Observational Investigation of the Low‐Level Jets in the Metropolitan Region of São Paulo, Brazil.

Autor: Sánchez, Maciel Piñero, Pereira de Oliveira, Amauri, Varona, Ramón Pérez, Tito, Janet Valdés, Codato, Georgia, Ynoue, Rita Yuri, Ribeiro, Flávia Noronha Dutra, Marques Filho, Edson Pereira, da Silveira, Lucas Cardoso
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Zdroj: Earth & Space Science; Sep2022, Vol. 9 Issue 9, p1-24, 24p
Abstrakt: The main features of low‐level jet (LLJ) in the metropolitan region of São Paulo (MRSP), Brazil, are assessed using rawinsondes carried out: (a) every 3‐hr during 10‐consecutive days in summer and winter field campaigns of the MCITY BRAZIL Project in 2013, (b) at 0900 and 2100 local time, from September 2009 to August 2013. These observations indicate that the LLJ is a typical feature of the MRSP, observed in 85% of the 20 days of the field‐campaigns and 77.6% of the 1,446 days of regular rawinsonde period. The fine temporal and spatial resolution soundings indicate that most of the LLJs occur during nighttime and early in the morning, with mean intensity of 8.5 ± 0.3 m s−1, height of 539 ± 26 m, and mostly (52.5%) from east and north. The coarse resolution soundings indicate the LLJ display a seasonal variation with maximum intensity in October (8.6 ± 0.3 m s−1) and a minimum in February (7.1 ± 0.2 m s−1), a maximum height in March (703 ± 151 m) and a minimum in June (577 ± 151 m). During MCITY campaigns about 76.4% of LLJ events show inertial oscillation and 35.3% of them are combined with sea breeze. Only 17.6% of LLJ events are associated with cold fronts and post‐frontal high pressure system. The urban heat island intensity, surface inversion layer strength, particulate matter 2.5 and carbon monoxide concentrations are negatively correlated with the LLJ intensity, suggesting the jet‐induced turbulent mixing may contribute to reduce them. Key Points: The low‐level jet (LLJ) is a remarkable robust feature of metropolitan region of São Paulo climate, occurring in more than 77% of timeThey occur during nighttime, under less disturbed synoptic conditions and more often in association to sea‐breeze circulationMost of LLJ display inertial oscillation and are correlated with urban heat island, surface inversion layer, and air pollution [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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