scholarly journals The Temporal Autocorrelation Structure of Sea Surface Winds

2012 ◽  
Vol 25 (19) ◽  
pp. 6684-6700 ◽  
Author(s):  
Adam H. Monahan
Keyword(s):  
Wind Speed ◽  
Zonal Wind ◽  
Large Scale ◽  
Strong Dependence ◽  
Meridional Wind ◽  
Sea Surface ◽  
Small Scale ◽  
Wind Component ◽  
Temporal Autocorrelation ◽  
Vector Wind

Abstract The temporal autocorrelation structures of sea surface vector winds and wind speeds are considered. Analyses of scatterometer and reanalysis wind data demonstrate that the autocorrelation functions (acf) of surface zonal wind, meridional wind, and wind speed generally drop off more rapidly in the midlatitudes than in the low latitudes. Furthermore, the meridional wind component and wind speed generally decorrelate more rapidly than the zonal wind component. The anisotropy in vector wind decorrelation scales is demonstrated to be most pronounced in the storm tracks and near the equator, and to be a feature of winds throughout the depth of the troposphere. The extratropical anisotropy is interpreted in terms of an idealized kinematic eddy model as resulting from differences in the structure of wind anomalies in the directions along and across eddy paths. The tropical anisotropy is interpreted in terms of the kinematics of large-scale equatorial waves and small-scale convection. Modeling the vector wind fluctuations as Gaussian, an explicit expression for the wind speed acf is obtained. This model predicts that the wind speed acf should decay more rapidly than that of at least one component of the vector winds. Furthermore, the model predicts a strong dependence of the wind speed acf on the ratios of the means of vector wind components to their standard deviations. These model results are shown to be broadly consistent with the relationship between the acf of vector wind components and wind speed, despite the presence of non-Gaussian structure in the observed surface vector winds.

scholarly journals Can We See the Wind? Statistical Downscaling of Historical Sea Surface Winds in the Subarctic Northeast Pacific

2012 ◽  
Vol 25 (5) ◽  
pp. 1511-1528 ◽  
Author(s):  
Adam H. Monahan
Keyword(s):  
Wind Speed ◽  
Sea Surface ◽  
Wind Component ◽  
Surface Winds ◽  
Northeast Pacific ◽  
Predictive Skill ◽  
Sea Surface Winds ◽  
Mean Wind Speed ◽  
Mean Vector ◽  
Vector Wind

The statistical predictability of wintertime (December–February) monthly-mean sea surface winds (both vector wind components and wind speed) in the subarctic northeast Pacific off the west coast of Canada is considered, in the context of surface wind downscaling. Predictor fields (zonal wind, meridional wind, wind speed, and temperature) are shown to carry predictive information on the large scales (both vertical and horizontal) that are well simulated by numerical weather prediction and global climate models. It is found that, in general, the monthly mean vector wind components are more predictable by indices of the large-scale flow than by the monthly mean wind speed, with no systematic vertical variation in predictive skill for either across the depth of the troposphere. The difference in predictive skill between monthly-mean vector wind components and wind speed is interpreted in terms of an idealized model of the vector wind speed probability distribution, which demonstrates that for the conditions in the subarctic northeast Pacific, the sensitivity of mean wind speed to the standard deviations of vector wind component fluctuations (which are not well predicted) is greater than that to the mean vector wind components. It is demonstrated that this sensitivity is state dependent, and it is suggested that monthly mean wind speeds may be inherently more predictable in regions where the sensitivity to the vector wind component means is greater than that to the standard deviations. It is also demonstrated that daily wind fluctuations (both vector wind and wind speed) are generally more predictable than monthly-mean variability, and that monthly averages of the predicted daily winds generally represent the monthly-mean surface winds better than the predictions directly from monthly mean predictors.

Semi-Empirical Model for the Ka-band Sea Surface Doppler Centroid

2020 ◽  
Author(s):  
Yury Yurovsky ◽  
Vladimir Kudryavtsev ◽  
Semyon Grodsky ◽  
Bertrand Chapron
Keyword(s):  
Wind Speed ◽  
Large Scale ◽  
Incidence Angle ◽  
Wave Spectrum ◽  
Sea Surface ◽  
Doppler Spectrum ◽  
The Black Sea ◽  
Small Scale ◽  
Ka Band ◽  
Semi Empirical

<p>The sea surface Doppler spectrum centroid is a principal parameter for the sea surface current retrieval from Doppler radar measurements. Satellite Doppler scatterometers are proposed to operate in the Ka-band (SKIM, DopplerScatt/WaCM, SEASTAR) in order to achieve sufficient measurement accuracy. Todays documentation of the Ka-band sea surface backscattering parameters is poor, thus this work is aimed at presenting a model for the sea surface Doppler spectrum centroid (DC) deducted from field data collected from the Black Sea research platform. The model relies on the well-known two-scale surface separation approach. Within this framework, the small-scale waves are the scatterers moving at their inherent speed (Bragg wave phase velocity or specular point velocity), which, in turn, are advected by the large-scale wave orbital velocities. These modulations lead to correlated variations of local scatterer cross-section and speed. The inherent scatterer velocity is computed theoretically, while the modulation term is described by the empirical modulation transfer function (MTF) which naturally involves both tilt and hydrodynamics components as a function of look geometry and sea state. The proposed semi-empirical DC model is in good agreement with measurements if in situ wave gauge directional spectrum is used as a wave input. Based on this finding, we extrapolate the semi-empirical DC model on the arbitrary surface described by the physical model of the wind wave spectrum. The resulting DC model is compared to the published empirical models and measurements (SAXON-FPN, DopplerScatt, AirSWOT, Wavemill field campaigns, and CDOP Envisat ASAR model). The model DC dependencies on incidence angle and wind speed are consistent with Ku-band<br>SAXON-FPN, Ka-band AirSWOT, and DopplerScatt datasets, but differs from C-band CDOP model and X-band Wavemill dataset, which generally have higher DC magnitude (besides longer operating radar wavelength, the difference can be attributed to swell dominated sea observed in the CDOP and Wavemill cases). The model predicts that the DC rises with wind speed at small incidence angles, 20–30<sup>o</sup>, but the DC level is almost independent of wind at larger incidence angles, 50–55<sup>o</sup>. Such behavior is explained by the balance between opposing wind dependencies of the MTF magnitude and the magnitude of modulating wave orbital velocities.</p><p>The work is supported by the Russian Science Foundation under grant No. 17-77-30019.</p>

scholarly journals Analisa Angin Zonal dan Meridional Dalam Menentukan Awal Musim Hujan di Kota Jambi

2020 ◽  
Vol 8 (1) ◽  
pp. 43-50
Author(s):  
Presli Panusunan Simanjuntak ◽  
◽  
Agus Safril ◽  
Keyword(s):  
Wind Speed ◽  
Zonal Wind ◽  
El Niño ◽  
Rainy Season ◽  
Prediction Models ◽  
El Nino ◽  
Meridional Wind ◽  
Wind Component ◽  
Meridional Winds ◽  
The City

In Indonesia, prediction models for the beginning of the rainy season have not developed intensively. Jambi City is the capital of Jambi Province as it has quite extensive rainfed gardens / fields and rice fields and contributes significantly to the economy of Jambi Province. Jambi City really needs an accurate prediction of the start of the rainy season to support the economic continuity through agriculture and plantations. This study aims to analyze the zonal and meridional wind components in the 1000 mb layer in determining the start of the rainy season in the city of Jambi. The prediction of the beginning of the season using zonal and meridional winds will be divided into 2 conditions, namely when the normal conditions of monthly rainfall in 1997-2017 and when the El Nino conditions are strong in 1997/1998 and 2015/2016. Based on data processing for 1997-2017, it shows that the beginning of the rainy season is December when the zonal wind speed is highest. In this study, the zonal wind component is more dominant than the meridional wind component in determining the start of the rainy season. However, when conditions are el nino, the zonal wind component is not good to become

scholarly journals Dynamic Loads and Response of a Spar Buoy Wind Turbine with Pitch-Controlled Rotating Blades: An Experimental Study

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3598
Author(s):  
Sara Russo ◽  
Pasquale Contestabile ◽  
Andrea Bardazzi ◽  
Elisa Leone ◽  
Gregorio Iglesias ◽  
...  
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Laboratory Data ◽  
Nonlinear Behavior ◽  
Offshore Wind ◽  
Small Scale ◽  
Wave Steepness ◽  
Design Factor

New large-scale laboratory data are presented on a physical model of a spar buoy wind turbine with angular motion of control surfaces implemented (pitch control). The peculiarity of this type of rotating blade represents an essential aspect when studying floating offshore wind structures. Experiments were designed specifically to compare different operational environmental conditions in terms of wave steepness and wind speed. Results discussed here were derived from an analysis of only a part of the whole dataset. Consistent with recent small-scale experiments, data clearly show that the waves contributed to most of the model motions and mooring loads. A significant nonlinear behavior for sway, roll and yaw has been detected, whereas an increase in the wave period makes the wind speed less influential for surge, heave and pitch. In general, as the steepness increases, the oscillations decrease. However, higher wind speed does not mean greater platform motions. Data also indicate a significant role of the blade rotation in the turbine thrust, nacelle dynamic forces and power in six degrees of freedom. Certain pairs of wind speed-wave steepness are particularly unfavorable, since the first harmonic of the rotor (coupled to the first wave harmonic) causes the thrust force to be larger than that in more energetic sea states. The experiments suggest that the inclusion of pitch-controlled, variable-speed blades in physical (and numerical) tests on such types of structures is crucial, highlighting the importance of pitch motion as an important design factor.

Superposed epoch analysis of coupling mechanisms captured by meteor radars during sudden stratospheric warmings

2021 ◽  
Author(s):  
Benedikt Gast ◽  
Ales Kuchar ◽  
Gunter Stober ◽  
Christoph Jacobi ◽  
Dimitry Pokhotelov ◽  
...  
Keyword(s):  
Zonal Wind ◽  
Lower Thermosphere ◽  
Rio Grande ◽  
Meridional Wind ◽  
Meteorological Conditions ◽  
Special Focus ◽  
Wind Component ◽  
Superposed Epoch Analysis ◽  
Epoch Analysis ◽  
Coupling Mechanisms

<p class="western" align="justify"><span lang="en-GB">Previous studies that analysed the mesosphere and lower thermosphere (MLT) dynamics during sudden stratospheric warmings (SSWs) were limited only to particular SSWs or focused on a particular station representative only for some regions. Here we describe a comprehensive study of the average meteorological conditions during SSWs with a special focus on the general contribution of planetary (PW) and gravity (GW) waves as primary coupling mechanisms between lower and upper atmosphere. The average meteorological conditions in the MLT during SSWs were analyzed using a superposed epoch analysis (Denton et al., 2019) of meteor radar measurements for stations in the northern (NH: Collm, Kiruna, Sodankyla, CMOR) and the southern hemisphere (SH: Rio Grande, Davis, Rothera) for the altitude range of 80–100 km Using the adaptive spectral filtering method (Stober et al., 2021), we study in detail PW and GW characteristics in addition to measured zonal and meridional wind components in a time period from 2000 to 2020.</span></p> <p class="western" align="justify"><span lang="en-GB">In the NH the zonal wind is typically decreasing from around two weeks before the SSW onset, corresponding to an increased PW activity. Around the SSW onset, latitudinal differences in the zonal wind component as well as the PW activity can be seen. In the weeks before the SSW onset, the stations in the NH also show an increased level of GW kinetic energy. The meridional wind at the NH stations fluctuates with a periodicity of about 10 days before and around the onset. In contrast to previous studies (e.g. Yasui et al., 2016), the measurements in the SH are consistent with the inter-hemispheric coupling hypothesis. The expected downward shift of GW drag (Körnich and Becker, 2010) was reproduced by a downward travelling layer of enhanced GW activity at Davis and Rio Grande. Finally, the role of the terdiurnal tide in the GW energy composite is considered.</span></p>

scholarly journals The Effects of Background Zonal and Meridional Winds on ENSO in a Coupled GCM

2020 ◽  
Vol 33 (6) ◽  
pp. 2075-2091 ◽  
Author(s):  
Bowen Zhao ◽  
Alexey Fedorov
Keyword(s):  
Zonal Wind ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Meridional Wind ◽  
Wind Component ◽  
Coupled Models ◽  
Positive Feedbacks ◽  
Zonal Winds ◽  
Meridional Winds

AbstractChanges in background zonal wind in the tropical Pacific are often invoked to explain changes in ENSO properties. However, the sensitivity of ENSO to mean zonal winds has been thoroughly explored only in intermediate coupled models (following Zebiak and Cane), not in coupled GCMs. The role of mean meridional winds has received even less attention. Accordingly, the goal of this study is to examine systematically the effects of both zonal (equatorial) and meridional (cross-equatorial) background winds on ENSO using targeted experiments with a comprehensive climate model (CESM). Changes in the mean winds are generated by imposing heat flux forcing in two confined regions at a sufficient distance north and south of the equator. We find that the strengthening of either wind component reduces ENSO amplitude, especially eastern Pacific SST variability, and inhibits meridional swings of the intertropical convergence zone (ITCZ). The effect of zonal winds is generally stronger than that of meridional winds. A stability analysis reveals that the strengthening of zonal and meridional winds weakens the ENSO key positive feedbacks, specifically the zonal advection and thermocline feedbacks, which explains these changes. Zonal wind enhancement also intensifies mean upwelling and hence dynamical damping, leading to a further weakening of El Niño events. Ultimately, this study argues that the zonal and, to a lesser extent, meridional wind strengthening of the past decades may have contributed to the observed shift of El Niño characteristics after the year 2000.

Dependencies of Polychlorinated Biphenyl Concentrations Measured at the Great Lakes on Climate Variables

2020 ◽  
Author(s):  
Sandy Ubl ◽  
Martin Scheringer
Keyword(s):  
Wind Speed ◽  
Great Lakes ◽  
Wind Direction ◽  
Seasonal Cycle ◽  
Large Scale ◽  
Polychlorinated Biphenyl ◽  
The Other ◽  
Small Scale ◽  
Local Conditions ◽  
Pcb Congeners

<p>Polychlorinated biphenyls (PCBs) are persistent and hazardous chemicals that are still detected in the atmosphere and other environmental compartments although their production was banned several decades ago. At the Great Lakes region PCBs have been monitored via the IADN network since 1993. In this study, we report results from seven different PCB congeners measured at six different sites around the Great Lakes. The PCBs exhibit a strong seasonal cycle with highest concentrations in summer and lowest concentrations in winter. The concentrations measured in Chicago and Cleveland are higher compared to the concentrations reported from more remote stations. We evaluated the correlations for the seven PCB congeners at each station. PCB-53,-101,-118 and -138 are highly correlated at each of the six stations. PCB-180 is the least correlated with all the other PCBs. This is explicitly true for Eagle Harbor, where PCB-180 and -153 are not correlated with the other 6 PCBs. This may be explained by the less pronounced seasonal cycle of these heavier PCBs at Eagle Harbor. We observed significant correlations between PCB-28 concentrations at the remote stations, but PCB concentrations at the stations of Chicago and Cleveland are only poorly correlated with PCB concentrations at the other stations. The weak correlation of the PCB concentrations measured at the different stations and the relatively high concentrations of the PCB congeners at each station indicate that local conditions and small scale processes (sources, temperature, wind direction, wind speed) dictate the spatial distribution of the  PCBs. We will feed available data on temperature, wind speed, wind direction, emissions, precipitation, ice cover of the Great Lakes and large scale atmospheric teleconnection patterns into a General Additive Model (GAM) to further investigate the relationships between the measured PCB concentrations and selected environmental conditions and atmospheric parameters.<span> </span></p>

scholarly journals Intercomparisons of Tropospheric Wind Velocities Measured by Multi-Frequency Wind Profilers and Rawinsonde

Atmosphere ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1284
Author(s):  
Zhao-Yu Chen ◽  
Yen-Hsyang Chu ◽  
Ching-Lun Su
Keyword(s):  
Wind Speed ◽  
Three Dimensional ◽  
Meridional Wind ◽  
Horizontal Wind ◽  
Wind Component ◽  
Horizontal Wind Speed ◽  
Order Of Magnitude ◽  
Wind Velocities ◽  
Mean Square Difference ◽  
Wind Profilers

Concurrent measurements of three-dimensional wind velocities made with three co-located wind profilers operated at frequencies of 52 MHz, 449 MHz, and 1.29 GHz for the period 12–16 September 2017 are compared for the first time in this study. The velocity–azimuth display (VAD) method is employed to estimate the wind velocities. The result shows that, in the absence of precipitation, the root mean square difference (RMSD) in the horizontal wind speed velocities U and wind directions D between different pairs of wind profilers are, respectively, in the range of 0.94–0.99 ms−1 and 7.7–8.3°, and those of zonal wind component u and meridional wind component v are in the respective ranges of 0.91–1.02 ms−1 and 1.1–1.24 ms−1. However, the RMSDs between wind profilers and rawinsonde are in the range of 2.89–3.26 ms−1 for horizontal wind speed velocity and 11.17–14.48° for the wind direction, which are around 2–3 factors greater than those between the wind profilers on average. In addition to the RMSDs, MDs between wind profilers and radiosonde are around one order of magnitude larger than those between wind profilers. These results show that the RMSDs, MDs, and Stdds between radars are highly consistent with each other, and they are much smaller than those between radar and rawinsonde. This therefore suggests that the wind profiler-measured horizontal wind velocities are much more reliable, precise, and accurate than the rawinsonde measurement.

scholarly journals Analisis Pola Distribusi Unsur-Unsur Cuaca di Lapisan Atas Atmosfer pada Bulan Januari dan Agustus di Manado

Jurnal MIPA ◽  
2014 ◽  
Vol 3 (1) ◽  
pp. 20
Author(s):  
Carisz Kainama ◽  
Seni H. J. Tongkukut ◽  
Wandayantolis .
Keyword(s):  
Temperature Distribution ◽  
Wind Speed ◽  
Distribution Pattern ◽  
Southern Hemisphere ◽  
Zonal Wind ◽  
Meridional Wind ◽  
The South ◽  
The West ◽  
The North ◽  
North Sulawesi

Telah dibuat peta pola distribusi suhu udara, kelembapan udara, dan kecepatan angin di lapisan atas pada bulan Januari dan Agustus di Manado, dengan menggunakan software Surfer 10. Hasil analisis menunjukkan bahwa di bulan Januari pada lapisan 850 mb suhu di belahan bumi selatan (BBS) lebih tinggi dari belahan bumi utara (BBU), kelembapan lebih besar ke arah Sulawesi Utara, angin zonal baratan di BBS dan angin zonal timuran di BBU, sedangkan angin meridional dominan dari arah utara. Pada lapisan 500 mb dan 300 mb penyebaran suhu hampir merata untuk setiap wilayah dengan suhu terendah terdapat di sekitar wilayah Sulawesi Utara, kelembapan lebih besar ke arah BBS, angin zonal dari arah timur, sedangkan angin meridional dari arah utara di BBU dan dari arah selatan di BBS. Perbedaan kecepatan angin antar lapisan tidak signifikan. Di bulan Agustus, pada lapisan 850 mb suhu di BBU lebih tinggi dari BBS, kelembapan lebih besar ke arah Maluku, angin zonal dari arah timur di BBU dan dari arah barat di BBS, sedangkan angin meridional dominan dari arah selatan. Pada lapisan 500 mb penyebaran suhu hampir merata dengan suhu tertingi terdapat di wilayah Davao, dan pada lapisan 300 mb penyebaran suhu sama dengan bulan Januari. Pada lapisan 500 mb dan 300 mb kelembapan lebih besar ke arah timur, sedangkan angin zonal dari arah timur. Angin meridional dominan dari arah selatan pada lapisan 500 mb dan dominan dari arah utara pada lapisan 300 mb.A map of distribution pattern of temperature, humidity, and wind speed and direction in the upper layer of Manado in January and August had been created using software Surfer 10. The analysis showed that, in January at 850 mb layer, the temperature in southern hemisphere (SH) is higher than that in northern hemisphere (NH), the humidity is higher to the North Sulawesi, westerly zonal wind is in SH and easterly zonal wind is in NH, and meridional wind is dominant from the north. At 500 mb and 300 mb layer, temperature distribution is almost evenly for each region with the lowest temperature is around the North Sulawesi area, the humidity is higher to the SH, the zonal wind is from the east, and the meridional wind is from the north at NH and from the south in SH. Wind speed difference between the layers is not significant. In August at 850 mb layer, the temperature in NH is higher than that in SH, the humidity is greater to Moluccas, the zonal wind is from the east at NH and from the west in the SH, and the meridional wind is dominant from the south. At 500 mb layer, temperature distribution is almost evenly with the highest one is in the Davao region, and at 300 mb layer, temperature is similar to that in January. At 500 mb and 300 mb layer, the humidity is greater eastward.

Assessing the influence of large-scale environmental conditions on rainfall structure of Atlantic tropical cyclones: An observational study

2020 ◽  
pp. 1-40
Author(s):  
Kim Dasol ◽  
Chang-Hoi Ho ◽  
Hiroyuki Murakami ◽  
Doo-Sun R. Park
Keyword(s):  
High Pressure ◽  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Tropical Cyclones ◽  
North Atlantic ◽  
Environmental Conditions ◽  
Large Scale ◽  
Environmental Flows ◽  
Sea Surface

AbstractUnderstanding the mechanisms related to the variations in the rainfall structure of tropical cyclones (TCs) is crucial in improving forecasting systems of TC rainfall and its impact. Using satellite precipitation and reanalysis data, we examined the influence of along-track large-scale environmental conditions on inner-core rainfall strength (RS) and total rainfall area (RA) for Atlantic TCs during the TC season (July to November) from 1998 to 2019. Factor analysis revealed three major factors associated with variations in RS and RA: large-scale low- and high-pressure systems (F1), environmental flows, sea surface temperature, and humidity (F2), and maximum wind speed of TCs (F3). Results from our study indicate that RS increases with an increase in the inherent primary circulation of TCs (i.e., F3), but is less affected by large-scale environmental conditions (i.e., F1 and F2), whereas RA is primarily influenced by large-scale low- and high-pressure systems (i.e., F1) over the entire North Atlantic and partially influenced by environmental flows, sea surface temperature, humidity, and maximum wind speed (i.e., F2 and F3). A multi-variable regression model based on the three factors accounted for the variations of RS and RA across the entire basin. In addition, regional distributions of mean RS and RA from the model significantly resembled those from observations. Therefore, our study suggests that large-scale environmental conditions over the North Atlantic are important predictors for TC rainfall forecasts, particularly regarding RA.

Sign in / Sign up

Export Citation Format

Share Document