An external view of the Met Office building at night.

Owen Lewis

Owen works on the use of Ground-based Global Navigation Satellite System and Radio Occultation data in Numerical Weather Prediction

Areas of expertise

  • GNSS observations
  • Assimilation of GNSS Zenith Total Delay data into NWP models
  • Data visualisation and analysis

Current activities

Owen's work is focused on developing, maintaining and improving the assimilation of Global Navigation Satellite System (GNSS) observations into the Met Office Numerical Weather Prediction (NWP) models, and monitoring the quality of the observations which are received. This includes both Ground-based GNSS and Radio Occultation.

Ground-based GNSS is used to observe the water vapour in the atmosphere. As a GNSS signal passes through the atmosphere it will be refracted. Refraction delays the time taken for the signal to travel from the satellite to the ground-based receiver, and this delay can be used to determine the amount of water vapour present above the receiver.  

The Met Office is a member of the EUMETNET GNSS Water Vapour Programme, for which Owen looks after the encoding, distribution and monitoring of data, and he is a member of the Expert Team on the use of GNSS water vapour measurements in NWP.

Radio Occultation measures the bending of the radio wave signals from a GNSS satellite to a low earth orbiting satellite (LEO). As the LEO satellite orbits the earth the GNSS satellites, which are orbiting at a much greater distance, appear to rise and set above the horizon from the perspective of the LEO. When the LEO and GNSS satellite are in direct sight the radio wave signals will pass through the ionosphere and the atmosphere, and the signal will be slightly delayed and the path taken bent. Information about the state of the atmosphere can be determined from this bending of the signal path.

Career background

Owen joined the Met Office in 2015 in his current role in Satellite and Surface Assimilation. This followed a postgraduate research assistant role at the University of Reading looking at Cloud Radar attenuation. This was preceded by an MSc in Applied Meteorology at the University of Reading and a BSc in Physics at Durham University.