辽东湾西岸三维海陆风特征的数值模拟

本文所用的数值模式为地形影响修正的三维流体静力的中尺度气象学模式,模式对中尺度的海陆风环流和山谷风环流有较好的模拟效果.利用该模式对一个海陆风个例(1999年7月15～16日)进行了数值模拟,分析了海陆风环流的日变化规律和三维结构特征,以及地形对海陆风环流的影响,模拟结果与实际观测数据和已有研究成果具有较好的一致性.     

梅雨涡旋与环境场动能的相互作用

在过渡湍流理论基础上建立二维非局地闭合模式，并用所建模式研究沿海地区中尺度海陆风环流和内国界层结构，得到了合理的平均场和湍流场。     

杭州湾沿岸海陆风环流的若干特征

以杭州湾沿岸１９个测站１９８２年１，７两个月风的自记记录为依据，对杭州湾沿岸海陆风环流进行了研究，得到了若干特征：（１）海风强而维持时间短；陆风弱而维持时间长。（２）海陆风相互转换的时间在海岸线附近最早。门）海陆风向内陆伸展的范围一般在５０ｋｍ左右。（４）陆风（海风）盛行时，在桐庐、绍兴、杭州湾中部和舟山群岛南部一带，存在一条辐合（辐散）线，主要辐合（辐散）中心也都在这一带。（５）杭州湾北岸海陆风比南岸弱。（６）海陆风相互转换时间北岸均比南岸迟６～８个小时。（７）南北两岸海陆风维持时间不同。     

湖/陆风过程中湍流摩擦作用的数值分析(英文)

本文利用一个湍流能量闭合的二维原始方程模式分析讨论了湍流交换对湖/陆风过程的影响。文中较详细地介绍了湍能闭合方法,分析了在湖(陆)风发展的不同阶段湍流交换强度的分布特征并讨论了大尺度风场对湍流交换系数场的影响。     

Observation of Sea Breeze Front and its Induced Convection over Chennai in Southern Peninsular India Using Doppler Weather Radar

Sea breeze, the onshore wind over a coastal belt during daytime, is a welcoming weather phenomenon as it modulates the weather condition by moderating the scorching temperature and acts as a favourable mechanism to trigger convection and induce precipitation over coastal and interior locations. Sea breeze aids dispersal of pollutants as well. Observational studies about its onset, depth of circulation and induced precipitation have been carried out in this paper for the period April to September, 2004–2005 using a S-band Doppler Weather Radar functioning at Cyclone Detection Radar Station, India Meteorological Department, Chennai, India. The onset of sea breeze has been observed to be between 0900 and 1000 UTC with the earliest onset at 0508 UTC and late onset at 1138 UTC. The frequency is greater during the southwest monsoon season, viz., June – September and the frequency of initial onset is greater in north Chennai. The modal length of sea breeze is between 20 and 50 km with extreme length as high as 100 km also having been observed. Though the inland penetration is on average 10 to 20 km, penetration reaching 100 km was also observed on a number of cases. The induced convection could be seen in the range 50–100 km in more than 53% of the cases. The mean depth of sea breeze circulation is 300–600 m but may go well beyond 1000 m on conducive atmospheric conditions.     

Occurrence of Kelvin-Helmholtz Billows in Sea-breeze Circulations

Centred at the interface between the sea-breeze and the return flow aloft, Kelvin-Helmholtz billows (KHB) are an important feature of the turbulent structure of some sea-breeze circulations (SBCs). In other SBCs, there are no prominent KHBs observed. Factors governing the appearance of billows are determined from a database of 139 sea breezes, constructed from two years of summertime surface observations at a site on the south coast of England. Post-frontal oscillations occur in the surface data for some SBCs and are interpreted as indicating possible KHBs aloft. The SBCs are formed under a wide range of synoptic conditions, enabling various measures of possible billow occurrence to be related to properties of the large-scale, ambient flow. Consistent with laboratory experiments of density currents, KHBs are suppressed for propagation into a head wind and enhanced with a tail wind. They are also found to be enhanced for stronger ambient wind speeds, while large-scale coast-parallel flow is effective in suppressing the billows.     

Sea-breeze scaling from numerical model simulations,Part I: Pure sea breezes

Numerical model simulations of sea-breeze circulations under idealized conditions are subjected to dimensional analyses in order to resolve sea-breeze dynamical relations and unify previous results based on observations. The analysis is motivated by the fact that sea-breeze depth scaling and volume flux scaling are only partially understood. The analysis is based on nonlinear numerical modelling simulations in combination with recent observational scaling analyses. The analysis confirms scaling laws for sea-breeze strength dependence on governing variables and shows how the sea-breeze speed scale is controlled by surface heat flux. It also shows that the sea-breeze depth scale is controlled by stability. By combining sea-breeze speed and depth scales, the sea-breeze volume flux scale is determined by an equilibrium between the accumulated convergence of heat over land since sunrise and stable air advection from the sea surface.     

Model evaluation of the atmospheric boundary layer and mixed-layer evolution

In the present study, an attempt is made to assess the atmospheric boundary-layer (ABL) depth over an urban area, as derived from different ABL schemes employed by the mesoscale model MM5. Furthermore, the relationship of the mixing height, as depicted by the measurements, to the calculated ABL depth or other features of the ABL structure, is also examined. In particular, the diurnal evolution of ABL depth is examined over the greater Athens area, employing four different ABL schemes plus a modified version, whereby urban features are considered. Measurements for two selected days, when convective conditions prevailed and a strong sea-breeze cell developed, were used for comparison. It was found that the calculated eddy viscosity profile seems to better indicate the mixing height in both cases, where either a deep convective boundary layer develops, or a more confined internal boundary layer is formed. For the urban scheme, the incorporation of both anthropogenic and storage heat release provides promising results for urban applications.