Towards a new generation of atmospheric vertical profiling

This is a joint proposal between the Observing Methods section of the Met Office and the University of Manchester to exploit combinations of vertical profiling instruments, generating new measurements for constraining and initialising fine-scale weather forecasting models. It builds on a long-standing collaboration between the proposers, arising from the NERC MST radar facility at Capel Dewi, Aberystwyth. This yields information on winds, turbulence and atmospheric structure, and it is the latter that is of interest here. Clear-air radar echoes are a function of humidity and temperature gradients, offering the potential for deriving profiles of these variables from the radar echoes. Recent comparison by D. Hooper (RAL) between a cloud radar and the VHF radar has shown that clouds as well as precipitation affect the radar measurements. This suggests that the radar may be used to derive information on cloud structure, and Dr. Hooper is a collaborator in the present project. The overall aims of this PhD project are as follows: a) establish the factors that influence the echo power of the MST radar and develop a quantitative model relating the echo power to atmospheric parameters, taking into account the fundamentals of radio physics and the existing measurement data base b) use the results of a) to derive temperature and humidity profiles using the radar and ancillary data. c) establish what quantitative information on cloud structure may be derived from the radar d) extend these results to UHF profiling radars e) evaluate how this information may be used to constrain numerical models The initial plan for the project is to exploit the existing data when ancillary profiling measurements were made at the MST radar site. This provides a starting point to relate the radar measurements to other instruments and develop hypotheses. Later, we plan to operate a cluster of profiling instruments - microwave radiometer, cloud radar, UHF radar, ceilometer and lidar - which will provide a novel and powerful assault on the problem. These will be operated on a campaign basis: one campaign of four weeks per year of the project with radiosondes providing 'ground truth' profiles of temperature and humidity. With careful calibration, the retrieval of humidity and temperature profiles will provide an excellent dataset for initialisation and constraining of numerical models. The student will build on the experimental work by simulating a cloud field in the vicinity of the measurement site, under the guidance of Dr Connolly. The numerical experiments will be chosen to evaluate the impact of the derived profiles on the simulation of a cloud field. Current work at Manchester under the aegis of the COPS consortium grant is preparing the ground for such studies. Towards the end of the project further numerical experiments will be conducted to evaluate the impact of the derived profiles on the initialisation of the Met Office forecast model. This work will be conducted at JCMM in Reading where Dr Gaffard has close links with colleagues in the Data Assimilation Group. Thus the student will also gain experience in the way measurements are used with a modern forecasting model. The student will thus obtain training in field work and operating state-of-the-art vertical profiling equipment. There will be a considerable amount of data handling, for which excellent IT skills will need to be developed, and theoretical work in radio physics and atmospheric physics to interpret the measurements properly. Finally, the student will gain experience with state-of-the-art numerical models of the atmosphere. The student will be based at Manchester and undergo the normal programme of student training provided by the School of Earth, Atmospheric and Environmental Sciences. As well as lectures in atmospheric physics and dynamics, there is a programme of skills training described in http://tinyurl.com/3brne3 and http://tinyurl.com/3eylkm.