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).
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.
|