NERC-CASE studentship with the Met Office, Exeter on

Evaluating the impact of MISR and (A)ATSR(2) cloud-top heights and wind data on the Met Office NWP and climate models

UCL-MSSL Supervisor: Prof. Jan-Peter Muller

Met Office Supervisor: Dr Mary Forsyth

Atmospheric Motion Vectors (AMVs) from geostationary and polar orbiting satellites are currently employed in data assimilation for the Met Office numerical weather prediction (NWP) forecasts. Their accuracy is assessed as part of the EUMETSAT NWP SAF (Satellite Application Facilities) activities by inter-comparison with the short-range model forecast. Most of these AMVs come from tracking visible and/or thermal IR cloud features with derived cloud-top heights which can have large errors. The assigned cloud top heights can potentially be particularly poor over polar ice and snow-covered regions due to problems of determining cloud-tops from cold surfaces.

The NASA MISR (Multi-angle Imaging Spectro-Radiometer) instrument has been operating flawlessly since February 2000 acquiring visible cloud-top heights and winds over a limited swath of 380km. The ESA/UK ATSR (Along Track Scanning Radiometer) was launched in 1991, ATSR2 in 1995 and AATSR in 2002. No operational cloud products are currently processed but longer term monthly, seasonal and annual products have been processed for limited areas. Their heritage will continue with Sentinel-3 SLSTR (Sea Land Surface Temperature Radiometer) from 2012 but only for the central swath (750 cf 1800km). Unlike existing operational AMVs, both MISR and (A)ATSR(2)/SLSTR employ geometric stereo photogrammetric technology rather than thermal IR-based brightness temperature with input required from NWP objective analyses. In the case of MISR, only data from the sensor itself is employed to retrieve cloud-top heights and winds. Currently, for the (A)ATSR(2)/SLSTR, wind data needs to be derived from NWP forecasts to correct the cloud-top-heights determined from stereo.

The student will evaluate existing level-2 (daily) and level-3 (monthly) MISR AMVs, particularly over polar regions using the methods developed for existing AMVs within the NWP SAF. Where available, data from ground-based radar/lidar (e.g. Barrow, Alaska), radiosondes and other systems will be employed to provide further insight into the potential of MISR AMVs over the poles. Armed with an understanding of the error characteristics of MISR AMVs, impact studies will be made of these AMVs on the accuracy of the Met Office NWP analyses and forecasts for several different seasons. In addition to polar regions, AMVs over severe weather systems whether at mid-latitudes or tropics will be evaluated, particularly with regard to determining under which conditions AMVs do NOT represent the advective wind-field and should be deleted or corrected. Finally, the potential of future dedicated AMV systems employing stereo will be evaluated.

NERC PhD studentship is for 3.5 years funding, stipend of £15,940 in 2009/10. The Met Office provides an additional annual payment to the student of £ 3,650 (i.e. £19,590 tax-free in 2009/10) and a bonus payment of £3,930 upon completion of the thesis.

Eligibility: only UK students and EU (minimum of 3 year residency) or non-EU who satisfy UK residency requirements should apply.

Application forms can be downloaded electronically here.

The closing date for applications is 17 July 2009.