A sequence of Doppler radar observations obtained during the PADRE project is used to identify a region of dry-air intrusion in a frontal system approaching the Alps. The study demonstrates the potential of Doppler radar to provide additional information to forecasters on fine spatial and temporal characteristics of frontal cyclogenesis.

Ground-based multi-parameter radar is used to validate and evaluate satellite passive microwave parameters related to rainfall over land. Light precipitation over the southern part of England is considered. The issues of diverse resolutions of radar and satellite data in space and time are investigated, as well as the satellite beam-filling problem, in relation to present passive microwave satellite algorithms related to rainfall over land, and their perceived behaviour. Several statistical analyses are applied and their sensitivities to data integration problems are quantified. Passive microwave parameters are evaluated and compared with each other. It is concluded that for radar passive microwave satellite data intercomparisons, calibrations and validations the time resolution seems to be more important than the spatial resolution, and high-resolution radar can be used operationally to tackle the satellite beam-filling problem. It is found that several passive microwave algorithms have performances very similar to each other.

A statistical verification of a number of forecast icing algorithms is presented. The algorithms are based on gridded forecasts of temperature and humidity from the global model of the European Centre for Medium-range Weather Forecasts. This study was undertaken with the use of a database of pilot reports issued from the Winter Icing and Storm Program and collected between 1993 and 1995 over the USA. The results are presented both in terms of percentage of detection and in terms of total surface of the forecast. They highlight the difficulty of having to make a choice between those two criteria. Taking into account vertical velocity in the algorithms reduces the percentage of detection, but the area where icing is forecast decreases to an even higher extent.

It is known that topography is an important factor controlling the variation of road surface temperature (RST). In order to explore possible relationships between RST and topography, the authors used Thermal Mapping data obtained by a vehicle-mounted thermometer in a mountainous area in Nevada, USA, under different weather conditions in December 1994. The data were validated against the measurements of road surface sensors. After that, a step-wise regression technique is employed to find out possible statistic relationships between RST and altitude at different surveying routes. It was found that the relationships exhibited different characteristics in different climate domains and under different weather types. In most cases, the relationships were non-linear. In order to obtain more information about the cause of the residuals and the variation, the error of regression fitting is related to near-ground meteorological parameters (air temperature, dew point and wind, etc.). This study proved that Thermal Mapping is a reliable and effective method to display spatial variation of road surface temperature.

Analysis of observational data of convective storms in Northern England suggests that the particular combination of effects such as sea breezes, elevated terrain and the presence of large cities has an influence on the initiation and development of convective storms. To study the importance of these effects for the development of convection, a cloud physics model has been initialised with the topography and surface characteristics of Northern England. The model enabled inclusion of three principal influences: sea breezes, topography and urban heat islands. The results suggested that the presence of the Pennines, a north-south orientated ridge, could influence the initiation of convection due to its long sun-facing slopes, and to a lesser degree forced lifting along the slopes. Inclusion of urban heat island effects focused convection downwind of the principal urban areas.

The application of kites as a platform for meteorological measurement within the boundary layer is examined. Kites are shown to fulfil a useful role within this research area, particularly when a highly mobile, lightweight and inexpensive instrumental platform is required. They are ideal for use at remote sites, or sites where terrain limits access for more conventional profiling equipment. The development of a reliable, tethered radiosonde atmospheric profiling system (TRAPS) is described, comparing the relative performance of two different sizes of two different types of kite. Basic kite aerodynamics are explained as well as a number of practical problems which have to be overcome or accommodated. Appropriate kite selection for given wind conditions and experimental requirements is suggested, providing an operational windspeed of between 2 and 14 m s-1. Finally, experimental results from three diverse remote sites illustrate practical applications of the profiling system, investigating firstly the structure of surface inversions over an ice shelf in the Antarctica, secondly flow over hills in Cumbria and thirdly convective boundary-layer structure on the Isle of Arran, Scotland.

A whole-farm-level decision model is used to examine the impact of the type of decisions producers make on the value of seasonal climate forecasts. Results suggest that precipitation forecasts directed towards crop mix and applied nitrogen level decisions would have the largest economic value. Further, the results show that the economic value of climate forecasts cannot be obtained by examining only a small set of decision types. Rather, all decision types must be modelled to value seasonal precipitation forecasts correctly. This occurs because in response to seasonal climate forecasts changes in one type of decision may override the need to change other decision types. Finally, forecasts of precipitation during the crop tasselling and grain filling stages may be more valuable than precipitation forecasts for earlier crop growth periods.

A workstation-based NWP scheme is described which allows forecasters to reposition and change in intensity features such as fronts and depressions, and thus alter model fields in a realistic way. The technique is based on distortion of either geopotential height or potential vorticity (PV). In the latter case, the PV is calculated from geopotential distribution, distorted, then inverted to yield a modified, yet consistent and dynamically balanced, set of grid-point data.

Meteorology at Reading

The Department of Meteorology at the University of Reading has recently moved into a new building, which was opened by the Chancellor, Lord Carrington, on April 14th, 1997. The building allows the Department, the NERC Centre for Global Atmospheric Modelling, and the Meteorological Office/University Joint Centre for Mesoscale Meteorology to come together in the same building for the first time.