BEHAVIOR OF THE CENTERS OF ACTION ABOVE THE ATLANTIC SINCE 1881 - PART-II - ASSOCIATIONS WITH REGIONAL CLIMATE ANOMALIES

This paper constitutes the second part of the analysis of the behaviou r of centres of action above the Atlantic since 1881. The present stud y examines the applicability of the generated time series of the centr al pressure and geographical location of the Iceland Low (IL), Azores High (AH), Inter Tropical Convergence Zone (ITCZ) and South Atlantic S ubtropical High (SSH) to the description of the surface circulation an d its influence on the climate anomalies above the Atlantic and adjace nt land areas in the period 1950-1989. Using the normalized anomalies of the pressure gradient between the cores of the AH and IL (AH-IL gra dient) as a NAO (North Atlantic Oscillation) index, it can be shown th at this index is a practicable tool for the detection of characteristi c spatial anomaly patterns in different climate variables above the No rth Atlantic and surrounding land areas. The 'strong' NAO (the AH-IL g radient above 'normal') in winter leads to a warning above northern an d central Europe as well as to the development of the dipole-like anom aly patterns in the wind speed, sea-surface temperature, surface and t ropospheric temperature and other variables above the western and east ern North Atlantic. The composite analysis for the 'weak' NAO reveals inverse patterns. The application of the characteristic parameters of the ITCZ and of the two subtropical highs as predictors of the rainfal l variability in northeast Brazil and the Sahel for the period 1950-19 83 shows that for the most part, these variations can be explained by the anomalies of the latitude position and intensity of the ITCZ. (C) 1998 Royal Meteorological Society.