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Modelling the variability of midlatitude storm activity on decadal to century time scales 总被引：1，自引：0，他引：1
Irene Fischer-Bruns H. von Storch J. F. González-Rouco E. Zorita 《Climate Dynamics》2005,25(5):461-476
The output of several multi-century simulations with a coupled ocean–atmosphere general circulation model is examined with
respect to the variability of global storm activity in winter on time scales of decades and longer. The frequency of maximum
wind speed events within a grid box, using the lower limits on the Beaufort wind speed scale of 8 and 10 Bft as thresholds,
is taken as the characteristic parameter. Two historical climate runs with time-dependent forcing of the last five centuries,
one control simulation, and three climate change experiments are considered. The storm frequency shows no trend until recently.
Global maps for the industrially influenced period hardly differ from pre-industrial maps, even though significant temperature
anomalies temporarily emerge in the historical runs. Two indicators describing the frequency and the regional shift of storm
activity are determined. In historical times they are decoupled from temperature. Variations in solar and volcanic forcing
in the historical simulations as well as in greenhouse gas concentrations for the industrially influenced period are not related
to variations in storm activity. Also, anomalous temperature regimes like the Late Maunder Minimum are not associated with
systematic storm conditions. In the climate change experiments, a poleward shift of storm activity is found in all three storm
track regions. Over the North Atlantic and Southern Ocean, storm activity increases, while it decreases over the Pacific Ocean.
In contrast to the historical runs, and with the exception of the North Pacific storm frequency index, the storm indices parallel
the development of temperature, exceeding the 2 σ-range of pre-industrial variations in the early twenty-first century. 相似文献
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ＩＮＴＲＯＤＵＣＴＩＯＮＡｎｔａｒｃｔｉｃｋｒｉｌｌ(ＥｕｐｈａｕｓｉａｓｕｐｅｒｂａＤａｎａ)ｉｓａｋｅｙｏｒｇａｎｉｓｍｏｆｔｈｅＡｎｔａｒｃｔｉｃｍａｒｉｎｅｅｃｏｓｙｓｔｅｍａｎｄａｐｏｔｅｎｔｉａｌｆｉｓｈｅｒｙｒｅｓｏｕｒｃｅ.Ｉｔｈａｓｂｅｅｎｔｈｅｓｕｂｊｅｃｔｏｆｍｕｃｈｒｅｓｅａｒｃｈ.Ｄｅｓｐｉｔｅｔｈｅｌｏｎｇｈｉｓｔｏｒｙｏｆｒｅｓｅａｒｃｈｄａｔｉｎｇｂａｃｋｔｏｔｈｅ1930’ｓ,ｔｈｅｒｅａｒｅｓｔｉｌｌｑｕｅｓｔｉｏｎｓａｂｏｕｔｉｔｓｐｏｐｕｌａｔｉｏｎｓｔｒｕｃｔｕ… 相似文献
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ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｏｎｓｏｏｎｈａｓａｃｉｒｃｕｌａｔｉｏｎｆｅａｔｕｒｅｔｈａｔｉｓｐｌａｎｅｔａｒｙｉｎｓｃａｌｅａｎｄａｎｉｄｅｎｔｉｆｉａｂｌｅｓｉｇｎａｌｒｅｇａｒｄｉｎｇｉｔｓｓｕｂｓｅｑｕｅｎｔｉｎｔｅｎｓｉｔｙｓｏｍｅｎｉｎｅｍｏｎｔｈｓｐｒｉｏｒｔｏｔｈｅａｃｔｉｖｅｓｔａｇｅｏｆｔｈｅｓｕｍｍｅｒｍｏｎｓｏｏｎ(ＷｅｂｓｔｅｒａｎｄＹａｎｇ,1992).Ｆｕｒｔｈｅｒｍｏｒｅ,ｔｈｅｍａｇｎｉｔｕｄｅｏｆｔｈｅｍｏｎｓｏｏｎｖａｒｉａｂｉｌｉｔｙｉｓｓｕｂｓｔａｎｔｉａ… 相似文献
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Sonia Jerez Juan Pedro Montavez Pedro Jimenez-Guerrero Juan Jose Gomez-Navarro Raquel Lorente-Plazas Eduardo Zorita 《Climate Dynamics》2013,40(11-12):3023-3046
This work assesses the influence of the model physics in present-day regional climate simulations. It is based on a multi-phyiscs ensemble of 30-year long MM5 hindcasted simulations performed over a complex and climatically heterogeneous domain as the Iberian Peninsula. The ensemble consists of eight members that results from combining different parametrization schemes for modeling the Planetary Boundary Layer, the cumulus and the microphysics processes. The analysis is made at the seasonal time scale and focuses on mean values and interannual variability of temperature and precipitation. The objectives are (1) to evaluate and characterize differences among the simulations attributable to changes in the physical options of the regional model, and (2) to identify the most suitable parametrization schemes and understand the underlying mechanisms causing that some schemes perform better than others. The results confirm the paramount importance of the model physics, showing that the spread among the various simulations is of comparable magnitude to the spread obtained in similar multi-model ensembles. This suggests that most of the spread obtained in multi-model ensembles could be attributable to the different physical configurations employed in the various models. Second, we obtain that no single ensemble member outperforms the others in every situation. Nevertheless, some particular schemes display a better performance. On the one hand, the non-local MRF PBL scheme reduces the cold bias of the simulations throughout the year compared to the local Eta model. The reason is that the former simulates deeper mixing layers. On the other hand, the Grell parametrization scheme for cumulus produces smaller amount of precipitation in the summer season compared to the more complex Kain-Fritsch scheme by reducing the overestimation in the simulated frequency of the convective precipitation events. Consequently, the interannual variability of precipitation (temperature) diminishes (increases), which implies a better agreement with the observations in both cases. Although these features improve in general the accuracy of the simulations, controversial nuances are also highlighted. 相似文献
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C. Matulla X. Zhang X. L. Wang J. Wang E. Zorita S. Wagner H. von Storch 《Climate Dynamics》2008,30(2-3):133-144
This study examines the performance of the analog method for downscaling daily precipitation. The evaluation is performed
for (1) a number of similarity measures for searching analogs, (2) various ways to include the past atmospheric evolution,
and (3) different truncations in EOF space. It is carried out for two regions with complex topographic structures, and with
distinct climatic characteristics, namely, California’s Central Valley (together with the Sierra Nevada) and the European
Alps. NCEP/NCAR reanalysis data are used to represent the large scale state of the atmosphere over the regions. The assessment
is based on simulating daily precipitation for 103 stations for the month of January, for the years 1950–2004 in the California
region, and for 70 stations in the European Alps (January 1948–2004). Generally, simulated precipitation is in better agreement
with observations in the California region than in the European Alps. Similarity measures such as the Euclidean norm, the
sum of absolute differences and the angle between two atmospheric states perform better than measures which introduce additional
weightings to principal components (e.g., the Mahalanobis distance). The best choice seems dependent upon the target variable.
Lengths of wet spells, for instance, are best simulated by using the angular similarity measure. Overall, the Euclidean norm
performs satisfactorily in most cases and hence is a reasonable first choice, whereas the use of Mahalanobis distance is less
advisable. The performance of the analog method improves by including large-scale information for bygone days, particularly,
for the simulation of wet and dry spells. Optimal performance is obtained when about 85–90% of the total predictor variability
is retained. 相似文献
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Hans von Storch Eduardo Zorita Fidel González-Rouco 《International Journal of Earth Sciences》2009,98(1):67-82
The performance of statistical climate reconstruction methods in the pre-instrumental period is uncertain, as they are calibrated
in a short instrumental period but applied to much longer reconstructions time spans. Here, the virtual reality created by
a climate simulation of the past millennium with the model ECHO-G is used as a test bed of three methods to reconstruct the
annual Northern Hemisphere temperature. The methods are Composite plus Scaling, the inverse regression method of Mann et al.
(Nature 392:779–787, 1998) and a direct principal-components regression method. The testing methodology is based on the construction of pseudo-proxies
derived from the climate model output, the application of each of these methods to pseudo-proxy timeseries, and the comparison
of their result with the simulated mean temperature. Different structures of the noise have been used to construct pseudo-proxies,
ranging from the simulated grid-point precipitation. Also, one sparse and one denser pseudo-proxy network, co-located with
two real networks, have been considered. All three methods underestimate the simulated variations of the Northern Hemisphere
temperature, but the Composite plus Scaling method clearly displays a better performance and is robust against the different
noise models and network size. The most relevant factor determining the skill of the reconstruction appears to be the network
size, whereas the different noise models tend to yield similar results. 相似文献
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Eduardo Zorita Anders Moberg Lotta Leijonhufvud Rob Wilson Rudolf Brázdil Petr Dobrovolný Jürg Luterbacher Reinhard Böhm Christian Pfister Dirk Riemann Rüdiger Glaser Johan Söderberg Fidel González-Rouco 《Climatic change》2010,101(1-2):143-168
Two European temperature reconstructions for the past half-millennium, January-to-April air temperature for Stockholm (Sweden) and seasonal temperature for a Central European region, both derived from the analysis of documentary sources and long instrumental records, are compared with the output of climate simulations with the model ECHO-G. The analysis is complemented by comparisons with the long (early)-instrumental record of Central England Temperature (CET). Both approaches to study past climates (simulations and reconstructions) are burdened with uncertainties. The main objective of this comparative analysis is to identify robust features and weaknesses in each method which may help to improve models and reconstruction methods. The results indicate a general agreement between simulations obtained with temporally changing external forcings and the reconstructed Stockholm and CET records for the multi-centennial temperature trend over the recent centuries, which is not reproduced in a control simulation. This trend is likely due to the long-term change in external forcing. Additionally, the Stockholm reconstruction and the CET record also show a clear multi-decadal warm episode peaking around AD 1730, which is absent in the simulations. Neither the reconstruction uncertainties nor the model internal climate variability can easily explain this difference. Regarding the interannual variability, the Stockholm series displays, in some periods, higher amplitudes than the simulations but these differences are within the statistical uncertainty and further decrease if output from a regional model driven by the global model is used. The long-term trend of the CET series agrees less well with the simulations. The reconstructed temperature displays, for all seasons, a smaller difference between the present climate and past centuries than is seen in the simulations. Possible reasons for these differences may be related to a limitation of the traditional ‘indexing’ technique for converting documentary evidence to temperature values to capture long-term climate changes, because the documents often reflect temperatures relative to the contemporary authors’ own perception of what constituted ‘normal’ conditions. By contrast, the amplitude of the simulated and reconstructed inter-annual variability agrees rather well. 相似文献
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Gómez-Navarro Juan José Werner Johannes Wagner Sebastian Luterbacher Jürg Zorita Eduardo 《Climate Dynamics》2015,45(5-6):1395-1413
Climate Dynamics - This study aims at assessing the skill of several climate field reconstruction techniques (CFR) to reconstruct past precipitation over continental Europe and the Mediterranean at... 相似文献