Simulations of the 2004 North American Monsoon: NAMAP2

Abstract

The second phase of the North American Monsoon Experiment (NAME) Model Assessment Project (NAMAP2) was carried out to provide a coordinated set of simulations from global and regional models of the 2004 warm season across the North American monsoon domain. This project follows an earlier assessment, called NAMAP, that preceded the 2004 field season of the North American Monsoon Experiment. Six global and four regional models are all forced with prescribed, time-varying ocean surface temperatures. Metrics for model simulation of warm season precipitation processes developed in NAMAP are examined that pertain to the seasonal progression and diurnal cycle of precipitation, monsoon onset, surface turbulent fluxes, and simulation of the low-level jet circulation over the Gulf of California. Assessment of the metrics is shown to be limited by continuing uncertainties in spatially averaged observations, demonstrating that modeling and observational analysis capabilities need to be developed concurrently. Simulations of the core subregion (CORE) of monsoonal precipitation in global models have improved since NAMAP, despite the lack of a proper low-level jet circulation in these simulations. Some regional models run at higher resolution still exhibit the tendency observed in NAMAP to overestimate precipitation in the CORE subregion; this is shown to involve both convective and resolved components of the total precipitation. The variability of precipitation in the Arizona/New Mexico (AZNM) subregion is simulated much better by the regional models compared with the global models, illustrating the importance of transient circulation anomalies (prescribed as lateral boundary conditions) for simulating precipitation in the northern part of the monsoon domain. This suggests that seasonal predictability derivable from lower boundary conditions may be limited in the AZNM subregion.

Impact of the Desert dust on the summer monsoon system over Southwestern North America

“…Monsoon onset occurs in June in most of western Mexico south of ∼30 • N and reaches the international border and then the southwestern US in July and August. Rainfall intensifies strongly and rapidly in July, with maximum rainfall rates along the western foothills of the Sierra Madre Occidental (SMO) in northwestern Mexico, consistent with previous studies (e.g., Gutzler, 2009). Although, TRMM observes the spatial variability of the NAM precipitation, it underestimates the NAM precipitation compared to the PERSIANN data.…”

Influence of initial soil moisture and vegetation conditions on monsoon precipitation events in northwest México

“…Here, the Noah with multi-parameterization (Noah-MP, Niu et al, 2011) land surface scheme is adopted to simulate water and energy fluxes in each two-way nested domain (Fig. 1, Table II) of 12, 4 and 1 km cell resolution, with the domains determined in a manner consistent with NAME modeling efforts (e.g., Gutzler et al, 2009). …”

Reanalysis-driven climate simulation over CORDEX North America domain using the Canadian Regional Climate Model, version 5: model performance evaluation

“…In order to better assess the performance of CRCM5 in simulating NAM and compare simulation results with observations, two small subdomains, located in the NAM area, are studied: the CORE subdomain, covering parts of Baja California peninsula and Gulf of California coast, and the AZNM subdomain, covering parts of Arizona and New Mexico states (Gutzler et al 2009). The CORE subdomain is located in the centre of NAM-influenced area, while the AZNM subdomain is at its northern limit.…”

“…The simulated winter precipitation maximum is notably higher Fig. 19 The map of subregions in the North American Monsoon zone: AZNM and CORE subregions (Gutzler et al 2009). Actual simulation grid tiles within these subregions are presented than that in the CRU TS3.1 and UDel data.…”

“…The first stage of the project was centred on the 1990 warm season (Gutzler et al 2005), and the second stage (NAMAP2), on the 2004 warm season when an extensive field campaign was performed. Six GCMs and four RCMs participated in NAMAP2 (Gutzler et al 2009); it has been shown that GCMs do not have sufficient horizontal resolution to correctly reproduce the complex structure of atmospheric circulation associated with NAM. In our assessment of the CRCM5 performance in simulating NAM, we will investigate the characteristics of precipitation over the subregions proposed by Gutzler et al (2009).…”