Met Society members in Wellington are reminded about the following
seminar, open to anyone interested.

Two seminars will be given by visitors from the University Corporation
for Atmospheric Research (UCAR, Boulder, CO, USA) in the Rainbow Room at
MetService, 30 Salamanca in Kelburn, Wellington, from 10 am to noon on
Thursday 29 January 2004.

Abstracts for the two seminars are given below. Richard Anthes is the
President of UCAR (see
<http://www.ucar.edu/pres/>http://www.ucar.edu/pres/
), Bill Kuo is the COSMIC Project Director, and Christian Rocken is an
expert in ground-based GPS meteorology.

For any queries on these seminars please contact
Neil.Gordon@...

To ensure entry please take along a copy of this notice.


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Application of GPS radio occultation data to weather analysis and
prediction and the COSMIC mission

Richard Anthes, Bill Kuo, and Christian Rocken
University Corporation for Atmospheric Research
Boulder, CO 80307, USA

The atmospheric limb sounding technique making use of radio signals
transmitted by the Global Position System (GPS) has emerged as a
promising approach for global meteorological observations. As
demonstrated by the proof-of-concept GPS Meteorology (GPS/MET)
experiment and more recently by the CHAMP and SAC-C missions, the GPS
radio occultation sounding data are of high accuracy and high vertical
resolution. In late 2005, the joint U.S.-Taiwan COSMIC mission will be
launched and is expected to collect up to 3,000 radio occultation
soundings per day. These data will be available in near real-time for
global weather analysis and prediction.

Radio occultation measures phase and amplitude of the microwave signals
emitted from GPS. These signals are inverted to obtain profiles of
signal bending, atmospheric refractivity, pressure temperature and water
vapor. The main purpose of the upcoming COSMIC mission is to demonstrate
the value of these radio occultation products for weather forecasting
and climate monitoring. This presentation will provide an overview of
the COSMIC program, the status of data inversion, and issues related to
assimilating
this new data type into weather models. It will also show some recent
results applicable to climate studies.

For more information on COSMIC please see
<http://www.cosmic.ucar.edu/>http://www.cosmic.ucar.edu/ .

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New Developments in Ground-Based GPS Meteorology
Christian Rocken
University Corporation for Atmospheric Research
Boulder, CO 80307, USA

The use of ground-based GPS observations for the estimation of
precipitable water vapor (PWV) is now a well proven, tested, and widely
applied technique. The strengths of ground-based GPS meteorology lie in
its high accuracy of about 1 mm in PWV, its high temporal resolution
ranging from seconds to hours, its all-weather capabilities, and
relatively low costs. In spite of its undeniable success, ground-based
GPS meteorology also has some shortcomings. It does not generally
provide atmospheric profile information, does presently not provide data
over the oceans, and most importantly GPS PWV has not yet yielded
consistent positive impact on weather models. This presentation will
describe the status of ground based GPS meteorology and discuss the
current activities to overcome some of
these shortcomings. In order to obtain information on the atmospheric
profile, GPS slant observations have to be combined in tomographic or
data assimilation analysis. Since low-elevation GPS observations contain
the most atmospheric information improved GPS mapping functions are
needed. We will describe a so-called dynamicor directmapping function
that utilizes time and location specific profiles of refractivity from
the NCEP AVN atmospheric analysis, and report results from its use. To
address the issue of GPS in the oceans we conducted two GPS experiments
on a Caribbean cruise ship. The goal of these experiments was to
determine the feasibility of low-resolution refractivity profiling with
GPS from a moving platform and the estimation of PWV from a ship in the
open ocean. Results depend strongly on the attainable position quality
of the ship but .2-3 mm rms PWV estimation on a ship appears feasible
Analysis of data from the ship experiments will be presented. Finally,
scientists at NCAR and at NOAA are now working to assimilate GPS PWV
estimates into numerical weather models. Results of these impact studies
will be presented.
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