UARS REFERENCE ATMOSPHERE PROJECT                                
Originator: John Remedios                               Date: 8th December 1998

UARS REFERENCE ATMOSPHERE PROJECT: DESCRIPTION


AIMS OF THE PROJECT

The UARS Reference Atmosphere Project (URAP) aims to provide a comprehensive
reference description of the stratosphere from data recorded by instruments on
the Upper Atmosphere Research Satellite (UARS). The UARS satellite was
launched on 12th September 1991 and continues to provide data today, although
not all of the instruments are now operational. Of the ten instruments, the
CLAES, HALOE, HRDI, MLS and ISAMS made near-global measurements of
stratospheric  temperature, constituent and wind fields, and their observations
form the  principal basis for reference datasets. Where possible, these data
have been  extended into the mesosphere, e.g. for  temperature and water
vapour. The coincident, detailed measurements of a large number of atmospheric 
variables means that the URAP datasets will be very useful for studies which
have hitherto employed the U.S. Standard Atmosphere or CIRA reference
atmospheres.

To achieve consistency, the URAP project has had to balance two conflicting
requirements:
1) To aim for a period of time with maximum coverage of species.
2) To minimise the effects of aerosol loading by Mt. Pinatubo; these aerosol
not only affected data quality but also influenced the chemical composition of
the lower stratosphere.

The URAP project therefore chose a period of April 1992 to March 1993 to
determine its BASELINE atmosphere (the end month is essentially determined by
the operation of the CLAES instrument which ceased recording data in May 1993
as planned). The project recognised that there are also species for which this
time period is not suitable or for which much longer terms datasets are
available. The following structure has therefore been adopted:

STRUCTURE OF THE URAP ATMOSPHERES

There are 3 categories of atmosphere:
1) BASELINE: Data for April 1992 to March 1993.
2) EXTENDED: Data for species averaged over a longer period of time (including
             the BASELINE period).
3) ADDITIONAL: Data for species averaged over a period of time not including
             the BASELINE period.
Within each category, there is a STANDARD dataset for a given species,
In addition, a number of datasets have been provided as EXTRAS. These were 
generated during the course of the URAP work and should prove useful for 
specific purposes.
N.B. To allow for updates, version numbers are provided with the data. Please 
refer to the datasets by version number in all presentations, reports and 
publications. We would be grateful if you could acknowledge the URAP project in
any use of the data and give a reference publication for the specific dataset
employed (contact the person named in the data description document if you are
unsure of the appropriate reference).

DATA TYPES

Expected products are: TEMPERATURE
                       WINDS
                       TRACERS: H2O, CH4, N2O, CFC12, HF, CO.
                       O3
                       CHLORINE SPECIES: ClO, HCl, ClONO2, Cly
                       NITROGEN SPECIES: NO, NO2, HNO3, N2O5, NOx, NOy
                       AEROSOL: EXTINCTIONS AT 23 WAVELENGTHS, AEROSOL SURFACE
                                AREAS, AEROSOL VOLUMES, MEAN RADII.
(see MASTER LIST for currently available products)  

Variabilities are also provided for the LNP vs. LAT case.

A data description document is provided with each product. Please read it
before using the data.

DATA FIELDS

MONTHLY ZONAL MEANS: Data are provided as monthly zonal means from January to 
December. 
The user should remember that for the BASELINE atmospheres, the data contain a 
temporal trend where data for January to March are months for which data were 
recorded in time after April to December. For this reason, the aerosol data 
are presented in the files as months 4-12 followed by months 1-3, the evolution
of the Mt. Pinatubo cloud being the most significant effect. Due to the time
period of the data employed, all the BASELINE atmospheres will be typical of
Pinatubo-affected conditions in the lower stratosphere, and will reflect
the dynamical state of the atmosphere and the level of solar flux in the year
chosen.

Zonal means are provided in two forms:
1) Ln(pressure) vs Latitude. (UARS surfaces: 6 per decade in pressure): LNP
   VS. LAT.

2) Theta vs. Equivalent latitude (theta spacing equivalent to pressure 
   spacing): THETA VS. EQL.

A list of UARS surfaces with corresponding pressures and theta levels.

LATITUDE GRID: 80S to 80N spaced by 4 degrees (where possible).

ALTITUDE RANGE: 100 mb to altitudes above 10 mb (where possible).

URAP file format

FURTHER INFORMATION


Please see our CONTACT LIST and REFERENCES for further information
on URAP data products.
PROGRAMS TO VIEW the data are provided.
A large number of people have provided input and constructive suggestions to
the URAP project and their help is gratefully acknowledged.

ADD YOURSELF TO OUR E-MAIL DISTRIBUTION LIST TO BE KEPT INFORMED OF
FUTURE DEVELOPMENTS IN THE URAP PROJECT ON THE REGISTRATION PAGE

Back to the Home page