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The relationships between atmospheric circulation and surface climatic elements in Europe
Pokorná, Lucie ; Huth, Radan (advisor)
The relationships between atmospheric circulation and surface climatic elements in Europe Lucie Pokorná Abstract The variability of atmospheric circulation is the most important factor determining the changes in surface climatic elements. In this work, the relationship between atmospheric circulation and surface climatic elements like the temperature and the precipitation amounts and occurrence over the European region and some other climatic elements in central Europe is focused. The atmospheric circulation during the year is represented by modes of low-frequency circulation variability in sea level pressure (SLP) and 500-hPa heights (Z500) obtained by using statistical method "Principal component analysis". The Pearson correlation coefficient is used to describe the relationship between modes and climatic elements. Four circulation patterns in Z500 over Euro-Atlantic sector influence climate in Europe all over the year: the North Atlantic Oscillation (NAO) pattern, the East Atlantic (EA) pattern, and two Eurasian patterns (EU1, EU2). There were found patterns in SLP that strongly correlate with modes of the Z500 and influence surface climate similar way. Statistically important correlations of modes in Z500 and SLP with maximum, minimum and mean temperature, precipitation amounts and occurrence of...
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Links between atmospheric circulation and surface air temperature distributions in climate models
Pejchová Plavcová, Eva ; Kyselý, Jan (advisor) ; Halenka, Tomáš (referee) ; Huth, Radan (referee)
Title: Links between atmospheric circulation and surface air temperature distributions in climate models Abstract: This thesis comprises a collection of five papers dealing with validation of regional climate model (RCM) simulations over Central Europe. The first paper illustrates and discusses problems with observed data that are used for model validation and how the choice of reference dataset affects the outcomes in validating the RCMs' performances. The second paper evaluates daily temperatures, and it indicates that some temperature biases may be related to deficiencies in the simulations of large- scale atmospheric circulation. RCMs' ability to simulate atmospheric circulation and the observed links between circulation and surface air temperatures are examined in detail in the third paper. This article also compares performances of individual RCMs with respect to the driving data by analysing the results for the driving data themselves. The fourth paper focuses on biases in the diurnal temperature range within RCMs and their possible causes by examining links of the errors to the at- mospheric circulation and cloud amount. The last paper investigates the observed relationships between atmospheric circulation and daily precipitation amounts over three regions in the Czech Republic, as well as how these...
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The influence of long-term changes of atmospheric circulation on observed trends of surface climatic elements in the Czech Republic and Europe
Cahynová, Monika ; Huth, Radan (advisor) ; Metelka, Ladislav (referee) ; Halenka, Tomáš (referee)
(English) RNDr. Monika Cahynová: The influence of long-term changes of atmospheric circulation on observed trends of surface climatic elements in the Czech Republic and Europe The aim of this thesis is to quantify the links between recent atmospheric circulation changes over Europe and local surface climatic trends. We employ several parallel classifications of circulation types that were collected and developed within the COST733 Action "Harmonisation and Applications of Weather Types Classifications for European Regions". To our knowledge, such a comparative approach has not been used so far. Atmospheric circulation changes over Europe were studied in terms of changing seasonal frequency and persistence of daily circulation types in the second half of the 20th century. The extensive collection of both subjective and objective catalogues of circulation types in European regions from the COST733 Action served as a platform for comparison of different classification methods, varying numbers of circulation types, and spatial scale of circulation processes. The most prominent trend - winter increase in the number of days with westerly flow - clearly stems from the strengthening of the North Atlantic Oscillation. The objective classifications did not show any systematic change of persistence of...
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Subseasonal temperature trends in Europe (1961-2000) and their links to atmospheric circulation
Cahynová, Monika ; Pokorná, L.
We use daily maximum and minimum temperatures and the daily temperature range from 136 stations in Europe in the period 1961–2000 to precisely locate their seasonal and subseasonal trends within the year. Linear trends are calculated for moving “subseasons” of 10, 20, 30, 60, and 90 days, each shifted by one day. Over most of Europe, the observed warming is greatest in winter. In Iceland and the Mediterranean, a pronounced warming is only present in summer. Significant autumn cooling was found in Eastern and Southeastern Europe for both TX and TN. Other non-warming periods occur in Western and Central Europe in February, April, and late June. Trends of DTR are inconclusive. Changes in the frequency of atmospheric circulation types usually explain a substantial part of the observed climatic trends; however, the influence varies between regions, times of the year, subseason lengths, numbers of circulation types, and input variables for the classification of circulation types.
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Subseasonal temperature trends in Europe (1961-2000) and their links to atmospheric circulation
Cahynová, Monika ; Pokorná, Lucie
We use daily maximum and minimum temperatures and the daily temperature range from 136 stations in Europe in the period 1961–2000 to precisely locate their seasonal and subseasonal trends within the year. Linear trends are calculated for moving “subseasons” of 10, 20, 30, 60, and 90 days, each shifted by one day. Over most of Europe, the observed warming is greatest in winter. In Iceland and the Mediterranean, a pronounced warming is only present in summer. Significant autumn cooling was found in Eastern and Southeastern Europe for both TX and TN. Other non-warming periods occur in Western and Central Europe in February, April, and late June. Trends of DTR are inconclusive. Changes in the frequency of atmospheric circulation types usually explain a substantial part of the observed climatic trends; however, the influence varies between regions, times of the year, subseason lengths, numbers of circulation types, and input variables for the classification of circulation types.
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Changes in atmospheric circulation in Central Europe and their influence on climate in the Czech Republic
Cahynová, Monika ; Huth, Radan
This work is concerned with the influence of changes of atmospheric circulation (represented by the Hess-Brezowsky and Brádka’s subjective catalogues of synoptic types) on observed linear trends of 11 climatic elements from 21 stations in the Czech Republic in the period 1961-1998. The ratio of "hypothetical" (caused only by changes in the frequency of synoptic types) and observed trends shows that changes in atmospheric circulation are the primary cause of massive winter warming, and autumn cooling connected with increasing precipitation and humidity. In spring and summer, the influence is insignificant except for precipitation, relative humidity and cloudiness changes that are related to trends in the Hess-Brezowsky catalogue, mostly in spring.
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