Methodology/work description :
This work package will attempt to exploit the advanced features of the partner 3 polarimetric weather radar to determine how operational observing networks might be better configured to serve the purposes of model assimilation. In so doing, it is recognised that there is a need to parameterise the weight given to an observation as well as the quantity which is being measured, this perhaps differing somewhat form the way in which weather radar has traditionally been used. Work will fall into three main areas, and will be supported by an extensive set of previously archived data, supplemented by new observations where these are required to ensure representativeness.
a) Differential propagation phase (F
DP) is an absolute measurement available from advanced polarimetric radar systems which can be used to "self-calibrate" the instrument itself. However, in this workpackage we will instead exploit this technique to measure variations in Z-R relationships which lead to uncertainties in model rainfall input at different spatial and temporal scales. The general idea will be for P3 to identify the Z-R relationship that will best match with the F
DP observed in a radar-ray segment, using the relationships between F
DP and rainfall intensity derived by P6. From analysis of a representative selection of events, this should help to establish the uncertainty in rainfall estimates from more conventional weather radar systems, and in combination with outputs from WP7, will provide a basis for projecting how these errors translate in terms of model output. Naturally, this should also provide a basis for assessing the extent to which the F
DP measurement itself might serve to minimise these errors.
b) Weather radar is only one form of instrumentation in the integrated observing networks which are being developed to serve NWP. An attempt will be made to assess the potentially complimentary or redundant characteristics of combined multiparameter radar and satellite measurements for clouds and clear air, arising due to differences in the scattering processes involved. Special attention will be given to charting the spatial distribution of precipitation phase and amount in order to estimate the latent heat energy released during the evolution of severe weather systems.