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Atlantic Sea-surface Temperature (atlantic + sea-surface_temperature)
Selected AbstractsModeling tropical cyclone intensity with quantile regressionINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2009Thomas H. Jagger Abstract Wind speeds from tropical cyclones (TCs) occurring near the USA are modeled with climate variables (covariates) using quantile regression. The influences of Atlantic sea-surface temperature (SST), the Pacific El Niño, and the North Atlantic oscillation (NAO) on near-coastal TC intensity are in the direction anticipated from previous studies using Poisson regression on cyclone counts and are, in general, strongest for higher intensity quantiles. The influence of solar activity, a new covariate, peaks near the median intensity level, but the relationship switches sign for the highest quantiles. An advantage of the quantile regression approach over a traditional parametric extreme value model is that it allows easier interpretation of model coefficients (parameters) with respect to changes to the covariates since coefficients vary as a function of quantile. It is proven mathematically that parameters of the Generalized Pareto Distribution (GPD) for extreme events can be used to estimate regression coefficients for the extreme quantiles. The mathematical relationship is demonstrated empirically using the subset of TC intensities exceeding 96 kt (49 m/s). Copyright © 2008 Royal Meteorological Society [source] Large-scale effect of aerosols on precipitation in the West African Monsoon regionTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 640 2009J. Huang Abstract We used multi-year satellite observations to study aerosol effects on the large-scale variability in precipitation of the West African Monsoon (WAM) region, which is often impacted by high concentrations of desert dust and biomass-burning smoke. We find a statistically significant precipitation reduction associated with high aerosol concentration near the coast of the Gulf of Guinea from late boreal autumn to winter. The largest aerosol-related precipitation reduction (,1.5 mm d,1) is about 50% of the climatological mean precipitation in the region and occurs mainly at rain rates in the range of 2,17 mm d,1 off the northern coast of the Gulf of Guinea. This reduction cannot be linearly attributed to known climate and weather factors such as El Niño,Southern Oscillation, North Atlantic Oscillation, Atlantic sea-surface temperature, or water vapour. The fractional precipitation variance related to aerosol is about 13%, a value comparable to those related to the known climate factors. Based on the spatial pattern and seasonality of the observed precipitation reduction and its dependence on the rain rate, the observed negative correlation cannot be readily attributed to precipitation effects on aerosol by wet deposition or to rain and cloud contamination of satellite aerosol retrievals. We therefore suggest that our results can be taken as observational evidence of aerosol effects on precipitation. The aerosol associated with the observed precipitation reduction can be traced back to various African sources where large quantities of desert dust and biomass-burning smoke are emitted during much of the year. Given that the emissions of dust and smoke have varied considerably over the past several decades, in part attributable to human activities, our observed rainfall reduction may reflect an anthropogenic impact to some degree. Copyright © 2009 Royal Meteorological Society [source] Ensemble simulations of the cold European winter of 2005-2006THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 636 2008A. A. Scaife Abstract There is only limited understanding of the processes driving year-to-year variability in European winter climate and the skill of seasonal forecasts for Europe in winter is generally low. The winter of 2005-2006 is a useful case-study because it was the coldest winter in large parts of western Europe for over a decade, and the coldest in central England since 1995-1996. Here, we present results of experiments with a range of general circulation models to investigate the importance of both the Atlantic Ocean and stratospheric circulation in producing the unusually cold winter of 2005-2006. We use models with different combinations of horizontal and stratospheric vertical resolution, allowing the sensitivity of the response to model formulation to be tested. The response to Atlantic sea-surface temperature (SST) anomalies is improved in a more recent model with higher horizontal resolution. The results show that both Atlantic SSTs and the January 2006 sudden stratospheric warming are likely to have contributed to the cold 2005-2006 European winter. © Crown Copyright 2008. Reproduced with the permission of HMSO. Published by John Wiley & Sons Ltd. [source] North Atlantic forcing of climate and its uncertainty from a multi-model experimentTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 601 2004M. J. Rodwell Abstract To understand recent climate change in the North Atlantic region and to produce better climate forecasts with uncertainty estimates it is important to determine the atmospheric ,response' to Atlantic sea-surface temperature (SST) forcing. There have been conflicting results regarding the strength, character and tropical-versus-extratropical origin of this response. For model-based studies, this may indicate differing sensitivities to Atlantic SST, but the comparison is complicated by changes in experimental design. Here, a highly controlled experiment with five atmospheric models is undertaken. The influence of realistic (if reasonably strong) and optimally chosen North Atlantic (equator to 70°N) SST anomalies is isolated. Unexpected global agreement between the models is found (e.g. the North Atlantic Oscillation (NAO), Eurasian temperatures, rainfall over the Americas and Africa, and the Asian monsoon). The extratropical North Atlantic region response appears to be associated with remote Caribbean and tropical Atlantic SST anomalies, and with local forcing. Some features such as the European winter-temperature response would be stronger than atmospheric ,noise' if the prescribed SST anomalies persisted for just two years. More generally, Atlantic air,sea interaction appears to be important for climate variability on the 30-year timescale and, thus, to be important in the climate-change context. The multi-model mean response patterns are in reasonable agreement with observational estimates, although the model response magnitudes may be too weak. The similarity between their responses helps to reconcile models. Inter-model differences do still exist and these are discussed and quantified. © Crown copyright, 2004. [source] The Gulf Stream and Atlantic sea-surface temperatures in AD1790,1825INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2010G. van der Schrier Abstract We present gridded sea-surface temperatures (SSTs) for the Atlantic basin (45°S,60°N) as averages over the period AD1790,1825, based on early-instrumental SST data. The original measurements were compiled by Major James Rennell and made by numerous British naval vessels on behalf of the British Admiralty. We describe the digitization of this dataset and the reconstruction of spatially coherent, averaged conditions for the boreal cold (November-March) and warm (May,September) season using a reduced space optimal interpolation (RSOI) technique, in which the data is projected on a limited number of empirical orthogonal functions. This approach is validated on modern data that are sampled in a similar way as the early-instrumental data. The reconstruction for the November,March period shows a large area with anomalously high temperatures from the point where the Gulf Stream separates from the coast until ca. 20°W. A tongue of anomalous cool water is found at the eastern side of the North Atlantic basin, along the coast of Europe and northern Africa. In the northeastern South Atlantic, anomalously high temperatures are found, while temperatures in the southwestern South Atlantic are anomalously cool. For the March,September season, anomalous temperatures in the South Atlantic are similar, but stronger, compared with those in the boreal cold season. Over the North Atlantic, there is not much similarity between the current SST reconstructions and those published in the late 1950s. Copyright © 2009 Royal Meteorological Society [source] Mediated and direct effects of the North Atlantic Ocean on winter temperatures in northwest EuropeINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2003Martina M. Junge Abstract This study has used a multiple regression model to quantify the importance of wintertime mean North Atlantic sea-surface temperatures (SSTs) for explaining (simultaneous) variations in wintertime mean temperatures in northwestern Europe. Although wintertime temperature variations are primarily determined by atmospheric flow patterns, it has been speculated that North Atlantic SSTs might also provide some additional information. To test this hypothesis, we have attempted to explain 1900,93 variations in wintertime mean central England temperature (CET) by using multiple regression with contemporaneous winter mean North Atlantic sea-level pressures (SLPs) and SSTs as explanatory variables. With no SST information, the leading SLP patterns (including the North Atlantic oscillation) explain 63% of the total variance in winter mean CET; however, SSTs alone are capable of explaining only 16% of the variance in winter mean CET. Much of the SST effect is ,indirect' in that it supplies no more significant information than already contained in the mean SLP; e.g. both SLP and SST together can only explain 68% of the variance. However, there is a small (5% variance) direct effect due to SST that is not mediated by mean SLP, which has a spatial pattern resembling the Newfoundland SST pattern identified by Ratcliffe and Murray (1970. Quarterly Journal of the Royal Meteorological Society 96: 226,246). In predictive mode, however, using explanatory variables from preceding seasons, SSTs contain more information than SLP factors. On longer time scales, the variance explained by contemporaneous SST increases, but the SLP explanatory variables still provide a better model than the SST variables. Copyright © 2003 Royal Meteorological Society [source] | ||||||||||