The Mediterranean has been identified as one of the most responsive regions to climate change. It has been conjectured that one of the effects of a warmer climate could be to make the Mediterranean ...Sea prone to the formation of hurricanes. Already in the present climate regime, however, a few of the numerous low pressure systems that form in the area develop a dynamical evolution similar to the one of tropical cyclones. Even if their spatial extent is generally smaller and the life cycle shorter compared to tropical cyclones, such storms produce severe damage on the highly populated coastal areas surrounding the Mediterranean Sea. This study, based on the analysis of individual realistically simulated storms in homogeneous long-term and high-resolution data from multiple climate change scenarios, shows that the projected effect of climate change on Mediterranean tropical-like cyclones is decreased frequency and a tendency toward a moderate increase of intensity.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
long-term climatology of medicanes Cavicchia, Leone; von Storch, Hans; Gualdi, Silvio
Climate dynamics,
09/2014, Letnik:
43, Številka:
5-6
Journal Article
Recenzirano
Medicanes, intense and destructive mesoscale cyclones exhibiting several similarities with tropical hurricanes, are known to struck occasionally the Mediterranean Sea. Thanks to a high-resolution ...dynamical downscaling effort, we are able to study for the first time the long-term climatology of those rare storms in a systematic way. The distribution of medicanes frequency in space and time is discussed, and the environmental factors responsible for their formation are investigated. We find that medicanes develop in those areas of the Mediterranean region where intrusions of cold air in the upper troposphere can produce configurations of thermodynamical disequilibrium of the atmosphere similar to those associated with the formation of tropical cyclones.
Medicanes, strong mesoscale cyclones with tropical-like features, develop occasionally over the Mediterranean Sea. Due to the scarcity of observations over sea and the coarse resolution of the ...long-term reanalysis datasets, it is difficult to study systematically the multidecadal statistics of sub-synoptic medicanes. Our goal is to assess the long-term variability and trends of medicanes, obtaining a long-term climatology through dynamical downscaling of the NCEP/NCAR reanalysis data. In this paper, we examine the robustness of this method and investigate the value added for the study of medicanes. To do so, we performed several climate mode simulations with a high resolution regional atmospheric model (CCLM) for a number of test cases described in the literature. We find that the medicanes are formed in the simulations, with deeper pressures and stronger winds than in the driving global NCEP reanalysis. The tracks are adequately reproduced. We conclude that our methodology is suitable for constructing multi-decadal statistics and scenarios of current and possible future medicane activities.
This open access book serves as a reference for the key elements and their significance of Klaus Hasselmann's work on climate science and on ocean wave research, all based on a rigorous and deeply ...physical thinking. It summarizes the original articles (mostly from the 1970 and 1980s; some of which are hard to find nowadays) and brings them in a present-day context. From 1975 until 2000, he was (founding) Director of the Max Planck Institute of Meteorology, which he made to one of the world-leading academic institutions. He first made the issue of anthropogenic climate change accessible to analysis and prediction and later transformed climate science into a significant factor in forming public policy. The book is written by co-workers and colleagues of Klaus Hasselmann, who—many under his immediate supervision—joined him in this effort. With this background, they present the key achievements and assess the significance of these for the present state of knowledge and scientific practice.
Changes in precipitation characteristics directly affect society through their impacts on drought and floods, hydro-dams, and urban drainage systems. Global warming increases the water holding ...capacity of the atmosphere and thus the risk of heavy precipitation. Here, daily precipitation records from over 700 Chinese stations from1956 to 2005 are analyzed. The results show a significant shift from light to heavy precipitation over eastern China. An optimal fingerprinting analysis of simulations from 11 climate models driven by different combinations of historical anthropogenic (greenhouse gases, aerosols, land use, and ozone) and natural (volcanic and solar) forcings indicates that anthropogenic forcing on climate, including increases in greenhouse gases (GHGs), has had a detectable contribution to the observed shift toward heavy precipitation. Some evidence is found that anthropogenic aerosols (AAs) partially offset the effect of the GHG forcing, resulting in a weaker shift toward heavy precipitation in simulations that include the AA forcing than in simulations with only the GHG forcing. In addition to the thermodynamic mechanism, strengthened water vapor transport from the adjacent oceans and by midlatitude westerlies, resulting mainly from GHG-induced warming, also favors heavy precipitation over eastern China. Further GHG-induced warming is predicted to lead to an increasing shift toward heavy precipitation, leading to increased urban flooding and posing a significant challenge for mega-cities in China in the coming decades. Future reductions in AA emissions resulting from air pollution controls could exacerbate this tendency toward heavier precipitation.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
German Bight storm activity, 1897–2018 Krieger, Daniel; Krueger, Oliver; Feser, Frauke ...
International journal of climatology,
January 2021, 2021-01-00, 20210101, Letnik:
41, Številka:
S1
Journal Article
Recenzirano
Odprti dostop
This study investigates the evolution of German Bight (southeastern North Sea) storminess from 1897 to 2018 through analysing upper quantiles of geostrophic wind speeds, which act as a proxy for past ...storm activity. Here, geostrophic wind speeds are calculated from triplets of mean sea level pressure observations that form triangles over the German Bight. The data used in the manuscript are provided by the International Surface Pressure Databank and the national meteorological services of Denmark, Germany, and the Netherlands. The derivation of storm activity is achieved by enhancing the established triangle proxy method via combining and merging storminess time series from numerous partially overlapping triangles in an ensemble‐like manner. The utilized approach allows for the construction of robust, long‐term and subdaily German Bight storminess time series. Further, the method provides insights into the underlying uncertainty of the time series. The results show that storm activity over the German Bight is subject to multidecadal variability. The latest decades are characterized by an increase in activity from the 1960s to the 1990s, followed by a decline lasting into the 2000s and below‐average activity up until present. The results are backed through a comparison with reanalysis products from four datasets, which provide high‐resolution wind and pressure data starting in 1979 and offshore wind speed measurements taken from the FINO‐WIND project. This study also finds that German Bight storminess positively correlates with storminess in the NE Atlantic in general. In certain years, however, notably different levels of storm activity in the two regions can be found, which likely result from shifted large‐scale circulation patterns.
Storm activity from proxy reconstructions of geostrophic winds in the German Bight (North Sea) over the last century is subject to multi‐decadal variability without an apparent trend. The reconstructions are derived from 18 triangles of surface pressure readings covering the German Bight. Past storm activity can be characterized by three phases of above‐average levels (around the 1910s, 1950s, 1990s) and three phases of below‐average levels (around the 1930s, 1960s/1970s, and during recent years) in the examined period.
Climate impacts and adaptation research increasingly uses ensembles of regional and local climate change scenarios. To do so, the ensembles are examined to evaluate whether they describe a systematic ...difference between present states (and impacts) and envisaged future states—and such differences are often characterized as being
s
tatistically significant. This term “significance” is well defined by statistical terminology as the result of a test of a null hypothesis that is applied to samples of observations that are obtained with a defined sampling strategy. However such a statistical null hypothesis may not be a well-posed problem in the context of the evaluation of climate change scenarios. Therefore, the usage of terms such “statistically significant scenario” may be misunderstood in the general discourse about the certainty of projected climate change. We propose to employ instead a simple
descriptive approach
for characterizing the information in an ensemble of scenarios. Physical plausibility in the light of theoretical reasoning often adds robustness to the interpretation of climate change scenarios.
A 34 year (1979–2012) high‐resolution (7 km grid) atmospheric hindcast over the Bohai Sea and the Yellow Sea (BYS) has been performed using COSMO‐CLM (CCLM) forced by ERA‐Interim reanalysis data ...(ERA‐I). The accuracy of CCLM in surface wind reproduction and the added value of dynamical downscaling to ERA‐I have been investigated through comparisons with the QuikSCAT Level2B 12.5 km version 3 (L2B12v3) swath data and in situ observations. The results revealed that CCLM has a reliable ability to reproduce the regional wind characteristics over the BYS. Added value to ERA‐I has been detected in the coastal areas with complex orography. CCLM wind quality had strong seasonal variability, with better performance in the summer relative to ERA‐I, even in the offshore areas. CCLM was better able to represent light and moderate winds but had even more added value for strong winds relative to ERA‐I. The spatial digital filter method was used to investigate the scale of the added value, and the results show that CCLM adds value to ERA‐I mainly in medium scales of wind variability. Furthermore, wind climatology was investigated, and significant increasing trends in the south Yellow Sea especially in winter and spring were found for seasonal mean wind speeds.
Key Points
CCLM is robust to reproduce the regional wind characteristics over the BYS
Added value is generated along coastal areas with complex orography
Wind speed has significant positive trends in south YS in winter and spring
This paper discusses the state of European research in historical climatology. This field of science and an overview of its development are described in detail. Special attention is given to the ...documentary evidence used for data sources, including its drawbacks and advantages. Further, methods and significant results of historical-climatological research, mainly achieved since 1990, are presented. The main focus concentrates on data, methods, definitions of the "Medieval Warm Period" and the "Little Ice Age," synoptic interpretation of past climates, climatic anomalies and natural disasters, and the vulnerability of economies and societies to climate as well as images and social representations of past weather and climate. The potential of historical climatology for climate modelling research is discussed briefly. Research perspectives in historical climatology are formulated with reference to data, methods, interdisciplinarity and impacts. PUBLICATION ABSTRACT
A regional ocean ensemble simulation with slightly different initial conditions demonstrates that internal variability is formed (not only) in the Bohai and Yellow Sea. In this paper, we analyze the ...relationship between the internal variability and the baroclinic instability, (represented by the Eady predicted theoretical diffusivity
K
t
; the larger the
K
t
, the stronger the baroclinic instability level). In the ensemble, with tidal forcing, the spatial correlation between the Eady predicted theoretical diffusivity
K
t
and the internal variability amounts to 0.80. Also, the time evolution trends of baroclinic instability and internal variability are similar. Based on this evidence, baroclinic instability may be a significant driver for internal variability. This hypothesis is validated using an additional ensemble of simulations, which is identical to the first ensemble, but this time, the tides are inactivated. This modification leads to an increase in internal variability, combined with the strengthening of baroclinic instability. In addition, the baroclinic instability level and internal variability variation co-vary consistently when comparing summer and winter seasons, both with and without tides. Our interpretation is that a stronger baroclinic instability causes more potential energy to be transformed into kinetic energy, allowing the unforced disturbances to grow.
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