Using reference radiosondes to characterise NWP model uncertainty for improved satellite calibration and validation
<p>The characterisation of errors and uncertainties in numerical weather prediction (NWP) model fields is a major challenge that is addressed as part of the Horizon 2020 Gap Analysis for Integrated Atmospheric ECV CLImate Monitoring (GAIA-CLIM) project. In that regard, observations from the GC...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-01-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/12/83/2019/amt-12-83-2019.pdf |
| Summary: | <p>The characterisation of errors and uncertainties in numerical
weather prediction (NWP) model fields is a major challenge that is addressed
as part of the Horizon 2020 Gap Analysis for Integrated Atmospheric ECV
CLImate Monitoring (GAIA-CLIM) project. In that regard, observations from the
GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN)
radiosondes are being used at the Met Office and European Centre for
Medium-Range Weather Forecasts (ECMWF) to assess errors and uncertainties
associated with model data.</p>
<p>The software introduced in this study and referred to as the GRUAN processor
has been developed to collocate GRUAN radiosonde profiles and NWP model
fields, simulate top-of-atmosphere brightness temperature at frequencies
used by space-borne instruments, and propagate GRUAN uncertainties in that
simulation. A mathematical framework used to estimate and assess the
uncertainty budget of the comparison of simulated brightness temperature is
also proposed.</p>
<p>A total of 1 year of GRUAN radiosondes and matching NWP fields from the Met Office and
ECMWF have been processed and analysed for the purposes of demonstration of
capability. We present preliminary results confirming the presence of known
biases in the temperature and humidity profiles of both NWP centres. The
night-time difference between GRUAN and Met Office (ECMWF) simulated
brightness temperature at microwave frequencies predominantly sensitive to
temperature is on average smaller than 0.1 K (0.4 K). Similarly, this
difference is on average smaller than 0.5 K (0.4 K) at microwave
frequencies predominantly sensitive to humidity.</p>
<p>The uncertainty estimated for the Met Office–GRUAN difference ranges from
0.08 to 0.13 K for temperature-sensitive frequencies and from 1.6 to 2.5 K
for humidity-sensitive frequencies. From the analysed sampling, 90 % of
the comparisons are found to be in statistical agreement.</p>
<p>This initial study has the potential to be extended to a larger collection
of GRUAN profiles, covering multiple sites and years, with the aim of
providing a robust estimation of both errors and uncertainties of NWP model
fields in radiance space for a selection of key microwave and infrared
frequencies.</p> |
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| ISSN: | 1867-1381 1867-8548 |