http://hdl.handle.net/2173/31803 Tue, 21 May 2013 17:44:43 GMT 2013-05-21T17:44:43Z http://hdl.handle.net/2173/111566 Title: Modelling atmospheric mercury transport and deposition across Europe and the UK Authors: Lee, David S.; Nemitz, E; Fowler, D; Kingdon, R. D. Abstract: There are inadequate measurements of surface ambient concentrations of mercury species and their deposition rates for the UK deposition budget to be characterized. In order to estimate the overall mercury flux budget for the UK, a simple long-term 1D Lagrangian trajectory model was constructed that treats emissions (1998), atmospheric transformation and deposition across Europe. The model was used to simulate surface concentrations of mercury and deposition across Europe at a resolution of 50 km×50 km and across the UK at 20 km×20 km. The model appeared to perform adequately when compared with the few available measurements, reproducing mean concentrations of elemental gaseous mercury at particular locations and the magnitude of regional gradients. The model showed that 68% of the UK's mercury emissions are exported and 32% deposited within the UK. Of deposition to the UK, 25% originates from the Northern Hemisphere/global background, 41% from UK sources and 33% from other European countries. The total mercury deposition to the UK is in good agreement with other modelling, 9.9 tonne yr−1 cf. 9.0 tonne yr−1, for 1998. However, the attribution differs greatly from the results of other coarser-scale modelling, which allocates 55% of the deposition to the UK from UK sources, 4% from other European countries and 60% from the global background atmosphere. The model was found to be sensitive to the speciation of emissions and the dry deposition velocity of elemental gaseous mercury. The uncertainties and deficiencies are discussed in terms of model parameterization and input data, and measurement data with which models can be validated. There is an urgent requirement for measurements of removal terms, concentrations, and deposition with which models can be parameterized and validated. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Atmospheric Environment, published by and copyright Pergamon. Thu, 01 Nov 2001 00:00:00 GMT http://hdl.handle.net/2173/111566 2001-11-01T00:00:00Z http://hdl.handle.net/2173/111565 Title: Aviation radiative forcing in 2000: an update on IPCC (1999) Authors: Sausen, Robert; Isaksen, Ivar; Grewe, Volker; Hauglustaine, Didier; Lee, David S.; Myhre, Gunnar; Köhler, Marcus O.; Pitari, Giovanni; Schumann, Ulrich; Stordal, Frode; Zerefos, Christos Abstract: New estimates of the various contributions to the radiative forcing (RF) from aviation are presented, mainly based on results from the TRADEOFF project that update those of the Intergovernmental Panel on Climate Change (IPCC, 1999). The new estimate of the total RF from aviation for 2000 is approximately the same as that of the IPCC’s estimate for 1992. This is mainly a consequence of the strongly reduced RF from contrails, which compensates the increase due to increased traffic from 1992 to 2000. The RF from other aviation induced cirrus clouds might be as large as the present estimate of the total RF (without cirrus). However, our present knowledge on these aircraft-induced cirrus clouds is too poor to provide a reliable estimate of the associated RF. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Meteorologische Zeitschrift, published by and copyright Gebrueder Borntraeger Verlagsbuchhandlung. Mon, 01 Aug 2005 00:00:00 GMT http://hdl.handle.net/2173/111565 2005-08-01T00:00:00Z http://hdl.handle.net/2173/111564 Title: Is there a trend in cirrus cloud cover due to aircraft traffic? Authors: Lee, David S.; Stordal, Frode; Myhre, Gunnar; Stordal, E. J.; Rossow, W. B.; Arlander, D. W.; Svendby, T. Abstract: Trends in cirrus cloud cover have been estimated based on 16 years of data from ISCCP (International Satellite Cloud Climatology Project). The results have been spatially correlated with aircraft density data to determine the changes in cirrus cloud cover due to aircraft traffic. The correlations are only moderate, as many other factors have also contributed to changes in cirrus. Still we regard the results to be indicative of an impact of aircraft on cirrus amount. The main emphasis of our study is on the area covered by the METEOSAT satellite to avoid trends in the ISCCP data resulting from changing satellite viewing geometry. In Europe, which is within the METEOSAT region, we find indications of a trend of about 1–2% cloud cover per decade due to aircraft, in reasonable agreement with previous studies. The positive trend in cirrus in areas of high aircraft traffic contrasts with a general negative trend in cirrus. Extrapolation in time to cover the entire period of aircraft operations and in space to cover the global scale yields a mean estimate of 0.03Wm−2 (lower limit 0.01, upper limit 0.08Wm−2) for the radiative forcing due to aircraft induced cirrus. The mean is close to the value given by IPCC (1999) as an upper limit. Description: Full-text of this article is not available in this e-prints service. This article was originally published [following peer-review] in Atmospheric Chemistry and Physics, published by and copyright Copernicus. Mon, 01 Aug 2005 00:00:00 GMT http://hdl.handle.net/2173/111564 2005-08-01T00:00:00Z http://hdl.handle.net/2173/108924 Title: Glacier volume response time and its links to climate and topography based on a conceptual model of glacier hypsometry Authors: Raper, Sarah C. B.; Braithwaite, Roger J. Abstract: Glacier volume response time is a measure of the time taken for a glacier to adjust its geometry to a climate change. It has been previously proposed that the volume response time is given approximately by the ratio of glacier thickness to ablation at the glacier terminus. We propose a new conceptual model of glacier hypsometry (area-altitude relation) and derive the volume response time where climatic and topographic parameters are separated. The former is expressed by mass balance gradients which we derive from glacier-climate modelling and the latter are quantified with data from the World Glacier Inventory. Aside from the well-known scaling relation between glacier volume and area, we establish a new scaling relation between glacier altitude range and area, and evaluate it for seven regions. The presence of this scaling parameter in our response time formula accounts for the mass balance elevation feedback and leads to longer response times than given by the simple ratio of glacier thickness to ablation at the terminus. Volume response times range from decades to thousands of years for glaciers in maritime (wet-warm) and continental (dry-cold) climates respectively. The combined effect of volume-area and altitude-area scaling relations is such that volume response time can increase with glacier area (Axel Heiberg Island and Svalbard), hardly change (Northern Scandinavia, Southern Norway and the Alps) or even get smaller (The Caucasus and New Zealand). Description: Full text of this article is available at http://www.the-cryosphere.net/3/183/2009/tc-3-183-2009.html Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2173/108924 2009-01-01T00:00:00Z