The starting point of wind turbine operation is the incoming wind. Wind turbines are positioned in the atmospheric boundary layer (ABL), the lower approximately 1 km of the atmosphere; here the wind tends to be dominated by turbulent structures generated through the transfer of momentum and heat with the Earth's surface, as well as interaction with the free atmosphere above governed by large-scale motion. In this chapter, we will look at the turbulence affecting wind turbines from a turbulence -simulation point of view. This means that the focus will be on the properties of atmospheric turbulence which directly affect the performance and operation of wind turbines. In the ABL, turbulence is produced by mean wind shear and enhanced or destructed by buoyancy effects. This results in profiles of the various turbulence quantities across wind turbine rotors. Examples include the mean wind speed itself; second order moments, like variances and stresses; and turning of the mean wind speed and even length scales of turbulence. The degree to which a wind turbine will be affected by the turbulence in the ABL depends on its size such as rotor diameter and hub height, its power generating properties such as thrust coefficient, as well as on the applied controller which ultimately decides the operation window of the turbine. Simulations of atmospheric turbulence can guide us in quantifying the effects.

In recent years, fog and haze are now becoming common in China, which produces unfavorable influence on the production and life of the residents, and further influences the electricity load and its trend. The severe air condition presents a challenge to power system short-term load forecasting. In this paper, air quality is brought into the comfortable degree index, which is used to power system short-term load forecasting during fog and haze occurrence. Basing on existing human body amenity indicator, a new concept of human body amenity considering AQI, temperature, humidity and wind is presented while analytic hierarchy process (AHP) is used to construct the human comfort index model. In short-term load forecasting, the human comfort index instead of various meteorological factors is taken as input, thus improving the precision of the power load forecast. The similar load days needed in power load forecasting are extracted by using the gray correlation analysis method, and based on that, the arithmetic of random forests is adopted in building forecasting model. The effectiveness and validity of proposed model and algorithm are verified by a city's practical load data and weather data of winter in North China area.

The urban land surface's composition has a great impact on the urban heat island. In the northeast, northwest and southwest vast areas of China, there is usually a layer of relatively stable snow covered on soil, grass and other urban land surfaces. Under the covered snow, the land surface heat transfer has unique properties. It's necessary to combine the upper snow layer and the related underlying land surfaces together to consider the heat transfer. In this paper the authors took the snow cover-soil union's heat transfer as the object of study, carried out field measurements on the temperature of soil and the snow itself under different thickness of covered snow, and based on the principle of energy balance, researched the dynamic characteristics of heat transfer in the snow cover-soil union, established mathematical models, numerically simulated the temperature of the snow cover-soil union using winter outdoor conditions in Harbin. The results indicate that both the simulated values and the measured values show the similar trend, despite they have some discrepancies with each other. The models in this paper can accurately simulate the urban district temperature with snow-covered underlying surfaces during the wintertime.

Millimetre wave propagation for both terrestrial and satellite communications is highly dependent on the dynamic nature of the atmospheric boundary layer. Small-scale changes in temperature, pressure and humidity may result in the formation of turbulence. Turbulence can affect radiowave propagation by either scattering a small part of the signal's energy outside of the incident beam or by focusing and defocusing energy within the beam. In the former case, this redirected energy may be used to provide communications on over-the-horizon paths (typically at frequencies up to 5 GHz), or may indeed result in interference with other systems. In the latter case, turbulence may result in rapid amplitude fluctuations in signal strength scintillation. Systems that employ power control algorithms may be adversely affected by the rapid fluctuation of a scintillation event. Therefore, as the characteristics of the channel will ultimately determine the data throughput, a technique to mitigate scintillation could prove to be very useful. One such mitigation technique that could be used is spatial diversity. To achieve the diversity advantage requires the spatial coherence of events. This paper therefore investigates the spatial coherency of scintillation to determine the suitability of small-scale spatial diversity as a mitigation technique.

Discusses the Terminal Doppler Weather Radar (TDWR) for the new airport at Chek Lap Kok (CLK) of Hong Kong. This paper discusses the radar characteristics that ensure that the TDWR is able to meet its mission requirements while working in the highly cluttered marine environment of Hong Kong. The Terminal Doppler Weather Radar (TDWR) system, developed by Raytheon Company for the US Federal Aviation Administration (FAA), provides automatic detection of microbursts and low-level wind shear. The second major function of TDWR is to improve air traffic management through forecasts of wind shifts, precipitation and other weather hazards. The TDWR system generates meteorological base data and wind shear products and automatically prepares warning messages for the air traffic controllers, through the timely detection and reporting of hazardous wind shear. It collects low altitude meteorological data and performs reliably in the terminal area environment characterized by natural and man-made ground clutter. The TDWR design specifically addresses the extraction of weather information in the presence of radar returns from severe ground clutter. The TDWR radar utilizes the Doppler effect to measure the radial velocity of rain or airborne microparticulates. This paper addresses the characteristics of the TDWR system design, siting, and signal processing techniques that are critical to optimal performance in the Hong Kong environment, and discusses observations during the optimisation of the TDWR.

This paper gives an outline of the principles that are used to model atmospheric pollution. It discusses relevant ideas of the atmospheric boundary layer, its stability, and how the mixing varies with atmospheric stability. The author considers examples of modelling ranging from: (1) forecasts of urban air quality using a box model; (2) plume calculations using a Gaussian formulation and the more recent UK-ADMS model; (3) photochemical ozone arriving in the UK from Europe modelled by a chemical trajectory box model; (4) nuclear accident dispersion modelling using many particle random walk modelling (the NAME model); and (5) application of the NAME model to sulphur pollution and eventually to ozone formation chemistry. The author begins with dispersion in the atmospheric boundary layer, then considers deposition before looking at examples of models. Since the boundary layer is the lowest part of the atmosphere nearest the ground, it is strongly influenced by temperature changes at the surface, and by the drag on the flow. (7 pages)

An estimate of the structure parameter C²_nis required to calculate the back-scattering of radar energy by turbulent eddies in the surface layer over sea. The theory of atmospheric boundary-layer turbulence may be applied, in conjunction with two spatial point measurements of meteorological parameters, to evaluate height profiles of C²_n. The paper presents contours of C²_n in the height/latitude plane using meteorological observations made on a cruise to Antarctica. Routinely monitored meteorological observations aboard ships have also been used to obtain the seasonal variations of C²_n over tropical oceans. The values of C²_n are found to be almost two orders of magnitude higher at heights up to 30 m at tropical latitudes compared to those at high latitudes. The values of C²_n are higher in the winter-summer periods, compared to postmonsoon and monsoon periods.

Estimates of winds at heights of around 100 m are required for the siting of large wind turbines. Because of uncertainties often attached to the normal method of extrapolating from data at 10 m, a method of extrapolating from upper-air data has been developed. The predictions of this method are compared with measurements at several stations on land and one offshore.