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141.
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Impact of the Rhône and Durance valleys on sea-breeze circulation in the Marseille area 总被引:2,自引:0,他引:2
Sophie Bastin Philippe Drobinski Alain Dabas Patricia Delville Oliver Reitebuch Christian Werner 《Atmospheric Research》2005,74(1-4):303-328
Sea-breeze dynamics in the Marseille area, in the south of France, is investigated in the framework of the ESCOMPTE experiment conducted during summer 2001 in order to evaluate the role of thermal circulations on pollutant transport and ventilation. Under particular attention in this paper is the sea-breeze channelling by the broad Rhône valley and the narrow Durance valley, both oriented nearly-north–south, i.e., perpendicular to the coastline, and its possible impact on the sea-breeze penetration, intensity and depth, which are key information for air pollution issues. One situation of slight synoptic pressure gradient leading to a northerly flow in the Rhône valley (25 June 2001) and one situation of a weak onshore prevailing synoptic wind (26 June 2001) are compared. The impact of the Rhône and Durance valleys on the sea-breeze dynamics on these two typical days is generalized to the whole ESCOMPTE observing period.The present study shows by combining simple scaling analysis with wind data from meteorological surface stations and Doppler lidars that (i) the Durance valley always affects the sea breeze by accelerating the flow. A consequence is that the Durance valley contributes to weaken the temperature gradient along the valley and thus the sea-breeze circulation. In some cases, the acceleration of the channelled flow in the Durance valley suppresses the sea-breeze flow by temperature gradient inhibition; (ii) the Rhône valley does not generally affect the sea breeze significantly. However, if the sea breeze is combined with an onshore flow, it leads to further penetration inland and intensification of the low-level southerly flow. In this situation, lateral constriction may accelerate the sea breeze. Simple scaling analysis suggests that Saint Paul (44.35°N, about 100 km from the coastline) is the lower limit where sea breeze can be affected by the Rhône valley. These conclusions have implications in air quality topics as channelled sea breeze may advect far inland pollutants which may be incorporated into long-range transport, particularly in the Durance valley. 相似文献
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南海南部海区的强风和大风特征分析 总被引:1,自引:0,他引:1
强风和大风天气在南海南部海区出现较频繁,据1984年起综合考察及永暑礁站等周边站资料分析,天气过程的持续时间差异;冬、夏季风盛行期间常出现强风和大风天气过程;热带云团对流易产生强风和大风天气;邻近海区热带气旋环流等天气系统对海区内风力增强起重要作用。 相似文献
146.
该文分析了海上长岛站与其相邻的龙口,蓬莱,烟台,牟平等沿海站气温的日变化差异与胶东半岛地区海陆风的关系。结果表明,胶东半岛海陆风向昼夜发生反向转换与海陆间因下垫面性质不同,受热不均产生的温度日变化差异是一致的;半岛地区海陆风昼夜风向反向转换一年四季都存在,并且有明显的规律,海陆风转换时间早晚及持续时间和长短随季节而豪华。 相似文献
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利用2009年7月—2015年12月河西走廊东部乌鞘岭和天祝逐时气温、日照、地面2 min风场及每隔6 h云量资料,详细分析乌鞘岭山区大气温差、云量特征的时间变化及其预报关系,旨在提高天祝最低气温的预报准确率。结果表明:冬季08时气温乌鞘岭高于天祝的频率超过50%,温差强度达4~6℃;春夏季5—9月气温乌鞘岭高于天祝的频率低于40%,温差强度较弱在2℃以下。云量中夜间至清晨(02—8时)少,傍晚较多;5—9月较多,冬季较少。天空状况除冬季晴天多,出现频率高于50%外,其它季节阴天较多,晴天次之,多云较少,不足20%。乌鞘岭谷风多,而天祝山风多。气温乌鞘岭高于天祝的频率和强度与云量、山谷风、太阳照射时间、季节和天气系统密切相关。晴天和阴雨天气报准,天祝最低气温预报准确率最多可能提高30%,晴天报准时预报准确率最多可提高10%以上。 相似文献
149.
The impact of modifications of the surface characteristics on local climate is simulated with a numerical mesoscale model in the Yangtze delta region, east of China. The simulated reference case with the current surface properties shows that there is urban heat island in Shanghai city which is located in the center of this region. The mod-ifications of surface characteristics due to the urbanization around Shanghai will lead to the change of local air circu-lation and redistribution of surface temperature. Simulation for this case shows that the urbanization around Shanghai has little effect on Shanghai, but will extend the area of heat island. Another case is assumed that the area of grassland is kept as 50% while the urban areas are extended. Compared with the case of pure urbanization, the max-imum reduction of surface air temperature is 2.0oC in the daytime and 2.3oC at night. 相似文献
150.
We describe a wavelet-based technique to determine the spectral turbulentcontribution to the vertical flux of sensible heat in a position-wavelength representation. This technique combines awavelet transform (Morlet wavelet) with conditional sampling. We apply this methodto aircraft datacollected during a sea-breeze circulation (BEMA97 experiment) with heterogeneousturbulence conditions horizontally and vertically as well. The turbulent fluxes are analysed with the conditional wavelet techniqueas a function of the wavelength and the horizontal distance.The turbulent processes within the thermal internal boundary layer associatedwith the sea breeze are clearly identified. The results exhibit the wavelength bands through which the upward flux (originating fromthe surface) and the downward flux (originating from the top of theboundary layer) are important. 相似文献