6A.9 LAND-ATMOSPHERE FEEDBACKS: PRECIPITATION RECYCLING IN THE NAMS REGION F. Dominguez * and P. Kumar Environmental Hydrology and Hydraulic Engineering Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign, Urbana, Illinois 1. Introduction It has long been thought that in the semi-arid North American Monsoon System (NAMS) region, the moisture sources for monsoon precipitation are predominantly of oceanic origin. In this study we show that precipitation recycling is also a significant source of moisture for monsoon precipitation and it plays an important role during long monsoons. Here we present the analysis of precipitation recycling over the NAMS using Dynamic Recycling Model (Dominguez et al. 2006), which enables us to cal- culate precipitation recycling at the daily timescale. The input data for the model is obtained from the North American Regional Reanalysis (NARR) data which was developed as an improvement upon the earlier Global Reanalysis, and has focused significant efforts on improved hydrologic modeling (Mesinger et al. 2006). Furthermore, the Level II ecoregions of North America are the geographical units of analysis (See Figure 1). This classification implicitly takes into account the complex feedback mechanisms between the vegetated surface and the overlying atmosphere. One of the innovative features of this analysis is the delineation of the source and sink regions of recycled precipitation within the NAMS domain. 2. Precipitation Recycling in the NAMS The climatological analysis of NAMS precipitation recycling reveals a positive feedback mechanism between monsoon precipitation and subsequent increase in recycling. Along with the abrupt increase * Corresponding author address: Francina Dominguez, e-mail: dominguz@uiuc.edu 10.2s 13.1 12.1 10.4 14.3 13.2 Figure 1: (Left) North American monsoon system domain, identified through six different Level II ecore- gions (CEC 1997): 10.2s Sonoran desert, 13.1 Up- per Gila Mountains, 14.3 Western Pacific Coastal Plain Hills and Canyons, 13.2 Western Sierra Madre, 12.1 Western Sierra Madre Piedmont, 10.4 Chi- huahuan Desert. This delimitation follows Gutzler (2004). (Right) 32 km resolution North American Regional Reanalysis (NARR) grid points within the NAMS region. in precipitation, the NAMS is characterized by higher evapotranspiration rates, lower sensible heat flux and higher recycling ratios (See Figure 2). In agree- ment with previous work by Bosilovich et al. (2003), our study finds that evapotranspiration within the NAMS region significantly contributes to monsoon 1