Diagnosing the role of atmosphere-land surface interactions during wet and dry seasons across the Americas

Wet and dry seasonal composites have been constructed for three separate regions of the Western Hemisphere using long climate model simulations made with the NCAR CCM3, and reanalysis products from NCEP and NASA/DAO: (1) the high-latitude Mackenzie Basin in northern Canada; (2) the mid-latitude GCIP region of the central US; and (3) the low-latitude LBA region of Brazil. Seasonal anomalies of soil moisture and precipitation are used to construct the composites. Each set of composites is diagnosed to identify the key factors responsible for the wet and dry periods and then the three composites are cross-compared to identify similarities and differences in wet and dry anomalies for these very disparate regions. The emphasis is on the role of land-surface interactions in accounting for the wet or dry conditions. Ultimately, we are interested in determining the relative roles of local land surface interactions and remote forcing due to factors such as ENSO, other SST anomalies, soil moisture, and snowcover.