The data file contains 25 columns: year, month, Lamb
circulation type, sea level pressure at the 16 points
shown in Figure 1 ofte paper in mb, the six indices
(u,v, V, zeta_u, zeta_v, and zeta). For definition
of the indices, read the paper:

Chen, D. 2000: A monthly circulation climatology for Sweden and its 
application to a winter temperature case study, Int. J. Climatology, 
Vol. 20, 1067-1076