科研之友
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摘要
The low level jet (LLJ) east of the Andes in South America plays a key role in the transport of heat and water vapour from tropical to subtropical latitudes. It also plays a major role in the regional transport of pollutants and biological matter. This study examines the main spatial variability modes of the LLJ whose exit area reaches the La Plata Basin with no precipitation associated (which would remove aerosols) - Chaco Jet 1 (CJ1). The events were identified by applying the modified Bonner's criteria on the 850 and 700 hPa wind fields of the period 2001-2005 from GDAS (NCEP). With the help of an hybrid approach to Principal Component Analysis T-mode applied on the JRA-25 Reanalysis from the Japan Meteorological Agency, the main spatial patterns were identified during CJ1 episodes. Selected variables are geopotential height, specific humidity, equivalent potential temperature and the zonal and meridional wind components at 850 hPa. The first two PC components explained 35.64% of the variance. The significant fields show the entrance of the CJ1 to high (first PC) and middle (second PC) latitudes. The first component, with an explained variance of 21.1%, identifies episodes of moisture transport into high latitudes, and an intense flow north of 40 degrees S. To the south, the most noticeable features for this component are moister conditions and weaker winds over Patagonia. The second component describes the situations where the flow turns towards the Atlantic Ocean at mid-latitudes, causing moisture to peak over the province of Buenos Aires and the north of Patagonia; with a stronger and more zonally oriented flow at high latitudes. The present analysis contributes to better understand the atmospheric circulation associated with CJ1 episodes and its implications on the regional transport of heat, moisture, pollutants and biological matter into La Plata Basin.
- 出版日期2015-11-30
