Identification of the distinctive circulation patterns of storminess on the Atlantic margin of Europe forms the main objective of this study; dealing with storm frequency, intensity and tracking. The climatology of the extratropical cyclones that affect this region has been examined for the period 1940–1998. Coastal meteorological data from Ireland to Spain have been linked to the cyclone history for the North Atlantic in the analysis of storm records for European coasts. The study examines the evolution in the occurrence of storms since the 1940s and also their relationship with the North Atlantic Oscillation (NAO). Results indicate a seasonal shift in the wind climate, with regionally more severe winters and calmer summers established. This pattern appears to be linked to a northward displacement in the main North Atlantic cyclone track.
An experiment with the ECHAM4 A-GCM at high resolution (T106) has also been used to model the effect of a greenhouse gases induced warming climate on the climatology of coastal storms in the region. The experiment consists of (1), a 30-year control time-slice representing present-day equivalent CO2 concentrations and (2), a 30-year perturbed period corresponding to a time when the radiative forcing has doubled in terms of equivalent CO2 concentrations. The boundary conditions have been obtained from an atmosphere-ocean coupled OA-GCM simulation at low horizontal resolution. An algorithm was developed to allow the identification of individual cyclone movements in selected coastal zones. For most of the northern part of the study region, covering Ireland and Scotland, results describe the establishment by ca. 2060 of a tendency for fewer but more intense storms.
The impacts of these changes in storminess for the vulnerability of European Atlantic coasts are considered. For low-lying, exposed and ‘soft’ sedimentary coasts, as in Ireland, these changes in storminess are likely to result in significant localised increases in coastal erosion. 相似文献
The effect of climate change on maize production in the semi-humid and semi-arid, agro-climatic zones III-IV of Kenya was evaluated using two General Circulation Models (GCMs): the Canadian Climate Center Model (CCCM) and the Geophysical Fluid Dynamics Laboratory (GFDL), as well as the CERES-Maize model. Long-term climate data was obtained from three meteorological stations situated in eastern, central and western regions of Kenya, while maize data was obtained from six sites within the regions. The climate scenarios were projected to the year 2030. Temperature increases of 2·29 and 2·89°C are predicted by the CCCM and GFDL, respectively. Rainfall levels are predicted to remain unchanged, but there are thought to be shifts in distribution. It is predicted that the short-rains season (October–January) will experience some increased rainfall, while the long-rains season (April–July) will show a decrease. Maize yields are predicted to decrease in zone III areas, while an increase is predicted in zone IV areas. However, the predicted changes in yields are low since they all fall below 500 kg ha−1, except the Homa Bay site. Thus, to counter the adverse effects of climate change on maize production, it may be necessary to use early maturing cultivars, practice early planting, and in eastern Kenya, shift to growing maize during the short-rains season. 相似文献
It is now widely recognised that the most significant impacts of global warming are likely to be experienced through changes in the frequency of extreme events, including flooding. This paper reviews physical and empirical arguments which suggest that global warming may result in a more intense hydrological cycle, with an associated increase in the frequency and/or magnitude of heavy precipitation. Results derived from enhanced-greenhouse experiments using global climate models (GCMs) are shown to be consistent with these physical and empirical arguments. Detailed analysis of output from three GCMs indicates the possibility of substantial increases in the frequency and magnitude of extreme daily precipitation, with amplification of the effect as the return period increases. Moreover, return period analyses for locations in Australia, Europe, India, China and the USA indicate that the results are global in scope. Subsequent discussion of the limitations of GCMs for this sort of analysis highlights the need for caution when interpreting the precipitation results presented here. However, the consistency between physically-based expectations, empirical observations, and GCM results is considered sufficient for the GCM results to be taken seriously, at least in a qualitative sense, especially considering that the alternative seems to be reliance by planners on the fundamentally flawed concept of a stationary climate. 相似文献
Attention has been directed towards both the impacts of future climate change on environmental systems and dunefield activity in the past, but there has been relatively little consideration of potential dune mobility in a future and possibly warmer world. This paper considers the use and limitations of four Global Circulation Models (GCMs) (Hadcm3, Hadcm2, CSIRO-mk2b and CGCM1), in combination with simple dune mobility indices to predict the activity of the Kalahari dunefield. It is clear that uncertainties surround GCM resolution and accuracy, mobility index robustness for the calculation of intra-annual dune mobility and data collection for mobility index calibration. Macro-scale studies that look at large areas of the world over long time scales are well suited to GCM and mobility index use, but dune mobility can be variable within a dunefield, and it is the extreme sand transporting events, occurring at high temporal resolutions, that are the most important for short term studies. To investigate intra-annual changes in dune mobility over a specific dunefield techniques such as downscaling, weather generators and probability curve fitting can help provide climate predictions for smaller areas over shorter time frames. However, these methods introduce uncertainty of their own, and they often rely on the accuracy of original GCM predictions or the climate parameter relationships observed at present. Analysis of intra-annual changes also requires mobility indices that can model monthly mobility patterns well, although existing indices have only been used for calculating annual dune mobility potential. When they are used for intra-annual predictions, the lack of lag response between precipitation decreases and the assumed vegetation dieback leads to an exaggerated amplitude pattern of dune mobility throughout the year. Calibration of dune mobility indices to dune mobility observed on the ground is therefore important but is hampered by a lack of observed measurements for individual months. Solutions are available to overcome some of the outlined problems, but they can provide their own set of uncertainties, which combine to further reduce the confidence given to future dune mobility predictions. 相似文献
Due to the close relationship between regional climate anomalies and social-economy andsociety development,climatologists worldwide paid great attention to the regional climateanomalies over a long period of time and the corresponding investigation of regional climatemodeling has made great progresses.Since 1990 the regional climate simulations have made a moresubstantial achievement.This paper will focus on the reliability and uncertainties of regionalclimate modeling by global climate models,the advances on regional climate modeling in the worldand the outlook of regional climate modeling. 相似文献