Articles de revues sur le sujet « Wind profilers »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Wind profilers.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleurs articles de revues pour votre recherche sur le sujet « Wind profilers ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Hartten, Leslie M., Paul E. Johnston, Valerie M. Rodríguez Castro et Paola S. Esteban Pérez. « Postdeployment Calibration of a Tropical UHF Profiling Radar via Surface- and Satellite-Based Methods ». Journal of Atmospheric and Oceanic Technology 36, no 9 (septembre 2019) : 1729–51. http://dx.doi.org/10.1175/jtech-d-18-0020.1.
Texte intégralRésumé :
Wind profiling radars are usually not calibrated with respect to reflectivity because such calibrations are both unnecessary for good wind measurements and costly. However, reflectivity from calibrated profilers can reveal many atmospheric attributes beyond winds. Establishing ways to calibrate these radars even after they have been taken out of service would expand the utility of archived profiler data. We have calibrated one operating mode of a 915-MHz profiler deployed at Manus, Papua New Guinea (1992–2001), using two methods. The first method adjusts a radar parameter until the profiler’s estimate of rainfall during stratiform events closely matches surface observations. The second adjusts the parameter so that mean brightband heights observed by the profiler (July 1992–August 1994) match the mean brightband reflectivities over the profiler as observed by the TRMM Precipitation Radar (January 1998–July 2001). The results differ by about 5% and yield very similar precipitation errors during tested stratiform events. One or both of these methods could be used on many other wind profilers, whether they have been decommissioned or are currently operational. Data from such calibrated profilers will enable research employing the equivalent reflectivity factor observed by profilers to be compared with that from other radars, and will also enable turbulent studies with C n2.
2
Monna, W. A. A. « On the use of wind profilers in meteorology ». Annales Geophysicae 12, no 6 (31 mai 1994) : 482–86. http://dx.doi.org/10.1007/s00585-994-0482-9.
Texte intégralRésumé :
Abstract. As an introduction to this special issue of Annales Geophysicae a review is given of the applicability and performance of wind profilers. In meteorology, wind profilers play an increasingly important role. They can provide upper-wind measurements with an accuracy comparable to radiosonde data, but with a significantly higher temporal resolution. Height coverage and vertical resolution depend on the operating frequency, which, depending on the application, is usually chosen to be around 50, 400 or 1000 MHz. Measurements from stand-alone profilers in sparse data areas as well as data from wind profiler networks - which have increased the spatial resolution of an existing radiosonde network - have shown a positive impact on numerical weather forecasting. Information from nearby profilers can help the individual meterologist to optimize local short-term weather forecasts. In atmospheric research, wind profilers have been used for various boundary layer studies. In several mesoscale monitoring experiments wind profilers have played an important role. In Europe the development and implementation of wind profiler networks have been supported since 1987 by the CEC-sponsored COST-74 project. A follow-up project will probably start in 1994. Several topics deserve attention. A further assessment of the quality of wind profiler measurements is important. Automatic quality control procedures should be refined. Improved data assimilation techniques in numerical models will enable a better use of the high temporal resolution of wind profiler data. For a cost-effective development and use of wind profilers, the realization of frequency allocations, as globally harmonized as possible, is essential. Finally, the integration of wind profilers with other complementary measuring techniques is important.
3
Barth, M. F., R. B. Chadwick et D. W. van de Kamp. « Data processing algorithms used by NOAA's wind profiler demonstration network ». Annales Geophysicae 12, no 6 (31 mai 1994) : 518–28. http://dx.doi.org/10.1007/s00585-994-0518-1.
Texte intégralRésumé :
Abstract. The National Oceanic and Atmospheric Administration's (NOAA) Wind Profiler Demonstration Network consists of 32 wind profiling radars, based primarily in the central United States. The network is being used to determine the operational feasibility and characteristics of a possible future nationwide profiler network. Data processing is performed both at the individual profiler sites and at a central hub processing system. This paper documents the algorithms used at the profilers to produce profiles of the moments of the velocity spectrum every 6 minutes, as well as those used on the hub to produce quality-controlled hourly winds.
4
Chen, Zhao-Yu, Yen-Hsyang Chu et Ching-Lun Su. « Intercomparisons of Tropospheric Wind Velocities Measured by Multi-Frequency Wind Profilers and Rawinsonde ». Atmosphere 12, no 10 (2 octobre 2021) : 1284. http://dx.doi.org/10.3390/atmos12101284.
Texte intégralRésumé :
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.
5
Schafer, Robert, Susan K. Avery, Kenneth S. Gage et George N. Kiladis. « Wind Profiler Observations over the Central Equatorial Pacific : Optimizing Processing to Improve Quality and Height Coverage ». Journal of Atmospheric and Oceanic Technology 24, no 10 (1 octobre 2007) : 1710–25. http://dx.doi.org/10.1175/jtech2072.1.
Texte intégralRésumé :
Abstract UHF (boundary layer) and VHF (troposphere–stratosphere) wind profilers have operated at Christmas Island (2°N, 157°W) in the central equatorial Pacific from 1986 to 2002. Observed profiles of winds are sparse over the tropical oceans, but these are critical for understanding convective organization and the interaction of convection and waves. While the zonal winds below about 10 km have previously shown good agreement with the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis (RI), significant differences were found above a height of 10 km that were attributed to the low detectability of the wind signal in the profiler observations. Meridional winds at all levels show less agreement, with differences attributed to errors of representativeness and the sparseness of observations in the region. This paper builds on previous work using the Christmas Island wind profilers and presents the results of reprocessing the 17-yr profiler record with techniques that enhance the detectability of the signal at upper heights. The results are compared with nearby rawinsonde soundings obtained during a special campaign at Christmas Island and the RI, NCEP–Department of Energy (DOE) reanalysis (RII), and the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). The newly processed profiler zonal and meridional wind observations show good agreement with rawinsonde observations from 0.5 to 19 km above sea level, with difference statistics similar to other studies. There is also significant improvement in the agreement of RI and RII reanalysis and profiler upper-level zonal and meridional winds from previous studies. A comparison of RII and ERA-40 reanalysis shows that difference statistics between the reanalyses are similar in magnitude to differences between the profiler and the individual reanalyses.
6
Wang, Cheng, Min Chen et Yaodeng Chen. « Impact of Combined Assimilation of Wind Profiler and Doppler Radar Data on a Convective-Scale Cycling Forecasting System ». Monthly Weather Review 150, no 2 (février 2022) : 431–50. http://dx.doi.org/10.1175/mwr-d-20-0383.1.
Texte intégralRésumé :
Abstract The two types of wind observations, profiler and radar radial velocity, have been successfully assimilated into numerical weather prediction (NWP) systems. However, the added value of profiler data, especially from a densely deployed profiler network, is unknown when assimilated together with Doppler radar radial velocity. In this article, two combined assimilation strategies of profilers along with radar radial winds are compared within a convective-scale data assimilation (DA) framework. In strategy I, the profiler data are assimilated with conventional observations to generate an intermediate analysis that acts as a prior for radar data assimilation. In strategy II, both profiler and radar data are considered as storm-scale and assimilated within the same pass. Single- and dual-observation assimilation experiments indicate that for strategy I, the profiler DA improvement can be partly canceled by the potentially negative impact of the assimilation of single-radar radial velocity afterward, particularly when the radial wind is nearly orthogonal to the prevailing wind. For strategy II, important complements are provided when profilers are assimilated within the same pass along with radial winds. The diagnostics for a low-level jet case demonstrate that both strategies facilitate improved analyses and forecasts. But strategy II may bring more moderate analysis increments, which indicate mutual constraints of the profiler and radial winds when assimilated within the same pass. The results obtained in 1-month, retrospective cycling experiments also show that the strategy II outperforms the strategy I with slightly better wind and precipitation forecasts. Significance Statement Due to the high spatial–temporal wind information provided by profiler and radar radial velocity measurements, their combined assimilation would be expected to improve wind analysis. To fully utilize dense profiler data and radar radial wind in future operational applications, this study proposes a suitable assimilation strategy. If the profilers are defined as synoptic-scale observations, the profiler and Doppler radar data must be assimilated in different passes to adopt different length and variance scales. Whereas it is more reasonable to use a small background correlation length consistent with the radial velocity and, therefore, assimilate in the same pass if the profiler data are considered to better sample storm-scale features. Single- and dual-observation experiments indicate that profiler data provide important complements, while the assimilation of single-radar radial wind may yield analyzed wind results that do not depict the ground truth. A low-level jet case and a 1-month impact study further show that the combined assimilation strategy of assimilating both profiler and Doppler radar using smaller background correlation lengths enhances the analysis and forecasting of wind, resulting in more accurate accumulated precipitation forecasts.
7
Adachi, Ahoro, Takahisa Kobayashi, Kenneth S. Gage, David A. Carter, Leslie M. Hartten, Wallace L. Clark et Masato Fukuda. « Evaluation of Three-Beam and Four-Beam Profiler Wind Measurement Techniques Using a Five-Beam Wind Profiler and Collocated Meteorological Tower ». Journal of Atmospheric and Oceanic Technology 22, no 8 (1 août 2005) : 1167–80. http://dx.doi.org/10.1175/jtech1777.1.
Texte intégralRésumé :
Abstract In this paper a five-beam wind profiler and a collocated meteorological tower are used to estimate the accuracy of four-beam and three-beam wind profiler techniques in measuring horizontal components of the wind. In the traditional three-beam technique, the horizontal components of wind are derived from two orthogonal oblique beams and the vertical beam. In the less used four-beam method, the horizontal winds are found from the radial velocities measured with two orthogonal sets of opposing coplanar beams. In this paper the observations derived from the two wind profiler techniques are compared with the tower measurements using data averaged over 30 min. Results show that, while the winds measured using both methods are in overall agreement with the tower measurements, some of the horizontal components of the three-beam-derived winds are clearly spurious when compared with the tower-measured winds or the winds derived from the four oblique beams. These outliers are partially responsible for a larger 30-min, three-beam standard deviation of the profiler/tower wind speed differences (2.2 m s−1), as opposed to that from the four-beam method (1.2 m s−1). It was also found that many of these outliers were associated with periods of transition between clear air and rain, suggesting that the three-beam technique is more sensitive to small-scale variability in the vertical Doppler velocity because of its reliance on the point measurement from the vertical beam, while the four-beam method is surprisingly robust. Even after the removal of the rain data, the standard deviation of the wind speed error from the three-beam method (1.5 m s−1) is still much larger than that from the four-beam method. Taken together, these results suggest that the spatial variability of the vertical airflow in nonrainy periods or hydrometeor fall velocities in rainy periods makes the vertical beam velocities significantly less representative over the area across the three beams, and decreases the precision of the three-beam method. It is concluded that profilers utilizing the four-beam wind profiler technique have better reliability than wind profilers that rely on the three-beam wind profiler technique.
8
St-James, Judy S., et Stéphane Laroche. « Assimilation of Wind Profiler Data in the Canadian Meteorological Centre’s Analysis Systems ». Journal of Atmospheric and Oceanic Technology 22, no 8 (1 août 2005) : 1181–94. http://dx.doi.org/10.1175/jtech1765.1.
Texte intégralRésumé :
Abstract Real-time horizontal wind observations from the National Oceanic and Atmospheric Administration’s (NOAA’s) Profiler Network (NPN) are assessed in preparation for their assimilation in the Canadian Meteorological Centre (CMC) analysis systems. As a first step, radiosonde winds from 20 stations were compared to the central U.S. profiler stations over the 2001/02 winter season. It was found that profilers are at least as good as conventional radiosonde data. The 2001/02 winter season data were also used to examine the vertical correlation structure of the observation error for profilers. Using a statistical analysis of innovations, the observation error standard deviation of the wind components is estimated as 2.2 m s−1 and the vertical correlation length is approximately 500 m. These results suggest that the data are vertically correlated because they are available every 250 m. Therefore, a thinning process is proposed in which one out of three data are selected in the vertical for each station. Since January 2004, a close monitoring of NPN profiler data revealed significant errors at some stations in the lower and upper troposphere. Consequently, a monthly blacklist of NPN profilers is built based on data from the previous month. A data impact study with both the three-dimensional variational data assimilation (3DVAR) and four-dimensional variational data assimilation (4DVAR) analysis systems was conducted using data from the 2003/04 winter season in which the vertical thinning was tested. It was found that the vertical thinning improves slightly the 6-h forecast error, especially in the 4DVAR over the central United States in which 6 times more profilers are assimilated. The impact of the vertical thinning is found to be neutral in the 3DVAR. Also, the impact of profiler data is significant over the central U.S. domain compared to a control run with the only difference being the addition of profiler data. These results were sufficiently good to implement NPN profilers in both the CMC global and regional analysis systems with the thinning process in fall of 2004.
9
Goodrich, Robert K., Corrinne S. Morse, Larry B. Cornman et Stephen A. Cohn. « A Horizontal Wind and Wind Confidence Algorithm for Doppler Wind Profilers ». Journal of Atmospheric and Oceanic Technology 19, no 3 (1 mars 2002) : 257–73. http://dx.doi.org/10.1175/1520-0426-19.3.257.
Texte intégralRésumé :
Abstract Boundary layer wind profilers are increasingly being used in applications that require high-quality, rapidly updated winds. An example of this type of application is an airport wind hazard warning system. Wind shear can be a hazard to flight operations and is also associated with the production of turbulence. A method for calculating wind and wind shear using a linear wind field assumption is presented. This method, applied to four- or five-beam profilers, allows for the explicit accounting of the measurable shear terms. An error analysis demonstrates why some shears are more readily estimated than others, and the expected magnitudes of the variance for the wind and wind shear estimates are given. A method for computing a quality control index, or confidence, for the calculated wind is also presented. This confidence calculation is based on an assessment of the validity of the assumptions made in the calculations. Confidence values can be used as a quality control metric for the calculated wind and can also be used in generating a confidence-weighted average wind value from the rapid update values. Results are presented that show that errors in the wind estimates are reduced after removing values with low confidence. The wind and confidence methods are implemented in the NCAR Wind and Confidence Algorithm (NWCA), and have been used with the NCAR Improved Moments Algorithm (NIMA) method for calculating moments and associated moment confidence from Doppler spectra. However, NWCA may be used with any moment algorithm that also computes a first moment confidence. For example, a very simple confidence algorithm can be defined in terms of the signal-to-noise ratio.
10
Baray, Jean-Luc, Yves Pointin, Joël Van Baelen, Marie Lothon, Bernard Campistron, Jean-Pierre Cammas, Olivier Masson et al. « Case Study and Climatological Analysis of Upper-Tropospheric Jet Stream and Stratosphere–Troposphere Exchanges Using VHF Profilers and Radionuclide Measurements in France ». Journal of Applied Meteorology and Climatology 56, no 11 (novembre 2017) : 3081–97. http://dx.doi.org/10.1175/jamc-d-16-0353.1.
Texte intégralRésumé :
AbstractThe authors present a climatological analysis of tropospheric horizontal wind profiles and jet stream events using long series of wind profiles from two VHF profilers located in France: Lannemezan (2001–14) and Opme (1999–2014). A case study of jet stream and stratospheric intrusion of air into the troposphere that occurred in January 2013 is first described and demonstrates the capability of the VHF profilers to detect jet stream events. The climatology study over the two sites reveals the strongest values of seasonal wind during winter (21.4 m s−1 at 8.7-km height at Opme; 25.1 m s−1 at 9.6-km height at Lannemezan). A methodology based on the automatic detection of maximum winds on a decadal series of hourly wind profiles allows the detection of jet stream events and establishes its climatology for each site. A frequency analysis of jet stream events of westerly winds over 50 m s−1 presents a clear seasonality at the two sites, with a maximum in winter (3.5%–9.7% of hourly profiles) and a minimum in summer (near 1%). Cosmogenic radionuclides sampled at Opme also exhibit a clear seasonal variation with maximum in spring and minimum in the cold seasons; the 7Be/22Na activity ratio confirms stratosphere-to-troposphere exchanges for the studied cases. The mean interannual variability of the frequency of jet stream events is 1.5% in Opme and 2.9% in Lannemezan. Positive decadal trends are observed for the two sites: +1.6 ± 1.2% decade−1 for Opme and +2.4 ± 2.2% decade−1 for Lannemezan.
11
Shaw, W. J., M. S. Pekour, R. L. Coulter, T. J. Martin et J. T. Walters. « The daytime mixing layer observed by radiosonde, profiler, and lidar during MILAGRO ». Atmospheric Chemistry and Physics Discussions 7, no 5 (19 octobre 2007) : 15025–65. http://dx.doi.org/10.5194/acpd-7-15025-2007.
Texte intégralRésumé :
Abstract. During the MILAGRO campaign centered in the Mexico City area, Pacific Northwest National Laboratory (PNNL) and Argonne National Laboratory (ANL) operated atmospheric profiling systems at Veracruz and at two locations on the Central Mexican Plateau in the region around Mexico City. These systems included radiosondes, wind profilers, a sodar, and an aerosol backscatter lidar. An additional wind profiler was operated by the University of Alabama in Huntsville (UAH) at the Mexican Petroleum Institue (IMP) near the center of Mexico City. Because of the opportunity afforded by collocation of profilers, radiosondes, and a lidar, and because of the importance of boundary layer depth for aerosol properties, we have carried out a comparison of mixing layer depth as determined independently from these three types of measurement systems during the campaign. We have then used results of this comparison and additional measurements to develop a detailed description of the daily structure and evolution of the boundary layer on the Central Mexican Plateau during MILAGRO. Our analysis indicates that the profilers were more consistently successful in establishing the mixing layer depth during the daytime. The boundary layer growth was similar at the three locations, although the mixing layer tended to be slightly deeper in the afternoon in central Mexico City. The sodar showed that convection began about an hour after sunrise. Maximum daily mixing layer depths always reached 2000 m a.g.l. and frequently extended to 4000 m. The rate and variability of mixing layer growth was essentially the same as that observed during the IMADA-AVER campaign in the same season in 1997. This growth did not seem to be related to whether deep convection was reported on a given day. Wind speeds within the boundary layer exhibited a daily low-altitude maximum in the late afternoon with lighter winds aloft, consistent with previous reports of diurnal regional circulations. Norte events, which produced high winds at Veracruz, did not appreciably modulate the winds on the plateau. Finally, despite the typically dry conditions at the surface, radiosonde profiles showed that relative humidity often exceeded 50% in the early morning and in the upper part of the boundary layer. This suggests that aerosol particles would have experienced hygroscopic growth within the boundary layer on many days.
12
Bond, Nicholas A., Carl F. Dierking et James D. Doyle. « Research Aircraft and Wind Profiler Observations in Gastineau Channel during a Taku Wind Event* ». Weather and Forecasting 21, no 4 (1 août 2006) : 489–501. http://dx.doi.org/10.1175/waf932.1.
Texte intégralRésumé :
Abstract The flow in Gastineau Channel near Juneau, Alaska, during the moderate Taku wind event of 18 October 2004 is examined using observations from the University of Wyoming’s King Air research aircraft, two wind profilers, and surface weather stations. These data sources reveal low-level winds directed down the central portion of Gastineau Channel, that is, gap flow. Farther down the channel, and above this gap flow, the winds were strongly cross channel in association with the downslope flow that characterizes Taku events. The transition region between these two flows included strong vertical wind shear and severe turbulence; measurements from the King Air indicate turbulent kinetic energy locally exceeding 50 m2 s−2. A high-resolution simulation of this case using the Naval Research Laboratory’s Coupled Ocean–Atmosphere Mesoscale Prediction System reproduced the observed character of the mean flow. This case illustrates the hazard to aviation posed by even a moderate Taku wind event and shows the value of a wind profiler for monitoring the vertical wind shear responsible for the hazard.
13
Teschke, Gerd, et Volker Lehmann. « Mean wind vector estimation using the velocity–azimuth display (VAD) method : an explicit algebraic solution ». Atmospheric Measurement Techniques 10, no 9 (6 septembre 2017) : 3265–71. http://dx.doi.org/10.5194/amt-10-3265-2017.
Texte intégralRésumé :
Abstract. This paper deals with the analysis of the sampling setup for Doppler profilers aiming at the determination of vertical profiles of the wind. An explicit solution for the retrieval of mean wind vectors under the assumption of local homogeneity is presented for the case of a symmetric velocity–azimuth display sampling, and a stability analysis is performed. Furthermore, the explicit solution allows a detailed investigation of the propagation of radial wind measurement errors on the retrieved wind vector.
14
Teshiba, M., M. D. Yamanaka, H. Hashiguchi, Y. Shibagaki, Y. Ohno et S. Fukao. « Secondary circulation within a tropical cyclone observed with L-band wind profilers ». Annales Geophysicae 22, no 11 (29 novembre 2004) : 3951–58. http://dx.doi.org/10.5194/angeo-22-3951-2004.
Texte intégralRésumé :
Abstract. In association with the passage of a Tropical Cyclone (TC) around Japan, the secondary circulation in the region from the outer side to the center was investigated in detail by two separately located L-band wind profilers and the rawinsonde observations from 1 to 2 October 2002, for the first time. As the wind profilers can observe wind fields not only within rainbands but also in between, the mesoscale wind circulation including the vertical wind component in wide areas from the lower layer to the upper layer was investigated. While the TC center approached the profiler stations, several rainbands associated with the TC subsequently passed. Relatively warm, moist inflow with a cyclonic rotation was observed in the lower-troposphere while the TC center approached. The inflow reached the inside of the main rainband where the updraft was observed. Above 5-km height (with temperature below 0°C), outflow and weak downdraft corresponding to falling frozen particles were observed. It is considered that the frozen particles formed precipitating clouds mainly in the outer rainband region. The continuous wind circulation transported water vapor from the lower troposphere to the upper troposphere via the vicinity of TC center. On the other hand, after the passage of the TC center, the developed rainband passed, which was located in the south and southwest quadrant of the TC. It is suggested with the profilers' data that the rainband was intensified mainly by warm and moist outflow below 3-km height.
15
Hu, Huiqin, Juanzhen Sun et Qinghong Zhang. « Assessing the Impact of Surface and Wind Profiler Data on Fog Forecasting Using WRF 3DVAR : An OSSE Study on a Dense Fog Event over North China ». Journal of Applied Meteorology and Climatology 56, no 4 (avril 2017) : 1059–81. http://dx.doi.org/10.1175/jamc-d-16-0246.1.
Texte intégralRésumé :
AbstractBecause fog is a high-impact weather phenomenon, there has been increased demand for its accurate prediction. Both surface data and wind profiler data possess great potential for improved fog prediction. This study aimed to quantitatively assess the impact of surface and wind profiler data on fog prediction in terms of their spatial resolutions and distributions and also to assess the relative effect of these two types of observations. A dense fog event in northern China that occurred on 20 February 2007 was studied using the Weather Research and Forecasting (WRF) Model’s three-dimensional variational data assimilation (3DVAR) system with observing system simulation experiments (OSSE). The results indicated that the incorporation of surface data has an obvious positive impact on fog forecasts, especially with respect to effective assimilation of automated weather station data. Dense planetary boundary layer (PBL) wind profilers are more beneficial for fog forecasting than troposphere wind profilers, and an even spatial distribution over a large region is superior to a localized distribution. Surface data show greater benefit for fog forecasting than wind profiler data, with a 6.6% increase of skill score as a result of the improvement of near-surface thermal stratification. Moreover, combining both types of data greatly enhances fog predictive skill, with a 13.6% increase in skill score relative to the experiment assimilating only surface data, as a result of better dynamically balanced fields of thermodynamic and kinematic variables within the PBL with the assimilation of PBL wind profiler data.
16
Strauch, R. G., D. A. Merritt, K. P. Moran, B. L. Weber, D. B. Wuertz et P. T. May. « Wind profilers for support of flight operations ». Journal of Aircraft 26, no 11 (novembre 1989) : 1009–15. http://dx.doi.org/10.2514/3.45874.
Texte intégral
17
Degelia, Samuel K., Xuguang Wang et David J. Stensrud. « An Evaluation of the Impact of Assimilating AERI Retrievals, Kinematic Profilers, Rawinsondes, and Surface Observations on a Forecast of a Nocturnal Convection Initiation Event during the PECAN Field Campaign ». Monthly Weather Review 147, no 8 (16 juillet 2019) : 2739–64. http://dx.doi.org/10.1175/mwr-d-18-0423.1.
Texte intégralRésumé :
Abstract Numerical weather prediction models often fail to correctly forecast convection initiation (CI) at night. To improve our understanding of such events, researchers collected a unique dataset of thermodynamic and kinematic remote sensing profilers as part of the Plains Elevated Convection at Night (PECAN) experiment. This study evaluates the impacts made to a nocturnal CI forecast on 26 June 2015 by assimilating a network of atmospheric emitted radiance interferometers (AERIs), Doppler lidars, radio wind profilers, high-frequency rawinsondes, and mobile surface observations using an advanced, ensemble-based data assimilation system. Relative to operational forecasts, assimilating the PECAN dataset improves the timing, location, and orientation of the CI event. Specifically, radio wind profilers and rawinsondes are shown to be the most impactful instrument by enhancing the moisture advection into the region of CI in the forecast. Assimilating thermodynamic profiles collected by the AERIs increases midlevel moisture and improves the ensemble probability of CI in the forecast. The impacts of assimilating the radio wind profilers, AERI retrievals, and rawinsondes remain large throughout forecasting the growth of the CI event into a mesoscale convective system. Assimilating Doppler lidar and surface data only slightly improves the CI forecast by enhancing the convergence along an outflow boundary that partially forces the nocturnal CI event. Our findings suggest that a mesoscale network of profiling and surface instruments has the potential to greatly improve short-term forecasts of nocturnal convection.
18
Lau, Elías, Scott McLaughlin, Frank Pratte, Bob Weber, David Merritt, Maikel Wise, Gary Zimmerman, Matthew James et Megan Sloan. « The DeTect Inc. RAPTOR VAD-BL Radar Wind Profiler ». Journal of Atmospheric and Oceanic Technology 30, no 9 (1 septembre 2013) : 1978–84. http://dx.doi.org/10.1175/jtech-d-12-00259.1.
Texte intégralRésumé :
Abstract The DeTect Inc. RAPTOR velocity–azimuth display boundary layer (VAD-BL) radar wind profiler is a pulsed Doppler radar used to make automatic unattended measurements of wind profiles in the lower atmosphere. All data products are produced on site, in real time, and utilize quality control software to screen out interference. The nominal frequencies are 915 and 1290 MHz but other frequencies can be accommodated. While the architecture is similar to other boundary layer wind profilers, the RAPTOR VAD-BL is designed to provide consistently superior data quality due to its antenna design and signal processing capabilities. The antenna is a high-performance parabolic reflector with a feed that is designed in house for the operational frequency of the radar. The antenna is mounted on a robust military-grade azimuth-only positioner. The RAPTOR VAD-BL can collect data from several opposing beam positions with the goal of producing higher-quality wind data using the velocity–azimuth display (VAD) algorithm. The Advanced Signal Processing Engine (ASPEN) software used to calculate winds outperforms conventional consensus algorithms. The health and status of all critical subsystems is monitored via the profiler health monitor (PHM), a stand-alone monitor with its own microprocessor. Results from systems deployed for operational applications show the potential for the retrieval of high-quality data with excellent height coverage and a solid design that allows the antenna to perform under sustained high wind loading.
19
Tridon, Frédéric, Alessandro Battaglia, Pavlos Kollias, Edward Luke et Christopher R. Williams. « Signal Postprocessing and Reflectivity Calibration of the Atmospheric Radiation Measurement Program 915-MHz Wind Profilers ». Journal of Atmospheric and Oceanic Technology 30, no 6 (1 juin 2013) : 1038–54. http://dx.doi.org/10.1175/jtech-d-12-00146.1.
Texte intégralRésumé :
Abstract The Department of Energy Atmospheric Radiation Measurement (ARM) Program has recently initiated a new research avenue toward a better characterization of the transition from cloud to precipitation. Dual-wavelength techniques applied to millimeter-wavelength radars and a Rayleigh reference have a great potential for rain-rate retrievals directly from dual-wavelength ratio measurements. In this context, the recent reconfiguration of the ARM 915-MHz wind profilers in a vertically pointing mode makes these instruments the ideal candidate for providing the Rayleigh reflectivity/Doppler velocity reference. Prior to any scientific study, the wind profiler data must be carefully quality checked. This work describes the signal postprocessing steps that are essential for the delivery of high-quality reflectivity and mean Doppler velocity products—that is, the estimation of the noise floor from clear-air echoes, the absolute calibration with a collocated disdrometer, the dealiasing of Doppler velocities, and the merging of the different modes of the wind profiler. The improvement added by the proposed postprocessing is confirmed by comparison with a high-quality S-band profiler deployed at the ARM Southern Great Plains site during the Midlatitude Continental Convective Clouds Experiment. With the addition of a vertically pointing mode and with the postprocessing described in this work in place, besides being a key asset for wind research wind profilers observations may therefore become a centerpiece for rain studies in the years to come.
20
Fast, Jerome D., Rob K. Newsom, K. Jerry Allwine, Qin Xu, Pengfei Zhang, Jeffrey Copeland et Juanzhen Sun. « An Evaluation of Two NEXRAD Wind Retrieval Methodologies and Their Use in Atmospheric Dispersion Models ». Journal of Applied Meteorology and Climatology 47, no 9 (1 septembre 2008) : 2351–71. http://dx.doi.org/10.1175/2008jamc1853.1.
Texte intégralRésumé :
Abstract Two entirely different methods for retrieving 3D fields of horizontal winds from Next Generation Weather Radar (NEXRAD) radial velocities have been evaluated using radar wind profiler measurements to determine whether routine wind retrievals would be useful for atmospheric dispersion model applications. The first method uses a physical algorithm based on four-dimensional variational data assimilation, and the second simpler method uses a statistical technique based on an analytic formulation of the background error covariance. Both methods can be run in near–real time, but the simpler method was executed about 2.5 times as fast as the four-dimensional variational method. The observed multiday and diurnal variations in wind speed and direction were reproduced by both methods below ∼1.5 km above the ground in the vicinity of Oklahoma City, Oklahoma, during July 2003. However, wind retrievals overestimated the strength of the nighttime low-level jet by as much as 65%. The wind speeds and directions obtained from both methods were usually similar when compared with profiler measurements, and neither method outperformed the other statistically. Within a dispersion model framework, the 3D wind fields and transport patterns were often better represented when the wind retrievals were included along with operational data. Despite uncertainties in the wind speed and direction obtained from the wind retrievals that are higher than those from remote sensing radar wind profilers, the inclusion of the wind retrievals is likely to produce more realistic temporal variations in the winds aloft than would be obtained by interpolation using the available radiosondes, especially during rapidly changing synoptic- and mesoscale conditions.
21
Browning, K. A., D. Jerrett, J. Nash, T. Oakley et N. M. Roberts. « Cold frontal structure derived from radar wind profilers ». Meteorological Applications 5, no 1 (mars 1998) : 67–74. http://dx.doi.org/10.1017/s1350482798000784.
Texte intégral
22
Nastrom, G. D., et T. E. VanZandt. « Mean Vertical Motions Seen by Radar Wind Profilers ». Journal of Applied Meteorology 33, no 8 (août 1994) : 984–95. http://dx.doi.org/10.1175/1520-0450(1994)033<0984:mvmsbr>2.0.co;2.
Texte intégral
23
Weisshaupt, Nadja, Juan Arizaga et Mercedes Maruri. « The role of radar wind profilers in ornithology ». Ibis 160, no 3 (3 janvier 2018) : 516–27. http://dx.doi.org/10.1111/ibi.12562.
Texte intégral
24
Williams, Christopher R., et Susan K. Avery. « Diurnal winds observed in the tropical troposphere using 50 MHz wind profilers ». Journal of Geophysical Research : Atmospheres 101, no D10 (1 juin 1996) : 15051–60. http://dx.doi.org/10.1029/96jd01013.
Texte intégral
25
McCaffrey, Katherine, James M. Wilczak, Laura Bianco, Eric Grimit, Justin Sharp, Robert Banta, Katja Friedrich et al. « Identification and Characterization of Persistent Cold Pool Events from Temperature and Wind Profilers in the Columbia River Basin ». Journal of Applied Meteorology and Climatology 58, no 12 (décembre 2019) : 2533–51. http://dx.doi.org/10.1175/jamc-d-19-0046.1.
Texte intégralRésumé :
AbstractCold pool events occur when deep layers of stable, cold air remain trapped in a valley or basin for multiple days, without mixing out from daytime heating. With large impacts on air quality, freezing events, and especially on wind energy production, they are often poorly forecast by modern mesoscale numerical weather prediction (NWP) models. Understanding the characteristics of cold pools is, therefore, important to provide more accurate forecasts. This study analyzes cold pool characteristics with data collected during the Second Wind Forecast Improvement Project (WFIP2), which took place in the Columbia River basin and Gorge of Oregon and Washington from fall 2015 until spring 2017. A subset of the instrumentation included three microwave radiometer profilers, six radar wind profilers with radio acoustic sounding systems, and seven sodars, which together provided seven sites with collocated vertical profiles of temperature, humidity, wind speed, and wind direction. Using these collocated observations, we developed a set of criteria to determine if a cold pool was present based on stability, wind speed, direction, and temporal continuity, and then developed an automated algorithm based on these criteria to identify all cold pool events over the 18 months of the field project. Characteristics of these events are described, including statistics of the wind speed distributions and profiles, stability conditions, cold pool depths, and descent rates of the cold pool top. The goal of this study is a better understanding of these characteristics and their processes to ultimately lead to improved physical parameterizations in NWP models, and consequently improve forecasts of cold pool events in the study region as well at other locations that experiences similar events.
26
Iwai, Hironori, Makoto Aoki, Mitsuru Oshiro et Shoken Ishii. « Validation of Aeolus Level 2B wind products using wind profilers, ground-based Doppler wind lidars, and radiosondes in Japan ». Atmospheric Measurement Techniques 14, no 11 (17 novembre 2021) : 7255–75. http://dx.doi.org/10.5194/amt-14-7255-2021.
Texte intégralRésumé :
Abstract. The first space-based Doppler wind lidar (DWL) on board the Aeolus satellite was launched by the European Space Agency (ESA) on 22 August 2018 to obtain global profiles of horizontal line-of-sight (HLOS) wind speed. In this study, the Raleigh-clear and Mie-cloudy winds for periods of baseline 2B02 (from 1 October to 18 December 2018) and 2B10 (from 28 June to 31 December 2019 and from 20 April to 8 October 2020) were validated using 33 wind profilers (WPRs) installed all over Japan, two ground-based coherent Doppler wind lidars (CDWLs), and 18 GPS radiosondes (GPS-RSs). In particular, vertical and seasonal analyses were performed and discussed using WPR data. During the baseline 2B02 period, a positive bias was found to be in the ranges of 0.5 to 1.7 m s−1 for Rayleigh-clear winds and 1.6 to 2.4 m s−1 for Mie-cloudy winds using the three independent reference instruments. The statistical comparisons for the baseline 2B10 period showed smaller biases, −0.8 to 0.5 m s−1 for the Rayleigh-clear and −0.7 to 0.2 m s−1 for the Mie-cloudy winds. The vertical analysis using WPR data showed that the systematic error was slightly positive in all altitude ranges up to 11 km during the baseline 2B02 period. During the baseline 2B10 period, the systematic errors of Rayleigh-clear and Mie-cloudy winds were improved in all altitude ranges up to 11 km as compared with the baseline 2B02. Immediately after the launch of Aeolus, both Rayleigh-clear and Mie-cloudy biases were small. Within the baseline 2B02, the Rayleigh-clear and Mie-cloudy biases showed a positive trend. For the baseline 2B10, the Rayleigh-clear wind bias was generally negative for all months except August 2020, and Mie-cloudy wind bias gradually fluctuated. Both Rayleigh-clear and Mie-cloudy biases did not show a marked seasonal trend and approached zero towards September 2020. The dependence of the Rayleigh-clear wind bias on the scattering ratio was investigated, showing that there was no significant bias dependence on the scattering ratio during the baseline 2B02 and 2B10 periods. Without the estimated representativeness error associated with the comparisons using WPR observations, the Aeolus random error was determined to be 6.7 (5.1) and 6.4 (4.8) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively. The main reason for the large Aeolus random errors is the lower laser energy compared to the anticipated 80 mJ. Additionally, the large representativeness error of the WPRs is probably related to the larger Aeolus random error. Using the CDWLs, the Aeolus random error estimates were in the range of 4.5 to 5.3 (2.9 to 3.2) and 4.8 to 5.2 (3.3 to 3.4) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively. By taking the GPS-RS representativeness error into account, the Aeolus random error was determined to be 4.0 (3.2) and 3.0 (2.9) m s−1 for Rayleigh-clear (Mie-cloudy) winds during the baseline 2B02 and 2B10 periods, respectively.
27
Newsom, Rob K., Larry K. Berg, Mikhail Pekour, Jerome Fast, Qin Xu, Pengfei Zhang, Qing Yang, William J. Shaw et Julia Flaherty. « Evaluation of Single-Doppler Radar Wind Retrievals in Flat and Complex Terrain ». Journal of Applied Meteorology and Climatology 53, no 8 (août 2014) : 1920–31. http://dx.doi.org/10.1175/jamc-d-13-0297.1.
Texte intégralRésumé :
AbstractThe accuracy of winds derived from Next Generation Weather Radar (NEXRAD) level-II data is assessed by comparison with independent observations from 915-MHz radar wind profilers. The evaluation is carried out at two locations with very different terrain characteristics. One site is located in an area of complex terrain within the State Line Wind Energy Center in northeastern Oregon. The other site is located in an area of flat terrain on the east-central Florida coast. The National Severe Storm Laboratory’s two-dimensional variational data assimilation (2DVar) algorithm is used to retrieve wind fields from the KPDT (Pendleton, Oregon) and KMLB (Melbourne, Florida) NEXRAD radars. Wind speed correlations at most observation height levels fell in the range from 0.7 to 0.8, indicating that the retrieved winds followed temporal fluctuations in the profiler-observed winds reasonably well. The retrieved winds, however, consistently exhibited slow biases in the range of 1–2 m s−1. Wind speed difference distributions were broad, with standard deviations in the range from 3 to 4 m s−1. Results from the Florida site showed little change in the wind speed correlations and difference standard deviations with altitude between about 300 and 1400 m AGL. Over this same height range, results from the Oregon site showed a monotonic increase in the wind speed correlation and a monotonic decrease in the wind speed difference standard deviation with increasing altitude. The poorest overall agreement occurred at the lowest observable level (~300 m AGL) at the Oregon site, where the effects of the complex terrain were greatest.
28
Pimenta, Felipe M., Osvaldo R. Saavedra, Denisson Q. Oliveira, Arcilan T. Assireu, Audálio R. Torres Júnior, Ramon M. de Freitas, Francisco L. Albuquerque Neto et al. « Characterization of Wind Resources of the East Coast of Maranhão, Brazil ». Energies 16, no 14 (22 juillet 2023) : 5555. http://dx.doi.org/10.3390/en16145555.
Texte intégralRésumé :
The objective of this work is to assess the wind resources of the east coast of Maranhão, Brazil. Wind profilers were combined with micrometeorological towers and atmospheric reanalysis to investigate micro- and mesoscale aspects of wind variability. Field campaigns recorded winds in the dry and wet seasons, under the influence of the Intertropical Convergence Zone. The dry season was characterized by strong winds (8 to 12 m s−1) from the northeast. Surface heat fluxes were generally positive (250 to 320 W m−2) at midday and negative (−10 to −20 W m−2) during the night. Convective profiles predominated near the beach, with strongly stable conditions rarely occurring before sunrise. Further inland, convective to strongly convective profiles occurred during the day, and neutral to strongly stable profiles at night. Wind speeds decreased during the rainy season (4 to 8 m s−1), with increasingly easterly and southeasterly components. Cloud cover and precipitation reduced midday heat fluxes (77 W m−2). Profiles were convective during midday and stable to strongly stable at night. Terrain roughness increased with distance from the ocean ranging from smooth surfaces (zo = 0.95 mm) and rough pastures (zo = 15.33 mm) to crops and bushes (zo = 52.68 mm), and trees and small buildings (zo = 246.46 mm) farther inland. Seasonal variations of the mean flow and sea and land breezes produced distinct diurnal patterns of wind speeds. The strongest (weakest) breeze amplitudes were observed in the dry (rainy) period. Daily changes in heat fluxes and fetch over land controlled the characteristics of wind profiles. During sea breezes, winds approached the coast at right angles, resulting in shorter fetches over land that maintained or enhanced oceanic convective conditions. During land breezes, winds blew from the mainland or with acute angles against the coastline, resulting in large fetches with nighttime surface cooling, generating strongly stable profiles. Coastal observations demonstrated that with increasing monopiles from 100 to 130 m it is possible to obtain similar capacity factors of beachfront turbines.
29
Lehmann, V., et G. Teschke. « Advanced intermittent clutter filtering for radar wind profiler : signal separation through a Gabor frame expansion and its statistics ». Annales Geophysicae 26, no 4 (13 mai 2008) : 759–83. http://dx.doi.org/10.5194/angeo-26-759-2008.
Texte intégralRésumé :
Abstract. A new signal processing method is presented for the suppression of intermittent clutter echoes in radar wind profilers. This clutter type is a significant problem during the seasonal bird migration and often results in large discrepancies between profiler wind measurements and independent reference data. The technique presented makes use of a discrete Gabor frame expansion of the coherently averaged time series data in combination with a statistical filtering approach to exploit the different signal characteristics between signal and clutter. The rationale of this algorithm is outlined and the mathematical methods used are presented in due detail. A first test using data obtained with an operational 482 MHz wind profiler indicates that the method outperforms the previously used clutter suppression algorithm.
30
Cohn, Stephen A., Vanda Grubišić et William O. J. Brown. « Wind Profiler Observations of Mountain Waves and Rotors during T-REX ». Journal of Applied Meteorology and Climatology 50, no 4 (avril 2011) : 826–43. http://dx.doi.org/10.1175/2010jamc2611.1.
Texte intégralRésumé :
A network of three boundary layer radar wind profilers is used to study characteristics of mountain waves and rotors and to explore the utility of such a network. The data employed were collected as part of the Terrain-Induced Rotor Experiment (T-REX), which took place in Owens Valley, California, in early 2006. The wind profilers provide a continuous time–height representation of wave and rotor structure. During intensive observing period 3 (IOP 3), the profiler network was positioned in an L-shaped configuration, capturing key features of the mountain waves and rotor, including the boundary layer vortex sheet (or shear layer), turbulence within this shear layer, the classical lower turbulence zone (LTZ), and wave motion above the LTZ. Observed features were found to be in good agreement with recent high-resolution numerical simulations. Using the wind profiler with superior time resolution (Multiple Antenna Profiler Radar), a series of updraft–downdraft couplets were observed beneath the first downwind wave crest. These are interpreted as signatures of subrotors. Such detailed observations of subrotors are rare, even though subrotors are believed to be a common feature of rotor circulations in Owens Valley. During IOP 6, the network was repositioned to form a line across the valley. A simple algorithm was used to determine the amplitude, wavelength, and phase of the primary wave over the valley and to observe their changes over time and height. In the IOP-6 case, the wavelength increased over time, the phase indicated an eastward-shifting wave crest, and the amplitude increased with height and also varied over time.
31
Tse, K. T., S. W. Li, P. W. Chan, H. Y. Mok et A. U. Weerasuriya. « Wind profile observations in tropical cyclone events using wind-profilers and doppler SODARs ». Journal of Wind Engineering and Industrial Aerodynamics 115 (avril 2013) : 93–103. http://dx.doi.org/10.1016/j.jweia.2013.01.003.
Texte intégral
32
Kobayashi, Takahisa, et Ahoro Adachi. « Measurements of raindrop breakup by using UHF wind profilers ». Geophysical Research Letters 28, no 21 (1 novembre 2001) : 4071–74. http://dx.doi.org/10.1029/2001gl013254.
Texte intégral
33
Augustine, John A., et Edward J. Zipser. « The Use of Wind Profilers in a Mesoscale Experiment ». Bulletin of the American Meteorological Society 68, no 1 (janvier 1987) : 4–17. http://dx.doi.org/10.1175/1520-0477(1987)068<0004:tuowpi>2.0.co;2.
Texte intégral
34
Kim, Campistron et Kwon. « Frontal Wind Field Retrieval Based on UHF Wind Profiler Radars and an S-band Radar Network ». Atmosphere 10, no 9 (14 septembre 2019) : 547. http://dx.doi.org/10.3390/atmos10090547.
Texte intégralRésumé :
The three-dimensional wind field (WPR3D) and the multiple WPR3D (M-WPR3D) associated with the passage of a stationary front was derived from observations made by a network of eight wind profiler radars (WPR) being operated by the Korea Meteorological Administration during the summer “Jangma” season. The effectiveness of the WPR3D was determined through numerical model analysis and wind profilers at three sites, and the accuracy of the M-WPR3D was validated by comparing the trajectory of the radiosonde. The discontinuity of the wind field near the frontal interface was clearly retrieved and the penetration of the air mass in the southern front was detected. Compared with either the wind vector of three single wind profiler or a local data assimilation and predication system, the WPR3D wind field showed a wind speed accuracy of approximately 70% at an altitude of 1.5 km and underestimated the wind speed by 0.5–1.5 m s−1. The M-WPR3D with three S-band Doppler radars successfully retrieved the backing wind field as well as the pre-Jangma-frontal jet. The results of this study showed that severe weather can be effectively analyzed using a three-dimensional wind field generated on the basis of a remote sensing network.
35
Compton, Jaime C., Ruben Delgado, Timothy A. Berkoff et Raymond M. Hoff. « Determination of Planetary Boundary Layer Height on Short Spatial and Temporal Scales : A Demonstration of the Covariance Wavelet Transform in Ground-Based Wind Profiler and Lidar Measurements* ». Journal of Atmospheric and Oceanic Technology 30, no 7 (1 juillet 2013) : 1566–75. http://dx.doi.org/10.1175/jtech-d-12-00116.1.
Texte intégralRésumé :
Abstract This article explores the application of the covariance wavelet transform (CWT) to lidar and, for the first time to the authors' knowledge, wind profiler data to examine the possibility of accurate and continuous planetary boundary layer (PBL) height measurements on short temporal resolution (1- and 15-min averages, respectively). Determining the mixing in the PBL was one goal of a study of the spatial and diurnal variations of the PBL height over Maryland for July 2011, during NASA's Earth Venture mission DISCOVER-AQ. The PBL heights derived from ground-based lidars [at University of Maryland, Baltimore County (UMBC); 39.25°N, 76.70°W], a 915-MHz wind profiler, and radiosondes (at Beltsville, Maryland; 38.92°N, 77.02°W) were compared. Results from the comparison show an R2 = 0.89, 0.92, and 0.94 correlation between the radiosonde PBL heights and two lidars and wind profiler PBL heights, respectively. Accurate determination of the PBL height by applying the CWT to lidar and wind profilers will allow for improved air quality forecasting and understanding of regional pollution dynamics.
36
Wullenweber, Nellie, Lars R. Hole, Peygham Ghaffari, Inger Graves, Harald Tholo et Lionel Camus. « SailBuoy Ocean Currents : Low-Cost Upper-Layer Ocean Current Measurements ». Sensors 22, no 15 (25 juillet 2022) : 5553. http://dx.doi.org/10.3390/s22155553.
Texte intégralRésumé :
This study introduces an alternative to the existing methods for measuring ocean currents based on a recently developed technology. The SailBuoy is an unmanned surface vehicle powered by wind and solar panels that can navigate autonomously to predefined waypoints and record velocity profiles using an integrated downward-looking acoustic Doppler current profiler (ADCP). Data collected on two validation campaigns show a satisfactory correlation between the SailBuoy current records and traditional observation techniques such as bottom-mounted and moored current profilers and moored single-point current meter. While the highest correlations were found in tidal signals, strong current, and calm weather conditions, low current speeds and varying high wave and wind conditions reduced correlation considerably. Filtering out some events with the high sea surface roughness associated with high wind and wave conditions may increase the SailBuoy ADCP listening quality and lead to better correlations. Not yet resolved is a systematic offset between the measurements obtained by the SailBuoy and the reference instruments of ±0.03 m/s. Possible reasons are discussed to be the differences between instruments (various products) as well as changes in background noise levels due to environmental conditions.
37
Gunter, W. Scott, John L. Schroeder et Brian D. Hirth. « Validation of Dual-Doppler Wind Profiles with in situ Anemometry ». Journal of Atmospheric and Oceanic Technology 32, no 5 (mai 2015) : 943–60. http://dx.doi.org/10.1175/jtech-d-14-00181.1.
Texte intégralRésumé :
AbstractTypical methods used to acquire wind profiles from Doppler radar measurements rely on plan position indicator (PPI) scans being performed at multiple elevation angles to utilize the velocity–azimuth display technique or to construct dual-Doppler synthesis. These techniques, as well as those employed by wind profilers, often produce wind profiles that lack the spatial or temporal resolution to resolve finescale features. If two radars perform range–height indicator (RHI) scans (constant azimuth, multiple elevations) along azimuths separated by approximately 90°, then the intersection of the coordinated RHI planes represents a vertical set of points where dual-Doppler wind syntheses are possible and wind speed and direction profiles can be retrieved. This method also allows for the generation of high-resolution wind time histories that can be compared to anemometer time histories. This study focuses on the use of the coordinated RHI scanning strategy by two high-resolution mobile Doppler radars in close proximity to a 200-m instrumented tower. In one of the first high-resolution, long-duration comparisons of dual-Doppler wind synthesis with in situ anemometry, the mean and turbulence states of the wind measured by each platform were compared in varying atmospheric conditions. Examination of mean wind speed and direction profiles in both clear-air (nonprecipitating) and precipitating environments revealed excellent agreement above approximately 50 m. Below this level, dual-Doppler wind speeds were still good but slightly overestimated as compared to the anemometer-measured wind speeds in heavy precipitation. Bulk turbulence parameters were also slightly underestimated by the dual-Doppler syntheses.
38
Dosser, Hayley V., Luc Rainville et John M. Toole. « Near-Inertial Internal Wave Field in the Canada Basin from Ice-Tethered Profilers ». Journal of Physical Oceanography 44, no 2 (1 février 2014) : 413–26. http://dx.doi.org/10.1175/jpo-d-13-0117.1.
Texte intégralRésumé :
Abstract Salinity and temperature profiles from drifting ice-tethered profilers in the Beaufort gyre region of the Canada Basin are used to characterize and quantify the regional near-inertial internal wave field over one year. Vertical displacements of potential density surfaces from the surface to 750-m depth are tracked from fall 2006 to fall 2007. Because of the time resolution and irregular sampling of the ice-tethered profilers, near-inertial frequency signals are marginally resolved. Complex demodulation is used to determine variations with a time scale of several days in the amplitude and phase of waves at a specified near-inertial frequency. Characteristics and variability of the wave field over the course of the year are investigated quantitatively and related to changes in surface wind forcing and sea ice cover.
39
Illingworth, A. J., D. Cimini, C. Gaffard, M. Haeffelin, V. Lehmann, U. Löhnert, E. J. O’Connor et D. Ruffieux. « Exploiting Existing Ground-Based Remote Sensing Networks to Improve High-Resolution Weather Forecasts ». Bulletin of the American Meteorological Society 96, no 12 (1 décembre 2015) : 2107–25. http://dx.doi.org/10.1175/bams-d-13-00283.1.
Texte intégralRésumé :
Abstract A new generation of high-resolution (1 km) forecast models promises to revolutionize the prediction of hazardous weather such as windstorms, flash floods, and poor air quality. To realize this promise, a dense observing network, focusing on the lower few kilometers of the atmosphere, is required to verify these new forecast models with the ultimate goal of assimilating the data. At present there are insufficient systematic observations of the vertical profiles of water vapor, temperature, wind, and aerosols; a major constraint is the absence of funding to install new networks. A recent research program financed by the European Union, tasked with addressing this lack of observations, demonstrated that the assimilation of observations from an existing wind profiler network reduces forecast errors, provided that the individual instruments are strategically located and properly maintained. Additionally, it identified three further existing European networks of instruments that are currently underexploited, but with minimal expense they could deliver quality-controlled data to national weather services in near–real time, so the data could be assimilated into forecast models. Specifically, 1) several hundred automatic lidars and ceilometers can provide backscatter profiles associated with aerosol and cloud properties and structures with 30-m vertical resolution every minute; 2) more than 20 Doppler lidars, a fairly new technology, can measure vertical and horizontal winds in the lower atmosphere with a vertical resolution of 30 m every 5 min; and 3) about 30 microwave profilers can estimate profiles of temperature and humidity in the lower few kilometers every 10 min. Examples of potential benefits from these instruments are presented.
40
Baidar, Sunil, Timothy J. Wagner, David D. Turner et W. Alan Brewer. « Using optimal estimation to retrieve winds from velocity-azimuth display (VAD) scans by a Doppler lidar ». Atmospheric Measurement Techniques 16, no 15 (10 août 2023) : 3715–26. http://dx.doi.org/10.5194/amt-16-3715-2023.
Texte intégralRésumé :
Abstract. Low-powered commercially available coherent Doppler lidar (CDL) wind profilers provide continuous measurement of vertical profiles of wind in the lower troposphere, usually close to or up to the top of the planetary boundary layer. The vertical extent of these wind profiles is limited by the availability of scatterers and thus varies substantially throughout the day and from one day to the next. This makes it challenging to develop continuous products that rely on CDL-observed wind profiles. In order to overcome this problem, we have developed a new method for wind profile retrievals from CDL that combines the traditional velocity-azimuth display (VAD) technique with optimal estimation (OE) to provide continuous wind profiles up to 3 km. The new method exploits the level-to-level covariance present in the wind profile to fill in the gaps where the signal-to-noise ratio of the CDL return is too low to provide reliable results using the traditional VAD method. Another advantage of the new method is that it provides the full error covariance matrix of the solution and profiles of information content, which more easily facilitates the assimilation of the observed wind profiles into numerical weather prediction models. This method was tested using yearlong CDL measurements at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) Central Facility in 2019. Comparison with the ARM operational CDL wind profile product and collocated radiosonde wind measurements shows excellent agreement (R2>0.99) with no degradation in results where the traditional VAD provided a valid solution. In the region where traditional VAD does not provide results, the OE wind speed and wind vector have uncertainties of 3.44 and 4.33 m s−1, respectively. As a result, the new method provides additional information over the standard technique and increases the effective range of existing CDL systems without the need for additional hardware.
41
Shestakova, Anna A., Ekaterina V. Fedotova et Vasily S. Lyulyukin. « Relevance Of Era5 Reanalysis For Wind Energy Applications : Comparison With Sodar Observations ». GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY 17, no 1 (3 avril 2024) : 54–66. http://dx.doi.org/10.24057/2071-9388-2023-2782.
Texte intégralRésumé :
ERA5 reanalysis is one of the most trusted climate data sources for wind energy modeling. However, any reanalysis should be verified through comparison with observational data to detect biases before further use. For wind verification at heights close to typical wind turbine hub heights (i.e. about 100 m), it is preferable to use either in-situ measurements from meteorological towers or remote sensing data like acoustic and laser vertical profilers, which remain independent of reanalysis. In this study, we validated the wind speed data from ERA5 at a height of 100 m using data from four sodars (acoustic profilers) located in different climatic and natural vegetation zones across European Russia. The assessments revealed a systematic error at most stations; in general, ERA5 tends to overestimate wind speed over forests and underestimate it over grasslands and deserts. As anticipated, the largest errors were observed at a station on the mountain coast, where the relative wind speed error reached 45%. We performed the bias correction which reduced absolute errors and eliminated the error dependence on the daily course, which was crucial for wind energy modeling. Without bias correction, the error in the wind power capacity factor ranged from 30 to 50%. Hence, it is strongly recommended to apply correction of ERA5 for energy calculations, at least in the areas under consideration..
42
He, Junyi, Qiusheng Li, Pak-Wai Chan, Chun-Wing Choy, Betty Mak, Ching-Chi Lam et Hong-Yan Luo. « An Observational Study of Typhoon Talim over the Northern Part of the South China Sea in July 2023 ». Atmosphere 14, no 9 (25 août 2023) : 1340. http://dx.doi.org/10.3390/atmos14091340.
Texte intégralRésumé :
Extensive surface and upper air measurements of a typhoon over the northern part of the South China Sea, namely, Typhoon Talim in July 2023, are documented and analysed in this paper. A number of features have been observed from the upper air measurements. First, the log law and the power law were found to be appropriate in fitting the wind profiles of the typhoon in the first 1000 m or so above the sea surface. Second, a low-level jet with the height of the maximum wind speed of around 1000 m was observed in the lower troposphere from the observations of the radar wind profilers. This paper is also novel from the perspectives that the vertical wind profile from a Doppler LIDAR on an offshore platform over the northern part of the South China sea and ocean radar data are used to analyse the surface wind observations of a typhoon in the region. The results of this paper would be useful in understanding the structure of tropical cyclones, e.g., in wind engineering applications.
43
Rogers, R. R., S. A. Cohn, W. L. Ecklund, J. S. Wilson et D. A. Carter. « Experience from one year of operating a boundary-layer profiler in the center of a large city ». Annales Geophysicae 12, no 6 (31 mai 1994) : 529–40. http://dx.doi.org/10.1007/s00585-994-0529-y.
Texte intégralRésumé :
Abstract. Since May 1992 a small, 915-MHz profiler has been operated continuously in downtown Montreal. It is a five-beam system employing a microstrip array antenna, located atop a 14-story office building that houses several academic departments of McGill University. The data are used for research on precipitation physics and the clear-air reflectivity in addition to wind profiling. We are especially interested in situations in which the reflectivities of the clear air and the precipitation are comparable. This permits the study of interactions between the precipitation and the clear air, a new area of research made possible by wind profilers. On clear days in the summer, 30-min consensus winds can often be measured to an altitude of 3 km, but ground clutter in the antenna sidelobes interferes with measurements below 600 m. Rain when present often permits wind profiling down to 100 m and up to 6 km or higher. On cold winter days there are some periods when the reflectivity is too weak at all levels to permit wind estimation. Falling snow, however, provides readily detectable echoes and serves as a good tracer of the wind and so allows profiling over its full altitude extent. The best conditions for observing interactions between precipitation and the clear air are when light rain falls through a reflective layer associated with a frontal surface or inversion. Unexpectedly, flocks of migrating birds sometimes completely dominate the signal at night in the spring and fall seasons.
44
Gossard, Earl E., Daniel E. Wolfe et B. Boba Stankov. « Measurement of Humidity Profiles in the Atmosphere by the Global Positioning System and Radar Wind Profilers ». Journal of Atmospheric and Oceanic Technology 16, no 1 (janvier 1999) : 156–64. http://dx.doi.org/10.1175/1520-0426(1999)016<0156:mohpit>2.0.co;2.
Texte intégral
45
Merceret, Francis J. « Rapid Temporal Changes of Boundary Layer Winds ». Journal of Applied Meteorology and Climatology 45, no 7 (1 juillet 2006) : 1016–20. http://dx.doi.org/10.1175/jam2377.1.
Texte intégralRésumé :
Abstract The statistical distribution of the magnitude of the vector wind change over 0.25-, 0.5-, 1-, and 2-h periods based on central Florida data from November 1999 through August 2001 is presented. The distributions of the 2-h u and υ wind-component changes are also presented for comparison. The wind changes at altitudes from 500 to 3000 m were measured using the Eastern Range network of five 915-MHz Doppler radar wind profilers. Quality-controlled profiles were produced every 15 min for up to 60 gates, each representing 101 m in altitude over the range from 130 to 6089 m. Five levels, each constituting three consecutive gates, were selected for analysis because of their significance to aerodynamic loads during the space-shuttle-ascent roll maneuver. The distribution of the magnitude of the vector wind change is found to be lognormal, consistent with earlier work in the midtroposphere. The parameters of the distribution vary with time lag, season, and altitude. The component wind changes are symmetrically distributed, with near-zero means, but the kurtosis coefficient is larger than that of a Gaussian distribution.
46
Anandan, V. K., et D. B. V. Jagannatham. « An Autonomous Interference Detection and Filtering Approach Applied to Wind Profilers ». IEEE Transactions on Geoscience and Remote Sensing 48, no 4 (avril 2010) : 1660–66. http://dx.doi.org/10.1109/tgrs.2009.2034258.
Texte intégral
47
Angevine, Wayne M. « Errors in Mean Vertical Velocities Measured by Boundary Layer Wind Profilers ». Journal of Atmospheric and Oceanic Technology 14, no 3 (juin 1997) : 565–69. http://dx.doi.org/10.1175/1520-0426(1997)014<0565:eimvvm>2.0.co;2.
Texte intégral
48
Eng, Ken, Richard L. Coulter et Wilfried Brutsaert. « Vertical Velocity Variance in the Mixed Layer from Radar Wind Profilers ». Journal of Hydrologic Engineering 8, no 6 (novembre 2003) : 301–7. http://dx.doi.org/10.1061/(asce)1084-0699(2003)8:6(301).
Texte intégral
49
Venkatesh Murthy, B. T., et I. Srinivasa Rao. « Design of narrow band UHF low noise amplifier for wind profilers ». Microwave and Optical Technology Letters 57, no 3 (23 janvier 2015) : 600–603. http://dx.doi.org/10.1002/mop.28909.
Texte intégral
50
Gaffard, C., J. Nash, E. Walker, T. J. Hewison, J. Jones et E. G. Norton. « High time resolution boundary layer description using combined remote sensing instruments ». Annales Geophysicae 26, no 9 (5 septembre 2008) : 2597–612. http://dx.doi.org/10.5194/angeo-26-2597-2008.
Texte intégralRésumé :
Abstract. Ground based remote sensing systems for future observation operations will allow continuous monitoring of the lower troposphere at temporal resolutions much better than every 30 min. Observations which may be considered spurious from an individual instrument can be validated or eliminated when considered in conjunction with measurements from other instruments observing at the same location. Thus, improved quality control of atmospheric profiles from microwave radiometers and wind profilers should be sought by considering the measurements from different systems together rather than individually. In future test bed deployments for future operational observing systems, this should be aided by observations from laser ceilometers and cloud radars. Observations of changes in atmospheric profiles at high temporal resolution in the lower troposphere are presented from a 12 channel microwave radiometer and 1290 MHz UHF wind profiler deployed in southern England during the CSIP field experiment in July/August 2005. The observations chosen were from days when thunderstorms occurred in southern England. Rapid changes near the surface in dry layers are considered, both when rain/hail may be falling from above and where the dry air is associated with cold pools behind organised thunderstorms. Also, short term variations in atmospheric profiles and vertical stability are presented on a day with occasional low cloud, when thunderstorms triggered 50 km down wind of the observing site Improved quality control of the individual remote sensing systems need to be implemented, examining the basic quality of the underlying observations as well as the final outputs, and so for instance eliminating ground clutter as far as possible from the basic Doppler spectra measurements of the wind profiler. In this study, this was performed manually. The potential of incorporating these types of instruments in future upper air observational networks leads to the challenge to improve the observing systems and also to exploit measurements at high temporal resolution in numerical weather prediction. These examples are intended to inform potential operational users of the changes in atmospheric structure that can be observed with the new types of observing system.