PRODUCT/VERSION: URAP V1.0 2000 ZONAL WIND (U) BASELINE STANDARD

DATA SOURCE: HRDI (Version 11), UKMO, and URAP Temperatures 

TIME PERIOD FOR AVERAGING OF DATA: April 1992 to March 1993

ALTITUDE RANGE: 1000 hPa to 0.0000316 hPa

LATITUDE RANGE: 80S to 80N

DESCRIPTION:

This data set comprises zonal-mean wind components, in m/s, derived 
from HRDI measurements in the stratosphere and mesosphere and lower 
thermosphere (MLT), supplemented by data from the UK Met Office 
(UKMO) stratospheric data assimilation system, and other data sources.  
Since there were significant periods when HRDI stratospheric data 
were not available, they were smoothed and interpolated in time to 
minimise the effect of data gaps.  Because of the strong tidal 
variations in the MLT region, those data were processed in a 
different manner, to minimise the effect of gaps in local time 
coverage.

The Met Office stratospheric analyses were used outside the region
covered by stratospheric winds; together the HRDI and Met Office 
data provide complete coverage of the troposphere and stratosphere.  
In the lowermost mesosphere, where there is a gap in the HRDI
coverage and the Met Office data stops, the wind data were calculated 
from the URAP temperature data (which was only available for the URAP 
baseline period).  

Where no data were available from any of those 3 sources, the data set
includes our best estimates of the zonal wind, based on: 1) data 
interpolated between HRDI MLT values at 0.1 hPa and UKMO at 1 hPa; 
2) HRDI MLT climatology for the calendar years 1992-5; 3) winds 
extrapolated at high latitudes (from about 72 degrees, where no
HRDI measurements are available).

The analysis procedure is described in the paper 
"Swinbank, R. and D.A. Ortland, 2003: Compilation of wind data for the 
Upper Atmosphere Research Satellite (UARS) Reference Atmosphere Project, 
J. Geophys. Res., 108, D19, 4615, doi:10.1029/2002JD003135."

The chief features of the data are:   
(1) This data set gives a coherent picture of the seasonal variations 
    in zonal wind from the surface to the lower thermosphere, for the
    first time.

(2) The data show clear annual and semi-annual cyles in the wind.  
    Quasi-biennial variations can also be seen in the monthly cross-
    sections covering the extended period.

WARNINGS:

(1) Interpolation, extrapolation or use of climatology was necessary at 
    some locations in the mesosphere and lower thermosphere; these data 
    are flagged by adding 10000 to the wind values.

REFERENCES:
Hays et al, "The High-Resolution Doppler Imager on the Upper Atmosphere
Research Satellite", J. Geophys. Res., 98, 10713-10723 (1993)
Swinbank and O'Neill, "A stratosphere-troposphere data assimilation 
system", Monthly Weather Review, 122, 686-702 (1994)

CONTACTS
Originators: Richard Swinbank, David Ortland
URAP co-ordinator: John Remedios