城市热岛和海风环流相互作用的数值模拟研究进展

在沿海城市地区,城市热岛环流和海风环流往往同时存在;它们在空气污染物的传输和扩散中均起至关重要的作用,对强对流天气亦有重要的触发作用.随着城市化的发展,空气污染等环境问题变得越来越严峻,突然性强对流天气所造成的灾害也越来越严重.因此,沿海城市地区城市热岛和海风环流相互作用的研究受到日益广泛的关注.本文回顾了近30 a来国内外关于城市热岛和海风环流相互作用数值模拟的研究历史,分析了目前的研究现状及存在的一些问题,概述了城市化、城市热岛对海风环流的影响,海风对城市热岛、城市热岛环流的影响,以及城市热岛环流和海风环流的耦合效应.最后,本文提出了一些有待于研究或需深入研究的问题;这些问题的研究将有助于进一步揭示沿海城市地区空气污染动力学机制、强对流天气触发机制.     

渤海湾海风锋与阵风锋碰撞形成雷暴天气的诊断特征

对2007年8月13日天津多普勒天气雷达(CIN RAD WSR/98D)探测的雷暴天气个例进行分析,结果表明:此次雷暴天气是由渤海湾海风锋与阵风锋碰撞形成的;碰撞后,在海风锋前端、阵风锋前部有新的雷暴单体形成;阵风锋后部的对流回波主体加强,对流回波主体由椭圆状加强为典型的弓状。应用天津36个自动气象站的地面六要素资料和北京850 hPa以上探空资料,组成新的诊断资料,对该个例进行诊断分析,结果表明:雷达探测的海风锋前端具有较强的低层垂直风切变梯度和露点温度梯度大值区,海风锋前沿与0～3 km垂直风切变梯度密集区相对应,且与露点温度梯度变化较快的区域基本吻合;海风锋与阵风锋相互碰撞时,0～3 km垂直风切变在2 h内变化较快,且有明显的增加趋势,CAPE(convective available potential energy,对流有效位能)值在雷暴形成前有较明显增加;随着雷暴天气结束,上述特征随之消失。     

The evolution and structure of a tropical island sea/land-breeze system, northern Australia

Summary This paper is concerned with sea/land-breeze systems over relatively flat tropical islands to the north of continental Australia. The purpose of this study is to contribute to the relatively small body of knowledge on tropical island sea/land-breeze systems in this region and to highlight their particular characteristics. The evolution and structure of coastal circulations over the Tiwi Islands, northern Australia are examined using observations made during the Maritime Continent Thunderstorm Experiment (MCTEX), November/December 1995. During the transition period between dry and wet (monsoon) seasons, strong diurnal surface heating dominates the local meteorology. Thermally modified pressure differences across the coastline are seen to control the timing, direction and intensity of local winds. The evolution and structure of the resulting circulations appear to be affected greatest by tropospheric stability and friction, while the Coriolis force, synoptic winds and topography are of much less importance in this case. Consequently, even small differences in surface properties seem to produce strong and well defined local wind circulations. The depth of the sea breeze averaged 1200 m, while the land breeze was considerably shallower (290 m). Return flows were evident in both circulations, although better defined in land breeze cases. Day to day variation in vertical structure was considerable and appeared to be controlled by stability in the lower troposphere. Spatial patterns of surface temperature, pressure and wind show formation of an island heat low by day and a cool high pressure centre at night, resulting in island scale convergence and divergence, respectively. Received February 27, 2000/Revised October 16, 2000     

渤海湾西岸海陆风特征对城市热岛响应的观测分析

利用2008年全年渤海湾西岸(天津)14个自动气象站逐小时资料和6 h一次的地面常规资料,采用统计分析的方法,研究了天津城市热岛效应对渤海湾西岸海陆风的影响.结果表明:在冷岛和强热岛条件下,渤海湾西岸海风的发生频率较低,强热岛阻碍了海风向内陆的传播;内陆站在弱热岛条件下出现最大海风的频次较高,但其海风强度与无热岛或冷岛状况下相比要小一些;城市热岛效应的出现,推迟了城市周围郊区站海风的开始时间,缩短了海风的持续时间;城市站的海风风速与热岛强度呈负相关关系,但热岛效应对陆风风速的影响较强,陆风风速在热岛强度小于2.6℃时,随着其值的增大而减小,反之则增加;当海风向内陆延伸时,热岛强度会在午后海风盛行时段内增强,并与传播到此处的海风环流叠加,导致近地层海风风速增强,并可西伸至城市中心.     

Development of the sea breeze as a gravity current in the atmosphere over the Crimea

The development of the sea breeze in the Crimea during the day is studied on the basis of the mesoscale atmospheric circulation modeling. It is revealed that the formation of gravity currents directed from the banks to the center of the peninsula is observed for the cases of the weak atmospheric circulation. The results of the simulation for August 4, 2007 illustrating this phenomenon are presented. The wind speeds and velocities of the breeze front propagation are determined.     

陕北地区雹暴与多单体传播特征

采用了Schmid，Houze，Schiesser与Fovell左移雹暴和右移雹暴的定义，利用2001—2002年延安、洛川711雷达回波资料，结合天气、气候资料，对陕北地区雹暴特征进行了研究，陕北雹暴大多由多单体系列组成，新老单体不断再生消亡，向最适合新单体生成的方向传播移动。左移雹暴较右移雹暴尺度小，移动速度慢，降雹时段也明显不同。雹暴是在中低层有利的次天气尺度条件下形成并在中小尺度环境影响下产生的，强雹暴是在500hPa西北气流引导下传播的。     

Impacts of topography and land degradation on the sea breeze over eastern Spain

Summary A three-dimensional non-hydrostatic atmospheric model RAMS, version3b, is used to examine the impact of complex topography on the sea breeze under heterogeneous and degradation land use characteristics. In the study, it is shown that topography plays an important role in the sea-breeze circulation by aligning the sea breeze front to the coastline and locating the convergence zones close to the mountain range. When the sea breeze is coupled with the upslope wind, the sea-breeze circulation is strengthened by the topography.Sensitivity analyses are carried out to determine the influence of vegetation and soil moisture, i.e., land surface modifications, to this thermally driven flow. Land degradation results in an enhanced sea-breeze circulation which is characterized by a stronger onshore flow, a stronger return current, a larger updraft velocity associated with the sea-breeze front and further inland penetration. Other important features are a deeper sea-breeze depth, a larger downdraft velocity behind the sea-breeze front, and a longer offshore extent. The results also show how land changes modify the sea breeze temporal evolution resulting in an earlier onset and later end. The study stresses the convenience of using three-dimensional models with detailed land surface information to model the sea breeze in complex terrain where land use is rapidly modified.Received February 25, 2002; accepted October 7, 2002 Published online April 10, 2003     

Sea-breeze scaling from numerical model simulations,part II: Interaction between the sea breeze and slope flows

Numerical model simulations of sea-breeze circulations in the presence of idealized topography are subjected to dimensional analysis in order to capture the dynamics of the sea-breeze circulation combined with an upslope-flow circulation. A secondary objective is to reconcile previous results based on observations. The analysis is based on a scaling analysis of sea-breeze speed, depth and volume flux. This study is motivated by the fact that the literature of sea breezes interacting with upslope flows is generally qualitative. Results show clear scaling regimes and strong interaction between the two thermally driven circulations. We distinguish three regimes, depending on slope length, slope angle, stability and surface heat flux. The first and third regimes obey the scaling laws of pure sea-breeze scaling. The second regime shows a significant decrease in the scaled volume flux relative to pure sea-breeze scaling. Dynamical relations in the second regime show a strong influence on the circulation of upslope stable air advection.     

渤海北部东岸海风锋活动及其触发对流特征分析

利用常规观测、雷达、卫星及加密自动气象站等资料,对2015年、2018年和2019年渤海北部东岸海风锋活动及其触发的对流特征进行统计分析.结果表明:不同年份渤海北部东岸海风锋活动的差异较大,海风锋主要出现在6—8月,其中7月最多;海风锋可分为沿山型、北部沿海型和混合型3种,其中沿山型占比70％以上,海风锋东移到达沿山地...     

斜坡地形下城市热岛和陆风相互作用的三维数值模拟

本文建立了一个采用地形坐标及高分辨率的行星边界层参数化方案的三维中尺度静力模式。模式中还采用能考虑边界上地形变化的开侧边界条件。利用该模式,本文研究了弱盛行风条件下的陆风以及平坦地形和斜坡地形下城市热岛和陆风的相互作用。结果表明:夜间下坡风的出现和消失都早于陆风;坡风增大了陆风强度,并延迟了陆风向海风的过渡。 结果还表明,城市对陆风的影响比坡风小。在陆风形成和发展阶段,城市主要起增大下垫面摩擦的动力作用;在陆风减弱和消亡阶段,城市热岛环流逐渐形成并增强,城市对周围风场主要起热力作用。另一方面,在盛行风,坡风和陆风的影响下,热岛环流的形成、发展、强度和辐合带轴线的方向等都会发生改变。     

Thermal effect of the sea breeze on the structure of the boundary layer and the heat budget over land

The daytime boundary-layer heating process and the air-land heat budget were investigated over the coastal sea-breeze region by means of observations over the Sendai plain in Japan during the summer. In this area, the onset of the sea breeze begins at the coast around 0900 LST, intruding about 35 km inland by late afternoon. The cold sea breeze creates a temperature difference of over 10°C between the coastal and inland areas in the afternoon. On the other hand, warm air advection due to the combination of the counter-sea breeze and land-to-sea synoptic wind occurs in the layer above the cold sea breeze in the coastal region. Owing to this local warm air advection, there is no significant difference in the daytime heating rate over the entire atmospheric boundary layer between the coastal and inland areas. The sensible heat flux from the land surface gradually decreases as distance from the coastline increases, being mainly attributed to the cold sea breeze. The daytime mean cold air advection due to the sea breeze is estimated asQ _adv ^local =–29 W m^–2 averaged over the sea breeze region (035 km from the coastline). This value is 17% of the surface sensible heat fluxH over the same region. The results of a two-dimensional numerical model show that the value ofQ _adv ^local /H is strongly affected by the upper-level synoptic wind direction. The absolute value ofQ _adv ^local /H becomes smaller when the synoptic wind has the opposite direction of the sea breeze. This condition occurred during the observations used in the present study.     

Recent trends in temperature and precipitation over the Balearic Islands (Spain)

Changes in climatic parameters are often given in terms of global averages even though large regional variability is generally observed. The study of regional tendencies provides not only supplementary conclusions to more large-scale oriented results but is also of particular interest to local policy-makers and resource managers to have detailed information regarding sensible and influential climatic parameters. In this study, changes in precipitation for the Balearic Islands (Spain) have been analyzed using data from 18 rain gauges with complete daily time series during the period 1951–2006 and two additional sites where only monthly totals were available. Tendencies for maximum and minimum 2-m temperatures have also been derived using data from three thermometric stations with daily time series for the period 1976–2006. The thermometric stations are located at the head of the runways in the airports of the three major islands of the archipelago, where urbanization has arguably not had a relevant impact on the registered values. The annual mean temperature in the mid-troposphere and lower stratosphere has also been analyzed using the Balearics radiosonde data for the period 1981–2006. Results show there is a negative tendency for annual precipitation (163 mm per century) with 85% significance on the sign of the trend. An abrupt decrease in mean yearly precipitation of 65 mm is objectively detected in the time series around 1980. Additionally, the analysis shows that light and heavy daily precipitation (up to 4 mm and above 64 mm, respectively) increase their contribution to the total annual, while the share from moderate-heavy precipitations (16–32 mm) is decreasing. Regarding the thermometric records, minimum temperatures increased at a rate of 5.8°C per century during the 31 years and maximum temperatures also increased at a rate of 5.0°C per century, both having a level of statistical significance for the sign of the linear trend above 99%. Temperatures in the mid-troposphere decreased at a rate of ??5.4°C per century while a tendency of ??7.8°C per century is found in the lower stratosphere. The level of statistical significance for the sign of both the tropospheric and stratospheric linear trends is above 98% despite the great inter-annual variability of both series.     

Analysis and numerical modelling of a frontal passage associated with thunderstorm development over the Po valley and the Adriatic sea

Summary A case study is presented of the meteorological situation of 26 July 1987, when a moderate lee cyclone formed south of the Alps associated with a cold front moving from the northwest. A convective line developed over the Po valley and the northern Adriatic sea, slightly in advance of the position of the cold front which, over that area, was associated with a north-easterly low-level flow. The mesoscale situation over the Po valley before and after the frontal passage was complex, with different flow configurations and weather phenomena affecting the eastern and western portions of the region.The analysis of observations has been complemented by the results of numerical experiments run with a limited area, high resolution model, initialized using interpolated ECMWF analyses. Sensitivity experiments show the important roles played by the orography and by the condensation-evaporation processes in determining the mesoscale field environment favourable for the development of the organized convection.With 26 Figures     

A climatological study of the influence of synoptic-scale flows on sea breeze evolution in the Bay of Alicante (Spain)

The focus of this study is on sea breeze (SB) characteristics during May and August in the Bay of Alicante (south-eastern coast of the Iberian Peninsula, IP, Spain) for the period 2000–2005 in relation to dominating synoptic-scale winds. A dataset containing 292 SB events was objectively constructed to study the impact of the daily synoptic winds at 850 hPa on the main characteristics of SBs. The winds were used to designate three major synoptic-scale regimes: offshore, onshore, and coast-parallel flows. The SB features examined include mean lag of the SB passage, wind speed and direction at the time of onset, mean lag of SB cessation, mean duration of SB, mean maximum velocity, and inland propagation of SB. Some of the characteristics had not been previously considered in the literature. It is found that in comparison with onshore synoptic flows, offshore favors the delayed arrival and termination of SBs, resulting in a longer mean duration. Further, they produce the most intense passages, cause a more frequent southeasterly component, and result in a higher SB gust speed and shorter mean inland penetration. Results from coast-parallel flows are also presented. The strength of the large-scale flows plays a major role upon SB parameters, which essentially support other numerical modeling results.     

Interannual variability of summer rainfall over the northern part of China and the related circulation features

In this study, interannual variability of summer rainfall over the northern part of China (NPC) and associated circulation patterns were investigated by using long-term (1961–2013) observational and reanalysis data. Two important NPC rainfall modes were identified by empirical orthogonal function analysis: the first is characterized by an almost uniformly distributed rainfall anomaly over most parts of the NPC, while the second shows rainfall variability in Northeast China (NEC) and its out-of-phase relationship with that in North China (NC) and the northern part of Northwest China. The results also suggest that the NPC summer rainfall anomalies are also closely associated with those in some other parts of China.It is revealed that the circumglobal teleconnection pattern associated with the anomalous Indian summer monsoon (ISM) and the Polar/Eurasia (PEA) pattern work in concert to constitute the typical circulation pattern of the first rainfall mode. The cooperative engagement of the anomalous ISM circulation and the PEA pattern is fundamental in transporting water vapor to the NPC. The study emphasizes that the PEA pattern is essential for the water vapor transport to the NPC through the anomalous midlatitude westerly.In the second NPC rainfall mode, the typical circulation pattern is characterized by the anomalous surface Okhotsk high and the attendant lower tropospheric circulation anomaly over NEC. The circulation anomaly over NEC leads to a redistribution of water vapor fluxes over the NPC and constitutes an out-of-phase relationship between the rainfall anomalies over NEC and NC.     

On theoretical wind speed and temperature profiles over the sea with applications to data from sable island,Nova Scotia

Abstract

In October 1985, the Boundary‐Layer Research Division of the Atmospheric Environment Service conducted an experiment on Sable Island, Nova Scotia, where 10‐m wind measurements were made at a number of locations. Wind data were also collected at 4 levels on one of the 10‐m masts and at 6 levels on a 26‐m mast, both located on the South Beach. Other data used in the present study consisted of air temperature measured at 9 m and sea temperature measured at the beach.

The theory for wind speed and temperature profiles over the sea is reviewed. A method of deriving over‐sea profile parameters (u_*, θ_*, Z₀, L) from wind data at one level and the air‐sea temperature difference is described. The method is limited to applications either over homogeneous open ocean or, provided measurements are taken above the internal boundary layer generated by the change of roughness at the coastline, over a flat beach (without coastal orography). The heights at which the method is applied must be within the surface layer which must not have any discontinuities in wind speed or temperature in the vertical, such as are often associated with inversion layers. An application to data collected at beach sites in onshore flow during the October 1985 experiment is illustrated.

Once the above parameters are obtained, theoretical wind profiles may be computed and compared with observed profiles. In order to make a proper comparison it is essential to account for internal boundary layers generated at the shoreline by the step‐change in surface roughness. Only the data measured above the internal boundary layer are representative of over‐sea conditions and may, therefore, be used for verifying the theoretical profiles. The agreement between calculated and measured data is generally very good. One complication, however, is a slight upstream‐blockage effect due to a 7‐m high dune located about 140 m downwind of the 26‐m mast. Estimates of the magnitude of this effect partially account for small discrepancies in the results at the 26‐ and 10‐m mast locations.

An estimation of the most probable errors in the calculated parameters, based on assumed measurement errors, is included in the computer program. Results suggest that small measurement errors can explain the above discrepancies.     

A numerical study of the nocturnal heat island over a medium-sized mid-latitude city (Columbus,Ohio)

A numerical investigation is conducted of the nocturnal heat island over Columbus, Ohio, a relatively flat mid-latitude city. Specifically, a cross-sectional steady-state numerical model to simulate the (thermal) structure of the nocturnal urban boundary layer is developed from a one-dimensional, time-dependent model due to Estoque. The model is applied to Columbus for special periods in September 1968 and March 1969 during which comparable experimental data were collected. The numerical simulations agree well with the observed data with respect to the detailed spatial form of the surface-based thermal boundary layer across the city. The use of the model for other metropolitan areas, for ascertaining the relative effect of city size and building geometry on the development of the thermal boundary layer, and for determining the effect of alternate land-use strategies on the thermal stratification are also discussed.Digest of portion of a dissertation submitted to the Pennsylvania State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy.Presented in part at the Air Pollution, Turbulence and Diffusion Symposium, Las Cruces, New Mexico, 7–10 December 1971.On assignment from the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce.     

Inorganic nutrients in precipitation over the Magdalen Islands area (Quebec, Canada) and their impact on the primary productivity of the lagoons

Concentrations of nitrate, ammonium and phosphate have been monitored from June to October 1989 in rain water collected at the Magdalen Islands (Gulf of St. Lawrence, Québec, Canada). Nitrate was the main dissolved organic nitrogen (DIN) compound with concentrations ranging from 2.2 to 95 μM. Ammonium was occasionally dominant and varied between 0.7 and 41 μM. Phosphate concentrations were low and extremely variable with values ranging from 0.2 μM to 2 μM. All three inorganic nutrients were positively correlated and the relationships best described by a non-linear regression model. NH₄⁺:NO₃₋ atomic ratios fell within the range of those previously measured, i.e. the northeast part of North America, and suggest a continental origin for both DIN and phosphate. Measured pH values failed to show high levels of acidity (pH=4.8 ±0.4).For the lagoonal system of the Magdalen Islands, atmospheric deposition is the major source of nitrate during the summer period we surveyed. In such an ecosystem the atmospheric inputs of DIN are greater than those from the sediment and may at times contribute up to 70% of the phytoplankton primary production requirements. In contrast, phosphate of rain origin was only of marginal importance relative to sediment inputs.     

An assessment of climate change impacts and adaptation for the Torres Strait Islands, Australia

Adaptive practices are taking place in a range of sectors and regions in Australia in response to existing climate impacts, and in anticipation of future unavoidable impacts. For a rich economy such as Australia’s, the majority of human systems have considerable adaptive capacity. However, the impacts on human systems at the intra-nation level are not homogenous due to their differing levels of exposure, sensitivity and capacity to adapt to climate change. Despite past resilience to changing climates, many Indigenous communities located in remote areas are currently identified as highly vulnerable to climate impacts due to their high level of exposure and sensitivity, but low capacity to adapt. In particular, communities located on low-lying islands have particular vulnerability to sea level rise and increasingly intense storm surges caused by more extreme weather. Several Torres Strait Island community leaders have been increasingly concerned about these issues, and the ongoing risks to these communities’ health and well-being posed by direct and indirect climate impacts. A government agency is beginning to develop short-term and long-term adaptation plans for the region. This work, however, is being developed without adequate scientific assessment of likely ‘climate changed futures.’ This is because the role that anthropogenic climate change has played, or will play, on extreme weather events for this region is not currently clear. This paper draws together regional climate data to enable a more accurate assessment of the islands’ exposure to climate impacts. Understanding the level of exposure and uncertainty around specific impacts is vital to gauge the nature of these islands’ vulnerability, in so doing, to inform decisions about how best to develop anticipatory adaptation strategies over various time horizons, and to address islanders’ concerns about the likely resilience and viability of their communities in the longer term.     

Effects of convective available potential energy,temperature and humidity on the variability of thunderstorm frequency over Bangladesh

Theoretical and Applied Climatology - The present study examines the effects of convective available potential energy (CAPE), temperature and humidity on the spatiotemporal variation of...