In this paper,the continuity and thermodynamic equations including moisture forcings were derived.Using these two equations and the basic momentum equation of local Cartesian coordinates,the budget equation of generalized moist potential vorticity(GMPV) was derived.The GMPV equation is a good generalization of the Ertel potential vorticity(PV) and moist potential vorticity(MPV) equations.The GMPV equation is conserved under adiabatic,frictionless,barotropic,or saturated atmospheric conditions,and it is closely associated with the horizontal frontogenesis and stability of the real atmosphere.A real case study indicates that term diabatic heating could be a useful diagnostic tool for heavy rainfall events.
Two kinds of measurement errors have been observed in the recently developed UAT-2 ultrasonic anemometer.One is the flow distortion produced by a"blocking effect",and the other is the angle of attack caused by the vertical misalignment of the instrument.Here,we study these errors and discuss the possible correction methods.Via a wind tunnel experiment and numerical simulation,a 3D calibration matrix was developed to correct the"blocking effect".In the field test,the angle of attack was detected by an inclinometer settled on the reference plane of the anemometer,and the instrumental misalignment or tilt was corrected by a coordinate transformation.The combined use of an inclinometer and the proposed correction method may help find a new approach for vertical velocity correction.
After the passage of a cold front,spring in northern China the outbreak of strong wind is often accompanied by dust emissions.Owing to the coherent structure of wind gust,dust particles can effectively overcome the systematic descending air motion and penetrate into the middle and upper levels of the atmospheric boundary layer,and then propagate further and diffuse into the troposphere where ascending air motion prevails.Here,we consider the coherent structure of wind gust in LS models,and construct a model suitable for the dust entrainment under the dust-storm canopy.With the parameter of gust,we simulate the dust entrainment during dust storms,and test that the coherent structures of wind gust make the sand particles to reach the upper of the boundary layer.
The Los Alamos sea ice model(CICE) is used to simulate the Arctic sea ice variability from 1948 to 2009. Two versions of CICE are validated through comparison with Hadley Centre Global Sea Ice and Sea Surface Temperature(Had ISST) observations. Version 5.0 of CICE with elastic-viscous-plastic(EVP) dynamics simulates a September Arctic sea ice concentration(SASIC) trend of –0.619 × 1012 m2 per decade from 1969 to 2009, which is very close to the observed trend(-0.585 × 1012 m2 per decade). Version 4.0 of CICE with EVP dynamics underestimates the SASIC trend(-0.470 × 1012 m2 per decade). Version 5.0 has a higher correlation(0.742) with observation than version 4.0(0.653). Both versions of CICE simulate the seasonal cycle of the Arctic sea ice, but version 5.0 outperforms version 4.0 in both phase and amplitude. The timing of the minimum and maximum sea ice coverage occurs a little earlier(phase advancing) in both versions. Simulations also show that the September Arctic sea ice volume(SASIV) has a faster decreasing trend than SASIC.
Wind direction forecasting plays an important role in wind power prediction and air pollution management. Weather quantities such as temperature, precipitation, and wind speed are linear variables in which traditional model output statistics and bias correction methods are applied. However, wind direction is an angular variable; therefore, such traditional methods are ineffective for its evaluation. This paper proposes an effective bias correction technique for wind direction forecasting of turbine height from numerical weather prediction models, which is based on a circular-circular regression approach. The technique is applied to a 24-h forecast of 65-m wind directions observed at Yangmeishan wind farm, Yunnan Province, China, which consistently yields improvements in forecast performance parameters such as smaller absolute mean error and stronger similarity in wind rose diagram pattern.
Statistical analysis of turbulent and gusty characteristics in the atmospheric boundary layer under weak wind period has been carried out.The data used in the analysis were from the multilevel ultrasonic anemometer-thermometers at 47 m,120 m,and 280 m levels on Beijing 325 m meteorological tower.The time series of 3D atmospheric velocity were analyzed by using conventional Fourier spectral analysis and decompose into three parts:basic mean flow(period > 10 min),gusty disturbances(1 min < period < 10 min)and turbulence fluctuations(period < 1 min).The results show that under weak mean wind condition:1)the gusty disturbances are the most strong fluctuations,contribute about 60% kinetic energy of eddy kinetic energy and 80% downward flux of momentum,although both the eddy kinetic energy and momentum transport are small in comparison with those in strong mean wind condition;2)the gusty wind disturbances are anisotropic;3)the gusty wind disturbances have obviously coherent structure,and their horizontal and vertical component are negatively correlated and make downward transport of momentum more effectively;4)the friction velocities related to turbulence and gusty wind are approximately constant with height in the surface layer.
