The research on boundary layer evolution characteristics of Typhoon Usagi based on observations by wind profilers

Vertically exploring the characteristics of the typhoon boundary layer（TBL） plays an important role in recognizing typhoon structure. The boundary layer radial direction and tangential wind characteristics of Typhoon Usagi based on the observational data of three boundary layer wind profiler stations along the route of Typhoon Usagi（No. 1319） and by combining with sounding data. The results show that：（1） maximum tangential wind appears in the vicinity of the eye area of Usagi, and it basically maintains a height of around 1 800 m when Usagi keeps a strong typhoon level, with the rapidly decreasing strength of Usagi after it lands, the speed of the maximum tangential wind and its vertical range both decrease;（2） the height of the maximum tangential wind is close to that of the inflow layer top of the typhoon, and is greater than that of the boundary layer estimated on the basis of Richardson number or potential temperature gradient, while the height of mixed layer judged on the basis of the signal-to-noise ratio（SNR） or its gradient is usually low;（3） the the boundary layer height can reach higher than2 100 m before Usagi lands. When the typhoon level or above is achieved, the boundary layer height observed by various stations does not change much, basically staying at between 1 200 and 1 600 m. With the decreasing strength of Usagi after its landfall, the boundary layer height rapidly drops.

Wind profiles in and over trees

风速是森林生态系统研究中最为重要的变量之一,同时也是控制气流运输过程最基本的要素。由于树木生理指标和生长过程对风速的改变十分敏感,因此风速随高度的变化规律,即风速廓线的研究十分重要。一般认为,在裸地或林冠上的风廓线均呈对数规律变化,但是在单株树木和林分内风速随高度的变化则不呈对数规律。本文根据最近在海岸松林内风的研究结果,总结了针叶树种单株树木内、林分内和林冠上层以及海岸林区的风速廓线变化规律,其主要结论如下:1)单株针叶树树冠内的风速廓线呈指数形式分布,2)在林分内的风速廓线可用风的减弱系数来表示,3)[(\267\347)(\300\252\317\337\324\332\301\326\271\332\262\343)]上的分布可由风廓线参数(摩擦速度、粗糙长度、零平面位移)确定,4)在海岸林区,极端风速的分布可以使用了建筑上的风荷载模型进行预测。另外,本文提出了该研究领域尚需进一步探讨的问题,主要包括:1)风速廓线与树木特征及林分特征间的关系,2)利用简单的方法预测了风速廓线参数,3)风速廓线在树木生理、生态研究的作用、树木生长过程中风的微生态学效应以及森林生态和管理应用等方面。图4表1参60。

PLANETARY BOUNDARY LAYER HEIGHT MEASURED BY A WIND PROFILER BASED ON THE WAVELET TRANSFORM

Planetary boundary layer height(PBLH) is an important input parameter for any boundary layer study or model, either climate or atmospheric. The variation of the PBLH is also of great significance to the physical processes of numerical prediction, diagnosis of weather forecasting and monitoring urban pollutants. However, effective ways to monitor the PBLH continuously are lack. Wind profilers are commonly used in monitoring PBLH continuously because of its high temporal and spatial resolution, coupled with capability of continuous detection. In this paper, the covariance wavelet transform(CWT) is used to analyze the range-corrected signal-to-noise ratio(SNR) of the wind profiler to determine the PBLH, which is then compared with the results measured by the gradient method and the radiosonde. The conclusions are as follows:(1) The scaling parameter a and translation parameter b of the wavelet are critical in determination of the PBLH by applying the CWT as different values may get completely different results, which requires to select appropriate values in the calculation carefully.(2) Quality control is crucial in determining the PBLH because good quality control can help remove mutation points, which makes the determined PBLH more consistent with the actual situation.(3) In clear-air, the gradient method is not applicable if the boundary layer turbulence is inhomogeneous and the impact of noise is large for that it is easy to be impacted by the mutation of SNR caused by the atmosphere turbulence instability and other factors, which will cause large errors, while the CWT method as an improvement of the gradient method can determine the PBLH quite well.(4) Through quality control, the PBLHs determined by the CWT are consistent with those of radiosonde, and the correlation coefficient between them is 0.87.

Turbulence and Rainfall Microphysical Parameters Retrieval and Their Relationship Analysis Based on Wind Profiler Radar Data

Rainfall is triggered and mainly dominated by atmospheric thermo-dynamics and rich water vapor.Nonetheless, turbulence is also considered as an important factor influencing the evolution of rainfall microphysical parameters. To study such an influence, the present study utilized boundary layer wind profiler radar measurements. The separation point of the radar power spectral density data was carefully selected to classify rainfall and turbulence signals;the turbulent dissipation rate ε and rainfall microphysical parameters can be retrieved to analyze the relationship betweenε and microphysical parameters. According to the retrievals of two rainfall periods in Beijing 2016, it was observed that(1) ε in the precipitation area ranged from 10^(-3.5) to 10^(-1) m^(2) s^(-3) and was positively correlated with the falling velocity spectrum width;(2) interactions between turbulence and raindrops showed that small raindrops got enlarge through collision and coalescence in weak turbulence, but large raindrops broke up into small drops under strong turbulence, and the separation value of ε being weak or strong varied with rainfall attributes;(3) the variation of rainfall microphysical parameters(characteristic diameters, number concentration, rainfall intensity, and water content) in the middle stage were stronger than those in the early and the later stages of rainfall event;(4) unlike the obvious impacts on raindrop size and number concentration, turbulence impacts on rain rate and LWC were not significant because turbulence did not cause too much water vapor and heat exchange.

Intermittent Clutter Removal Approach for Wind Profiler Data Based on Fractional Fourier Transform

Through the analysis of the target characteristics and according to the intermittent clutter bursting and short duration characteristics,a new method for the clutter recognition based on the fractional Fourier transform（FRFT）is proposed.This method is predicated on the fact that the FRFT perfectly localizes a chirp signal as an impulse when the angle parameter of the transform matches the chirp rate of the chirp signal.The method involves detecting the presence of the intermittent clutter and correctly estimating its orientation in the time-frequency plane,removing the intermittent clutter in the fractional domain,and completing wind estimation by the power spectrum.By testing the artificial WPR-like signal and data measured from the field,we verify that the FRFT-based method is very effective.

Comparative Analysis on Physical Quantity Diagnosis and Wind Profile Radar Data of Two Heavy Rainfalls

[ Objective] The research aimed to contrast physical quantity diagnosis and wind profile radar data of two heavy rainfalls. [ Method ] From circulation background, physical quantity field and wind profile radar data, we analyzed two big rainstorm weather processes （8 -9 July and August 10） in Lianyungang City in 2012. [ Result] Rainstorm generation was related to favorable large-scale circulation situation. The first-stage precipitation during 8 -9 July was warm-zone precipitation, and the precipitation at the second stage was triggered by shear line. Precipitation on August 10 was generated by typhoon low-pressure inverted trough and cold air. Sufficient water vapor content and strong water vapor transportation were favorable for generation of the heavy precipitation. Suction effect by divergence at high layer and convergence at middle and low layers was favorable for maintenance of the strong ascending motion. Occurrence of the heavy precipitation must have ascending motion condition. But it was not that the stronger the ascending motion, the stronger the rainfall intensity. Kindex and θse500 -θse 850 were closely related to rainstorm occurrence. Horizontal wind data of the wind profile radar provided fine structure of the atmospheric horizontal motion at vertical direction, could clearly display vertical structure of the wind field in rainstorm process, and directly reflected change characteristics of the wind field in precipitation process. [ Conclusion] The research could provide reference for future forecast work.

Construction of Vertical Wind Profile from Satellite-Derived Winds for Objective Analysis of Wind Field

During summer Monex-79, a variety of observing systems viz. research ships, research aircrafts, constant pressure balloons and geostationary satellite etc. were deployed, besides the regular conventional observations. The purpose of these additional systems was to make the best possible data for the studies on various aspects of monsoon circulation. The present study is aimed at the construction of vertical wind profile using cloud motion vectors obtained from GOES (I-O) satellite and to examine whether the constructed wind profiles improves the representation of the monsoon system, flow pattern etc. in the objective analysis. For this purpose, climatological normals of the wind field are considered as the initial guess and the objective analyses of the wind field are made with, first using only data from conventional observations over land areas, subsequently including the constructed winds from cloud motion vectors. These analyses are then compared with the standard analyses of wind field obtained from Quick Look Atlas by T. N. Krishnamurti et al. (1979).It is inferred that satellite estimated mean wind profiles show good agreement with the mean wind profiles of the research ships with RMS errors less than 5 mps below 500 hPa and less than 8 mps above 500 hPa. It is further inferred that the inclusion of constructed winds shows a positive impact on the objective analysis and improvement is seen to be more marked in the data-sparse region of the Arabian sea. Analyses which include the constructed winds show better agreement with the standard analysis, than the analyses obtained using only conventional winds. Thus, results of our study suggest that the wind profiles constructed using cloud motion vectors are of potential use in objective analysis to depict the major circulation features over the Indian region.

Secondary Product Inversion of Wind Profile Data and Its Application in Weather Forecast

Using wind field data of boundary-layer wind profile of Changsha national comprehensive meteorological observation test base,the inversion of atmospheric temperature advection was studied.Moreover,four typical heavy precipitation processes in Changsha region during 2018-2019 were analyzed in detail,and low-level jet index product was calculated.The results showed that the retrieved temperature advection can well reflect the change details of atmospheric temperature advection,and there was a good corresponding relationship between change of the cold and warm advection and the heavy precipitation process;low-level jet index generally had an explosion and enhancement process before precipitation,but the time was not consistent with prior research result,and a large number of samples need to be further studied.

Application of wind profiler data to rainfall analyses in Tazhong Oilfield region,Xinjiang,China

To improve the level of meteorological service for the Oilfield region in the Taklimakan Desert, the Urumqi Institute of Desert Meteorology of the China Meteorological Administration （CMA） conducted a detection experiment by means of wind profiling radar （WPR） in Tazhong Oilfield region of Xinjiang, China in July 2010. By using the wind profiler data obtained during the rainfall process on 27 July, this paper analyzed the wind field fea- tures and some related scientific issues of this weather event. The results indicated that： （1） wind profiler data had high temporal resolution and vertical spatial resolution, and could be used to analyze detailed vertical structures of rainfall processes and the characteristics of meso-scale systems. Before and after the rain event on 27 July, the wind field showed multi-layer vertical structures, having an obvious meso-scale wind shear line and three airflows from different directions, speeding up the motion of updraft convergence in the lower atmosphere. Besides, the wind directions before and after the rainfall changed inversely with increasing height. Before the rain, the winds blew clockwise, but after the onset of the rain, the wind directions became counterclockwise mainly; （2） the temperature advection derived from wind profiler data can reproduce the characteristics of low-level thermodynamic evolution in the process of rainfall, which is capable to reflect the variation trend of hydrostatic stability in the atmosphere. In the early stage of the precipitation on 27 July, the lower atmosphere was mainly affected by warm advection which had accumulated unstable energy for the rainfall event and was beneficial for the occurrence of updraft motion and precipitation; （3） the ＂large-value zone＂ of the radar reflectivity factor Z was virtually consistent with the onset and end of the rainfall, the height for the formation of rain cloud particles, and precipitation intensity. The reflectivity factor Z during this event varied approximately in the range of 18-38 dBZ and the rain droplets formed mainly at the layer of 3,800-4,500 m.

A Model of the Sea-Land Transition of the Mean Wind Profile in the Tropical Cyclone Boundary Layer Considering Climate Changes

The tropical cyclone boundary layer(TCBL)connecting the underlying terrain and the upper atmosphere plays a crucial role in the overall dynamics of a tropical cyclone system.When tropical cyclones approach the coastline,the wind field inside the TCBL makes a sea-land transition to impact both onshore and offshore structures.So better understanding of the wind field inside the TCBL in the sea-land transition zone is of great importance.To this end,a semiempirical model that integrates the sea-land transition model from the Engineering Sciences Data Unit(ESDU),Huang's refined TCBL wind field model,and the climate change scenarios from the Coupled Model Intercomparison Project Phase 6(CMIP6)is used to investigate the influence of climate changes on the sea-land transition of the TCBL wind flow in Hong Kong.More specifically,such a semiempirical method is employed in a series of Monte-Carlo simulations to predict the wind profiles inside the TCBL across the coastline of Hong Kong under the impact of future climate changes.The wind profiles calculated based on the Monte-Carlo simulation results reveal that,under the influences of the most severe climate change scenario,slightly higher and significantly lower wind speeds are found at altitudes above and below 400 m,respectively,compared to the wind speeds recommended in the Hong Kong Wind Code of Practice.Such findings imply that the wind profile model currently adopted by the Hong Kong authorities in assessing the safety of low-to high-rise buildings may be unnecessarily over-conservative under the influence of climate change.On the other hand,the coded wind loads on super-tall buildings slightly underestimate the typhoon impacts under the severe climate change conditions anticipated for coastal southern China.

Statistics for Size and Radial Wind Profile of Tropical Cyclones in the Western North Pacific

The 6-yr best-track data of tropical cyclones （TCs） in the western North Pacific are used to study the statistical features of TC size and radial wind profile. A TC size is defined as the azimuthal mean radius of 34-kt surface wind. On average, the TCs in the western North Pacific have a size of 203 km, and the size is larger for stronger TCs. Further analyses show that larger TCs tend to move faster than smaller ones, with a 23–24 km difference in size corresponding to a difference of about 10 km h -1 in moving speed. The TCs that recurve from westward to eastward moving have a mean size of 218 km, significantly larger than that of those without a turning point （179 km）. Regional TC distributions demonstrate that the TCs affecting the Korean Peninsula and southwestern Japan have the largest mean size （250–280 km）. There are also some large TCs affecting southern Philippines, while TCs over the South China Sea are generally small in size. Comparison of intensity and size of all TCs during their lifespan demonstrates that a TC tends to reach its maximum size 6 h after it reaches its maximum intensity, and the decrease rate of size during the weakening stage of a TC is much smaller than the increase rate of size during its developing stage. Thus, linear regression relations between TC size and intensity are established for its developing and weakening stages respectively, which can be used as a forecast tool for TC size. Features of TC radial wind profile are studied by analyzing a parametric wind model based on the radius data of 34-, 50-, and 64-kt surface winds. The results show that the shape parameter d most frequently takes the values of 0.3, 0.4, and 0.5. It generally increases （decreases） as the TC develops （weakens）, implying a sharper （flatter） radial wind profile. Changes in d leads the tendency of intensity. The two parameters for the asymmetric model, namely p and q, are mostly 0.85–1.05 and 0–0.2, respectively, embodying the fact that the asymmetric component is generally much smaller than the symmetric component. The asymmetry in 34-kt surface wind is much stronger than that in 50and 64-kt surface winds, with the maximum radius often in the northeast quadrant.

Ship speed power performance under relative wind profiles in relation to sensor fault detection

Statistical data analysis and visualization approaches to identify ship speed power performance under relative wind(i.e.apparent wind)profiles are considered in this study.Ship performance and navigation data of a selected vessel are analyzed,where various data anomalies,i.e.sensor related erroneous data conditions,are identified.Those erroneous data conditions are investigated and several approaches to isolate such situations are also presented by considering appropriate data visualization methods.Then,the cleaned data are used to derive various relationships among ship performance and navigation parameters that have been visualized in this study,appropriately.The results show that the wind profiles along ship routes can be used to evaluate vessel performance and navigation conditions by assuming the respective sea states relate to their wind conditions.Hence,the results are useful to derive appropriate mathematical models that represent ship performance and navigation conditions.Such mathematical models can be used for weather routing type applications(i.e.voyage planning),where the respective weather forecast can be used to derive optimal ship routes to improve vessel performance and reduce fuel consumption.This study presents not only an overview of statistical data analysis of ship performance and navigation data but also the respective challenges in data anomalies(i.e.erroneous data intervals and sensor faults)due to onboard sensors and data handling systems.Furthermore,the respective solutions to such challenges in data quality have also been presented by considering data visualization approaches.

Sensitivity of tropical cyclone damage costs to integrated wind profile

The dramatic tropical cyclone(TC)damages in coastal areas around the world have gained significant attention from asset owners,policy makers and engineers.The estimate of TC damage for a specific region of interest is informative of the preparedness and resilience of the area subjected to TC hazards,and thus should be conducted using a quantitative approach.A reasonable indicator of TC damage should incorporate not only the TC characteristics(e.g.,intensity,frequency and duration)but also the vulnerability of the TC-prone areas.In this paper,a new indicator is proposed to measure the TC threat,which takes into account both the TC characteristics and the vulnerability of the area.The indicator has two forms:the first one considers the maximum wind speed only and the second incorporates the integrated wind speed profile.The historical damage scenarios along the US East Coast,as well as those in Hong Kong,China,are examined to demonstrate the applicability of the proposed indicator.Results show that the proposed indicator is capable of representing the impact of TC wind field profile on the TC damage costs.The proposed indicator could be further used to project the future TC damages for areas subjected to TC hazards.

INFLUENCES OF NONSTATIONARY PROCESS ON INTERNAL PARAMETERS AND WIND PROFILES IN THE PLANETARY BOUNDARY LAYER

In this paper,under the assumption of neutral and barotropic atmosphere,by means of the analytic solution of motion equation of PBL,the influences of nonstationary process on the internal parameters u_*/A(A is the wind speed at the top of PBL)and ■(the angle between winds near the surface and at the top of PBL)of PBL are investigated in which the wind direction at the top of PBL is a periodic function of time but the wind speed at the top of PBL does not change.The u_*/A increases and ■ decreases when the wind direction at the top of PBL rotates anticlockwise and vice versa.Hence the parameterization of PBL in the large-scale models derived under the stationary condition should be corrected by accounting for the nonstationary process.The similar results are obtained in the numerical solution of the motion equation of PBL.The influences of this nonstationary process on the profiles of the wind in PBL are also analyzed.

Computational fluid dynamics evaluation of the effect of different city designs on the wind environment of a downwind natural heritage site

Disturbance in wind regime and sand erosion deposition balance may lead to burial and eventual vanishing of a site.This study conducted 3D computational fluid dynamics(CFD)simulations to evaluate the effect of a proposed city design on the wind environment of the Crescent Spring,a downwind natural heritage site located in Dunhuang,Northwestern China.Satellite terrain data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER)Digital Elevation Model(DEM)were used to construct the solid surface model.Steady-state Reynolds Averaged Navier-Stokes equations(RANS)with shear stress transport(SST)k-ωturbulence model were then applied to solve the flow field problems.Land-use changes were modeled implicitly by dividing the underlying surface into different areas and by applying corresponding aerodynamic roughness lengths.Simulations were performed by using cases with different city areas and building heights.Results show that the selected model could capture the surface roughness changes and could adjust wind profile over a large area.Wind profiles varied over the greenfield to the north and over the Gobi land to the east of the spring.Therefore,different wind speed reduction effects were observed from various city construction scenarios.The current city design would lead to about 2 m/s of wind speed reduction at the downwind city edge and about 1 m/s of wind speed reduction at the north of the spring at 35-m height.Reducing the city height in the north greenfield area could efficiently eliminate the negative effects of wind spee.By contrast,restricting the city area worked better in the eastern Gobi area compared with other parts of the study area.Wind speed reduction in areas near the spring could be limited to 0.1 m/s by combining these two abatement strategies.The CFD method could be applied to simulate the wind environment affected by other land-use changes over a large terrain.

Wind Measurement with a Wind Profiling Radar

The first troposphere wind profiling radar in China has been in operation. The paper describes the radar parameters and characteristics with some experimental results presented.

Effects of gravel mulch on aeolian transport:a field wind tunnel simulation

The shape,size and coverage of gravels have significant impacts on aeolian sand transport.This study provided an understanding of aeolian transport over the gravel mulching surfaces at different wind velocities by means of a mobile wind tunnel simulation.The tested gravel coverage increased from 5% to 80%,with a progressive increment of 5%.The gravels used in the experiments have three sizes in diameter.Wind velocities were measured using 10 sand-proof pitot-static probes,and mean velocity fields were obtained and discussed.The results showed that mean velocity fields obtained over different gravel mulches were similar.The analysis of wind speed patterns revealed an inherent link between gravel mulches and mean airflow characteristics on the gravel surfaces.The optimal gravel coverage is considered to be the critical level above or below which aeolian transport characteristics differ strongly.According to the present study,the optimal gravel coverage was found to be around 30% or 40%.Threshold velocity linearly increased with gravel coverage.Sand transport rate first increased with height above the wind tunnel floor（Hf）,reaching a peak at some midpoint,and then decreased.

THE INFLUENCE OF INHOMOGENEOUS WIND DISTRIBUTION ON DATA QUALITY FOR WIND PROFILING RADAR

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.

Study on Characteristics of Wind in Low-level Air in Anqing from 2004 to 2008

[Objective] The characteristics and rules of low-level air in Anqing from 2004 to 2008 were studied.[Method] By dint of L waveband radar air-exploration meteorological data in Anqing station from 2004 to 2008,the characteristics in the lower air in Anqing were studied based on wind speed profile and wind rose profile.[Result] Anqing,which locates in the lower reaches of Yangtze River,was influenced by monsoon and wind seasonal changes were distinct.The northeast wind prevailed in the near-ground layer and average annual frequency was 34.6%.The still wind frequency was relatively high and annual average reached 18.5%.The frequency of southwest wind in the summer-half-year increased.The frequency of wind from 700 m to the upper air was relatively diverged,and it was mainly westerly to 3 000 m high.According ot the wind speed profile,wind speed in the height below 700 m enlarged and then it slowed down from 700 to 2 000 m high and in winter the wind above 2 000 m fastened dramatically.[Conclusion] The characteristics of wind speed and wind direction in Anqing in recent years were summarized,which provided reference for climate changes in Anqing.

Re-evaluating the vertical mass-flux profiles of aeolian sediment at the southern fringe of the Taklimakan Desert, China

Reliable estimation of the mass-flux profiles of aeolian sediment is essential for predicting sediment transport rates accurately and designing measures to cope with wind-erosion. Vertical mass-flux profiles from seventeen wind-erosion events were re-evaluated using five typical models based on observed data obtained from a smooth bare field at the southern fringe of the Taklimakan Desert, China. The results showed that the exponential-function model and the logarithmic-function model exhibited the poorest fit between observed and predicted mass-flux profiles. The power-function model and the modified power-function model improved the fit to field data to an equivalent extent, while the five-parameter combined-function model with a scale constant（σ） of 0.00001 m（different from the σ value proposed by Fryear, which represented the height above which 50% of the total mass flux occurred） was verified as the best for describing the vertical aeolian sediment mass-flux profiles using goodness of fit（R2） and the Akaike Information Criterion（AIC） values to evaluate model performance. According to relationships among model parameters, the modified power model played a prominent explanatory role in describing the vertical profiles of the observed data, whereas the exponential model played a coordinating role. In addition, it was found that the vertical profiles could not be extrapolated using the five selected models or easily estimated using an efficient model without field observations by a near-surface sampler at 0 to 0.05 m.