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| Titel |
Comparison between SMOS brightness temperature observations and ECMWF ERA-Interim based brightness temperature |
| VerfasserIn |
Patricia de Rosnay, Joaquín Muñoz Sabater, Clément Albergel, Lars Isaksen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250139671
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| Publikation (Nr.) |
 EGU/EGU2017-2960.pdf |
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| Zusammenfassung |
| We present radiative transfer modelling activities conducted at the
European Centre for Medium-Range Weather Forecasts (ECMWF) to use Soil
Moisture and Ocean Salinity (SMOS) brightness temperature observations
for Numerical Weather Forecast (NWP) applications. The Community
Microwave Emission Modelling Platform (CMEM) is used as the SMOS
forward operator to simulate L-band brightness temperatures (TBs). In
a first part simulated brightness temperature are compared to the
observed SMOS near real time reprocessed brightness temperature (TB)
product for 2010-2011 for several configurations, using different
parameterisations, of CMEM. We show that simulated brightness
temperatures are more sensitive to the choice of opacity and soil
roughness models than to the dielectric model. Best configurations of
CMEM are shown to be those using the so-called Wigneron vegetation
opacity model with the simple empirical Wigneron soil roughness
model. The Wang and Schmugge and the Mironov soil dielectric models
perform similarly and lead to better agreement with SMOS observations
than the Dobson dielectric model. Based on this intercomparison the
configuration of CMEM retained for ECMWF forward modelling activities
is the one based Wang and Schmugge, Wigneron simple and Wigneron for
the dielectric, roughness and vegetation components, respectively. In
a second part, this report presents the SMOS brightness temperature
bias correction developed and used at ECMWF. It is a monthly
Cumulative Distribution Function bias correction based on SMOS and
ECMWF re-analysis-based brightness temperatures for the period from 1
January 2010 to 31 December 2013. Results show that it efficiently
corrects for systematic differences between model and observations,
with global root mean square differences and global mean bias for
2010-2013 for 30,\degree 40\degree, 50\degree incidence angles
decreasing from 16.8$\ $K and 2.08$\ $K before bias correction to
7.91K and 0.0016$\ $K after bias correction, respectively. The
monthly bias correction allows to also correct for seasonal cycles
systematic differences, with correlation values improved from 0.516
before bias correction and 0.621 after bias correction. Residual
differences remaining after bias correction correspond to random
differences between the model and observations which provide relevant
information for monitoring and data assimilation purposes. Finally,
time series and anomalies of SMOS TB and ECMWF re-analysis-based TB
are compared for the 4-year period 2010-2013 at both polarisation and
three incidence angles. RMSE, correlation and anomaly correlation
statistics consistently show that SMOS and ECMWF TB agreement steadily
improves between 2010 and 2013, indicating improvement of SMOS
products quality. |
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