Using the mean pressure gradient and NCEP/NCAR reanalysis to estimate the strength of the South Atlantic Anticyclone

作者：Salcedo Castro Julio^*; de Camargo Ricardo; Marone Eduardo; Sepulveda Hector H

来源：Dynamics of Atmospheres and Oceans, 2015, 71: 83-90.

DOI：10.1016/j.dynatmoce.2015.06.003

• Pressure gradient force
• Horizontal gradient
• Wind field
• Vectorial field

A new methodology is proposed to estimate the strength of the South Atlantic Anticyclone (SAA), using the gridded sea level pressure (SLP) of the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data. The top quartile (1017.3 hPa) of the SLP data was found a reasonable criterion to delimit the SAA area. Consequently, we defined the SAA area as the quadrangle containing 80% of the observations with pressure >1017.3 hPa. In this quadrangle, an area weighted pressure gradient (AWPG) was computed for the whole area and for the north-south and west-east halves. When compared with maximum pressure, the AWPG showed a better correlation with the significant wave height (SWH) and wind speed (WS) derived from altimetry. The mean value of the AWPG was 8 x 10(-4) Pa/m, with representative values of 9.1 x 10(-4) Pa/m and 7.4 x 10(-4) Pa/m for austral winter and summer, respectively. The phase difference between the monthly AWPG in the north and south sub-quadrangles accounts for the evolution of the spatial pattern of the anticyclone throughout a year. This quantitative approach proved to be a useful estimate of the strength of South Atlantic Anticyclone. Further improvements of this approach are discussed.

• 出版日期2015-9