What are Planetary Winds Winds are currents of air that move from one direction to another. Planetary winds, however, are much larger and span larger regions. They help influence temperatures in surrounding areas, as well as other types of winds. This heating effect causes updrafts along slopesdowndrafts in the center. Mountain and valley breezes are under wind types. During the daytime hillsides heat quickly. COOL DOWN- DRAFT AG5f0328 COLD WARM WARM Figure 3-28.Valley breeze or anabatic wind. To reveal the effect of Mountain Valley Breeze (MVB) and Sea Land Breeze (SLB) in winter on the spatial-temporal distribution of air pollutants in the. Results show the importance of orography.
hence wind blows from valley to the mountain slopes known as valley breeze (Anabatic Winds). The interaction between the sea breeze and the valley breeze and their combination. The cooled air drains to lowest point of the terrain. The easy drainage of water from the slopes of mountains.
#Mountain and valley breeze free
During the night outgoing radiation cools air along hillsides below free air temperature. 3-25 UP- DRAFT WARM RADIATION AG5f0327 COLD Figure 3-27.Mountain breeze or katabatic wind. They are diurnally strongest in the late afternoon and are seasonally strongest in summer. The valley breezes are generally restricted to slopes facing south or the more direct rays of the sun, and they are more pronounced in southern latitudes. Consequently, the valley breeze is much more likely to be superposed as a prevailing wind than is the mountain breeze, which by its very nature can develop only in the absence of any appreciable gradient wind. It is difficult to isolate the valley breeze effect because of the prevailing gradient winds. It is a stronger and deeper wind than the mountain breeze. The valley breeze usually reaches its maximum strength in the early afternoon. The updrafts along the valley walls continue to be active, particularly at the head of the valley. As the heating becomes stronger, convective currents begin to rise vertically from the valleys (figure 3-28). The expansion of the heated air next to the surface produces a slight local pressure gradient against the ground surface. If the slopes are steep, the ascending breeze tends to move up the valley walls. In the winter, the effect of MVB on the recycling and accumulation of air pollutants plays an important role in severe atmospheric pollution incidents in Beijing, south of Beijing, and the eastern areas of the Taihang Mountains.Īir pollution convergence line mountain valley breeze(MVB) sea land breeze(SLB) transportation and aggregation of air pollutants.Sandy slopes devoid of vegetation are the most effective heating surfaces. From midnight to early morning, the air pollutants in Beijing were gradually blown away by the mountain breeze and stayed south of Beijing and northwest of Tianjin. The severe pollution zone formed in the plains of Beijing and south of Beijing. In the evening, the air pollutants converged near the convergence lines, which were formed by the mountain breeze and southerly wind. From noon to afternoon, the air pollutants were blown to Beijing by valley wind. The influence of MVB and SLB on the distribution of air pollutants in the heavy pollutions process were surveyed by analyzing the temporal variation relationship between the vertical distribution of wind over 0-325 m tower (at the Institute of Atmospheric Physics) and PM 2.5 concentration of urban area, and by using the Cressman method to interpolate the 10 m wind data and PM 2.5 concentration data to 2D grid field. For the MVB days, from noon until midnight, the sea breeze appeared in the eastern coastal areas and reached the southeastern part of Tianjin, the PM 2.5 concentration increased towards the front of the sea breeze. For the SLB days, the PM 2.5 concentration increased in the piedmont areas of the Taihang Mountains due to the influence of valley wind from noon to afternoon. The PM 2.5 concentration increased in Beijing, Langfang, Baoding, Shijiazhuang, and Xingtai according to the concentration of the convergence lines.
In the evening, "herringbone" convergence lines formed between the emerging mountain breeze in the western and northern parts of Beijing, as well as in the piedmont areas of the Taihang Mountains, and the southerly wind.
The prevailing factor for the MVB days was the southerly wind (valley wind) in the Beijing-Tianjin-Hebei region from noon to afternoon, this valley wind transports air pollutants from the eastern areas of the Taihang Mountains and southwestern areas of Beijing northward. The change rule of MVB and SLB and its influence on the distribution of PM 2.5 concentration were analyzed. To reveal the effect of Mountain Valley Breeze (MVB) and Sea Land Breeze (SLB) in winter on the spatial-temporal distribution of air pollutants in the Beijing-Tianjin-Hebei region, hourly data from Automatic Weather Stations (AWS) and hourly air pollutant concentration data in December 2016 from the China National Environmental Monitoring Center were used to calculate the average wind vector fields and PM 2.5 concentration fields.
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