NRT Monitoring: Operational Model Upgrades

A comprehensive list of operational changes made at ECMWF and the Met Office can be found at:

https://www.ecmwf.int/en/forecasts/documentation-and-support/changes-ecmwf-model (ECMWF)
https://code.metoffice.gov.uk/trac/nwpscience/wiki/ModelInfo/global/history (Met Office - page only visible to registered users).

A selected list of changes relevant to GNSS-RO is given in the table below:

Centre	Upgrade date	Upgrade version	Comments
ECMWF	18/05/2011	cy37r2	Tangent point drift used in the GNSS-RO operator
ECMWF	15/11/2011	cy37r3	Aircraft bias correction should reduce ECMWF BA bias in UT/LS
ECMWF	26/06/2013	cy38r2	Improved vertical interpolation used in 1D operator. Forecast model vertical resolution increased to use 137 levels
ECMWF	12/05/2015	cy41r1	2D GNSS-RO operator. Model changed to using semi-lagrangian interpolation, which reduced noise in the stratosphere
ECMWF	08/03/2016	cy41r2	Assumed GNSS-RO bending angle errors above 10 km increased from 1% to 1.25%
ECMWF	11/07/2017	cy43r3	Tighter quality control applied to GNSS-RO data
Met Office	20/01/2015	N/A	Bending angle and refractivity forward models upgraded for monitoring to reduce systematic biases
Met Office	03/02/2015	PS35	Numerous changes, including implementation of the improved bending angle forward model for operational RO assimilation
Met Office	15/03/2016	PS37	Numerous changes including the implementation of variational bias correction
Met Office	15/11/2017	N/A	Improved consistency in the forward model operator used by different systems. Avoids small jump in the biases that occurred from time to time

This list describes changes to the operational global NWP systems at the Met Office and ECMWF. Such changes can affect the model backgrounds which are used to produce the NRT monitoring plots. Anticipated changes will be posted here in advance of the upgrades.

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