Characteristics of the atmospheric state and the surface radiation budget at the tropical western Pacific ARM site

The Department of Energy's Atmospheric Radiation Measurement (ARM) program has been operating a radiation and cloud observing station in the tropical western Pacific (TWP) since October, 1996. This station includes instruments for measuring the surface radiation budget, characteristics of the atmospheric column that affect that budget, and surface meteorological parameters. Our purpose here is both to introduce some of the fundamental characteristics of the tropical western Pacific region and to show some interesting properties of the data that have emerged from our analyses thus far. The column concentration of water vapor is very high in this region and dominates the downward flux of infrared at the surface. For shortwave radiation, clouds dominate the surface budget. We have compared the surface shortwave cloud forcing from the ARM site with previous observations from this region. Finally, we have examined the vertical distribution of clouds in periods of active and suppressed convection and find interesting contrasts between these regimes.