave radiometer (MWR) techniques and to confirm whether they are suitable for supporting key missions of national weather services, such as timely and accurate weather advisories and warnings. We evaluate reliability and accuracy of atmospheric temperature profiles retrieved continuously by the microwave profiler system HATPRO (Humidity And Temperature PROfiler) operated at the aerological station of Payerne (MeteoSwiss) in the time period August 2006–December 2009. Assessment is performed by comparing temperatures from the radiometer against temperature measurements from a radiosonde accounting for a total of 2107 quality-controlled all-season cases. In the evaluated time period, the MWR delivered reliable temperature profiles in 86% of all-weather conditions on a temporal resolution of 12–13 min. Random differences between MWR and radiosonde are down to 0.5 K in the lower boundary layer and increase to 1.7 K at 4 km height. The differences observed between MWR and radiosonde in the lower boundary layer are similar to the differences observed between the radiosonde and another in-situ sensor located on a close-by 30 m tower. Temperature retrievals from above 4 km contain less than 5% of the total information content of the measurements, which makes clear that this technique is mainly suited for continuous observations in the boundary layer. Systematic temperature differences are also observed throughout the retrieved profile and can account for up to ±0.5 K. These errors are due to offsets in the measurements of the microwave radiances that have been corrected for in data post-processing and lead to nearly bias-free overall temperature retrievals. Different reasons for the radiance offsets are discussed, but cannot be unambiguously determined retrospectively. Monitoring and, if necessary, corrections for radiance offsets as well as a real-time rigorous automated data quality control are mandatory for microwave profiler systems that are designated for operational temperature profiling. In the analysis of a subset of different atmospheric situations, it is shown that lifted inversions and data quality during precipitation present the largest challenges for operational MWR temperature profiling.

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