Problem: The goal of this PhD is to improve the ability of weather radars to accurately make quantitative estimates of precipitation by classifying the observed hydrometeor types (i.e. rain, snow, hail, etc.) using the novel data provided by dual-polarisation radar observations.
One of the most critical forecasting challenges to meteorologists is when the 0 degrees C isotherm (i.e. the freezing level) is close to the surface. This results in large uncertainty in the prediction of precipitation type and amount. The radar hydrometeor type product (i.e. the information from radar that identifies rain, snow, hail, etc.) can be used to identify changes and trends in such conditions, particularly if data suggests a divergence from forecasts. Extrapolating such trends allows forecasters to provide better information to emergency response teams and other customers to take mitigating action. Thus, accurately forecasting such weather is absolutely essential for the National Severe Weather Warning Service in terms of safety of life. In addition, marginal rain/snow events have profound impacts on the transport sector, for example: airports, rail operators and road gritting.
Current Met Office hydrometeor classifications rely on numerical weather predictions (NWP) as conventional (single polarisation) observations provide limited data on the phase of precipitation. Due to this reliance on secondary information, the accuracy of the existing hydrometeor type product in the UK is greatly impacted by the NWP’s errors.
Novel Observations: The Met Office is upgrading all weather radars in the UK network to make dual-polarisation observations. By September 2016 upgrades of 13 of 15 radars will be complete. Unlike single polarisation, dual-polarisation allows the size, shape, and orientation of targets to be measured due to the differences these physical parameters have on the scattering of the two transmitted polarizations. A classification of hydrometeor type can be derived from these measurements with less reliance on NWPs.
The PhD will use novel polarimetric radar observations to improve our ability to observe and understand the evolution of hydrometeors within extratropical precipitation events. By tacking this problem the PhD will:
1. Become an expert in analysing dual-polarisation Doppler radar observations;
2. Determine and evaluate the use of polarimetric parameters to quantify hydrometer size, concentration, phase, shape, and orientation (i.e. hydrometeor type) using the upgraded UK radar network;
3. Use dual-polarisation observations to improve parameterizations of precipitation in forecast models by comparing synthetic radar data derived from NWPs to observations.
To accomplish this, the student will work with the Met Office to develop the hydrometeor classification algorithms to be used operationally with the upgraded radars. The student will evaluate the skill of the algorithms by validating it with other observations, which include observations from the Met Office’s and NCAS’s research radars (provided by on-going schemes to improve the UK’s national capability which the supervisors are actively involved in) as well as in situ observations made by the FAAM BAe-146 aircraft in previous and upcoming campaigns over the UK (including PIKNMIX-C and D (Nov. 2013 & Nov./Dec. 2014) and COSMICS (Mar. 2015) that were funded by NERC). To execute this work, the PhD will create a novel framework for the inter-comparison radar data with other observations.
Eligibility for this fully-funded NERC Industrial CASE award will normally be UK and some EU nationals who meet the residency requirements. The funding is for up to 4 years and will include tuition fees (£4,100 for 2015/16), tax-free stipend (£14,057 for 20115/16), a research budget, and additional benefits through collaboration with the CASE partner.
• Kumjian, M. (2013), Principles and applications of dual-polarization weather radar. Part I: Description of the polarimetric radar variables, J. Operational Meteor., 1(19), 226–242, doi:10.15191/nwajom.2013.0119.
• Kumjian, M. (2013), Principles and applications of dual-polarization weather radar. Part II: Warm- and cold-season applications, J. Operational Meteor., 1(20), 243–264, doi:10.15191/nwajom.2013.0120.
• M. Galletti (2009), Fully polarimetric analysis of weather radar signatures, Ph.D. Thesis, Technische Universität Chemnitz: Germany.
How good is research at University of Leeds in Earth Systems and Environmental Sciences?
FTE Category A staff submitted: 79.20
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