Roger Timmis

Long-term variations in orographic rainfall: analysis and implications for upland catchments

Abstract Climatic changes could alter the frequency and magnitude of rainfall events and the distribution of rainfall with altitude, with important consequences for management of aquatic ecosystems, water resources and flood risk. This study investigates changes in observed rainfall amounts across a range of altitudes in the Lake District region, northwest England, and spatial and temporal changes to the orographic “rainshadow” effect. Between the 1970s and 1990s there have been marked changes to the seasonality of precipitation, such that winters have become wetter, and increasingly dominated by heavy precipitation events. The intensity of these events has increased most markedly at higherelevation sites. Such changes could hinder recovery of sensitive upland sites from acidification and increase the risk of downstream flooding. An inter-decadal weakening of the regions rainshadow suggests a greater proportion of winter precipitation crosses the high-elevation Lake District dome. This is linked to changes in the frequency and character of wet weather patterns.

The atmosphere in England and Wales: an environmental management review

Abstract Air pollution in England and Wales is reviewed to identify priorities for management and research. The main human drivers of emissions are the production and consumption of energy and materials, disposal of waste, transport and land use. Pollutants are assigned to seven types: (i) nuisance (e.g. odour, noise), (ii) toxic, (iii) acidifying/eutrophying, (iv) photochemical oxidant precursors, (v) radionuclides, (vi) stratospheric ozone depleting substances and (vii) greenhouse gases. Dominant trends in activity and emissions are highlighted. New technologies and fuels are partially decoupling emissions from activity in power generation, industry and transport, but the gains are being offset by growth in demand and output in all major sectors. The evidence for impacts on human health, the atmosphere and other environmental systems is discussed. Priorities for management are climate change, ground-level ozone, acidification and eutrophication by nitrogen, urban air quality and nuisance pollution. Management responses require greater foresight, technological improvements and new instruments to control polluting activities. More scientific information is needed on the impacts on human health, quality of life and ecosystems, and on the links between different types of pollution. The policy challenges include generating energy sustainably, reducing transport impacts, devising effective economic instruments, improving societal awareness and contributing to cleaner global development.

A new flow–through directional passive air sampler: design, performance and laboratory testing for monitoring ambient nitrogen dioxide

Abstract A new type of passive air sampler for monitoring trace air pollutants in ambient air is introduced. It has a rotatable upper part that can turn into the prevailing wind direction. Pollutants from different directions are transported through a specially–shaped air channel in the upper part and retained on different parts of a sample carousel in the fixed lower part. Pollution sources are trackable by examining the pollutant distribution in the carousel. The design of this new directional passive air sampler (DPAS) is described. Wind tunnel tests show the DPAS responding to wind direction changes at wind velocities as low as 0.9 m s-1. Measurements of wind velocities inside and outside the DPAS revealed good correlation for potential quantitative results. The DPAS was tested at a wind velocity of 2.0 m s-1 using stainless steel meshes impregnated with triethanolamine (TEA) for nitrogen dioxide (NO2). The source direction was clearly identifiable. Further tests and field trials are advocated.

Using GIS to Investigate Spatial and Temporal Variations in Upland Rainfall

A method is presented for conditional analysis of spatial and temporal (1961–2007) variations in rainfall under different synoptic situations and different geographic sub-regions, using Cumbria in NW England as a study area. A daily synoptic typing scheme, the Lamb Weather Catalogue, was applied to identify rainfall under three different weather types: south-westerly (SW), westerly (W) and cyclonic (C). Topographic descriptors developed using GIS were used to classify rain gauges into six geographic sub-regions: coastal, windward-lowland, windward-upland, leeward-upland, leeward-lowland, secondary upland. Examining temporal rainfall trends associated with different weather types, in different geographic sub-regions, reveals useful information on changes in rainfall processes. The total rainfall under SW and W weather types is increasing, particularly in upland regions. The increase in SW rainfall is driven by more frequent wet-days, whereas the increase in W rainfall is driven by increases in both wet-day frequency and yield per wet-day. The rainfall under C weather types is decreasing. Combining GIS and synoptic climatology gives insights into rainfall processes under a changing climate. The conditional analysis method can be applied at both local and regional scales, and its success is largely due to the ability of GIS to integrate, visualise, and efficiently model spatial data.