The effect of Atlantic and Pacific sea surface temperatures on the mid-summer drought of Costa Rica

Abstract

The mid-summer drought of Central America is an important feature of the regional precipitation regime within the Pacific drainage ranging from Mexico to Panama. The drought is less severe when the Atlantic is warmer. Cooler temperatures in the tropical Atlantic signify a strengthening of the North Atlantic anticyclone and the alisos. When combined with warmer than usual temperatures (lower atmospheric pressures) in the eastern equatorial pacific, the pressure gradient across the isthmous increases and the orographic effects of the Cordillera are emphasized. When the Atlantic is warmer, the resultant reduction in the strength of the alisos reduces rainfall over most of the country.