North American Monsoon Experiment (NAME) 2004

The North American Monsoon System (NAMS) is an important large-scale feature of the warm season climatology of Mexico and the southwest U.S. The variability of summertime convective activity in this region results from a complex interaction between atmospheric circulation features at both the synoptic scale and mesoscale and the extremely varied topography.

The North American Monsoon Experiment (NAME) was designed to identify the sources and limits of the predictability of warm season precipitation over southwestern North America by observing and understanding the key components of the NAMS and the variability within the context of the evolving land surface-atmosphere-ocean annual cycle. NAME is part of the CLIVAR/VAMOS program, US CLIVAR Pan American research, and the GEWEX America Prediction Project (GAPP).

Surface Network

NAME seeks improved understanding of the key physical processes that must be parameterized for improved simulations and predictions with coupled models. To address these goals and to document the key roles of the boundary layer and the diurnal cycle in NAMS, ETL and CU/CIRES designed a coastal supersite to measure the physical, dynamical, and microphysical properties of the convective storms that make up the NAMS. The supersite includes measurements to characterize the prestorm environment including surface energy fluxes and spectrally resolved solar radiation. Another component of the supersite is devoted to measuring convective clouds, integrated precipitable water, and precipitation microphysics. A subset of the instruments will be deployed in additional monsoon seasons during the summers of 2005 and 2006 to provide much needed information on NAMS interannual variability.

High Resolution Ocean Flux Measurements

ETL and CU/CIRES joined the Colorado State University (CSU) in conducting six weeks of observations from the Mexican Navy research vessel Altair off the tip of Baja California. The primary purpose of the Altair cruise was to obtain climate-quality observations of important air-sea interaction processes relevant to monsoon dynamics in this key region. The mouth of the Gulf is the entrance point for southerly wind surges that feed moisture into the monsoon system that provides much-needed rain to several states in the SW United States. Measurement systems installed by ETL on the ship included near-surface bulk meteorology, a balloon sounding system, direct turbulent fluxes, radiative fluxes, cloud-base height, and a motion-stabilized Doppler wind profiler. Profiles of temperature and salinity in the ocean were obtained with a conventional oceanographic CTD system. Scientists from ETL and CU/CIRES were joined by graduate students from CSU and the University of Miami. In addition, the cruise hosted a teacher James Cronin from the Cherry Creek School District in Denver.

SMEX/NAME

One of the main objectives of NAME is to improve prediction of warm season precipitation which is dependent on convection, which is in part determined by soil moisture and surface temperature. The 2004 Soil Moisture Experiment/NAME campaign builds on preceding experiments (SGP99, SMEX02 and SMEX03) by focusing specifically on topography, vegetation and strengthening the soil moisture components of NAME. The principal airborne system used during SMEX04/NAME was the NOAA/ETL Polarimetric Scanning Radiometer (PSR) system observing in the C- and X-band range, passive microwave channels similar to those on AMSR-E and future L-band satellite soil moisture measurements.

The goal of the PSR/CXI was to acquire images with high spatial resolution along with strategically located and designed automated and manual surface observations to verify and extend the satellite soil moisture observations over regions with sparse vegetation. Two regional study sites were established in Arizona (AZ) and Sonora, Mexico (SO) for the campaign. Measurements were timed to coincide with satellite data acquisition from the Aqua AMSR-E, Coriolis Windsat, TRMM TMI, DMSP SSM/I, Terra MODIS and ASTER, and Envisat ASAR. By the end of the campaign, a total of 11 and 11 mappings of the AZ and SO grids were obtained, respectively, over a 23 day period.