Numerical Weather Prediction

About the ITWG DA/NWP Working Group

Aim and Scope

The aim of the Working Group on Data Assimilation and Numerical Weather Prediction is to increase the impact of satellite data in NWP. The group considers sounding instruments currently in orbit that build on the “TOVS heritage”, such as ATOVS, SSMI/S, ATMS, AIRS, IASI and CrIS. The group achieves its goals by exchanging ideas and information on new techniques and progress and by providing a means of communication between NWP centres, satellite agencies and other groups engaged in work with satellite data.

The scope of the group includes global models and regional models as well as high resolution models. The group’s recommendations and actions are to make satellite data and metadata easily available for NWP centres to use, to provide feedback to satellite agencies on any practical difficulties being experienced with the data and for NWP centres to share information and experiences on techniques and assumptions. Occasionally the group suggests new areas of work or advises NWP centres to change their data processing in a particular way. The most obvious example was in promoting the assimilation of radiances rather than sounding products.

Impact of Sounding data in NWP

Starting with ATOVS in 1999, the use of sounder data has become widespread with many NWP centres reporting strong positive impact, especially when directly assimilating the radiances.

Adjoint-based sensitivity studies have shown that the impact of satellite sounding data is far larger than for any other observation type within a variational analysis system. Observing system experiments (OSEs) also show that the impact of observations, particularly from ATOVS and IASI is comparable to or larger than that from radiosondes.

To find out more about the use of microwave and infrared sounder data, the ITSC proceedings are a vital source of information. Regular progress reports and reports on OSEs are provided by meteorological services. For results of OSEs including satellite data OSEs see link to the latest WMO workshop on the subject (7th WMO Workshop on the Impact of Various Observing Systems on NWP , held virtually, 30th Nov – 3rd Dec 2020).

ITWG NWP Working Group Reports

The reports of the NWP Working Group from previous ITSC conferences are provided here in PDF format

Interactions with other groups

This ITWG working group is a long standing sub-group of the Radiation Commission of the International Association of Meteorology and Atmospheric Sciences (IAMAS).

From time to time, the group also discusses relevant issues for radiative transfer models and radio frequency interference: these issues are fed back to the respective ITWG sub-groups that lead on these matters.

Monitoring and Data Quality Resources