Air Wind Research Articles

Numerical simulation of typhoon surges along the coast of Taiwan

A numerical model has been designed to study the storm surge induced by typhoon along the coast of Taiwan. The governing equations have been expressed in spherical coordinate system, and a finite difference method has been used to solve them. In the system of hydrodynamical equations, the nonlinear advection and lateral eddy viscosity terms are prominent in shallow coastal waters. Air pressure gradient and wind stresses are the driving forces in the model of typhoon surge. The model has been verified with storm surges induced by Typhoons Herb in 1996, and by typhoons Kai-Tak and Bilis in 2000.

Mathematical models for accurate prediction of atmospheric visibility with particular reference to the seasonal and environmental patterns in Hong Kong

Atmospheric visibility impairment has gained increasing concern as it is associated with the existence of a number of aerosols as well as common air pollutants and produces unfavorable conditions for observation, dispersion, and transportation. This study analyzed the atmospheric visibility data measured in urban and suburban Hong Kong (two selected stations) with respect to time-matched mass concentrations of common air pollutants including nitrogen dioxide (NO(2)), nitrogen monoxide (NO), respirable suspended particulates (PM(10)), sulfur dioxide (SO(2)), carbon monoxide (CO), and meteorological parameters including air temperature, relative humidity, and wind speed. No significant difference in atmospheric visibility was reported between the two measurement locations (p > or = 0.6, t test); and good atmospheric visibility was observed more frequently in summer and autumn than in winter and spring (p < 0.01, t test). It was also found that atmospheric visibility increased with temperature but decreased with the concentrations of SO(2), CO, PM(10), NO, and NO(2). The results showed that atmospheric visibility was season dependent and would have significant correlations with temperature, the mass concentrations of PM(10) and NO(2), and the air pollution index API (correlation coefficients mid R: R mid R: > or = 0.7, p < or = 0.0001, t test). Mathematical expressions catering to the seasonal variations of atmospheric visibility were thus proposed. By comparison, the proposed visibility prediction models were more accurate than some existing regional models. In addition to improving visibility prediction accuracy, this study would be useful for understanding the context of low atmospheric visibility, exploring possible remedial measures, and evaluating the impact of air pollution and atmospheric visibility impairment in this region.

Ecological effects of lawn greens with pure and mixed stands in an urban setting

We studied the ecological benefits of four types of urban green spaces (lawn, a Robinia pseudoacacia stand, a Pinus tabulaeformis stand and a mixed stand of both species) in Yuan Dynasty Wall Relics Park, Beijing. Each of the eight sampling sites was about 0.1 hm2. The experiment was carried out in June, 2006 over a period of eight consecutive days, during which we continuously measured air temperature, relative humidity (RH) and wind speed at the four green spaces in both horizontal and vertical directions. The results were as follows: in the horizontal direction, the all-day average temperature at the pine stand was the lowest and itsRHwas the highest under three different climate conditions. During the daytime high temperature period, the temperature of the lawn was the highest and its RH the lowest. The temperature was lowest for the mixed stand, and the RH was highest for the pine stand. The highest average daily temperature occurred in the locust stand. The temperature and RH of the four green spaces were statistically different at the 0.05 level of significance. In the vertical direction, the average daily temperature of the four green spaces increased with height. The average daily RH of the four green spaces decreased slightly with increased height. During the high temperature period of the day, the average temperature of the lawn and the P. tabulaeformis stand declined with the increased height, but the temperature at the R. pseudoacacia stand and the mixed P. tabulaeformis-R. pseudoacacia stand fluctuated greatly. With regard to the effect of lowering the wind speed, the mixed stand was better than the other green spaces. Based on these results, it can be concluded that the mixed Chinese pine and locust stand was the best choice for the establishment of urban green spaces.

Modeling fast ice formation and destruction in the Sea of Japan

The problems of parametric representation of the initial formation and the subsequent evolution of fast ice in freezing seas are discussed within the framework of the model of marine ice cover evolution. The mathematical form of this representation takes into account the processes of transformation of sea ice formations in open water areas in coastal regions into fast ice during its formation and inverse processes at the stage of its destruction. The parametric identification of the model was based on samples of long-term distributions of ice cover characteristics in the Sea of Japan, as well as the distributions of air temperature and wind speeds over sea water area. The model can be used to predict the state of fast ice in the ice cover of the Sea of Japan.

Fluctuation analysis of meteo-marine data

We study long-term behaviour of air temperature, wave heights and wind speed time series recorded for the period 1993–1997 at a meteo-marine station located in the Adriatic Sea. The scaling analysis shows that fluctuations of air temperature display long-range autocorrelations, while those for wave heights show a more complex behaviour, crossing over from a persistent regime at intermediate time scales (up to about 20 days) to an anti-persistence behaviour at longer times. Furthermore, the crosscorrelations of their records are found to be large, with a covariance of about -0.3 (indicating anti-crosscorrelations) within the full 5-years period, giving a quantitative measure of the actual coupling between the two data sets. Wind speed fluctuations are found to be strongly crosscorrelated (about 0.6) with those of wave heights, indicating as expected that wind is the main driving force for wave height fluctuations.

Particulate PAHs levels at Mt. Halla site in Jeju Island, Korea: Regional background levels in northeast Asia

The levels of PM.25 PAHs at Mt. Halla site, Jeju Island, a background site in Korea were observed between March 1999 and March 2002. A seasonal variation was observed for the particulate PAHs concentrations with high levels during cold season similar to Gosan, a nearby coastal background site, due to the seasonal variations of fossil fuel usage in Asia. The total average concentration of ambient particulate PAHs was 404 ± 579 pg m − 3, about one order lower than the ambient level at Gosan. However, the ratios of the anthropogenic inorganic ion concentrations between Mt. Halla and Gosan were smaller, 1.5 for non sea-salt (nss) sulfate and 2.7 for nitrate. Two possible explanations for these characteristics are (1) two sites measured different air parcels and/or (2) the effect of local emissions were different at two sites. Based on the Bep/BaP ratio result, upper air wind direction data, backward trajectory analysis, and LIDAR measurement data at Gosan, it was found that the degree of the effects of local emissions to the sampling sites be the major reason for the different PAHs levels at two sites though, in some cases, the air parcels arriving at Mt. Halla were different from those arriving at Gosan. For secondary aerosol such as nss sulfate, the lower concentration difference indicates both site are affected by regional transport. It points that the measurement result for directly emitted species such as PAHs at Gosan might be significantly influenced by local emissions.

A non-linear dynamic approach to the motion of four-wheel-steering vehicles under various operation conditions

This research aims to analyse systematically the non-linear dynamic behaviour of four-wheel-steering (4WS) vehicles. A practical non-linear dynamic model of multiple degrees of freedom for 4WS vehicles is established. The non-linear model presented is shown to be feasible for the vehicles under normal and the other operation manoeuvres. Compared with those of documented investigations, this model may be employed to analyse the motions of the vehicle and motions of the vehicle wheels in turning and braking processes together with the consideration of the effects of air drag and wind. Numerical simulation for the motion of the 4WS vehicles under various operation manoeuvres is performed with the model established. Comparison of the behaviours of 4WS and two-wheel-steering vehicles is also presented with respect to the inputs on the steering system, the manoeuvrability, the stability, and the relationship between the steering phase and vehicle speed.

Comparison of Observed 10-m Wind Speeds to Those Based on Monin–Obukhov Similarity Theory Using IHOP_2002 Aircraft and Surface Data

AbstractComparisons of 10-m above ground level (AGL) wind speeds from numerical weather prediction (NWP) models to point observations consistently show that model daytime wind speeds are slow compared to observations, even after improving model physics and going to smaller grid spacing. Previous authors have attributed the discrepancy to differences between the areas represented by model and observations, and the small surface roughness upstream of wind vanes compared with the corresponding model grid value. Using daytime fair-weather data from the May–June 2002 International H2O Experiment (IHOP_2002), the effect of wind-vane exposure is explored by comparing observed 10-m winds from nine surface-flux towers in well-exposed locations to modeled 10-m winds found by applying Monin–Obukhov (MO) similarity for unstable conditions to flight-track-averaged data collected by the University of Wyoming King Air over flat to rolling terrain with occasional trees and buildings. In the calculations, King Air winds and fluxes are supplemented with thermodynamic means and fluxes from the surface-flux towers. After exercising considerable care in characterizing and reducing biases in aircraft winds and fluxes, the authors found that MO-based surface winds averaged 0.5–0.7 ± 0.2 m s−1 less than those measured—about the same as the smaller reported discrepancies between NWP models and observed winds.

Composite Atmospheric Environments of Jet Contrail Outbreaks for the United States

Abstract The cirrus-level “condensation trails” (contrails) produced by jet aircraft are considered to influence surface climate and its recent changes. To reveal the synoptic atmospheric environments typically associated with multiple co-occurrences of contrails occurring in otherwise clear or partly cloudy skies (outbreaks) for the United States, and ultimately to assist in forecasting these events, a composite (i.e., multicase average) “synoptic climatology” at regional scales is developed for the midseason months (January, April, July, October) of 2000–02. The NCEP–NCAR reanalysis data that emphasize upper-troposphere (UT) variables are allied with manually identified outbreaks appearing on satellite Advanced Very High Resolution Radiometer digital data, using a geographic information system. The highest frequencies of outbreaks by far occur in the Midwest (32.6% of all-U.S. total), followed by the Northeast (17.6%) and Southeast (17.2%). In these regions, all of which have a high density of jet air traffic, an additional 2% cirrus cloud coverage from outbreak-related contrails is inferred. Large interannual and interseasonal variations in contrail outbreak frequencies support the role of meteorological variations. For most regions, the outbreak-associated synoptic circulation composite conditions involve UT ridging and a higher and colder tropopause than the climatological average; meridionally enhanced gradients of the UT vertical motion, located between sinking air to the east (in the ridge) and rising air to the west, in advance of a trough; similarly strong gradients of mid–upper-troposphere humidity, comprising dry air located to the east and moist air to the west; and horizontal speed shear ahead of an advancing jet stream. Notwithstanding, there is a geography (i.e., areal differentiation) to contrail outbreak environments: composites for the Northeast suggest an influence of land–sea contrasts on synoptic systems and, therefore, on contrail outbreaks. For the Northwest, there is evident a greater impact of horizontal wind shear contrasted with other regions. The synoptic climatology results are supported by the all-U.S. averages of contrail outbreak UT conditions [climate diagnostics (CDNs)] previously determined for early–mid-September periods of 1995–2001. Moreover, a comparison of these CDNs with those derived for nearby thick natural clouds, including cirrus, helps to clarify their different synoptic associations: the UT conditions typical of thick clouds represent an intensification of those associated with contrail outbreaks and include the greater upward vertical motion, moister air, and stronger westerly winds characteristic of a trough. Given the location of most contrail outbreaks downstream of multilayered cloud systems, contrails may help to extend the “natural” cirrus and cirrostratus spatial coverage.

Validation of the Deardorff model for estimating energy balance components for a sugarcane crop

The quantification of the available energy in the environment is important because it determines photosynthesis, evapotranspiration and, therefore, the final yield of crops. Instruments for measuring the energy balance are costly and indirect estimation alternatives are desirable. This study assessed the Deardorff's model performance during a cycle of a sugarcane crop in Piracicaba, State of São Paulo, Brazil, in comparison to the aerodynamic method. This mechanistic model simulates the energy fluxes (sensible, latent heat and net radiation) at three levels (atmosphere, canopy and soil) using only air temperature, relative humidity and wind speed measured at a reference level above the canopy, crop leaf area index, and some pre-calibrated parameters (canopy albedo, soil emissivity, atmospheric transmissivity and hydrological characteristics of the soil). The analysis was made for different time scales, insolation conditions and seasons (spring, summer and autumn). Analyzing all data of 15 minute intervals, the model presented good performance for net radiation simulation in different insolations and seasons. The latent heat flux in the atmosphere and the sensible heat flux in the atmosphere did not present differences in comparison to data from the aerodynamic method during the autumn. The sensible heat flux in the soil was poorly simulated by the model due to the poor performance of the soil water balance method. The Deardorff's model improved in general the flux simulations in comparison to the aerodynamic method when more insolation was available in the environment.

MODELUNG OF PAN EVAPORATION USING SUPPORT VECTOR MACHINES ALGORITHM

ABSTRACT This paper present results of pan evaporation estimations using Support Vector Machines (SVMs) based approach for the meteorological data from Manasgaon climatic station near Anand Sagar Reservoir, Shegaon. At this station four meteorological variables are measured simultaneously, namely, air temperature, wind speed, sunshine hours and relative humidity. The SVMs architecture involves in using one output parameter (i.e. evaporation) and up to four input parameters representing air temperature, wind speed, sunshine hours and relative humidity. The performance of SVMs approach was compared with multiple linear regression using different combination of meteorological parameters so as to judge the significance of the input parameters in estimating the evaporation. The SVMs algorithm provide good estimation of evaporation with high correlation coefficient along with low Root Mean Square Error. Further, the Scatter Plot between the actual and estimated values of evaporation suggests that most of the values lie within a scatter of ±15%. The findings of this study suggest the usefulness of SVMs algorithm technique in estimating the pan evaporation from reservoirs.

Estimativa da evapotranspiração de referência em Campina Grande, Paraíba

Deste trabalho se objetivou estimar, através de uma fórmula empírica, a evapotranspiração de referência diária no município de Campina Grande, PB (EToT), utilizando-se a amplitude térmica diária. Estimou-se, também, a ETo diária usando-se os métodos de FAO-Penman-Monteith (EToPM), Hargreaves (EToH) e Linacre (EToL), sendo depois correlacionados com a EToT proposta na pesquisa, por estação do ano; para isto foram coletados valores diários das temperaturas, umidade relativa do ar, radiação solar, precipitação, pressão atmosférica e velocidade do vento a 2 m da Estação Meteorológica Automática, instalada na Universidade Federal de Campina Grande (UFCG), no período de 1 de janeiro a 31 de dezembro de 2004. Tais valores foram registrados no intervalo de 10 min. Verificou-se que as correlações da EToT com EToH, obtiveram o melhor ajuste, cujos coeficientes foram: R² = 0,7882 (no ano), R² = 0,9796 (no verão), R² = 0,8253 (no outono), R² = 0,878 (no inverno) e R² = 0,914 (na primavera). Conclui-se que os métodos de EToPM e EToL não se ajustaram bem para Campina Grande, PB, o que evidencia que a EToT poderá ser utilizada na forma proposta para estimativa da ETo desta localidade. Das equações propostas, a única restrição é o EToT para o verão caso em que se recomenda o uso da equação anual.

How do weather conditions affect the huddling behaviour of emperor penguins?

Huddling allows emperor penguins to conserve energy and survive their long winter fast while facing harsh climatic conditions. Here we report the first investigation into the effects of changes in wind speed and ambient temperature on different components of penguin huddling behaviour. We attached light and temperature recorders to male emperor penguins at the Pointe Geologie colony, Antarctica, which recorded huddling events. We then compared the frequency, duration, occurrence and intensity of huddling bouts, with ambient air temperatures and wind speeds. Huddling occurrence increased with lower ambient temperatures and higher wind speeds, whereas huddling intensity was mainly enhanced by lower ambient temperatures. Moreover, huddling group movements were linked to wind direction and its global density to lower ambient temperatures. Hence, emperor penguins complex huddling behaviour was modulated differently depending on these two parameters. Weather conditions may then affect emperor penguins ability to save energy and survive their winter fast.

Benefits of promulgating higher resolution wind data for airline route planning

AbstractA study has been undertaken to determine whether there are useable incremental benefits from providing upper air wind data at high horizontal resolution to the process of airline flight planning. Currently winds are provided on a horizontal resolution of approximately 140 km. The study looked at resolutions varying between 160 and 40 km. A theoretical calculation was undertaken using published variance power spectra, which quantify the wind variability as a function of horizontal scale. This calculation also used a published formula for the time saving in flying across an area of constant vorticity. The results of the theoretical calculation were expressed in terms of the time saving on a transatlantic flight lasting typically 8 h stemming from a resolution change from 160 to 80 km. In this case the answer was well under one second. It is thought that such a small incremental benefit could not be used to justify the practical steps needed to exploit high resolution data. The more practical part of the study involved running an optimum routes diagnosis package with variable resolution input data. Input data at resolutions of 160 and 40 km were considered. Although this approach was only applied to a restricted number of cases and routes, it confirmed the theoretical result. © Crown Copyright 2007. Reproduced with the permission of the Controller of HMSO. Published by John Wiley &amp; Sons, Ltd

Significant Inversions and Rapid In Situ Cooling at a Well-Sited Oklahoma Mesonet Station

Abstract The El Reno Oklahoma Mesonet (ELRE) site is one of a few Oklahoma Mesonet sites that has measured inversions of 10°C or greater between 1.5 and 9 m. Historical analyses revealed that strong inversions at ELRE have occurred because of rapid cooling near the surface shortly after sunset when conditions are calm, clear, and dry. In addition, ELRE is a very well sited station and is located on very slightly sloped terrain with no obstructions nearby. Four Portable Automated Research Micrometeorological Stations (PARMS) were deployed along a transect orthogonal to ELRE for 3 months in the spring of 2005 to quantify the micrometeorological processes that caused rapid cooling and subsequent strong inversions to form. One-minute data collected from the PARMS and ELRE during the study verified the variability and duration of strong inversion events. Analyses from the field study also revealed that significant horizontal and vertical differences in air temperature and wind speed existed during periods of differential wind speeds between the PARMS and ELRE.

Comparing the impact of meteorological variability on surface ozone during the NEAQS (2002) and ICARTT (2004) field campaigns

This paper investigates linkages between weather, climate, and air quality that contributed to the large difference in the number of ozone exceedances encountered in the northeastern United States (U.S.) during 2002 and 2004. Major air quality research field campaigns were conducted in the northeast during July and August of each year. Both the 2002 New England Air Quality Study (NEAQS‐02) and the International Consortium for Atmospheric Research on Transport and Transformation 2004 field study (ICARTT‐04) had research components focused on regional air quality. The primary environmental difference between the two field campaigns was the underlying climatic conditions. The July–August period in 2002 was much sunnier, warmer, and drier than normal. In contrast, the July–August period in 2004 was cloudier, cooler, and much wetter than normal. We conclude that these extreme climatic conditions were the underlying cause for the significant difference in the number of ozone exceedances that occurred during NEAQS‐02 and ICARTT‐04. We rule out the impact of other meteorological processes as the primary cause of this difference. We gauge horizontal transport using surface and upper air wind observations collected on Appledore Island (ADI), off the coast of New Hampshire and Maine, along with back trajectories based solely on wind observations collected by profiler networks deployed for each study. The wind conditions that favor pollutant transport to the northeast were more prevalent in 2004 than in 2002, yet the number of ozone exceedances in 2004 was more than a factor of three less than in 2002. Neither was daytime boundary layer mixing the cause for this discrepancy. Unlike other parts of the U.S. where poor air quality is generally associated with shallow boundary layers, in New England the boundary layers were deeper on high‐ozone days than on clean days because the same sunny, warm, and dry conditions that favor boundary layer ozone production also produce deeper boundary layers. Both field campaigns were synoptically active. Lulls in synoptic activity explained most of the high‐ozone events observed in 2002, whereas even an extended lull in synoptic activity during the summer of 2004 did not produce a single high‐ozone day.

Modeling and identification of solar energy water heating system incorporating nonlinearities

Prediction accuracy is a fundamental modeling requirement. This work explores different models for a solar domestic water heating system located near Viña del Mar, Chile, in order to improve model prediction accuracy over some existing alternatives. The main approach is semi-physical modeling, which combines phenomenological modeling and system identification. The former helps to organize in a conceptual form the available system knowledge, and the latter allows to adjust that knowledge into a particular model structure for a working system. Thus, with semi-physical modeling we take advantage of a basic property of classical identification models: they are linear-in-the-parameters, but may contain nonlinear regressors. Hence, while physical knowledge suggests nonlinear data regressors, system identification adjusts linear weighting parameters. The models proposed here incorporate nonlinearities based on physical system knowledge and they include, among other inputs and disturbances, air wind speed ( v) and air relative humidity (RH), signals not usually considered in these model structures. Specifically, this work shows model predictive accuracy of storage tanks temperature for three model types: semi-physical, state-space and, a combination of semi-physical and a feedforward neural network with one hidden layer and eight neurons. The best models found here, according to prediction accuracy, are of semi-physical nature, and are obtained using stepwise regressor elimination algorithms which retain disturbances such as v and RH. Additionally, final models are validated with classical statistical tests such as AIC and correlation analysis.

Caracterización de bordes de bosque altoandino e implicaciones para la restauración ecológica en la Reserva Forestal de Cogua (Colombia)

The growth of a forest patch through colonization of the adjacent matrix is mostly determined by the particular characteristics of the edge zone. Knowing how these characteristics are related to a specific edge type and how they influence the regeneration process, is important for High Andean forest edges restoration. This study aimed to characterize three types of High Andean forest edge in Cogua Forest Reserve (Colombia): 1) edge of Chusquea scandens, 2) "paramizado", and 3) old edge, characterized for being in a later successional state. Two forest patches were chosen for each edge type and 13 criteria were analyzed; these were of topographic order, micro-environmental order, vegetation structure and species composition. In each patch the vegetation was evaluated by means of two 60 m transects perpendicular to the edge and along the matrix-edge-interior of the forest gradient. All woody plant species were identified and counted to determine their abundance. Environmental variables (air temperature, relative humidity, wind speed, and light radiation) were measured in one of the transects. Three of the 13 criteria were of little importance in shaping the type of edge habitat (slope, patch shape and area). The others were closely related with the micro-environmental conditions and in turn with the vegetation structure and composition; this relationship confers particular characteristics to each edge type. The microclimate and floristic edge limits coincided; edges extend between 10 and 20 m into the forest depending on the edge type. The paramizado edge has the smallest environmental self-regulation capacity and is more exposed to fluctuations of the studied variables, because of its greatest exposition to the wind action and loss of the tallest trees (between 10 and 15 m) which regulate the understorey microclimate. This low environmental buffer capacity prevents the establishing of mature forest species (for example, Schefflera sp. and Oreopanax bogotensis) although they are found in other areas within the same patch. All these results show that the paramizado edge needs the most intervention for its restoration. The Chusquea scandens edge forest is the most sheltered since this species acts as a protecting shield. However it still needs to be controlled to allow the adjacent matrix colonization by the forest species and natural regeneration, as it does in the old edge type forest, which moreover has an intermediate self-regulating capacity relative to the other two. The vegetation composition reveals that most of the edge species can also grow inside, beyond the forest edge.

Temperature stratification of the lower atmosphere over Moscow

Features of diurnal and annual cycles and of seasonal changes of temperature stratification in the lower 800-m air layer over Moscow are discussed on the basis of analysis of long-term data of acoustic (sodar) observations at Moscow State University (MSU). Of about 34 000 separate hours of height-time sweep of echo signal during 1988–2003, refined estimates are presented of occurrence frequencies of surface and elevated inversions, unstable stratification, etc., in Moscow. On the basis of long series of hourly sodar data and surface weather observations at MSU, special features of temperature stratification are considered under extremely low and high values of air temperature, wind speed, and relative humidity. A review is presented of existing data on temperature stratification in central Russia for the whole period of aerological observations; results of acoustic sounding are compared against the data obtained using other techniques.

Effect of weather conditions on somatic cell score in Sicilian Valle del Belice ewe

Mastitis susceptibility of Valle del Belice ewes from the south of Sicily to temperature, humidity, precipitation, solar radiation, sun hours, air pressure, wind-speed and wind-direction measured by a public weather station was investigated using 65,848 test-day somatic cell score (SCS) records of 5,237 ewes. All weather parameters had an effect on SCS in a regression approach. Extreme values of maximum and minimum temperature-humidity indices resulted in increased SCS. Higher precipitation, solar radiation and sun hours resulted in increased SCS, whereas higher air pressure and wind speed resulted in reduced SCS.