High Frequency Wind Research Articles

Abundance and diversity of diatoms and dinoflagellates in an embayment off Central Chile (30°S): evidence of an optimal environmental window driven by low and high frequency winds

Abundance and diversity of diatoms and dinoflagellates in an embayment off Central Chile (30°S): evidence of an optimal environmental window driven by low and high frequency winds

High and low frequency wind power prediction based on Transformer and BiGRU-Attention

An accurate and reliable wind power prediction model has important significance for the operation of power systems and large-scale grid connection. This paper proposes a hybrid deep learning model, CEEMDAN-SE-TR-BiGRU-Attention, for high and low frequency wind power prediction by combining complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), sample entropy (SE), Transformer (TR) and bidirectional gated recurrent unit with attention mechanism (BiGRU-Attention). Firstly, the CEEMDAN decomposes the original wind power sequence into multiple sub-modes and a residual, and the sample entropy of each sub-sequence is calculated by restructuring the sequence, which can effectively alleviate the impact of the original non-stationary series on the accuracy and computational complexity. Next, the reconstructed sequences are further divided into high and low frequency sequences according to the sample entropy value of the original sequence. The Transformer and BiGRU-Attention models are respectively applied to the prediction of high frequency and low frequency sequences according to the characteristics of each sequence. Finally, the predicted values of all components are superimposed to obtain the final prediction results. Experiments are carried out on four datasets with different seasons, and different models are compared to illustrate the effectiveness and superiority of the proposed model. The experimental results show that the proposed model achieves better prediction accuracy.

Analytical Modeling of High-Frequency Winding Loss in Round-Wire Toroidal Inductors

Toroidal inductors are used in many industrial applications in which they are key components regarding cost and volume. In the inductor design process, it is paramount to accurately estimate its high-frequency winding loss. Finite element analysis (FEA) software and analytical models can be used for this purpose. However, the former employs too much time and the latter lacks accuracy when applied to toroidal windings, leading to an overestimation that can exceed 200%. As a consequence, designers would benefit from a reliable method to calculate high-frequency loss in toroidal windings. This paper proposes an analytical model that considers the 2-D characteristic of the magnetic field and the geometrical particularities of toroidal windings. Furthermore, it provides an easy-to-use method, which avoids the unaffordable computational cost of FEA software. Simulations and experimental measurements are carried out for six toroidal power inductors, from 10 Hz up to 200 kHz. Three different well-known state-of-the-art analytical models are used for comparison purposes. The results obtained with the proposed model are in good agreement with those from FEA and the experiments. The proposed model shows a maximum deviation below 20%, while the overestimation of the existing analytical methods reaches values from 93% to 226%.

Experimental investigation and analysis on the cross flow characteristics over inline tube bundles with S/D=1.875

Helical tube bundles are usually used for steam generators (SGs) and intermediate heat exchangers (IHXs) of High Temperature Gas-cooled Reactors (HTGRs). The thermal hydraulic performance of SGs/IHXs is dominated by the cross flow convection over tube bundles in the primary side. Though cross flow over tube bundles were widely investigated as a basic flow pattern, few of them focused on tube bundles with 1.4-1.6<S/D<2-2.2 (S, tube pitch, D, tube diameter). However, the designs of HTGR SGs or IHXs prefer smaller tube pitches due to the relatively low heat transfer coefficient. In present investigation, velocity distribution, surface pressure distribution and drag/lift force of cross flow over tube bundle with S/D=1.875 are measured and investigated thoroughly in a wind tunnel. The velocity fields are measured using time resolved PIV and split hot film methods. The surface pressure distribution is measured using dynamic pressure transducers. The drag and lift forces are measured using high frequency wind tunnel balance. Due to the friction drag introduced by the bounded wall, the time averaged velocity in the flow passage next to the bounded wall is smaller than those in the middle flow passages. The surface pressure distributions between the impinging point and the separation point on tubes are characterized by the acceleration effects when fluid flowing into the region between neighboring tubes in the same row. The increasingly significant pressure recovery after separation results in the decreasing tendency of flow resistance coefficient with Reynolds number (Re) increment. A main frequency corresponding to Sr=0.114 (Sr, Strouhal number) is observed in both surface pressure and velocity spectrums, indicating that the vortex shedding induces the turbulent wake swinging. The turbulent wakes after tubes in the same row swing with no phase lag, while turbulent wakes of tubes in neighboring rows swing with a phase lag around 0.33 periods. By using an improved phase average method, phase averaged turbulent statistics and instantaneous coherent structures are obtained. The main flow region swings with vortex shedding. The region with larger 〈u′u′〉 (u′, fluctuating component of stream wise velocity) mainly locates at the shear layer, swinging with the vortex shedding. The region with larger 〈v′v′〉, (v′, fluctuating component of transverse velocity) mainly locates in front of the tubes, where transverse flow sweeps the upwind side of the tubes.

Impacts of terrain on convective surface layer turbulence over central Himalaya based on Monin–Obukhov similarity theory

In the context of non-uniform Monin–Obukhov similarity scaling of unstable surface layer turbulence over complex terrain, this study attempts to identify the range of slope angles (as a proxy for terrain complexity) over which convective turbulence behaviour is similar to that over flat terrain. Attempts are also made to optimize constants of numerical relationships between integral turbulence parameters (ϕu,v,w) and the stability parameter (z/L) for observations having a significantly strong signature of terrain undulation. High frequency wind observations during the Indian winter season obtained from two field stations (on-slope and ridge-top) in the central Himalaya near Kosi-Katarmal, Uttarakhand, India, are analysed. Convective day-time period observations from rain-free days at these two sites are used with measures of terrain heterogeneity, represented by the vertical wind-derived slope angle (θw), vertical wind-derived slope angle normalized with respect to maximum θw (θwˆ), and the terrain-derived slope angle (θt). When the relationship of wind-derived slope angle and terrain derived slope angle was assessed, we found that wind-derived slope angle(θw) sufficiently represents the terrain undulation with a correlation coefficient of 0.86 at a p-value < 0.001. Optimization was undertaken of the numerical relationships between the integral turbulence parameters (ϕu,v,w) and z/L for observations having a significantly strong signature of terrain undulation characterized by |θˆw|> 0.2. Results indicated that for selected runs with increasing terrain complexity, c1 decreases and d1 increases in ϕu,v,w=c1(1−d1zL)1/3 having ranges of c1 and d1 between 0.85–2.39, and 0.98–13.85, respectively.

Evaluation of high-resolution atmospheric and oceanic simulations of the California Current System

This paper is the first of two that present a 16-year hindcast solution from a coupled physical and biogeochemical model of the California Current System (CCS) along the U. S. West Coast and validate the physical solution with respect to mean, seasonal, interannual, and subseasonal fields and, to a lesser degree, eddy variability. Its companion paper is Deutsch et al. (2021). The intent is to construct and demonstrate a modeling tool that will be used for mechanistic explanations, attributive causal assessments, and forecasts of future evolution for circulation and biogeochemistry, with particular attention to the increasing oceanic stratification, deoxygenation, and acidification. A well-resolved mesoscale (dx=4 km) simulation of the CCS circulation is made with the Regional Oceanic Modeling System over a hindcast period of 16 years from 1995 to 2010. The oceanic solution is forced by a high-resolution (dx=6 km) regional configuration of the Weather and Research Forecast (WRF) atmospheric model. Both of these high-resolution regional oceanic and atmospheric simulations are forced by lateral open boundary conditions taken from larger-domain, coarser-resolution parent simulations that themselves have boundary conditions from the Mercator and Climate Forecast System reanalyses, respectively. We show good agreement between the simulated atmospheric forcing of the oceanic and satellite measurements for the spatial patterns and temporal variability for the surface fluxes of momentum, heat, and freshwater. The simulated oceanic physical fields are then evaluated with satellite and in situ measurements. The simulation reproduces the main structure of the climatological upwelling front and cross-shore isopycnal slopes, the mean current patterns (including the California Undercurrent), and the seasonal, interannual, and subseasonal variability. It also shows agreement between the mesoscale eddy activity and the windwork energy exchange between the ocean and atmosphere modulated by influences of surface current on surface stress. Finally, the impact of using a high frequency wind forcing is assessed for the importance of synoptic wind variability to realistically represent oceanic mesoscale activity and ageostrophic inertial currents.

Future Changes in Oceanography and Biogeochemistry Along the Canadian Pacific Continental Margin

Model projections of ocean circulation and biogeochemistry are used to investigate large scale climate changes under moderate mitigation (RCP 4.5) and high emissions (RCP 8.5) scenarios along the continental shelf of the Canadian Pacific Coast. To reduce computational cost, an approach for dynamical downscaling of climate projections was developed that uses atmospheric climatologies with augmented winds to simulate historical (1986–2005) and future (2046–2065) periods separately. The two simulations differ in initial and lateral open boundary conditions. For each simulation, the daily climatology of surface winds in the driving model was augmented with high-frequency variability from an atmospheric reanalysis product. The “time-slice” approach was able to reproduce the observed climate state for the historical period. Sensitivity tests confirmed that the high frequency wind variability plays an essential role in freshwater distribution in this region. Projections suggest that sea surface temperature will increase by 1.8–2.4°C and surface salinity will decrease between −0.08 and −0.23 depending on whether a moderate or high emissions scenario is used. Stratification increases throughout the region and there is some evidence of nutrient limitation near the surface. Primary production and phytoplankton productivity (chlorophyll) also increase. Density surfaces are relocated deeper in the water column and this change is mainly driven by surface heating and freshening. Changes in saturation state are mainly due to anthropogenic CO2with minor contributions from solubility, remineralization and advection. There is little difference between RCP 4.5 and RCP 8.5 with regard to projections of deoxygenation and acidification. The depths of the aragonite saturation state and the oxygen minimum zone are projected to become shallower by ≃ 100 and ≃ 75 m respectively. Extreme states of temperature, oxygen and acidification are projected to become more frequent and more extreme, with the frequency of occurrence of[O2]&lt;60 mmolm-3expected to approximately double under either scenario.

A Novel In-Situ Measurement Method of High-Frequency Winding Loss in Cored Inductors With Immunity Against Phase Discrepancy Error

Evaluating the high-frequency winding loss accurately is crucial for the design of modern high-frequency power converters. This paper proposes a novel experimental method to accurately measure the in-situ inductor winding loss, which separates out the winding loss from the core loss through the reactive voltage cancellation concept. The proposed in-situ measurement can account for the complete winding loss including impacts from non-ideal field distributions by testing the inductor with the core attached, e.g., the winding edge effect, bypass flux, fringing flux, and the non-linear dynamic behaviour of the core, which cannot be well modelled with the existing analytical or simulation methods. This method has immunity against the probe phase discrepancy error, since it is designed to measure a pair of voltage and current that are in phase. This approach can be considered as the first attempt of applying the reactive voltage cancellation concept in measuring winding loss, while this concept was originally brought up for core loss and applied for core loss measurement only. By performing a Triple Pulse Test (TPT) procedure, the winding losses under practical large signals with dc-bias and rectangular voltage can be evaluated with the proposed testing circuit. The proposed approach is compared and verified against the conventional methods relying on ( <xref ref-type="disp-formula" rid="deqn1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</xref> ) small-signal impedance measurements and FFT analysis ( <xref ref-type="disp-formula" rid="deqn2-deqn3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</xref> ) in-situ measurement with the two winding method to exclude the core loss. The presented method provides a foundation for the accurate in-situ evaluation of winding loss covering all the large-signal and non-linear effects.

District energy system modeling and optimal operation considering CHP units dynamic response to wind power ramp events

With the increase in clean energy penetration, its power curtailment during operation is made increasingly evident. In this circumstance, it is imperative to address the conflict between inflexible combined heat and power (CHP) units and variable wind and solar power. In this paper, a novel coordinated optimal operation strategy of a district energy system with CHP, wind power and energy storage is established with the following characteristics: the optimal installed capacity of electric energy storage (EES) is determined to smooth the high frequency fluctuation of wind power generation; the CHP units achieve dynamic response to wind power ramp events timely after EES smoothing; and the CHP model with start-stop and dynamic response mechanism is able to reduce the installed capacity of electric boiler (EB) significantly. One-week operation data is adopted in the case studies to increase the reliability of simulation results. The simulation results show that with EES integration, high frequency wind energy curtailment is reduced, the capability of peak regulation and power ramp of CHP units is enhanced by start-stop and the proposed dynamic response mechanism and environmentally sustainable and socially resilient cities is promoted.

Comparison of Weibull and Gaussian Mixture Models for Wind Speed Data Analysis

In order to have a reliable estimate of wind energy potential of a site, high frequency wind speed and direction data recorded for an extended period of time is required. Weibull distribution function is commonly used to approximate the recorded data distribution for estimation of wind energy. In the present study a comparison of Weibull function and Gaussian mixture model (GMM) as theoretical functions are used. The data set used for the study consists of hourly wind speeds and wind directions of 54 years duration recorded at Ijmuiden wind site located in north of Holland. The entire hourly data set of 54 years is reduced to 12 sets of hourly averaged data corresponding to 12 months. Authenticity of data is assessed by computing descriptive statistics on the entire data set without average and on monthly 12 data sets. Additionally, descriptive statistics show that wind speeds are positively skewed and most of the wind data points are observed to be blowing in south-west direction. Cumulative distribution and probability density function for all data sets are determined for both Weibull function and GMM. Wind power densities on monthly as well as for the entire set are determined from both models using probability density functions of Weibull function and GMM. In order to assess the goodness-of-fit of the fitted Weibull function and GMM, coefficient of determination (R2) and Kolmogorov-Smirnov (K-S) tests are also determined. Although R2 test values for Weibull function are much closer to ‘1’ compared to its values for GMM. Nevertheless, overall performance of GMM is superior to Weibull function in terms of estimated wind power densities using GMM which are in good agreement with the power densities estimated using wind data for the same duration. It is reported that wind power densities for the entire wind data set are 307 W/m2 and 403.96 W/m2 estimated using GMM and Weibull function, respectively.

Comparison of Weibull and Gaussian Mixture Models for Wind Speed Data Analysis

In order to have a reliable estimate of wind energy potential of a site, high frequency wind speed and direction data recorded for an extended period of time is required. Weibull distribution function is commonly used to approximate the recorded data distribution for estimation of wind energy. In the present study a comparison of Weibull function and Gaussian mixture model (GMM) as theoretical functions are used. The data set used for the study consists of hourly wind speeds and wind directions of 54 years duration recorded at Ijmuiden wind site located in north of Holland. The entire hourly data set of 54 years is reduced to 12 sets of hourly averaged data corresponding to 12 months. Authenticity of data is assessed by computing descriptive statistics on the entire data set without average and on monthly 12 data sets. Additionally, descriptive statistics show that wind speeds are positively skewed and most of the wind data points are observed to be blowing in south-west direction. Cumulative distribution and probability density function for all data sets are determined for both Weibull function and GMM. Wind power densities on monthly as well as for the entire set are determined from both models using probability density functions of Weibull function and GMM. In order to assess the goodness-of-fit of the fitted Weibull function and GMM, coefficient of determination (R2) and Kolmogorov-Smirnov (K-S) tests are also determined. Although R2 test values for Weibull function are much closer to ‘1’ compared to its values for GMM. Nevertheless, overall performance of GMM is superior to Weibull function in terms of estimated wind power densities using GMM which are in good agreement with the power densities estimated using wind data for the same duration. It is reported that wind power densities for the entire wind data set are 307 W/m2 and 403.96 W/m2 estimated using GMM and Weibull function, respectively.

A remote long-term and high-frequency wind measurement system: design, comparison and field testing

The wind field measurement of severe winds such as hurricanes (or typhoons), thunderstorm downbursts and other gales is important issue in wind engineering community, both for the construction and health monitoring of the wind-sensitive structures. Although several wireless data transmission systems have been available for the wind field measurement, most of them are not specially designed for the wind data measurement in structural wind engineering. Therefore, the field collection is still dominant in the field of structural wind engineering at present, especially for the measurement of the long-term and highfrequency wind speed data. In this study, for remote wind field measurement, a novel wireless long-term and high-frequency wind data acquisition system with the functions such as remote control and data compression is developed. The system structure and the collector are firstly presented. Subsequently, main functions of the collector are introduced. Also novel functions of the system and the comparison with existing systems are presented. Furthermore, the performance of this system is evaluated. In addition to as the wireless transmission for wind data and hardware integration for the collector, the developed system possesses a few novel features, such as the modification of wind data collection parameters by the remote control, the remarkable data compression before the data wireless transmission and monitoring the data collection by the cell phone application. It can be expected that this system would have wide applications in wind, meteorological and other communities.

Field study of atmospheric boundary layer observation in a hilly Gobi Desert region and comparison with the CALMET/CALPUFF model

Abstract A field campaign consisting of atmospheric boundary layer (ABL) observations and tracer experiments was conducted in September 2016 in a hilly region of the Gobi Desert in northwest China. High-frequency wind shears were observed between 70 and 200 m based on both 100-meter tower data and wind profiles. The ABL observations indicated that sub-layers of different atmospheric stability present within the ABL weakened the vertical transfer of momentum and tracer gas, resulting in low wind speed and high surface concentration. The CALMET model showed thermal heterogeneity to some extent in the temperature fields and mixing height distributions, and large deviations in the friction velocity between the model and observations were noted. The comparison of the CALPUFF model with the tracer measurements indicated a general tendency toward under-prediction of the concentration in the far distance because of wind shears and vertical thermal discontinuity. The results of the SCIPUFF model showed the same trend as those of CALPUFF, and comparisons demonstrated a good consistency of the two models.

Analysis of Wind Speed and Wind Pressure on the Facades in Frequency Domain for the Modelling of Air Change Rate

Air exchange in buildings is driven by pressure difference across the building envelope caused by wind and difference in density between external and internal air. The evaluation of the influence of wind on the air change rate is usually limited to the analysis of the hourly mean wind speed. Wind is a random phenomenon characterized by the broad energy spectrum. The high frequency part can be responsible for the oscillation of the air through the openings resulting in the increased air exchange. Wind pressure coefficient on the leeward site mostly depends on the form characteristics of the object in relation to wind direction. The analysis of wind speed and wind pressure on the facades in frequency domain can deliver interesting data to air change rate model. Some of the results of continuous measurements carried out on a single-family house for 8 months are presented in frequency domain. The statistics of wind speed, wind direction and pressure differences across the 6 building components are calculated. The wind turbulence and the pressure fluctuations on the facades and the roof of the building are being investigated using energy spectra of their signals. Farther analysis of the experimental results is needed to be able to include high frequency wind in the infiltration model.

Measurement, modeling and simulation of wind turbulence in typhoon outer region

Typhoon is one of the most destructive natural hazards, causing tremendous economic loss and fatalities every year all over the world. High-frequency wind observing tools have been deployed in many projects, which have been utilized in many recent studies to obtain data on typhoon winds, as well as turbulence. This study utilized field measurement data from the Xihoumen Bridge health monitoring system and examined the wind characteristics over water terrain at single point from four typhoons when their outer regions passed the bridge. This study firstly reviews the typhoon structure, which consists of two airflow circulations in horizontal and vertical directions. Results of this study suggest that the near ground wind turbulence characteristics should be analyzed for both directions separately. Next, the turbulence intensity, length scale, spectrum, and non-Gaussian features (skewness and kurtosis) are presented. Correlations among these parameters are also analyzed, and simplified mathematical models are introduced to quantify the correlation among various turbulence characteristics. Then, a Hermite-model based translation function method is used to simulate the non-Gaussian turbulences for different typhoon configurations. Gaussian turbulence neglecting skewness and kurtosis is also generated, and the comparison shows that non-Gaussian turbulence tends to have larger extreme gusts.

Wave Measurements From Radar Tide Gauges

Currently the NOAA Center for Operational Oceanographic Products and Services (CO-OPS) is transitioning the primary water level sensor at most NWLON stations from an acoustic ranging system to microwave radars. With no stilling well and higher resolution of the open sea surface, microwave radars have the potential to provide real-time wave measurements at NWLON sites. Radar sensors at tide stations may offer a low cost, convenient way to increase nearshore wave observational coverage throughout the U.S. to support navigational safety and ocean research applications. Here we present the results of a field study comparing wave height measurements from four radar water level sensors with two different signal types (pulse and continuous wave swept frequency modulation-CWFM). A nearby bottom acoustic wave and current sensor is used as a reference. An overview of field setup and sensors will be presented, along with an analysis of performance capabilities of each radar sensor. The study includes results from two successive field tests. In the first, we examine the performance from a pulse microwave radar (WaterLOG H-3611) and two CWFM (Miros SM-94 and Miros SM-140). While both types of radars tracked significant wave height well over the test period, the pulse radar had less success resolving high frequency wind wave energy and showed a high level of noise towards the low frequency end of the spectrum. The pulse WaterLOG radar limitations were most apparent during times of high winds and locally developing seas. The CWFM radars demonstrated greater capability to resolve those higher frequency energies while avoiding low frequency noise. The initial field test results motivated a second field test, focused on the comparison of wave height measurements from two pulse radar water level sensors, the WaterLOG H3611 and the Endress and Hauser Micropilot FMR240. Significant wave height measurements from both radar water level sensors compared well to reference AWAC measurements over the test period, but once again the WaterLOG radar did not adequately resolve wind wave energy in high frequency bands and showed noise towards the low frequency end of the spectrum. The E+H radar demonstrated greater capability to measure waves.

Wave Measurements from Radar Tide Gauges.

Currently the NOAA Center for Operational Oceanographic Products and Services (CO-OPS) is transitioning the primary water level sensor at most NWLON stations from an acoustic ranging system to microwave radars. With no stilling well and higher resolution of the open sea surface, microwave radars have the potential to provide real-time wave measurements at NWLON sites. Radar sensors at tide stations may offer a low cost, convenient way to increase nearshore wave observational coverage throughout the U.S. to support navigational safety and ocean research applications. Here we present the results of a field study comparing wave height measurements from four radar water level sensors with two different signal types (pulse and continuous wave swept frequency modulation-CWFM). A nearby bottom acoustic wave and current sensor is used as a reference. An overview of field setup and sensors will be presented, along with an analysis of performance capabilities of each radar sensor. The study includes results from two successive field tests. In the first, we examine the performance from a pulse microwave radar (WaterLOG H-3611) and two CWFM (Miros SM-94 and Miros SM-140). While both types of radars tracked significant wave height well over the test period, the pulse radar had less success resolving high frequency wind wave energy and showed a high level of noise towards the low frequency end of the spectrum. The pulse WaterLOG radar limitations were most apparent during times of high winds and locally developing seas. The CWFM radars demonstrated greater capability to resolve those higher frequency energies while avoiding low frequency noise. The initial field test results motivated a second field test, focused on the comparison of wave height measurements from two pulse radar water level sensors, the WaterLOG H3611 and the Endress and Hauser Micropilot FMR240. Significant wave height measurements from both radar water level sensors compared well to reference AWAC measurements over the test period, but once again the WaterLOG radar did not adequately resolve wind wave energy in high frequency bands and showed noise towards the low frequency end of the spectrum. The E+H radar demonstrated greater capability to measure waves.

Taylor Dispersion of Contaminants by Dual-peak Spectral Random Waves

Recent extensive and important studies have provided detailed information and compelling evidence on how the presence of waves influences the vertical diffusivity/dispersivity in the coastal environment, which can affect various water quality considerations such as the distribution of suspended sediments in the water column as well as the potential of eutrophication. Comparatively, how the presence of waves influences the horizontal diffusivity/dispersivity has received only scant attention in the literature. Our previous works investigated the role played by the Taylor mechanism due to the wave-induced drift profile which leads to the longitudinal dispersion of contaminants in the horizontal direction, under regular sinusoidal waves and random waves with single-peak spectra. Natural waves in the coastal environment, however, often possess dual-peak spectra, comprising both higher frequency wind waves and lower frequency swells. In this study, the Taylor dispersion of contaminants under random waves with dual-peak spectra is examined through analytical derivation and numerical calculations. The effects of various dual-peak spectral parameters on the horizontal dispersion, including the proportion of lower frequency energy, peak frequency ratio and spectral shape parameter, are investigated. The results show that the relative energy distribution between the dual peaks has the most significant effect. Compared with single-peak spectra with equivalent energy, the Taylor dispersion with dual-peak spectra is stronger when the lower frequency is close to the peak frequency of the single-peak spectrum, and weaker with the higher frequency instead. Thus, it can be concluded that with a dual-peak wave spectrum, wind-dominated seas with higher frequency lead to stronger dispersion in the horizontal direction than swell-dominated seas with lower frequency.

A Numerical Study on the Impact of High-Frequency Winds on the Peru Upwelling System during 2014–2016

The contribution of high-frequency wind to the Peruvian upwelling system during 2014–2016 was studied using the Regional Ocean Modeling System (ROMS), forced by four different temporal resolution (six-hourly, daily, weekly, and monthly) wind forcing. A major effect of the high-frequency wind is its warming of the water at all depths along the Peruvian coast. The mechanism for the temperature changes induced by high-frequency wind forcing was analyzed through heat budget analysis, which indicated a three-layer structure. Vertical advection plays a leading role in the warming of the mixed layer (0–25 m), and enhanced vertical mixing balances the warming effect. Analysis suggests that around the depths of 25–60 m, vertical mixing warms the water by bringing heat from the surface to deeper depths. In waters deeper than 60 m, the effect of vertical mixing is negligible. The differences among the oceanic responses in the sensitivity experiments suggest that wind forcing containing variabilities at higher than synoptic frequencies must be included in the atmospheric forcing in order to properly simulate the Peru upwelling system.

Wavelet variance scale-dependence as a dynamics discriminating tool in high-frequency urban wind speed time series

High frequency wind time series measured at different heights from the ground (from 1.5 to 25.5 meters) in an urban area were investigated by using the variance of the coefficients of their wavelet transform. Two ranges of scales were identified, sensitive to two different dynamical behavior of the wind speed: the lower anemometers show higher wavelet variance at smaller scales, while the higher ones are characterized by higher wavelet variance at larger scales. Due to the relationship between wavelet scale and frequency, the results suggest the existence of two frequency ranges, where the wind speed variability change according to the position of the anemometer from the ground.This study contributes to better understanding of the high frequency wind speed in urban areas and to a better knowledge of the underlying mechanism governing the wind fluctuations at different heights from the ground in particular in urban area.