NAME logo North American Monsoon Experiment
CSU Mesoscale Dynamics Group
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The North American Monsoon Experiment is an internationally coordinated, joint CLIVAR-GEWEX process study aimed at determining the sources and limits of predictability of warm season precipitation over North America. It focuses on observing and understanding the key components of the North American monsoon system and their variability within the context of the evolving land surface-atmosphere-ocean annual cycle. It seeks improved understanding of the key physical processes that must be parameterized for improved simulations and predictions with coupled models. NAME employs a multi-scale approach with focused monitoring, diagnostic and modeling activities in the core monsoon region, on the regional-scale and on the continental-scale. NAME is part of the CLIVAR/VAMOS program, US CLIVAR Pan American research, and the GEWEX Americas Prediction Project (GAPP).

NAME instruments Observing facilities requested from the NSF are principally in support of Tier I objectives for a six week period in July-August 2004. These objectives include the observation, understanding and numerical representation of convective and mesoscale processes in the core monsoon region. These processes are hypothesized to be a central factor in the variability of the North American monsoon and monsoons elsewhere. Foremost among the objectives is to quantify the diurnal cycle of precipitation; to understand which factors regulate the observed pattern; to statistically reproduce that behavior in numerical simulations; and to forecast observed variability at the intra-seasonal to inter-annual ranges of prediction.

The region of NAME is complex in its topography; in the variability of upper oceanic heat content; and with respect to the transport of moisture into the region. It contains deserts, tropical rainforests, complex atmospheric boundary layers, and very large gradients of atmospheric properties that potentially influence rainfall variability. Much of the world's heaviest monsoon rainfall occurs in similar complex, coastal environments. In North America there exist some unique scientific assets that render these objectives tractable at this time.

Our group is responsible for the following instrument systems:
  • Integrated Sounding Systems (and VISSs) combine the capability of continuous wind profiles in the low-to-mid troposphere with full-tropospheric thermodynamic and wind soundings. These also include standard surface meteorological observations. The data provide critical information on environmental convective available potential energy (CAPE) and vertical shear of the horizontal wind, which together are the principal modulators of sustained mesoscale rainfall systems. These data also are central to estimation of latent heating/cooling profiles and the redistribution of momentum as a direct consequence of convective overturning. Co-location of sounding and profiling systems enhances the interpretation of both individual observing systems.

  • UHF wind profilers provide continuous low-to-mid tropospheric wind profiles from approximately 150 m AGL through 2-6 km MSL, depending upon location, atmospheric conditions and instrument performance specifications. RASS capabilities, in conjunction with all profilers, provide continual virtual temperature (air density) soundings in the lowest 1-2 km. A network of these systems describes the general wind field and some of its first order derivative properties; the depth of the planetary boundary layer and its thermal stratification; and the passage of breeze fronts, surges, cold pools, other convergence lines; and limited information about the position of rainfall systems in relation to the above. A robust network of profilers is essential to Tier I diagnostic studies including core monsoon budget calculations and the initialization and validation of limited-area models.