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1.
In the present study, the performance of the GRAPES model in wind simulation over south China was assessed. The simulations were evaluated by using surface observations and two sounding stations in south China. The results show that the GRAPES model could provide a reliable simulation of the distribution and diurnal variation of the wind. It showed a generally overestimated southerly wind speed especially over the Pearl River Delta region and the south of Jiangxi Province as well as the coastal region over south China. GRAPES also exhibited a large number of stations with the opposite surface wind directions over the east of Guangxi and the south of Jiangxi during the nocturnal- to-morning period, as well as an overall overestimation of surface wind over the coastal regions during the afternoon. Although GRAPES could simulate the general evolutional characteristics of vertical wind profile, it underestimated wind speed above 900 hPa and overestimated wind speed below 900 hPa. Though the parameterization scheme of gravity wave drag proved to be an effective method to alleviate the systematic deviation of wind simulation, GRAPES still exhibited large errors in wind simulation, especially in the lower and upper troposphere.  相似文献   

2.
This study assesses the predictive capabilities of the CMA-GD model for wind speed prediction in two wind farms located in Hubei Province, China. The observed wind speeds at the height of 70m in wind turbines of two wind farms in Suizhou serve as the actual observation data for comparison and testing. At the same time, the wind speed predicted by the EC model is also included for comparative analysis. The results indicate that the CMA-GD model performs better than the EC model in Wind Farm A. Th...  相似文献   

3.
Temporal and spatial distribution characteristics of sea surface wind in Guangdong''s coastal areas were analyzed with data from four offshore observational stations between 2012 and 2015. The results are shown as follows: (1) The probability distribution of wind speed was basically consistent with Gaussian distribution characteristics; winds of Beaufort force 6 or higher were observed mainly in far offshore stations from October to March. (2) The probability distribution of wind direction was represented well by Weibull distribution. The deviation of wind direction of far station was relatively small for it was mainly controlled by monsoon over the South China Sea, while the near offshore station had a relatively large diurnal variation because of the influence of local synoptic systems such as sea-land breeze. (3) There were significant seasonal differences in wind speed and direction observed by different offshore observational stations. In strong wind seasons, the deviation of wind direction was relatively small while the deviation of wind speed was relatively large, and vice versa. In contrast with Class I station, the other three stations exhibited approximately normal distribution of wind direction and wind speed deviations. (4) Wind direction diurnal variation was moderate in windy periods, while it was obvious in relatively lower speed conditions. The deviation of wind speed in windy periods was generally greater because it was influenced by mesoscale weather systems for 10-20 h, and the influence was complicated, resulting in greater local differences in wind speed.  相似文献   

4.
Assessing wind energy is a key step in selecting a site for a wind farm. The accuracy of the assessment is essential for the future operation of the wind farm. There are two main methods for assessing wind power: one is based on observational data and the other relies on mesoscale numerical weather prediction(NWP). In this study, the wind power of the Liaoning coastal wind farm was evaluated using observations from an anemometer tower and simulations by the Weather Research and Forecasting(WRF) model, to see whether the WRF model can produce a valid assessment of the wind power and whether the downscaling process can provide a better evaluation. The paper presents long-term wind data analysis in terms of annual, seasonal, and diurnal variations at the wind farm, which is located on the east coast of Liaoning Province. The results showed that, in spring and summer, the wind speed, wind direction, wind power density, and other main indicators were consistent between the two methods. However, the values of these parameters from the WRF model were significantly higher than the observations from the anemometer tower. Therefore, the causes of the differences between the two methods were further analyzed. There was much more deviation in the original material, National Centers for Environmental Prediction(NCEP) final(FNL) Operational Global Analysis data, in autumn and winter than in spring and summer. As the region is vulnerable to cold-air outbreaks and windy weather in autumn and winter, and the model usually forecasted stronger high or low systems with a longer duration, the predicted wind speed from the WRF model was too large.  相似文献   

5.
Three typhoons, Goni, Morakot and Etau which were generated in Western Pacific in 2009, are successfully simulated by the WRF model. The horizontal and vertical vorticity and their interaction are analyzed and diagnosed by using the simulation results. It is shown that their resultant vectors had a fixed pattern in the evolution process of the three typhoons: The horizontal vorticity converged to the tropical cyclone (TC) center below 900 hPa level, flowed out from it at around 900 to 800 hPa, and flowed in between 800 hPa and 700 hPa. If multiple maximum wind speed centers showed up, the horizontal vorticity converged to the center of the typhoon below the maximum wind speed center and diverged from the TC center above the maximum wind speed center. At low levels, the three typhoons interacted with each other through vertical circulation generated by the vortex tube. This circulation was mainly generated by the eastward or westward horizontal vorticity vectors. Clouds and precipitation were generated on the ascending branch of the vertical circulation. The vortex tubes often flowed toward the southwest of the right TC from the northeast of the left TC. According to the full vorticity equation, the horizontal vorticity converted into the vertical vorticity near the maximum wind speed center below 850 hPa level, and the period of most intense conversion was consistent with the intensification period of TC, while the vorticity advection was against the intensification. The vertical vorticity converted into the horizontal vorticity from 800 hPa to 600 hPa, and the wind speed decreased above the maximum wind speed region at low levels.  相似文献   

6.
The impact of ground heating on flow fields in street canyons under different ambient wind speed conditions was studied based on numerical methods.A series of numerical tests were performed,and three factors including height-to-width(H/W) ratio,ambient wind speed and ground heating intensity were taken into account.Three types of street canyon with H/W ratios of 0.5,1.0 and 2.0,respectively,were used in the simulation and seven speed values ranging from 0.0 to 3.0 m s 1 were set for the ambient wind speed.The ground heating intensity,which was defined as the difference between the ground temperature and air temperature,ranged from 10 to 40 K with an increase of 10 K in the tests.The results showed that under calm conditions,ground heating could induce circulation with a wind speed of around 1.0 m s 1,which is enough to disperse pollutants in a street canyon.It was also found that an ambient wind speed threshold may exist for street canyons with a fixed H/W ratio.When ambient wind speed was lower than the threshold identified in this study,the impact of the thermal effect on the flow field was obvious,and there existed a multi-vortex flow pattern in the street canyon.When the ambient wind speed was higher than the threshold,the circulation pattern was basically determined by dynamic effects.The tests on the impact of heating intensity showed that a higher ground heating intensity could strengthen the vortical flow within the street canyon,which would help improve pollutant diffusion capability in street canyons.  相似文献   

7.
Horizontal wind measured by wind profiling radar (WPR) is based on uniform wind assumption in volume of lateral beam. However, this assumption cannot completely meet in the real atmosphere. The subject of this work is to analyze the influence of atmospheric inhomogeneities for wind measurement. Five-beam WPR can measure two groups of horizontal wind components U and V independently, using the difference of horizontal wind components U and V can evaluate the influence of the inhomogeneity of the atmospheric motion on wind measurement. The influences can be divided into both inhomogeneous distribution of horizontal motion and vertical motion. Based on wind measurements and meteorological background information, a new means of coordinate rotation the two kinds of inhomogeneous factor was separated, and the impact in different weather background was discussed. From analysis of the wind measured by type of PB-II WPR (445MHz) during 2012 at Yanqing of Beijing, it is shown that the inhomogeneity of horizontal motion is nearly the same in U and V direction. Both the inhomogeneities of horizontal motion and vertical motion have influence on wind measurement, and the degrees of both influences are associated with changes of wind speed. In clear air, inhomogeneity of horizontal motion is the main influence on wind measurement because of small vertical velocity. In precipitation, the two influences are larger than that in clear air.  相似文献   

8.
Wind speed variations are influenced by both natural climate and human activities. It is important to understand the spatial and temporal distributions of wind speed and to analyze the cause of its changes. In this study, data from 26 meteorological stations in the Jing–Jin–Ji region of North China from 1961 to 2017 are analyzed by using the Mann–Kendall(MK) test. Over the study period, wind speed first decreased by-0.028 m s-1 yr-1(p 0.01) in1961–1991, and then increased by 0.002 m s1-yr1-(p 0.05) in 1992–2017. Wind speed was the highest in spring(2.98 m s-1), followed by winter, summer, and autumn. The largest wind speed changes for 1961–1991 and1992–2017 occurred in winter(-0.0392 and 0.0065 m s-1 yr1-, respectively); these values represented 36% and 58%of the annual wind speed changes. More than 90.4% of the wind speed was concentrated in the range of 1–5 m s-1,according to the variation in the number of days with wind speed of different grades. Specifically, the decrease in wind speed in 1961–1991 was due to the decrease in days with wind speed of 3–5 m s-1, while the increase in wind speed in 1992–2017 was mainly due to the increase in days with wind speed of 2–4 m s-1. In terms of driving factors,variations in wind speed were closely correlated with temperature and atmospheric pressure, whereas elevation and underlying surface also influenced these changes.  相似文献   

9.
In southern China,cold air is a common weather process during the winter season;it can cause strong wind,sharp temperature decreases,and even the snow or freezing rain events.However,the features of the atmospheric boundary layer during cold air passage are not clearly understood due to the lack of comprehensive observation data,especially regarding turbulence.In this study,four-layer gradient meteorological observation data and one-layer,10-Hz ultrasonic anemometer-thermometer monitoring data from the northern side of Poyang Lake were employed to study the main features of the surface boundary layer during a strong cold-air passage over southern China.The results show that,with the passage of a cold air front,the wind speed exhibits low-frequency variations and that the wind systematically descends.During the strong wind period,the wind speed increases with height in the surface layer.Regular gust packets are superimposed on the basic strong wind flow.Before the passage of cold air,the wind gusts exhibit a coherent structure.The wind and turbulent momentum fluxes are small,although the gusty wind momentum flux is slightly larger than the turbulent momentum flux.However,during the invasion of cold air,both the gusty wind and turbulent momentum fluxes increase rapidly with wind speed,and the turbulent momentum flux is larger than the gusty wind momentum flux during the strong wind period.After the cold air invasion,this structure almost disappears.  相似文献   

10.
Renewable energy sources, especially wind power, were believed to be able to slow down global warming; however, evidence in recent years shows that wind farms may also induce climate change. With the rapid development of wind power industry, the number of wind farms installed in mountains has gradually increased. Therefore, it is necessary to study the impact of wind farms in mountainous areas on local climate. The Suizhou and Dawu wind farms in northern Hubei Province were chosen for the present study on the impact of wind farm operations on the local climate in mountainous areas. The mesoscale meteorological numerical model Weather Research and Forecasting Model (WRF) and the Fitch model, together with turbulence correction factor, were used to simulate wind farm operations and study their effects on local climate. The results showed the characteristics of wind speed attenuation in mountainous wind farms: the amplitude and range of wind speed attenuation were stronger in the nighttime than in the daytime, and stronger in summer than in winter. The surface temperature increased and became more significant in summer. However, a cooling variation was observed above the surface warming center. The height of this center was higher in the daytime than it was in the nighttime. The latent heat flux in the wind farms decreased at night, accompanied by an increase in sensible heat flux. However, these changes were not significant. Some differences were observed between the impact of wind farms on the climate in the plains and the mountains. Such differences are more likely to be related to complex terrain conditions, climate conditions, and the density of wind turbines. The present study may provide support for the development and construction of wind farms in mountainous areas.  相似文献   

11.
The mobile incoherent Doppler lidar(MIDL),which was jointly developed by State Key Laboratory of Severe Weather(LaSW) of the Chinese Academy of Meteorological Sciences(CAMS) and Ocean University of China,provided meteorological services during the Olympic sailing events in Qingdao in 2008.In this study,two experiments were performed based on these measurements.First,the capabilities of MIDL detection of sea-surface winds were investigated by comparing its radial velocities with those from a sea buoy.MIDL radial velocity was almost consistent with sea-buoy data;both reflected the changes in wind with time.However,the MIDL data was 0.5 m s 1 lower on average than the sea-buoy data due to differences in detection principle,sample volume,sample interval,spatial and temporal resolution.Second,the wind fields during the Olympic sailing events were calculated using a four-dimensional variation data assimilation(4DVAR) algorithm and were evaluated by comparing them with data from a sea buoy.The results show that the calculations made with the 4DVAR wind retrieval method are able to simulate the fine retrieval of sea-surface wind data-the retrieved wind fields were consistent with those of sea-buoy data.Overall,the correlation coefficient of wind direction was 0.93,and the correlation coefficient of wind speed was 0.70.The distribution of retrieval wind fields was consistent with that of MIDL radial velocity;the root-mean-square error between them had an average of only 1.52 m s 1.  相似文献   

12.
From several towers in Hami, Xinjiang of Northwest China, built by the national wind power resources professional observation network, we selected three towers with synchronous 10-min average wind speed data for one year(May 2011–April 2012) under strict quality control. The towers are located where large-scale wind power development is projected. We analyzed the frequency and variation of extreme wind speed at low wind condition(LWC), rated wind condition(RWC), and cut-out wind condition(CWC), which may significantly impact the electric power grid configuration in large-scale wind power development. The correlation between duration and frequency of LWC/RWC/CWC is obtained. Major findings are: 1) The frequency of CWC is the lowest among all conditions, its synchronous rate at all three towers tends to be zero, and the frequency of LWC is always greater than that of RWC. 2) Among the three towers, the synchronous rate of RWC steadily increases with height, and LWC differs little between different levels. The synchronous rate of LWC concentrates in winter, while that of RWC mainly occurs in spring and summer.Diurnal variation of LWC/RWC during the entire year is significantly different. 3) During the study year,the longest durations of synchronous LWC and RWC among the three towers are up to 640 and 700 min,respectively. The duration and frequency of LWC/RWC can be quantitatively well described by a logarithmic function. Consequently, the synchronous rates of LWC and RWC over any duration in the region can be easily calculated by using the fitting function equation from observed data. These results are of value to the planning of large-scale wind power transmission and grid dispatching in this area.  相似文献   

13.
Using real analysis data of 1°×1° resolution of the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR), the nondivergent wind component and irrotational wind component obtained by the harmonic-cosine(H-C) method, and the wind structure of Typhoon Fung-Wong (coded 0808 in China) in 2008 was analyzed. The results indicated that the irrotational component was advantageous over the total wind in reflecting both the changes in convergent height and the asymmetrical convergence of Fung-Wong. In Fung-Wong, the nondivergent component was larger than the irrotational component, but the latter was much more variable than the former, which was obtained only from the wind partition method. Further analyses on the irrotational component demonstrated that the location of the convergent center at lower levels was almost the same as the divergent center during the development of Fung-Wong, and its convergent level was high in its life cycle, with the most highest up to 400 hPa when it became stronger. After the typhoon landed in the provinces of Taiwan and Fujian, respectively, its convergent center at lower levels was slowly detached from the divergent center at high levels and the convergent height was also depressed from high levels to lower levels. Gradually, this weakened the intensity of Fung-Wong. This kind of weakening was slow and Fung-Wong maintained its circulation for a long time over land because of its very thick convergent height. Analyses on wind partitioning provided one possible explanation to why Fung-Wong stayed for a long time after it landed. Furthermore, the asymmetric vertical ascending motion was induced by the asymmetric convergence at lower levels. In general, when typhoons (such as Fung-Wong) land, the rainfall region coincides with that of the convergence region (indicated by the irrotational component at lower layers). This means that the possible rainfall regions may be diagnosed from the convergent area of the irrotational component. For an observational experiment on typhoons, the convergent region may be considered as a key observational region.  相似文献   

14.
Daily observations of wind speed at 12 stations in the Greater Beijing Area during 1960–2008 were homogenized using the Multiple Analysis of Series for Homogenization method. The linear trends in the regional mean annual and seasonal (winter, spring, summer and autumn) wind speed series were-0.26,-0.39,-0.30,-0.12 and-0.22 m s-1 (10 yr)-1 , respectively. Winter showed the greatest magnitude in declining wind speed, followed by spring, autumn and summer. The annual and seasonal frequencies of wind speed extremes (days) also decreased, more prominently for winter than for the other seasons. The declining trends in wind speed and extremes were formed mainly by some rapid declines during the 1970s and 1980s. The maximum declining trend in wind speed occurred at Chaoyang (CY), a station within the central business district (CBD) of Beijing with the highest level of urbanization. The declining trends were in general smaller in magnitude away from the city center, except for the winter case in which the maximum declining trend shifted northeastward to rural Miyun (MY). The influence of urbanization on the annual wind speed was estimated to be about-0.05 m s-1 (10 yr)-1 during 1960–2008, accounting for around one fifth of the regional mean declining trend. The annual and seasonal geostrophic wind speeds around Beijing, based on daily mean sea level pressure (MSLP) from the ERA-40 reanalysis dataset, also exhibited decreasing trends, coincident with the results from site observations. A comparative analysis of the MSLP fields between 1966–1975 and 1992–2001 suggested that the influences of both the winter and summer monsoons on Beijing were weaker in the more recent of the two decades. It is suggested that the bulk of wind in Beijing is influenced considerably by urbanization, while changes in strong winds or wind speed extremes are prone to large-scale climate change in the region.  相似文献   

15.
In this study,the ability of the Weather Research and Forecasting(WRF)model to generate accurate near-surface wind speed forecasts at kilometer-to subkilometer-scale resolution along race tracks(RTs)in Chongli during the wintertime is evaluated.The performance of two postprocessing methods,including the decaying-averaging(DA)and analogy-based(AN)methods,is tested to calibrate the near-surface wind speed forecasts.It is found that great uncertainties exist in the model’s raw forecasts of the near-surface wind speed in Chongli.Improvement of the forecast accuracy due to refinement of the horizontal resolution from kilometer to subkilometer scale is limited and not systematic.The RT sites tend to have large bias and centered root mean square error(CRMSE)values and also exhibit notable underestimation of high-wind speeds,notable overestimation or underestimation of the near-surface wind speed at high altitudes,and notable underestimation during daytime.These problems are not resolved by increasing the horizontal resolution and are even exacerbated,which leads to great challenges in the accurate forecasting of the near-surface wind speed in the competition areas in Chongli.The application of postprocessing methods can greatly improve the forecast accuracy of near-surface wind speed.Both methods used in this study have comparable abilities in reducing the(positive or negative)bias,while the AN method is also capable of decreasing the random error reflected by CRMSE.In particular,the large biases for high-wind speeds,wind speeds at high-altitude stations,and wind speeds during the daytime at RT stations can be evidently reduced.  相似文献   

16.
The southwesterly low-level jet (LLJ) over southeast China in the summer of 2003 is analyzed in this study. The analysis is based on the National Centers for Environmental Prediction (NCEP) Final (FNL) operational global analysis data on 1.0×1.0-degree grids at 6-h intervals. The major criteria for choosing the LLJ included the following: a maximum wind speed equal to or greater than 12.0 m s -1 , a wind direction of between 180° and 270°, and the height of wind maximum at 900-700 hPa, not confined to single pressure level. The results show that the LLJs over southeast China dominate at 850 and 800 hPa. These LLJs are closely associated with the topography of this area and tend to locate regions with large terrain gradients, including the northeastern and eastern Yunnan-Guizhou Plateau. Under the influence of mid-latitude westerly winds, the LLJs above 750 hPa move northward to the Yangtze-Huai River Basin. Compared to the ten-year (2000-2009) mean climate conditions, the LLJs in the warm season of summer 2003 were exceptionally active and strong, as reflected by the positive anomalies of LLJ occurrence numbers and wind speed. In addition, the 2003 LLJs showed strong diurnal variation, especially at pressure levels below 800 hPa. The majority of the LLJs appeared between midnight and the early morning hours (before 8 a.m.). Finally, the summary of LLJ grid numbers indicates that more than 80% of LLJs in June and July 2003 occurred within the 33-d rainy period. Thus, these LLJs are directly related to the anomalously heavy rainfall in the Yangtze-Huai River Basin.  相似文献   

17.
In order to understand the activity characteristics of low-level jets in the Nanjing area, statistical analysis and comparative study are carried out on their monthly and diurnal variations, characteristics of their cores and accompanying weather conditions using wind profile data in 2005—2008 collected by two wind profilers. The results show that low-level jets have significant monthly and diurnal variations. They occur more frequently in spring and summer than in autumn and winter and are more active in early morning and at night, with the maximum wind speed usually occurring at midnight. The central part of the low-level jet occurs mainly at the height of less than 1400 meters, and the enhancement of central speed is beneficial to the appearance of precipitation. Meanwhile, when the low-level jet appears in summer, it helps cause heavy rain. The statistical results of the boundary wind profiler are well consistent with those of the tropospheric wind profiler. Two kinds of wind profilers also have the capability of continuously detecting the development of low-level jets.  相似文献   

18.
Leveraging the commercial CFD software FLUENT, the fine-scale three-dimensional wind structure over the Paiya Mountains on the Dapeng Peninsula near Shenzhen, a city on the seashore of South China Sea, during the landfall of Typhoon Molave has been simulated and analyzed. Through the study, a conceptual wind structure model for mountainous areas under strong wind condition is established and the following conclusions are obtained as follows: (1) FLUENT can reasonably simulate a three-dimensional wind structure over mountainous areas under strong wind conditions; (2) the kinetic effect of a mountain can intensify wind speed in the windward side of the mountain and the area over the mountain peak; and (3) in the leeward side of the mountain, wind speed is relatively lower with relatively stronger wind shear and turbulence.  相似文献   

19.
The removal of noise and velocity ambiguity and retrieval and verification of horizontal wind field is a prerequisite to make the best and fullest use of Doppler radar measurements. This approach was applied to the Doppler radar data collected during August 2005 for a landing typhoon Matsa (0509) in Yantai, Shangdong Province, and the verified result shows that the quality control for this dataset was successful. The horizontal wind field was retrieved and then verified by studying the characteristics of the radar radial velocity and large-scale wind field and the vertical cross section of the radial velocity determined with the typhoon center as the circle center and comparing it with satellite imagery. The results show that the meso- and small-scale systems in Matsa and its horizontal and vertical structure could be clearly retrieved using the dataset collected by single Doppler radar, and a shear or a convergence was corresponding with a band of severe storm around Matsa. At the same time, the retrieved wind field from single Doppler radar is proved to be a reliable and high-resolution dataset in analyzing the inner meso-scale structure of Matsa. It is also proved that the method for removing the velocity ambiguity could be an effective approach for preliminary quality control of the Doppler radar data, and the VAP method could also be a reasonable solution for the analysis of mesoscale wind field.  相似文献   

20.
The purpose of this study is to select a suitable sea wind retrieval method for FY-3B(MWRI). Based on the traditional empirical model of retrieving sea surface wind speed, and in the case of small sample size of FY-3B satellite load regression analysis, this paper analyzes the channel differences between the FY-3B satellite microwave radiation imager(MWRI) and TMI onboard the TRMM. The paper also analyzes the influence of these differences on the channel in terms of receiving temperature, including channel frequency, sensitivity and scaling precision. Then, the limited range of new model coefficient regression analysis is determined(in which the channel range settings include the information and features of channel differences), the regression methods of the finite field are proposed, and the empirical model of wind speed retrieval applicable to MWRI is obtained, which achieves robust results. Compared to the TAO buoy data, the mean deviation of the new model is 0.4 m/s, and the standard deviation is 1.2 m/s. In addition,the schematic diagram of the tropical sea surface wind speed retrieval is provided.  相似文献   

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