The main features of the urban boundary layer in the metropolitan region of S?o Paulo are estimated based on rawinsondes carried out (a) every 3 hr in two 10‐day field campaigns of the MCITY BRAZIL Project during the summer and winter of 2013 and (b) regularly once per day and continuously for 4 years from 2009 to 2013. On average, the boundary layer height showed a daytime maximum of 1476 ± 149 m in summer and 1122 ± 168 m in winter campaigns. The differences are related to seasonal variations in the (a) buoyancy flux at the surface, which was 30% larger in summer (4.7 ± 0.6 MJ m?2 day?1), and the (b) static stability of the free atmosphere, which was 15% smaller in summer (3.3 ± 0.1 K km?1). The average nighttime boundary layer height, estimated from equilibrium empirical expression, indicated maximum of 126 ± 13 m in summer and 122 ± 10 m in winter campaigns. The presence of a low‐level jet was identified in 80% of the field campaign nights, with intensity varying from 2.7 to 14 m s?1 and height ranging from 95 to 962 m. The nighttime residual‐mixing layer is well estimated using the air temperature gradient method and is a good indication of the maximum vertical evolution of the previous daytime boundary layer. The monthly average maximum boundary layer height varied from a minimum of 1,061 ± 77 m in September to maximum of 1,632 ± 96 m in May.
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机译:S-O Paulo大都市地区城市边界层的主要特点是根据2013年夏季和冬季的MCITY Brazil项目的两个10天野外活动,每3小时进行一次Rawinsondes(a) (b)每天定期一次,从2009年到2013年持续4年。平均而言,夏季,边界层高度显示最大1476±149米,冬季运动中1122±168米。差异与表面的(a)浮力通量的季节变异有关,夏季的30%较大(4.7±0.6 mJ m 2,2天Δ1),以及(b)自由大气的静态稳定性,夏季较小的15%(3.3±0.1 k km?1)。平均夜间边界层高度,估计从均衡经验表达,夏季最多126±13米,冬季运动中122±10米。低级射流的存在在80%的野战活动中确定了强度,强度从2.7到14 m s?1和高度从95到962米。使用空气温度梯度方法估计夜间残留混合层,并且是前一天边界层的最大垂直演进的良好指示。月平均最大边界层高度在9月份最低5061±77米,最多可在5月份1,632±96米。
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