MERGED SOUNDING PROFILES FOR ARM SOUTHERN GREAT PLAINS CENTRAL FACILITY

Time Period: March 2000

In order to perform accurate calculations of the transfer of electromagnetic 
radiation through the atmosphere, information on the vertical profiles of 
temperature and water vapor concentration are needed. While these quantities are 
measured by balloon-borne radiosondes (at 4 to 24 hour intervals) and some 
specialized remote sensing instruments (e.g. profiling microwave radiometers), 
the need for continuous estimates of these vertical profiles required the 
development of a value-added product (VAP) that combined observations from 
several different platforms. This product is referred to as the merged sounding 
VAP.   
	The merged sounding VAP uses a combination of observations from several 
different platforms, output from computer model simulations of atmospheric 
conditions, and a sophisticated scaling/interpolation/smoothing scheme in order 
to define profiles of the atmospheric thermodynamic state at one-minute time 
resolution. The vertical profile of atmospheric state variables from the 
periodic balloon-borne radiosonde observations are used as a starting point for 
the algorithm. The time lag of upper air observations compared to the surface is 
taken into account as these measurements are distributed over the time-height 
domain. Surface-based meteorology observations are also used as a boundary 
condition at the surface. In order to fill the remaining locations in the time-
height domain we use output from computer model simulations from the European 
Centre for Medium-Range Weather Forecasting (ECMWF). These observations and 
model output are then interpolated over the merged sounding grid giving an 
initial estimate of the atmospheric thermodynamic state at one-minute time 
intervals and a total of 266 altitude levels which vary such that greater detail 
(20 meters) is captured near the surface with the resolution becoming coarser 
(200 meters) as the maximum altitude - 20 km above mean sea level - is attained. 
The thermodynamic fields are them smoothed in the horizontal dimension, in order 
to avoid anomalously large gradients, with a greater weighting towards 
observations compared to model output. Finally, the vertically integrated water 
vapor amount measured by the microwave radiometer is used to scale the vertical 
profile of water vapor at each one-minute interval.