Weak Wind Velocity Research Articles

Inter-comparison study of wind measurement between the three-lidar-based virtual tower and four lidars using VAD techniques

ABSTRACT The accurate three-dimensional wind field obtained from a Doppler lidar not only helps to comprehend the refined structure of complex airflow but also provides important and valuable solutions for many fields. However, the underlying homogeneity assumption of the typical wind retrieval methods, such as Doppler Beam Swinging (DBS) and Velocity Azimuth Display (VAD) based on a single-lidar, will introduce the measurement uncertainty in complex terrain. In this paper, a new design of a wind measurement campaign involving seven lidars was carried out, which contained the three-lidar-based Virtual Tower (VT) using a time-space synchronization technique and four single-lidars with different elevation angles. This study investigates the performance of VT and VAD measurements under various conditions and evaluates the sensitivity of wind measurement uncertainty of VAD to the horizontal spatial- and probe volume-average effects associated with elevation angles of the laser beam. The inter-comparison results between VT and four VADs show consistent trends with small relative errors under neutral atmospheric conditions with weak wind velocity. Under convective or high Turbulence Intensity (TI) conditions, the relative errors between VT and VAD become larger and more fluctuant. Moreover, it is found that the measurement uncertainty of VAD increases at a given elevation angle with the increasing measurement heights, which is caused by the horizontal homogeneity associated with the conical scanning area. Additionally, the simulated and measured results of four VADs indicate that a larger elevation angle corresponds to a lower measurement uncertainty for a given height.

Spatiotemporal Dynamics of Surface Ozone and Its Relationship with Meteorological Factors over the Beijing-Tianjin-Tangshan Region, China, from 2016 to 2019.

In recent years, ozone pollution has been increasing in some parts of the world. In this study, we used the Beijing–Tianjin–Tangshan (BJ-TJ-TS) urban agglomeration region as a case study and used satellite remotely sensed inversion data and hourly ground monitoring observations of surface ozone concentrations, meteorological data, and other factors from 2016 to 2019 to explore the spatiotemporal dynamic characteristics of surface ozone concentration and its pollution levels. We also investigated their coupling relationships with meteorological factors, including temperature, pressure, relative humidity, wind velocity, and sunshine duration, in order to support the development of effective control measures for regional ozone pollution. The results revealed that the surface ozone concentration throughout the BJ-TJ-TS region from 2016 to 2019 exhibited an overall pattern of high values in the northwest and low values in the southeast, as well as an obvious difference between built-up and non-built-up areas (especially in Beijing). Meanwhile, a notable increasing trend of ozone levels was discovered in the BJ and TJ areas from 2016 to 2019, whereas this upward trend was not evident in the TS area. In all three areas, the highest monthly average ozone values occurred in the summer month of June, while the lowest monthly average levels occurred in the winter month of December. Their diurnal variation values reached a maximum value at approximately 3:00–4:00 p.m. and a minimum value at approximately 7:00 a.m. It is clear that high temperature, long sunshine duration, low atmospheric pressure, and weak wind velocity conditions, as well as certain relative humidity levels, readily led to high-concentration ozone pollution. Meanwhile, the daily average values of the five meteorological factors on days with Grade I and Grade II ozone pollution displayed different characteristics.

Highly Sensitive Interlocked Piezoresistive Sensors Based on Ultrathin Ordered Nanocone Array Films and Their Sensitivity Simulation.

Achieving a continuously adjustable micro-nanostructure of sensing materials is crucial and still a challenge for the flexible pressure sensor. We proposed a new method to prepare ultrathin ordered nanocone array films by designing tunable tapered anodized aluminum oxide templates and to prepare highly sensitive flexible pressure sensors by the interlocking nanocone arrays. Meanwhile, the theoretical prediction model of the sensitivity of interlocked nanocone arrays is proposed, and its result shows that the resistance change rate is positively correlated with the height of interlocked nanocone arrays and the contact area between interlocked nanocones. According to the finite element simulation and experimental results, the interlocked ordered nanocone array pressure sensor exhibits a high sensitivity of 268.36 kPa-1 in the pressure range of 0-200 Pa, an ultralow detection limit of 0.98 Pa, a fast response/recovery time of 48/56 ms, a low hysteresis of ±3.156%, stability under 5000 cycles of loading, and continuity and repeatability under different loads and loading speeds. Furthermore, the pressure sensor can accurately monitor weak wind velocities, wrist torsion and bending movement, and book opening and closing angles. The sensor has broad application prospects in wearable medical monitoring, electronic skin, and human-computer interaction.

Assessment of the impact of a twin industrial area on the air quality in Bandar Baru Bangi, Selangor

The rapid industrial development in an equatorial developing country poses a dilemma where sustainable and human development should be dynamically balanced in an otherwise interdependent ecosystem. The impact of the presence of two industrial designated areas on the air quality of the surrounding residents in a satellite town of Bandar Baru Bangi (BBB), in the state of Selangor in Peninsular Malaysia was investigated by selecting four air quality sampling stations at the Selaman Industrial Park (SIP), the Bangi Industrial Estate (BIE) and two nearby BBB residential areas. Air quality samplings for particulates of aerodynamic diameter of 10 microns (PM 10 ) and gases such as carbon monoxide (CO) and nitrogen dioxide (NO 2 ) were conducted. ANOVA analysis showed that the concentrations between the four stations were different, where higher daily average concentrations for all air parameters exist at the BIE. The PM 10 and CO concentrations were below the New Malaysia Ambient Air Quality Standard (2020) (NMAAQS) unlike the NO 2 concentrations at both the industrial parks that exceeded the NMAAQS (2020) of 0.15 ppm. The HYSPLIT modelled air trajectory analysis indicated that weak wind velocities during the southwest monsoon over Malaysia dispersed the pollutants from the industrial areas. The predicted dispersion from the HYSPLIT model simulated different plume patterns for the five days from the two industrial areas due to different wind regime of the day during the southwest monsoon. The results emphasize the importance of good proper urban planning particularly for the placement of industrial areas within a township. Keywords : air quality, equatorial, light industry, monsoon, residential, twin industrial area

High resolution modelling of severe wind patterns over the north-west Black Sea Region

The research studies the performance of the convective-permitting Harmonie model in reproducing mesoscale features of the wind regime over the north-western part of the Black Sea. It allowed establishing the optimum configuration, projection and geometry of the model's high spatial resolution area over Ukrainian part of the Black Sea, preparing a digital format for a coastline based on the resolution and conducting numerical experiments to verify informativeness and stability of computations. It also presents a detailed description of the forecasting procedure which includes a data flow from the Meteorological Archiving and Retrieving System (MARS) of the European Center, creating boundary conditions, forecast computations and a model output composition for the particular region and domain resolution.
 The results have shown that the Harmonie model with the 2.5 km spatial resolution and the 60 second time step is able to reproduce detailed spatial variability of a near-surface wind field and its evolution to the corresponding scales. In particular, the model is able to simulate mesoscale circulation features of approximately ten km over a homogeneous sea surface and to track their evolution; to monitor the position of convergence zones; to highlight the spatial characteristics of a lee-side wind attenuation band along the coast line when wind blows from the shore; to specify mesoscale wind patterns in bays and along the coastline with complex orography; to reproduce the weakening of a wind velocity over an urban area due to increased surface roughness.
 Two operational forecasting systems, GFS-WRF and ARPEGE/IFS-Harmonie are compared by the following components: numerical solvers, sub-grid parameterizations, efficiency of computer resources and intellectual potential. The GFS model output with the 25 km spatial resolution is able to correctly reproduce over the region only large-scale atmospheric patterns. However, for rapid changes in the atmospheric circulation accompanied by changes in the wind direction to the opposite and wind increase, the model simulations are delayed in terms of wind field evolution. Additionally, because of crude spatial resolution, the GFS model is unable to describe mesoscale atmospheric features due to differences in surface types, orography, thermal contrasts, etc. Comparison of the both model outputs versus observations from Odesa, Chornomorsk and Yuzhnyi port during severe wind conditions has shown that the discrepancy between the models and observations within the allowable error value (5 m/s) occurred only for Odesa port with regard to the Harmonie model for weak wind velocity. The difference partially increases for moderate wind from the shore, while for strong wind from east and south directions indicates disagreement between the model results and observations and achieves critical values of 20-25 m/s. Such values are mainly determined by the discrepancy in wind direction (up to 180°). The comparison results clearly indicate the doubtful representativeness of wind observations at Chornomorsk and Yuzhnyi stations in general, and at Odesa station in particular.

The function of the turbulent energy dissipation in the atmospheric surface layer

Introduction. The problem of energetics of atmospheric processes is one of the important problem in the modern meteorology. Distribution of the sources and sinks of energy, especially near the surface, also turbulent transport and transformation of energy reflect all features of the processes generated in the atmospheric boundary layer, their behavior and intensity.
 Purpose. A purpose of the work is a description of processes of production of turbulent kinetic energy (TKE) and dissipation rate of TKE in the surface layer, because transition of heat energy into TKE and vice versa, occurs continuously in the presence of wind shift. These changes are reflected in the actual state of the surface layer, which is registered with the meteorological observations.
 Investigation methods. On the basis of the assumption that the TKE dissipation rate is directly proportional to its production, an atmospheric surface layer model, including the surface layer parameterization based on the Monin-Obukhov similarity theory and the modified Businger relationships, is proposed. The model provides sufficiently accurate assessment of the energy conservation law both on the surface and in the air flux. Statistical features of atmospheric turbulence, such as the vertical gradients of substances, dispersion and covariance are universal functions of hydrostatic stability of the surface layer, therefore non-dimensional functions of TKE dissipation and smoothing of temperature inhomogeneity are determined from the TKE budget equation, which are given to a non-dimensional form.
 Results. The dependence of dissipation from stratification and wind velocity over surfaces with different roughness is defined. Under unstable stratification the function of dissipation is greater than 1 (je>1) and in-creases with its growth, under stable stratification the function decreases to zero. If the conditions are close to neutral, the function form becomes an S-shape one. Under weak wind velocities (u £ 2m/s), the dissipation rate is small and does not exceed 5 cm2/c3. With increasing wind velocities, the stratification of layer tends to the neutral condition and the dissipation rate increases to 100-150 cm2/c3 depending on the surface roughness. The results are good consistent with the measurements, carried out for different stratifications and wind velocities.
 A similar test of “closure” of the TKE budget equation is executed for the forces, representing the buoyancy effect. Ratio of the non-dimensional function of rate of smoothing of temperature inhomogeneity, jq, and temperature gradient, jT, is equal to 1 ((jq/jT)»1,0), that confirms satisfiability of all the energy budget equations for the surface layer, used in the proposed model.
 Conclusion. The results are obtained not by observations, but by the atmospheric surface layer model, including all the energy budget equations, which provides execution of energy conservation law both on the surface and in the air flux. Standard meteorological observations contain information not only about meteorological parameters, representing the actual weather conditions, but also information about the surface layer scaling parameters, which allow to determine both the internal and sometimes external parameters of the surface layer and the atmospheric boundary layer.

Synoptic Meteorological Classification of the Days on Which Asthma Deaths Occurred Due to High PM10 Concentrations in Seoul

Asthma deaths in Seoul peaked on the third, fifth, and second days after the PM concentration exceeded the daily average concentration standard. We classified the synoptic meteorological conditions, based on the days involving such cases, into three categories. Type 1 included the meteorological condition likely to cause high air pollution concentrations in the leeward region, the dominant wind direction of which is the northwest. Type 2 included the meteorological condition likely to cause high air pollution concentrations due to the weak wind velocity under stable atmospheric conditions. Type 3 was when the passage low atmospheric pressure and the expansion of high atmospheric pressure occurred at the rear, indicating a meteorological condition likely to cause high air pollution, in certain regions. Type 1 occurred 11 times, with high concentrations of over 100 ㎍/ ㎥ being observed in the southeastern part of Seoul. Type 2 occurred 24 times, often accompanied by a PM concentration of 100~400 ㎍/ ㎥ . Type 3 occurred 11 times, and was accompanied by several days of yellow dust that accounted for the highest concentrations.

Research on Sand-Blocking Mechanism of Fence Based on CFD Technology

The airflow field and sand movement path around fences of 0 and 40% porosity are of numerical calculation by CFD technology and the sand-blocking mechanism of fence is analyzed comprehensively. The results show that the two preconditions for the good sand-blocking performance of fence are to greatly reduce the coming wind velocity and form a large weak wind velocity area, and ensure the sand movement path in the weak wind velocity area. The numerical simulation research of the sand-blocking mechanism of fence is an useful supplement of traditional experimental research and of reference significance in further understanding the dynamic mechanism of fence protection.

Radar Echo Population of Air-Mass Thunderstorms and Nowcasting of Thunderstorm-Induced Local Heavy Rainfalls Part 1: Statistical Characteristics

A radar echo population of 179 thunderstorms generated in the Tokyo metropolitan area on August 5, 2008, when the Zoshigaya rainstorm occurred in the center of Tokyo, is presented. Analysis was made using three-dimensional radar data from the Japan Meteorological Agency. One third of total convective cells had diameters of less than 3.5 km and the average diameter was 5.5 km. The mode of lifetimes of cells was from 20 to 40 minutes, and 88% of cells disappeared within 60 minutes after their initiation. The echo-top height of half of the cells reached 15 km, which was the limit of radar observation. Although the rainfall amount estimated from the radar echo was less than 40 mm for half of the cells, whereas one third of total cells counted were estimated atmore than 60 mm. Vertically integrated liquid water (VIL) ranged from 1.4 to 42.4 kgm-2. Maximum VIL was equivalent to 70% of precipitable water estimated from upper sounding on that day. The speed of cell travel was less than 2 ms-1in accordance with the weak wind velocities in the lower to middle troposphere. The time from echo initiation to rainfall peak was as short as 10 to 30 minutes for almost all cells. Thunderstorms composing the Zoshigaya rainstorm ranked at the highest class in horizontal size, lifetime and total rainfall amount among 179 thunderstorms. The horizontal size of cells in the thunderstorms was nearly equal to those reported for other areas in the world, whereas the echo top height was higher than in the other cases.

Seasonality and variability of coccolithophore fluxes in response to diverse oceanographic regimes in the Bay of Bengal: Sediment trap results

A study on coccolithophores from the sediment trap samples, collected over a period of one year (January 1992–December 1992) from three trap locations in the Bay of Bengal (BOB) were used to understand their production and export processes in relation to diverse oceanographic regimes associated with the reversing monsoons. A total of 25 species of coccolithophores were identified, which include some of the ecologically important species: viz: Gephyrocapsa oceanica, Umbilicosphaera sibogae, Florisphaera profunda, Umbellosphaera irregularis, Emiliania huxleyi, Oolithotus antillarum, U. tenuis, Helicosphaera carteri and Calcidiscus leptoporus. The total coccolithophore fluxes increased from the northern to southern Bay of Bengal where G. oceanica, U. sibogae and E. huxleyi were dominant species displaying seasonality with peak fluxes occurring during southwest (SW) and northeast (NE) monsoons reflecting their affinity for nutrient-rich waters brought in by river plumes, divergences and cyclonic eddies. U. irregularis, an indicator of oligotrophic/warm water, recorded peak abundance fluxes only during the spring intermonsoon period at all trap locations thus inferring its preference for oligotrophic conditions caused by increased Sea Surface Temperature (SST), stratification and lack of nutrient supply due to weak wind velocities. The deep dwelling species, F. profunda recorded high fluxes during the fall intermonsoon (October/November) in the northern and southern traps during the spring intermonsoon. The peak fluxes observed during the spring intermonsoon (April/May) in the central and southern traps indicated the prevalence of a deep nutricline when oligotrophic conditions prevailed at the surface. The interannual variability of coccolithophore assemblages between the years 1992 and 1994 may be attributed to the prevalence of ENSO (El Nino–Southern Oscillation) and negative IOD (Indian Ocean Dipole) during 1992 and moderate ENSO and positive IOD with different ocean dynamics in 1994. Interestingly, dissolution was encountered as evidenced by the presence of corroded coccoliths. Similarly, mechanical breakage of coccoliths was also observed. It is believed that the biologically mediated processes were the main factors responsible for both the dissolution and mechanical breakage of coccoliths.

Environmental changes in Chaohu Lake (southeast, China) since the mid 20th century: The interactive impacts of nutrients, hydrology and climate

Abstract Chaohu Lake, the fifth largest freshwater lake in the Yangtze floodplain, is faced with multiple stresses from anthropogenic disturbances and climate change. To explore the ecological changes in Chaohu Lake since the mid 20th century, we examined diatoms, geochemical indicators and particle size in 210 Pb-dated sediment core from the lake. Diatom succession revealed that the lake had switched to a eutrophic state since the late 1970s. Redundancy analysis using limnological data, hydrological and meteorological variables showed that sedimentary total phosphorus (TP) and total organic carbon (TOC), annual mean temperature, annual mean wind velocity, and water-level amplitude (WLA) were five significant factors influencing diatom succession. Diatom assemblages from 1950 till 1978 were driven by WLA and wind. The establishment of Chaohu Dam baffled hydrological connectivity between the lake and the Yangtze River in 1962, and reducing water exchange-induced flow. Meanwhile, weak wind velocity reduced the wind-induced flow in the 1960s. Due to the weak hydrodynamic intensity, the dominant species ( Aulacoseira granulata , a species with high sinking rate) became less important during this period. From 1979 till 2006, diatom assemblages were mainly driven by TP, TOC and temperature, which were highly correlative. Increasing nutrient loading promoted the blooms of eutrophic species (e.g., Cyclostephanos dubius ). In addition, rising temperature would indirectly influence diatom assemblages by mediating nutrient release process. As a consequence, multiple stresses in concert have caused the lake switch to a further eutrophic state indicated by prominent increases in more eutrophic species (e.g., Stephanodiscus parvus ) since 2000. This study provided information on complex trajectories of aquatic ecosystem shifts driven by increasing nutrient loading, hydrological alteration and climate warming in the Yangtze floodplain lake.

Characteristics of water-soluble components of atmospheric aerosols in Yokohama and Mt. Oyama, Japan from 1990 to 2001

Abstract We continuously collected aerosol samples of PM7 from 1990 to 1997 and of PM10–2 and PM2 from 1998 to 2001 and measured their water-soluble components of pH, conductivity, major ions, dissolved organic carbon (DOC) and total mass (TM) in an urban site, Yokohama (35°28′N, 139°38′E) and the mountainside (680 m asl) of Mt. Oyama (35°28′N, 139°46′E, 1252 m asl), Japan, to contrast the aerosol composition between an urban site and a mountain site. In Yokohama, annual mean TM concentration decreased gradually for over 10 years with the decrease of NH4+, Mg2+, Cl−, and SO42− concentrations, and TM concentrations were the highest in winter and the lowest in summer. At Mt. Oyama, there was no significant change in the duration, and TM concentrations were the highest from late spring to early summer, although the seasonal variation was smaller. Equivalent concentration ratio of Cl− to Na+ at Mt. Oyama was lower than that in Yokohama, because Cl loss which occurred was larger for the aerosol collected at Mt. Oyama remote from the sea rather than Yokohama. The conversion ratio of sulfur to sulfate was calculated and the ratio was not affected strongly by the variation of Ox concentration at both sites and was high at Mt. Oyama in summer. NH4+, NO3−, SO42−, and DOC concentrations were higher under weak wind velocity than those under strong wind velocity regardless of the wind direction in both the sites.

大阪湾および播磨灘におけるギムノディニウムの高密度発生と水質，気象要因との関係

Relatioship between the blooming of Gymnodinium mikimotoi and water quality or meteorological factors was examined in Osaka Bay and Harima-nada, referring to the Meteorological Agency's data.The comparison of the average of each water quality parameter with the dominant species among phytoplankton from June to August of 1995-1997 showed that G. mikimotoi dominantly occurred in the waters with high water temperature, salinity, TN:DIN (total nitrogen: dissolved inorganic nitrogen) and TP:DIP (total phosphorus: dissolved inorganic phosphorus) ratios, moderate TN×TP and DIN:DIP ratio, and low TN, TP, DIN, DIP, and DSi (dissolved silicate). The red tide of G. mikimotoi occurred from late July to mid August of 1995 with meteorological conditions of high precipitation, high air temperature, long sunshine duration, and weak wind velocity in July.These characteristics of water quality and meteorological factors suggested that the abnormal occurrence of G. mikimotoi was closely connected with the increase of dissolved organic matter by the sudden increase and following decomposition of phytoplankton and the capability of utilization of dissolved organic matters of G. mikimotoi.

Variation of Aerodynamical Characteristics of a Barley Field with Growth

The data of wind and temperature profiles in the low-level air layers over the barley field were used to study the magnitudes of the profile parameters (z0, d, V* and Cd) and their variations with wind velocity and the growth conditions of the crop plants. The profile measurements were made on a 1.5ha field of the barley during the period from November 1964 to June 1965. All wind profile parameter computations are based on the data of ten-minute mean wind velocity profiles. The results obtained are summarized as follows:1. The zero plane displacement (d) increases with the plant height but decreases inversely with the wind velocity. An exponential function of the plant height approximates the variation of d. The value of exponent decreases with wind velocity.2. The roughness parameter (z0) decreases slightly with the wind velocity in the early stages of plant growth, but it increases inversely with the wind velocity in the later stages of the growth. Under the conditions that h is larger than 5cm, z0 is found to be proportional to hl. The exponent varies also from 0.75 at weak wind velocity to 1.35 at at strong wind velocity.3. Surface drag coefficient (Cd) varies with the wind velocity and the plant height. The coefficient is proportional to a power of the plant height in the same manner as z0 (see Fig. 5). The variation of friction velocity (V*) with both the wind velocity and the plant growth is expressed approximately byV*=0.4/0.74+Fu1501.02+0.29F.