Analysis Of Wind Field Research Articles

Comparative Performance Analysis of Different Wind Fields in Southern and North-Western Coastal Areas of the Black Sea

This study determines the qualities of atmospheric wind field data in comparison with wind measurements at five locations along the Black Sea coast. For this purpose, four different wind fields were obtained from three different weather centres (NCEP, NASA, and ECMWF). Three of these are reanalyses winds (Climate Forecast System Reanalysis CFSR, Modern-Era Retrospective-analysis for Research and Applications MERRA, ECMWF reanalyses ERA-Interim) and one is the operational dataset (ECMWF operational). The performance of them was determined using the wind measurements from 2000 to 2014 at five coastal locations along the southern coastline of the Black Sea (Kumköy, Amasra, Sinop, Giresun, Hopa) and from 2006 to 2009 at offshore location (Gloria) off the coast of Romania. Performances of these wind fields were determined based on statistical characteristics (mean, standard deviation and variation coefficient etc.), statistical error analysis for all data and for different wind speed intervals, wind roses and probability distributions. Besides, long-term variations of yearly error values (SI and bias) of wind speeds from wind data sources during 2000 - 2014 were discussed. Finally, it was concluded that the CFSR winds give the best performance at most stations. The ECMWF datasets yield better results along the western side but CFSR wind fields have shown better performance along the eastern side of the Black Sea coast and at Gloria offshore location.

Contributions of modern Gobi Desert to the Badain Jaran Desert and the Chinese Loess Plateau

It is well known that the Gobi Desert is the dominant source area of the Badain Jaran Desert (BJD) and the Chinese Loess Plateau (CLP). However, due to the absence of quantitative analyses, there are nearly no exact assessments of its actual contribution. Combinations of field investigations, wind tunnel experiments, and wind field analyses revealed that the potential erosion depth on modern Gobi Desert varied between 0.41 and 0.89 mm a−1. Results indicated it would take an average theoretical time of 80.8 ka and 4,475.9 ka to form the current dimensions of the BJD and CLP, respectively, which means the Gobi Desert may provide substantial sand sources to the modern BJD, while its contribution to the loess of modern CLP might be overestimated despite it was the key sources of the CLP in Quaternary.

Feature analysis of stratospheric wind and temperature fields over the Antigua site by rocket data

The wind and temperature fields at 20 to 55 km above the Antigua launch site (17°N, 61°W) were analyzed by using sounding rocket data published by the research organization on Stratosphere-Troposphere Processes and their Role in Climate (SPARC). The results showed distinct variations in the wind and temperature fields at different heights from the 1960s to the 1990s. The overall zonal wind speed showed a significant increasing trend with the year, and the overall change in meridional wind speed showed a falling trend from 1976 to 1990, whereas the temperature field showed a significant cooling trend from 1964 to 1990. The times the trends mutated varied at different levels. By taking the altitudes at 20, 35, and 50 km as representatives, we found that the zonal wind speed trend had mutated in 1988, 1986, and 1986, respectively; that the meridional wind speed trend had mutated in 1990, 1986, and 1990, respectively; and that the temperature trend had mutated separately in 1977, 1973, and 1967, respectively. Characteristics of the periodic wind and temperature field variations at different heights were also analyzed, and obvious differences were found in time scale variations across the different layers. The zonal and meridional wind fields were basically characterized as having a significant periodic variation of 5 years across the three layers, and each level was characterized as having a periodic variation of less than 5 years. Temperature field variation at the three levels was basically characterized as occurring in 10-year and 5-year cycles.

Numerical analysis of wind field induced by moving train on HSR bridge subjected to crosswind

To investigate the characteristics of the combined wind field produced by the natural wind field and the train-induced wind field on the bridge, the aerodynamic models of train and bridge are established and the overset mesh technology is applied to simulate the movement of high-speed train. Based on ten study cases with various crosswind velocities of 0~20 m/s and train speeds of 200~350 km/h, the distributions of combined wind velocities at monitoring points around the train and the pressure on the car-body surface are analyzed. Meanwhile, the difference between the train-induced wind fields calculated by static train model and moving train model is compared. The results show that under non-crosswind condition, the train-induced wind velocity increases with the train speed while decreases with the distance to the train. Under the crosswind, the combined wind velocity is mainly controlled by the crosswind, and slightly increases with the train speed. In the combined wind field, the peak pressure zone on the headstock surface moves from the nose area to the windward side with the increase of wind velocity. The moving train model is more applicable in analyzing the train induced wind field.

Analysis of Wind Field over an Artificial Straight Dune by LES Simulations

ABSTRACT Kuribayashi., T. and Udo., K., 2018. Analysis of wind field over an artificial straight dune by LES simulations. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 301–305. Coconut Creek (Florida), ISSN 0749-0208. This study analyzed the wind fields around an artificial straight dune by large eddy simulations to investigate the mechanism of its separation into smaller dunes in more than 10 years at the Kashima Coast. The results showed that the change in ground height at the leeward slope was positive at almost all locations, but negative approximately every 50 m when the inflow wind was from an onshore direction. The change decreased approximately every 100 m where the inflow wind was from an offshore direction. The change in 15 years was positive at almost all locations, but at some locations on the south side, the change was negative; however, the cha...

Prediction of Uncertainty Using the Third Generation Wave Model WAVEWATCH III Driven By ERA-40 and Blended Winds in the North Indian Ocean

Simulation of waves in North Indian Ocean using ERA-40 and QuikSCAT/NCEP blended winds over 1° × 1° grid resolutions has been realised globally as well regionally using the third-generation wave model WAVEWATCH III (WWIII). Moreover, the model performance was evaluated by quantifying the uncertainty`s. So, WWIII simulations have been carried out for the North Indian Ocean from 50°E to 100°E and 0°N to 30°N with the past analysed winds (hindcasting) and the boundary conditions from the global run. The model outputs such as significant wave height (Hs) and mean wave period (Tc) are compared with the buoy measurements. To assess the performance, various statistical errors have been estimated by validating the model results against moored buoy data in the Arabian Sea and Bay of Bengal. The validation of WWIII with buoy measurements gave promising results for the North Indian Ocean with Model Performance Index ranging from 0.86 to 0.99, irrespective of the input winds. Also, Percentage Error ranges from 3.1 to 18.8% for the selected periods (January, July and October) except April. Further, the model was examined with different wind forcing’s and the study revealed better performances with blended winds, which could accurately predict Hs and Tc at buoy locations. This study concludes that, WWIII model predicts the sea-state evolution with acceptable uncertainty, which is reliable for the Indian Seas (North Indian Ocean) using the analysed wind fields. Further, better accuracy is achieved using blended wind products.

Regional characteristics of NO2 column densities from Pandora observations during the MAPS-Seoul campaign.

Vertical column density (VCD) of nitrogen dioxide (NO2) was measured using Pandora spectrometers at six sites on the Korean Peninsula during the Megacity Air Pollution Studies-Seoul (MAPS-Seoul) campaign from May to June 2015. To estimate the tropospheric NO2 VCD, the stratospheric NO2 VCD from the Ozone Monitoring Instrument (OMI) was subtracted from the total NO2 VCD from Pandora. European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis wind data was used to analyze variations in tropospheric NO2 VCD caused by wind patterns at each site. The Yonsei/SEO site was found to have the largest tropospheric NO2 VCD (1.49 DU on average) from a statistical analysis of hourly tropospheric NO2 VCD measurements. At rural sites, remarkably low NO2 VCDs were observed. However, a wind field analysis showed that trans-boundary transport and emissions from domestic sources lead to an increase in tropospheric NO2 VCD at NIER/BYI and KMA/AMY, respectively. At urban sites, high NO2 VCD values were observed under conditions of low wind speed, which were influenced by local urban emissions. Tropospheric NO2 VCD at HUFS/Yongin increases under conditions of significant transport from urban area of Seoul according to a correlation analysis that considers the transport time lag. Significant diurnal variations were found at urban sites during the MAPS-Seoul campaign, but not at rural sites, indicating that it is associated with diurnal patterns of NO2 emissions from dense traffic.

Analysis of the 6 September 2015 Tornadic Storm Around the Tokyo Metropolitan Area Using Coupled 3DVAR and Incremental Analysis Updates

This study reports preliminary results from the three-dimensional variational method (3DVAR) with incremental analysis updates (IAU) of the surface wind field, which is suitable for real-time processing. In this study, 3DVAR with IAU was calculated for the case of a tornadic storm using 500-m horizontal grid spacing with updates every 10 min, for 6 h. Radial velocity observations by eight X-band multi-parameter Doppler radars and three Doppler lidars around the Tokyo Metropolitan area, Japan, were used for the analysis. In this study, three types of analyses were performed between 1800 to 2400 LST (local standard time: UTC + 9 h) 6 September 2015. The first used only 3DVAR (3DVAR), the second used 3DVAR with IAU (3DVAR+IAU), and the third analysis did not use data assimilation (CNTL). 3DVAR+IAU showed the best accuracy of the three analyses, and 3DVAR alone showed the worst accuracy, even though the background was updated every 10 min. Sharp spike signals were observed in the time series of wind speed at 10 m AGL, analyzed by 3DVAR, strongly suggesting that a “shock” was caused by dynamic imbalance due to the instantaneous addition of analysis increments to the background wind components. The spike signal was not shown in 3DVAR+IAU analysis, therefore, we suggest that the IAU method reduces the shock caused by the addition of analysis increments. This study provides useful information on the most suitable DA method for the real-time analysis of surface wind fields.

Spatio-temporal modelling of extreme wave heights in the Mediterranean Sea

This study reveals characteristics of the Mediterranean Seas wave climate by illustrating the results of a spatial assessment of extreme significant wave heights. The assessment was based on a 37-year wind and wave hindcast database covering the entire area at 10-km resolution. A point-wise GEV (Generalized Extreme Values) model was employed to generate the assessments results. Overall, the spatial model proved capable of providing an accurate description of extreme return levels of significant wave heights and their spatial variability, especially on a basin-wide scale and with greatest precision on the mesoscale. However, return level estimates are found less reliable in certain coastal areas because the traditional point-wise approach is not refined enough to address the entire wave spectrum of an area as complex as the Mediterranean Sea. Therefore, MSLP (Mean Sea Level Pressure) fields were incorporated as covariates to improve localized assessment. These covariates represent meteorological forcing and allow analysis of the role of different cyclonic regimes in defining wave features and their spatial variability. Finally, the broad temporal span and high spatial resolution of the hindcast database allow for EOF (Empirical Orthogonal Function) and CCA (Canonical Correlation Analysis) analysis of wind and waves fields. This analysis validates spatial wave distribution assessment, revealing that the main processes governing the Mediterranean Seas wave climate can be attributed to four main modes.

Wave Hindcast Experiments Using Wam Cycle 4.5.3 - Validation with In situ Measurements in the North Indian Ocean

In this investigation, the execution of the wave model WAM Cycle 4.5.3 was evaluated; based on the forcings by two distinct wind fields namely ERA-40 and QuikSCAT-NCEP Blended winds in the North Indian Ocean. Using the past analysed winds (hindcasting) and with boundary conditions generated from 1° x 1° global runs the wave model have been implemented for the North Indian Ocean from 50°E to 100°E and 0°N to 30°N. The model simulated parameters namely significant wave height (Hs), mean wave periods (Tc), mean wave direction, swell wave height (Hsw), swell wave period (Tsw) and swell wave directions are presented. Further, the predicted waves are compared against in-situ wave measurements. The simulated wave parameters obtained as outputs from numerical simulations such as Hs and Tc; collocated in space and time have been compared with buoy measurements in the Arabian Sea and Bay of Bengal with the aid of statistical error indicators. Comparison between the predicted and observed wave parameters are very encouraging, excepting the higher model estimates of significant wave height and the disagreement in lower wave heights at few buoy locations. Further, the sensitivity of the model to two different wind fields was analyzed and it is noted that the blended winds could accurately reproduce Hs and Tc at the buoy locations. The present study suggests that, WAM Cycle 4.5.3 model predictions are quite reliable for the Indian seas using the analysed wind fields such as ERA-40 and QuikSCAT/NCEP Blended wind fields. However, the performance of wave model was best when blended winds were used. Despite several limitations, the results reveal that the performance of third generation wave model is promising and the correlation and deviation of simulated and measured waves are critically inspected.

Fluctuating wind field analysis based on random Fourier spectrum for wind induced response of high-rise structures

An accurate calculation of the stochastic wind field is the foundation for analyzing wind-induced structure response and reliability. In this research, the spatial correlation of structural wind field was considered based on the time domain method. A method for calculating the stochastic wind field based on cross stochastic Fourier spectrum was proposed. A flowchart of the proposed methodology is also presented in this study to represent the algorithm and workflow. Along with the analysis of regional wind speed distribution, the wind speed time history sample was calculated, and the efficiency can therefore be verified. Results show that the proposed method and programs could provide an efficient simulation for the wind-induced structure response analysis, and help determine the related parameters easily.

Distribution and sources of air pollutants in the North China Plain based on on-road mobile measurements

Abstract. The North China Plain (NCP) has been experiencing severe air pollution problems with rapid economic growth and urbanisation. Many field and model studies have examined the distribution of air pollutants in the NCP, but convincing results have not been achieved, mainly due to a lack of direct measurements of pollutants over large areas. Here, we employed a mobile laboratory to observe the main air pollutants in a large part of the NCP from 11 June to 15 July 2013. High median concentrations of sulfur dioxide (SO2) (12 ppb), nitrogen oxides (NOx) (NO + NO2; 452 ppb), carbon monoxide (CO) (956 ppb), black carbon (BC; 5.5 µg m−3) and ultrafine particles (28 350 cm−3) were measured. Most of the high values, i.e. 95 percentile concentrations, were distributed near large cities, suggesting the influence of local emissions. In addition, we analysed the regional transport of SO2 and CO, relatively long-lived pollutants, based on our mobile observations together with wind field and satellite data analyses. Our results suggested that, for border areas of the NCP, wind from outside this area would have a diluting effect on pollutants, while south winds would bring in pollutants that have accumulated during transport through other parts of the NCP. For the central NCP, the concentrations of pollutants were likely to remain at high levels, partly due to the influence of regional transport by prevalent south–north winds over the NCP and partly by local emissions.

Trans-boundary aerosol transport during a winter haze episode in China revealed by ground-based Lidar and CALIPSO satellite

By employing PM2.5 observation data, ground-based lidar measurements, MODIS and CALIPSO satellite images, meteorological data, and back trajectories analysis, we investigate a trans-boundary transport of aerosols during a large-area haze episode in China during 3–5 January 2015. The ground-based lidar observations indicated similar episodes of external aerosols passing through and mixing into three East China cities. A considerable amount of total AOD below 3 km (46% in average) was contributed by the external aerosol layers during passing over and importing. CALIPSO satellite observations of central and eastern China revealed a high altitude pollutant belt on January 3. Although the severest ground pollution was found in central and south-eastern Hebei, the high altitude pollution transport was greater in south-western Shandong, north-western Jiangsu, and north-western Anhui. These observations along with the analysis of air mass trajectories and wind fields indicates pollutants moving from Hebei, Henan and Hubei probably contributed to the haze pollution in Shandong and Jiangsu. This study reveals haze transports from North China Plain to East China could be a common phenomenon influenced by the winter monsoon in northern China. Hence, effective control of air pollution requires collaboration among different cities and provinces throughout China. The long-term measurements of aerosol vertical properties by ground-based lidar and CALIPSO are extremely valuable in quantifying the contributions of external factors and will be helpful in validating and improving various air quality models.

OSSEs for an Ensemble 3DVAR Data Assimilation System with Radar Observations of Convective Storms

Abstract An ensemble of the three-dimensional variational data assimilation (En3DA) method for convective-scale weather has been developed. It consists of an ensemble of three-dimensional variational data assimilations and forecasts in which member differences are introduced by perturbing initial conditions and/or observations, and it uses flow-dependent error covariances generated by the ensemble forecasts. The method is applied to the assimilation of simulated radar data for a supercell storm. Results indicate that the flow-dependent ensemble covariances are effective in enabling convective-scale analyses, as the most important features of the simulated storm, including the low-level cold pool and midlevel mesocyclone, are well analyzed. Several groups of sensitivity experiments are conducted to test the robustness of the method. The first group demonstrates that incorporating a mass continuity equation as a weak constraint into the En3DA algorithm can improve the quality of the analyses when radial velocity observations contain large errors. In the second group of experiments, the sensitivity of analyses to the microphysical parameterization scheme is explored. Results indicate that the En3DA analyses are quite sensitive to differences in the microphysics scheme, suggesting that ensemble forecasts with multiple microphysics schemes could reduce uncertainty related to model physics errors. Experiments also show that assimilating reflectivity observations can reduce spinup time and that it has a small positive impact on the quality of the wind field analysis. Of the threshold values tested for assimilating reflectivity observations, 15 dBZ provides the best analysis. The final group of experiments demonstrates that it is not necessary to perturb radial velocity observations for every ensemble number in order to improve the quality of the analysis.

Modulation of surface meteorological parameters by extratropical planetary-scale Rossby waves

Abstract. This study examines the link between upper-tropospheric planetary-scale Rossby waves and surface meteorological parameters based on the observations made in association with the Ganges Valley Aerosol Experiment (GVAX) campaign at an extratropical site at Aryabhatta Research Institute of Observational Sciences, Nainital (29.45° N, 79.5° E) during November–December 2011. The spectral analysis of the tropospheric wind field from radiosonde measurements indicates a predominance power of around 8 days in the upper troposphere during the observational period. An analysis of the 200 hPa meridional wind (v200 hPa) anomalies from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis shows distinct Rossby-wave-like structures over a high-altitude site in the central Himalayan region. Furthermore, the spectral analysis of global v200 hPa anomalies indicates the Rossby waves are characterized by zonal wave number 6. The amplification of the Rossby wave packets over the site leads to persistent subtropical jet stream (STJ) patterns, which further affects the surface weather conditions. The propagating Rossby waves in the upper troposphere along with the undulations in the STJ create convergence and divergence regions in the mid-troposphere. Therefore, the surface meteorological parameters such as the relative humidity, wind speeds, and temperature are synchronized with the phase of the propagating Rossby waves. Moreover, the present study finds important implications for medium-range forecasting through the upper-level Rossby waves over the study region.

An efficient and visually accurate multi-field visualization framework for high-resolution climate data

Recent advances in high-performance computing technologies, applied in climate science, are allowing increases in model complexity, model resolution, and the number of simulations run. The interactive exploration and analysis of these complex, multi-field climate data sets have been identified as one of the major current challenges in scientific visualization. For example, without direct 3D multi-field visualization, it is difficult to recognize the important correlative effects between vertical wind velocities and transport of the volumetric atmosphere. As such data have complicated 3D structures and are highly time-dependent, a visualization approach must handle these dynamic data in a highly interactive way. In this paper, an efficient multi-field visualization framework is proposed for Earth climate simulation data. A novel visualization pipeline is presented for on-demand data processing, enabling scalable handling of large-scale climate data sets. The hardware-accelerated multi-field visualization method used in the framework allows interactive and accurate visualization of multiple intersecting climate phenomena. An information-theoretic-based wind-field analysis method is also implemented within the visualization framework to help scientists gain a deeper understanding of the underlying multi-field climate data.

Dynamics of the Typhoon Haitang Related High Ozone Episode over Hong Kong

It has been previously established that photochemical smog occurring in the Pearl River Delta Region (PRD) was associated with stagnant meteorological conditions. However, the photochemical smog (17 July to 20 July 2005) induced by typhoon Haitang was associated with moderate wind speed and nonstagnant meteorological conditions. The dynamic process of this ozone episode was studied using an integrated numerical model, that is, a mesoscale meteorological model and Community Multiscale Air Quality (CMAQ) model. Model performance has been evaluated using both ground-based meteorological and air quality observations. Analysis of simulated wind fields and ozone budget has been performed. This dynamic process is summarized into three physical factors. First, the westerly wind placed Hong Kong directly downwind of the PRD emissions. Second, the convergence of wind flow stimulated a vertical local circulation near the surface layer. This recirculation allowed primary and secondary pollutants to accumulate. Third, the conditions of high air temperature and low humidity resulted in active photochemical reactions. These combined effects resulted in the formation of high ozone in this episode.

Attribution of variations in the quasi-biennial oscillation period from the duration of easterly and westerly phases

This study reports the main features of quasi-biennial oscillation (QBO) period variability at stratospheric levels from 70 to 10 hPa and its attribution from the duration variability of westerly and easterly phases using monthly mean zonal wind data from August 1956 to July 2013, archived by Free University of Berlin. A total of 24 QBO events have been distinguished based on the zonal wind field and wavelet analysis for it. The QBO period varies in phase at various stratospheric levels and shows no significant long-term trend but decadal to multi-decadal variability. The noted case-to-case variations in QBO period are due to variations in durations of the westerly and easterly phases at the same level. The highly coupled variability of the easterly duration in the upper levels above 30 hPa and westerly durations in the lower levels below, which manifests the stalling or accelerating of the descent rate of easterly wind regimes around 30 hPa, is found to be the dominant variability of the easterly and westerly durations at various stratospheric levels. Accordingly, the period of QBO in the lower levels below 40 hPa/upper levels above 20 hPa is determined by the westerly/easterly durations there in about 75 % of the 24 QBO events; and at 30 hPa, variations in the durations of both easterly and westerly phases contribute to the QBO period variability. On the contrary, in only 4 out of 24 QBO events, the variations of the westerly/easterly durations in the upper/lower levels are greater than the variations of the easterly/westerly durations in the upper/lower levels, making deterministic contributions to the QBO period variability.

Long-term trends of dust events over Tibetan Plateau during 1961–2010

In this study we analyzed dust events records of surface meteorological stations on Tibetan Plateau (TP) during 1961–2010 and provided the spatial and temporal distribution of dust events. The occurrence of dust events has significantly decreased since the 1970s. We defined the Tibetan Plateau Dust Index (TPDI) for the most dust active periods, spring and winter, to characterize the large scale variability of dust events over TP. Mann–Kendall test suggested the decreasing trend was possibly an abrupt change in the 1990s. The decline of surface wind speeds could partly explain the decrease of dust events over TP. TPDI is positively correlated to the surface winds, with correlation coefficients of 0.42 for spring and 0.46 for winter, respectively. The averaged number days with strong winds (wind speed greater than 6.5 ms-1) for the 4 selected stations, which were chosen to define TPDI, are significantly correlated with TPDI for both spring (correlation coefficient = 0.69) and winter (correlation coefficient = 0.76) and also showed a deceasing trend. The upward trend of vegetation cover was indicated by the normalized difference vegetation index (NDVI), which can be attributed as another factor driving the decrease of dust events over TP. TPDI is negatively correlated to the NDVI, with correlation coefficients of −0.48 for spring and −0.29 for winter. Additionally, analysis of geopotential height fields and wind fields indicate an enhanced ridge in the north of TP and weakened westerly jet in the low-frequency years of dust events, which also drive the decline of dust events over TP.

Analyzing Vortex Winds in Radar-Observed Tornadic Mesocyclones for Nowcast Applications

Abstract A computationally efficient method is developed to analyze the vortex wind fields of radar-observed mesocyclones. The method has the following features. (i) The analysis is performed in a nested domain over the mesocyclone area on a selected tilt of radar low-elevation scan. (ii) The background error correlation function is formulated with a desired vortex-flow dependence in the cylindrical coordinates cocentered with the mesocyclone. (iii) The square root of the background error covariance matrix is derived analytically to precondition the cost function and thus enhance the computational efficiency. Using this method, the vortex wind analysis can be performed efficiently either in a stand-alone fashion or as an additional step of targeted finescale analysis in the existing radar wind analysis system developed for nowcast applications. The effectiveness and performance of the method are demonstrated by examples of analyzed wind fields for the tornadic mesocyclones observed by operational Doppler radars in Oklahoma on 24 May 2011 and 20 May 2013.