The figure shows the annual-average atmospheric mass circulation in the latitude pressure plane (the meridional plan). The arrows depict the direction of air movement in the meridional plane. The contour interval is 2x10¹⁰ Kg/sec - this is the amount of mass that is circulating between every two contours. The total amount of mass circulating around each "cell" is given by the largest value in that cell. Data based on the NCEP-NCAR reanalysis project 1958-1998. Clicking on the figure will bring you to the data viewer.