Extreme associated functions: optimally linking local extremes to large-scale atmospheric circulation structures

Abstract. We present a new statistical method to optimally link local weather extremes to large-scale atmospheric circulation structures. The method is illustrated using July–August daily mean temperature at 2 m height (T2m) time-series over the Netherlands and 500 hPa geopotential height (Z500) time-series over the Euroatlantic region of the ECMWF reanalysis dataset (ERA40). The method identifies patterns in the Z500 time-series that optimally describe, in a precise mathematical sense, the relationship with local warm extremes in the Netherlands. Two patterns are identified; the most important one corresponds to a blocking high pressure system leading to subsidence and calm, dry and sunny conditions over the Netherlands. The second one corresponds to a rare, easterly flow regime bringing warm, dry air into the region. The patterns are robust; they are also identified in shorter subsamples of the total dataset. The method is generally applicable and might prove useful in evaluating the performance of climate models in simulating local weather extremes.

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Trends and regime shifts in climatic conditions and river runoff in Estonia during 1951–2015

Earth System Dynamics ◽

10.5194/esd-8-963-2017 ◽

2017 ◽

Vol 8 (4) ◽

pp. 963-976 ◽

Cited By ~ 15

Author(s):

Jaak Jaagus ◽

Mait Sepp ◽

Toomas Tamm ◽

Arvo Järvet ◽

Kiira Mõisja

Keyword(s):

Time Series ◽

Snow Cover ◽

Atmospheric Circulation ◽

Air Temperature ◽

Large Scale ◽

Regime Shifts ◽

The Arctic ◽

Dry Period ◽

Snow Cover Duration ◽

Large Scale Atmospheric Circulation

Abstract. Time series of monthly, seasonal and annual mean air temperature, precipitation, snow cover duration and specific runoff of rivers in Estonia are analysed for detecting of trends and regime shifts during 1951–2015. Trend analysis is realised using the Mann–Kendall test and regime shifts are detected with the Rodionov test (sequential t-test analysis of regime shifts). The results from Estonia are related to trends and regime shifts in time series of indices of large-scale atmospheric circulation. Annual mean air temperature has significantly increased at all 12 stations by 0.3–0.4 K decade−1. The warming trend was detected in all seasons but with the higher magnitude in spring and winter. Snow cover duration has decreased in Estonia by 3–4 days decade−1. Changes in precipitation are not clear and uniform due to their very high spatial and temporal variability. The most significant increase in precipitation was observed during the cold half-year, from November to March and also in June. A time series of specific runoff measured at 21 stations had significant seasonal changes during the study period. Winter values have increased by 0.4–0.9 L s−1 km−2 decade−1, while stronger changes are typical for western Estonia and weaker changes for eastern Estonia. At the same time, specific runoff in April and May have notably decreased indicating the shift of the runoff maximum to the earlier time, i.e. from April to March. Air temperature, precipitation, snow cover duration and specific runoff of rivers are highly correlated in winter determined by the large-scale atmospheric circulation. Correlation coefficients between the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) indices reflecting the intensity of westerlies, and the studied variables were 0.5–0.8. The main result of the analysis of regime shifts was the detection of coherent shifts for air temperature, snow cover duration and specific runoff in the late 1980s, mostly since the winter of 1988/1989, which are, in turn, synchronous with the shifts in winter circulation. For example, runoff abruptly increased in January, February and March but decreased in April. Regime shifts in annual specific runoff correspond to the alternation of wet and dry periods. A dry period started in 1964 or 1963, a wet period in 1978 and the next dry period at the beginning of the 21st century.

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Past long-term summer warming over western Europe in new generation climate models: role of large-scale atmospheric circulation

Environmental Research Letters ◽

10.1088/1748-9326/ab8a89 ◽

2020 ◽

Vol 15 (8) ◽

pp. 084038

Author(s):

Julien Boé ◽

Laurent Terray ◽

Marie-Pierre Moine ◽

Sophie Valcke ◽

Alessio Bellucci ◽

...

Keyword(s):

Atmospheric Circulation ◽

Large Scale ◽

Western Europe ◽

Climate Models ◽

Summer Warming ◽

New Generation ◽

Large Scale Atmospheric Circulation

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The construction of a Central Netherlands temperature

Climate of the Past Discussions ◽

10.5194/cpd-6-2517-2010 ◽

2010 ◽

Vol 6 (6) ◽

pp. 2517-2555 ◽

Cited By ~ 2

Author(s):

G. van der Schrier ◽

A. van Ulden ◽

G. J. van Oldenborgh

Keyword(s):

Time Series ◽

The Netherlands ◽

Large Scale ◽

Climate Models ◽

Temperature Series ◽

Homogeneity Analysis ◽

Temperature Changes ◽

Long Time Series ◽

Scale Temperature ◽

Long Time

Abstract. The Central Netherlands Temperature (CNT) is a monthly daily mean temperature series constructed from homogenised time series from the centre of the Netherlands. The purpose of this series is to offer a homogeneous time series representative of a larger area to study large-scale temperature changes. It will also facilitate a comparison with climate models, which resolve similar scales. From 1906 onwards, temperature measurements in the Netherlands have been sufficiently standardised to construct a high-quality series. Long time series have been constructed by merging nearby stations, using the overlap to calibrate the differences. These long time series and a few time series of only a few decades in length, have been subjected to a homogeneity analysis in which significant breaks and artificial trends have been corrected. Many of the detected breaks correspond to changes in the observations that are documented in the station metadata. This version of the CNT, to which we attach the version number 1.1, is constructed as the unweighted average of four stations (De Bilt, Winterswijk/Hupsel, Oudenbosch/Gilze-Rijen and Gemert/Volkel) with the stations Eindhoven and Deelen added from 1951 and 1958 respectively onwards.

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Trends and regime shifts in climatic conditions and river runoff in Estonia during 1951–2015

10.5194/esd-2017-24 ◽

2017 ◽

Author(s):

Jaak Jaagus ◽

Mait Sepp ◽

Toomas Tamm ◽

Arvo Järvet ◽

Kiira Mõisja

Keyword(s):

Time Series ◽

Snow Cover ◽

Atmospheric Circulation ◽

Air Temperature ◽

Large Scale ◽

Regime Shifts ◽

The Arctic ◽

Dry Period ◽

Snow Cover Duration ◽

Large Scale Atmospheric Circulation

Abstract. Time series of monthly, seasonal and annual mean air temperature, precipitation, snow cover duration and specific runoff of rivers in Estonia are analysed for detecting trends and regime shifts during 1951–2015. Trend analysis is performed using the Mann-Kendall test and regime shifts are detected with the Rodionov test (Sequential T-test Analysis of Regime Shifts). The results from Estonia are related to trends and regime shifts in time series of indices of large-scale atmospheric circulation. Annual mean air temperature has significantly increased at 12 observed stations by 0.3–0.4 K per decade. The warming trend was detected in all seasons but with the higher magnitude in spring and winter. Snow cover duration has decreased in Estonia by 3–4 days per decade. Changes in precipitation are not clear and uniform due to their very high spatial and temporal variability. The most significant increase in precipitation was observed during the cold half-year, from November to March. Time series of specific runoff measured at 21 stations has had significant seasonal changes during the study period. Winter values have increased by 0.4–0.9 l/s per km2 per decade while stronger changes are typical for western Estonia and weaker changes for eastern Estonia. At the same time, specific runoff in April and May has notably decreased indicating the shift of the runoff maximum to earlier time, i.e. from April to March. All meteorological and hydrological variables are highly correlated in winter, determined by the large-scale atmospheric circulation. Correlation coefficients between the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) indices reflecting the intensity of westerlies, and the studied variables were 0.5–0.8. The main result of the analysis of regime shifts was the detection of coherent shifts for air temperature, snow cover duration and specific runoff in the late 1980s, mostly since the winter 1988/1989, which are, in turn, synchronous with the shifts in winter circulation. For example, runoff abruptly increased in January, February and March but decreased in April. Regime shifts in the annual specific runoff correspond to the alternation of wet and dry periods. A dry period started since 1964 or 1963, a wet period since 1978 and the next dry period since the beginning of the 21st century.

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Winter extreme weather in EURO-CORDEX climate models and their links to large-scale atmospheric circulation

10.5194/ems2021-377 ◽

2021 ◽

Author(s):

Eva Plavcová ◽

Ondřej Lhotka ◽

Jan Stryhal

Keyword(s):

Atmospheric Circulation ◽

Large Scale ◽

Climate Models ◽

Climate Model ◽

Regional Scale ◽

Global Climate Models ◽

Wind Gust ◽

Climate Change Scenarios ◽

Winter Weather ◽

Large Scale Atmospheric Circulation

Regional Climate Models (RCMs) are powerful tools to study changes in the climate system on the regional scale. However, the reliability of their simulations has been considerably limited by the longstanding issue that climate models often fail to reproduce various aspects of the historical climate. In our study, we analyse how RCMs from the EURO-CORDEX project are able to reproduce extreme winter weather. We analyse temporal and spatial characteristics of extreme wind gust, extremely cold temperature, and extreme precipitation. Model outputs are validated against observed data from the European gridded observational&#160;database (EOBS) and the novel ERA5 reanalysis. We focus on the Central European domain (defined between 48&#8211;52&#176;N and 10&#8211;19&#176;E) over the 1979 &#8211; 2017 period. We investigate a set of 9 simulations of 3 different RCMs driven by 3 different global climate models which allow us to analyse the influence of driving data on the RCM&#8217;s performance. Since local climate elements are relatively tightly linked to a large-scale atmospheric circulation over Europe in winter, we also evaluate the ability of RCMs to reproduce the atmospheric circulation and its links to selected high-impact winter weather in detail. We use the classification of circulation based on the method of Sammon mapping. Investigation of these links can lead to better physical understanding of the climate and to the identification of inadequacies in simulated characteristics of the studied events. All of this is an important step forward in further improving the models and enhancing the credibility of climate change scenarios based on climate model simulations.

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Projections of northern hemisphere extratropical climate underestimate internal variability and associated uncertainty

Communications Earth & Environment ◽

10.1038/s43247-021-00268-7 ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Christopher H. O’Reilly ◽

Daniel J. Befort ◽

Antje Weisheimer ◽

Tim Woollings ◽

Andrew Ballinger ◽

...

Keyword(s):

Climate Variability ◽

Atmospheric Circulation ◽

Large Scale ◽

Climate Models ◽

Regional Climate ◽

Coupled Model ◽

Internal Variability ◽

Uncertainty Range ◽

Coupled Climate Models ◽

Large Scale Atmospheric Circulation

AbstractInternal climate variability will play a major role in determining change on regional scales under global warming. In the extratropics, large-scale atmospheric circulation is responsible for much of observed regional climate variability, from seasonal to multidecadal timescales. However, the extratropical circulation variability on multidecadal timescales is systematically weaker in coupled climate models. Here we show that projections of future extratropical climate from coupled model simulations significantly underestimate the projected uncertainty range originating from large-scale atmospheric circulation variability. Using observational datasets and large ensembles of coupled climate models, we produce synthetic ensemble projections constrained to have variability consistent with the large-scale atmospheric circulation in observations. Compared to the raw model projections, the synthetic observationally-constrained projections exhibit an increased uncertainty in projected 21st century temperature and precipitation changes across much of the Northern extratropics. This increased uncertainty is also associated with an increase of the projected occurrence of future extreme seasons.

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The 2018 northern European hydrological drought and its drivers in a historical perspective

Hydrology and Earth System Sciences ◽

10.5194/hess-24-5621-2020 ◽

2020 ◽

Vol 24 (11) ◽

pp. 5621-5653 ◽

Cited By ~ 1

Author(s):

Sigrid J. Bakke ◽

Monica Ionita ◽

Lena M. Tallaksen

Keyword(s):

High Pressure ◽

Atmospheric Circulation ◽

Large Scale ◽

Northern Europe ◽

Pressure System ◽

Northern Norway ◽

Nordic Region ◽

Northern European ◽

Groundwater Drought ◽

Large Scale Atmospheric Circulation

Abstract. In 2018, large parts of northern Europe were affected by an extreme drought. A better understanding of the characteristics and the large-scale atmospheric circulation driving such events is of high importance to enhance drought forecasting and mitigation. This paper examines the historical extremeness of the May–August 2018 meteorological situation and the accompanying meteorological and hydrological (streamflow and groundwater) drought. Further, it investigates the relation between the large-scale atmospheric circulation and summer streamflow in the Nordic region. In May and July 2018, record-breaking temperatures were observed in large parts of northern Europe associated with blocking systems centred over Fennoscandia and sea surface temperature anomalies of more than 3 ∘C in the Baltic Sea. Extreme meteorological drought, as indicated by the 3-month Standardized Precipitation Index (SPI3) and Standardized Precipitation Evapotranspiration Index (SPEI3), was observed in May and covered large parts of northern Europe by July. Streamflow drought in the Nordic region started to develop in June, and in July 68 % of the stations had record-low or near-record-low streamflow. Extreme streamflow conditions persisted in the southeastern part of the region throughout 2018. Many groundwater wells had record-low or near-record-low levels in July and August. However, extremeness in groundwater levels and (to a lesser degree) streamflow showed a diverse spatial pattern. This points to the role of local terrestrial processes in controlling the hydrological response to meteorological conditions. Composite analysis of low summer streamflow and 500 mbar geopotential height anomalies revealed two distinct patterns of summer streamflow variability: one in western and northern Norway and one in the rest of the region. Low summer streamflow in western and northern Norway was related to high-pressure systems centred over the Norwegian Sea. In the rest of the Nordic region, low summer streamflow was associated with a high-pressure system over the North Sea and a low-pressure system over Greenland and Russia, resembling the pattern of 2018. This study provides new insight into hydrometeorological aspects of the 2018 northern European drought and identifies large-scale atmospheric circulation patterns associated with summer streamflow drought in the Nordic region.

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The construction of a Central Netherlands temperature

Climate of the Past ◽

10.5194/cp-7-527-2011 ◽

2011 ◽

Vol 7 (2) ◽

pp. 527-542 ◽

Cited By ~ 17

Author(s):

G. van der Schrier ◽

A. van Ulden ◽

G. J. van Oldenborgh

Keyword(s):

Time Series ◽

The Netherlands ◽

Large Scale ◽

Climate Models ◽

Warming Trend ◽

Homogeneity Analysis ◽

Temperature Changes ◽

Long Time Series ◽

Scale Temperature ◽

Long Time

Abstract. The Central Netherlands Temperature (CNT) is a monthly daily mean temperature series constructed from homogenized time series from the centre of the Netherlands. The purpose of this series is to offer a homogeneous time series representative of a larger area in order to study large-scale temperature changes. It will also facilitate a comparison with climate models, which resolve similar scales. From 1906 onwards, temperature measurements in the Netherlands have been sufficiently standardized to construct a high-quality series. Long time series have been constructed by merging nearby stations and using the overlap to calibrate the differences. These long time series and a few time series of only a few decades in length have been subjected to a homogeneity analysis in which significant breaks and artificial trends have been corrected. Many of the detected breaks correspond to changes in the observations that are documented in the station metadata. This version of the CNT, to which we attach the version number 1.1, is constructed as the unweighted average of four stations (De Bilt, Winterswijk/Hupsel, Oudenbosch/Gilze-Rijen and Gemert/Volkel) with the stations Eindhoven and Deelen added from 1951 and 1958 onwards, respectively. The global gridded datasets used for detecting and attributing climate change are based on raw observational data. Although some homogeneity adjustments are made, these are not based on knowledge of local circumstances but only on statistical evidence. Despite this handicap, and the fact that these datasets use grid boxes that are far larger then the area associated with that of the Central Netherlands Temperature, the temperature interpolated to the CNT region shows a warming trend that is broadly consistent with the CNT trend in all of these datasets. The actual trends differ from the CNT trend up to 30 %, which highlights the need to base future global gridded temperature datasets on homogenized time series.

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The 2018 northern European hydrological drought and its drivers in a historical perspective

10.5194/hess-2020-239 ◽

2020 ◽

Author(s):

Sigrid J. Bakke ◽

Monica Ionita ◽

Lena M. Tallaksen

Keyword(s):

High Pressure ◽

Atmospheric Circulation ◽

Large Scale ◽

Northern Europe ◽

Pressure System ◽

Northern Norway ◽

Nordic Region ◽

Northern European ◽

Groundwater Drought ◽

Large Scale Atmospheric Circulation

Abstract. In 2018, large parts of northern Europe were affected by an extreme drought. A better understanding of the characteristics and the large-scale atmospheric circulation driving such events is of high importance to enhance drought forecasting and mitigation. This paper examines the historical extremeness of the May–August 2018 meteorological situation and the accompanying meteorological and hydrological (streamflow and groundwater) drought. Further, it investigates the relationship between the large-scale atmospheric circulation and summer streamflow in the Nordic region. In May and July 2018, record-breaking temperatures were observed in large parts of northern Europe associated with blocking systems centred over Fennoscandia and sea surface temperature anomalies of more than 3 °C in the Baltic Sea (May, July) and the Barents Sea (July). Extreme meteorological drought, as indicated by the three-month standard precipitation index (SPI3) and precipitation-evapotranspiration index (SPEI3), was observed in May, and covered large parts of northern Europe by July. Streamflow drought in the Nordic region started to develop in June, and in July 68 % of the stations had record-low or near-record-low streamflow. Extreme streamflow conditions persisted in the southeastern part of the region throughout 2018. Many groundwater wells had record-low or near-record-low levels in July and August. However, extremeness in groundwater levels and (to a lesser degree) streamflow show a diverse spatial pattern. This points to the role of local terrestrial processes in controlling the hydrological response to meteorological conditions, including aquifer properties. Composite analysis of low summer streamflow and 500 mb geopotential height anomalies revealed a distinction between summer streamflow variability in western/northern Norway and the rest of the region. Low summer streamflow in western/northern Norway is related to high-pressure systems centred over the Norwegian Sea. In the rest of the Nordic region, low summer streamflow is associated with a high-pressure system over the North Sea and a low-pressure system over Greenland and Russia at similar latitudes, resembling the pattern of 2018. This study provides new insight into different hydro-meteorological aspects of the 2018 northern European drought, as well as identification of large-scale atmospheric circulation patterns associated with summer streamflow drought in the Nordic region.

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Evaluation of the tropical water vapor of CMIP6 GCMs with ESA CCI+ “Water Vapor” climate data records: Insights from large-scale atmospheric circulation

10.5194/egusphere-egu21-2082 ◽

2021 ◽

Author(s):

Helene Brogniez ◽

Jia He ◽

Laurence Picon ◽

Marc Schroder ◽

René Preusker ◽

...

Keyword(s):

Water Vapor ◽

Atmospheric Circulation ◽

Large Scale ◽

Climate Models ◽

Global Climate Models ◽

Tropical Region ◽

Tropical Atmosphere ◽

Climate Data ◽

Dynamical Regimes ◽

Large Scale Atmospheric Circulation

Water vapor is one of the fundamental elements in the atmosphere. Its distribution is strongly associated with large-scale atmospheric circulation. Here the new global water vapor climate data records (CDR) generated within the ESA Water Vapor CCI+ project (WV_cci) is used to perform a comprehensive evaluation of total column water vapor provided by 21 global climate models (CMIP6 framework). The ESA WV_cci CDRs cover the period 2002-2017 with a daily frequency and a regular 0.5&#176; spatial resolution. The focus is on the tropical region (30&#176;S - 30&#176;N). The observational diagnostic relies on the decomposition of the tropical atmosphere into large-scale dynamical regimes using the 500 hPa atmospheric vertical velocity w500 (in hPa/day) as a proxy. The ESA WV_cci and the CMIP6 data are then sorted according to dynamical regimes (intervals of 10 hPa/day) allowing to study the evolution of the regimes in terms of frequency of occurrence and is linked to water vapor variation. While the basic picture of the tropical atmosphere is properly represented by the models (moister in ascending branches, drier in subsiding branches) there are noticeable differences in the patterns that will be discussed. The inter-annual variation of water vapor for both observation and the models will be analyzed, and the trend significance are assessed using Mann-Kendall test. This highlights the interest of water vapor climate data records for model evaluation.

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