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Dr Warren Tennant

Warren manages the Global Data Assimilation and Ensembles Group with a research interest in understanding and estimating model forecast error.

Current activities

Warren is a scientific manager of the Global Data Assimilation and Ensembles Group. His research background is developing stochastic physics schemes in the Met Office Ensemble Prediction System (MOGREPS). Other responsibilities of the group he manages are to exploit the use of conventional observations (land, marine, aircraft) in the global NWP system; support operational changes through providing standard research suites, verification tools and guidance for trialling; plan the process for possible implementation of a weakly-coupled Ocean-Atmosphere data assimilation NWP system; and improve the collaboration between scientific research and operational meteorology through subjective verification and forecast monitoring.

As ensemble forecasting becomes part of mainstream weather forecasting, it is important to generate accurate estimates of forecast uncertainty. This is done by using initial condition perturbations and stochastic physics perturbations, which control the rate of growth of spread within the ensemble. The recent focus of Warren's work in stochastic physics includes tests with a spatially-varying Random Parameter scheme. This scheme allows physics parameters to vary both over space and time during a forecast. Earlier work included the SKEB scheme, SST and SMC perturbations. The SKEB scheme injects wind increments into the model at every time-step, and are based on a random stream-function forcing pattern that is modulated by locally diagnosed energy dissipation fields. In this way the model forecasts are forced to diverge more rapidly in regions where there is a perceived drain of energy from the model. SST and SMC perturbations are provided at the start of the model forecast.

Career background

Warren joined the Met Office in 2008 after having worked at the South African Weather Service since 1993. He was involved in Numerical Weather Prediction (NWP) for most of that time and was responsible for implementing and maintaining various modelling systems including the COLA T30 GCM, NCEP T126 GFS, NCEP Eta and Met Office UM (regional 12km and 4km). He also developed a forecast verification system and managed the NWP group for several years.

Warren completed his PhD at the University of Cape Town in 2002. This work involved a new approach to understanding large-scale atmospheric variability on a seasonal time-scale through atmospheric energetics.

Warren was a member of the (THORPEX) GIFS-TIGGE working group from its inception in 2005 until 2008 and he helped introduce the successful concept of local forecast processing centres into the plan of a Global Interactive Forecast System (GIFS). This has been a big step forward in transferring NWP output from global producing centres into products with local value. More recently, until December 2013, he was a member of the EUMETNET Short-Range Numerical Weather Prediction Expert Team on Ensemble Prediction Systems, which addresses predictability issues and uncertainties in the NWP models, LAMEPS and ensemble data assimilation.

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