Hameed95 Hameed, S., W. Shi, J. Boyle and B. Santer, 1995: Investigation of the centers of action in the North Atlantic and North Pacific in the AMIP simulations (Diagnostic Subproject 23). Abstracts of the First International AMIP Scientific Conference, Monterey, California, 78.

We present seasonal characteristics of the Icelandic and Aleutian Lows and the Azores and Hawaiian Highs simulated in the 10 year AMIP GCM calculations.

Indices characterizing the monthly means of the intensities and the locations of the centers of action in the simulated SLP fields are calculated and their seasonal variations are quantitatively compared with the variations of the indices in the observed SLP field.

Additional diagnostics of the centers of action simulated in the ECHAM GCM are presented. For this GCM the geopotential height fields at 200 and 500 mb and the longitude-height sections of the geopotential height field for the temperate and subtropical latitudes are compared with the NMC and ECMWF analyses, and reasonable agreement with features of the stationary waves is found.

In wintertime the surface temperature field has pronounced gradients in mid- and high-latitudes because of cold continents and warmer oceans. Maps of diabatic cooling rates at the surface show that the Icelandic and Aleutian Lows are located to the east of the maxima in surface cooling in their respective basins.

The divergence field at 200 mb and streamlines of the divergent circulation are used to estimate the sources of converging air masses over the subtropical highs in summer and winter.