Wednesday, 12 January 2005: 2:00 PM
Regional aspects of the North American land surface-atmosphere interactions: Analysis of North American Regional Reanalysis (NARR) Data
Our effort is directed toward improving the understanding of the feedbacks between soil states and precipitation processes, focusing on the variability and predictability of the hydrologic cycle of North American basins. In this study, by employing the recently released NCEPís North American Regional Reanalysis (NARR) data, first we investigate the basin scale surface water and energy budgets as the background for the analysis of the land surface and atmosphere feedbacks; then, we diagnose the regional land surface-atmosphere interactions from diurnal, monthly to seasonal time scales. To examine those interactions, the soil states are correlated to the more relevant surface and atmospheric variables. There is solid evidence for strong interactions during summer, while this mechanism is likely to be less relevant during the cold season. A multiyear basin-by-basin analysis reveals that during the summer months positive feedbacks between soil moisture and precipitation are most likely in most of the North American basins, although with a different degrees in strength. Results from NARR have produced different degrees of feedbacks between the soil moisture conditions and precipitation intensity: the monsoon-affected regions in Mexico can be identified as strong feedback regions; feedbacks are weaker in the Mississippi basin and its sub-basins; and finally, no clear linkages are found in the western US basins (Columbia and Colorado). Advective processes, ocean influence, winter snow and spring runoff effects are potential factors that may have a stronger effect over the regions with weak land-atmosphere feedback.