scholarly journals Improved Consistency of Climate Projections over Europe after Accounting for Atmospheric Circulation Variability

2017 ◽  
Vol 30 (18) ◽  
pp. 7271-7291 ◽  
Author(s):  
Claudio Saffioti ◽  
Erich M. Fischer ◽  
Reto Knutti
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Forced Response ◽  
Climate Projections ◽  
Multimodel Ensemble ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Temperature And Precipitation ◽  
The Impact ◽  
Precipitation Trends

Abstract The influence of atmospheric circulation on winter temperature and precipitation trends over Europe in the period 2006–50 is investigated in a 21-member initial condition ensemble from a fully coupled global climate model and in a multimodel framework consisting of 40 different models. Five versions of a dynamical adjustment method based on empirical orthogonal function analysis of sea level pressure are introduced, and their performance in removing the effect of atmospheric circulation on temperature and precipitation is tested. The differences in atmospheric circulation as simulated by different models in their control runs and under the historical and representative concentration pathway 8.5 (RCP8.5) forcing scenarios are investigated. Dynamical adjustment is applied to the multimodel ensemble to demonstrate that a substantial fraction of the uncertainty in projected European temperature and precipitation trends is explained by atmospheric circulation variability. A statistically significant response of sea level pressure to anthropogenic forcing is identified in the multimodel ensemble under the RCP8.5 scenario. This forced response in atmospheric circulation is associated with a dynamical contribution to the long-term multimodel mean temperature and precipitation trends. The results highlight the importance of accounting for the impact of atmospheric circulation variability on trends in regional climate projections.

On the Design of Paleoenvironmental Data Networks for Estimating Large-Scale Patterns of Climate

1980 ◽  
Vol 14 (2) ◽  
pp. 169-187 ◽  
Author(s):  
J. E. Kutzbach ◽  
P. J. Guetter
Keyword(s):  
Regression Model ◽  
Sea Level ◽  
Atmospheric Circulation ◽  
Sampling Strategies ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Temperature And Precipitation ◽  
Area Of Interest ◽  
Site Density ◽  
Instrumental Records

AbstractGuidelines are determined for the spatial density and location of climatic variables (temperature and precipitation) that are appropriate for estimating the continental- to hemispheric-scale pattern of atmospheric circulation (sea-level pressure). Because instrumental records of temperature and precipitation simulate the climatic information that is contained in certain paleoenvironmental records (tree-ring, pollen, and written-documentary records, for example), these guidelines provide useful sampling strategies for reconstructing the pattern of atmospheric circulation from paleoenvironmental records. The statistical analysis uses a multiple linear regression model. The sampling strategies consist of changes in site density (from 0.5 to 2.5 sites per million square kilometers) and site location (from western North American sites only to sites in Japan, North America, and western Europe) of the climatic data. The results showed that the accuracy of specification of the pattern of sea-level pressure: (1) is improved if sites with climatic records are spread as uniformly as possible over the area of interest; (2) increases with increasing site density-at least up to the maximum site density used in this study; (3) is improved if sites cover an area that extends considerably beyond the limits of the area of interest. The accuracy of specification was lower for independent data than for the data that were used to develop the regression model; some skill was found for almost all sampling strategies.

scholarly journals Interdependence of the Northern Hemisphere ice-sheets build-up during the last glaciation: the role of atmospheric circulation

2013 ◽  
Vol 9 (2) ◽  
pp. 2183-2216
Author(s):  
P. Beghin ◽  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Waves ◽  
Sea Level Pressure ◽  
Orographic Effect ◽  
Level Pressure ◽  
The Impact

Abstract. The development of large continental-scale ice sheets over Canada and Northern Europe during the last glacial cycle likely modified the track of stationary waves and influenced the location of growing ice sheets through changes in accumulation and temperature patterns. Although they are often mentioned in the literature, these feedback mechanisms are poorly constrained and have never been studied throughout an entire glacial-interglacial cycle. Using the climate model of intermediate complexity CLIMBER-2 coupled with the 3-D ice-sheet model GRISLI, we investigate the impact of stationary waves on the construction of past Northern Hemisphere ice sheets during the past glaciation. The stationary waves are not explicitly computed in the model but their effect on sea-level pressure is parameterized. Several parameterizations have been tested allowing to study separately the effect of surface temperature (thermal forcing) and topography (orographic forcing) on sea-level pressure, and therefore on atmospheric circulation and ice-sheet surface mass balance. We show that the response of ice sheets to thermal and/or orographic forcings is rather different. At the beginning of the glaciation, the orographic effect favors the growth of the Laurentide ice sheet, whereas Fennoscandia appears rather sensitive to the thermal effect. Using the ablation parameterization as a trigger to artificially modify the size of one ice sheet, the remote influence of one ice sheet on the other is also studied as a function of the stationary wave parameterizations. The sensitivity of remote ice sheets is shown to be highly sensitive to the choice of these parameterizations with a larger response when orographic effect is accounted for. Results presented in this study suggest that the various spatial distributions of ice sheets could be partly be explained by the feedbacks mechanisms occurring between ice sheets and atmospheric circulation.

scholarly journals Impacts of the North Atlantic Warming Hole in Future Climate Projections: Mean Atmospheric Circulation and the North Atlantic Jet

2019 ◽  
Vol 32 (10) ◽  
pp. 2673-2689 ◽  
Author(s):  
Melissa Gervais ◽  
Jeffrey Shaman ◽  
Yochanan Kushnir
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
Forced Response ◽  
Future Climate ◽  
Climate Projections ◽  
Transient Eddy ◽  
The North ◽  
Climate Simulations ◽  
The North Atlantic ◽  
The Impact

Abstract In future climate simulations there is a pronounced region of reduced warming in the subpolar gyre of the North Atlantic Ocean known as the North Atlantic warming hole (NAWH). This study investigates the impact of the North Atlantic warming hole on atmospheric circulation and midlatitude jets within the Community Earth System Model (CESM). A series of large-ensemble atmospheric model experiments with prescribed sea surface temperature (SST) and sea ice are conducted, in which the warming hole is either filled or deepened. Two mechanisms through which the NAWH impacts the atmosphere are identified: a linear response characterized by a shallow atmospheric cooling and increase in sea level pressure shifted slightly downstream of the SST changes, and a transient eddy forced response whereby the enhanced SST gradient produced by the NAWH leads to increased transient eddy activity that propagates vertically and enhances the midlatitude jet. The relative contributions of these two mechanisms and the details of the response are strongly dependent on the season, time period, and warming hole strength. Our results indicate that the NAWH plays an important role in midlatitude atmospheric circulation changes in CESM future climate simulations.

scholarly journals What Surface Observations Are Important for Separating the Influences of Anthropogenic Aerosols from Other Forcings?

2016 ◽  
Vol 29 (11) ◽  
pp. 4165-4184 ◽  
Author(s):  
Xiaoqin Yan ◽  
Timothy DelSole ◽  
Michael K. Tippett
Keyword(s):  
Spatial Structure ◽  
Surface Temperature ◽  
Sea Level ◽  
Climate Models ◽  
Accurate Estimate ◽  
Forced Response ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol ◽  
Sea Level Pressure ◽  
Level Pressure

Abstract This paper shows that joint temperature–precipitation information over a global domain provides a more accurate estimate of aerosol forced responses in climate models than does any other combination of temperature, precipitation, or sea level pressure. This fact is demonstrated using a new quantity called potential detectability, which measures the extent to which a forced response can be detected in a model. In particular, this measure can be evaluated independently of observations and therefore permits efficient exploration of a large number of variable combinations before performing optimal fingerprinting on observations. This paper also shows that the response to anthropogenic aerosol forcing can be separated from that of other forcings using only spatial structure alone, leaving the time variation of the response to be inferred from data, thereby demonstrating that temporal information is not necessary for detection. The spatial structure of the forced response is derived by maximizing the signal-to-noise ratio. For single variables, the north–south hemispheric gradient and equator-to-pole latitudinal gradient are important spatial structures for detecting anthropogenic aerosols in some models but not all. Sea level pressure is not an independent detection variable because it is derived partly from surface temperature. In no case does sea level pressure significantly enhance potential detectability beyond that already possible using surface temperature. Including seasonal or land–sea contrast information does not significantly enhance detectability of anthropogenic aerosol responses relative to annual means over global domains.

scholarly journals Interdependence of the growth of the Northern Hemisphere ice sheets during the last glaciation: the role of atmospheric circulation

2014 ◽  
Vol 10 (1) ◽  
pp. 345-358 ◽  
Author(s):  
P. Beghin ◽  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Stationary Waves ◽  
Sea Level Pressure ◽  
Feedback Mechanisms ◽  
Orographic Effect ◽  
Level Pressure

Abstract. The development of large continental-scale ice sheets over Canada and northern Europe during the last glacial cycle likely modified the track of stationary waves and influenced the location of growing ice sheets through changes in accumulation and temperature patterns. Although they are often mentioned in the literature, these feedback mechanisms are poorly constrained and have never been studied throughout an entire glacial–interglacial cycle. Using the climate model of intermediate complexity CLIMBER-2 coupled with the 3-D ice-sheet model GRISLI (GRenoble Ice Shelf and Land Ice model), we investigate the impact of stationary waves on the construction of past Northern Hemisphere ice sheets during the past glaciation. The stationary waves are not explicitly computed in the model but their effect on sea-level pressure is parameterized. We tested different parameterizations to study separately the effect of surface temperature (thermal forcing) and topography (orographic forcing) on sea-level pressure, and therefore on atmospheric circulation and ice-sheet surface mass balance. Our model results suggest that the response of ice sheets to thermal and/or orographic forcings is rather different. At the beginning of the glaciation, the orographic effect favors the growth of the Laurentide ice sheet, whereas Fennoscandia appears rather sensitive to the thermal effect. Using the ablation parameterization as a trigger to artificially modify the size of one ice sheet, the remote influence of one ice sheet on the other is also studied as a function of the stationary wave parameterizations. The sensitivity of remote ice sheets is shown to be highly sensitive to the choice of these parameterizations with a larger response when orographic effect is accounted for. Results presented in this study suggest that the various spatial distributions of ice sheets could be partly explained by the feedback mechanisms occurring between ice sheets and atmospheric circulation.

scholarly journals Future changes in Beijing haze events under different anthropogenic aerosol emission scenarios

2021 ◽  
Vol 21 (10) ◽  
pp. 7499-7514
Author(s):  
Lixia Zhang ◽  
Laura J. Wilcox ◽  
Nick J. Dunstone ◽  
David J. Paynter ◽  
Shuai Hu ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
North Pacific ◽  
Anthropogenic Aerosol ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Aerosol Emission ◽  
Circulation Patterns ◽  
The North Pacific

Abstract. Air pollution is a major issue in China and one of the largest threats to public health. We investigated future changes in atmospheric circulation patterns associated with haze events in the Beijing region and the severity of haze events during these circulation conditions from 2015 to 2049 under two different aerosol scenarios: a maximum technically feasible aerosol reduction (MTFR) and a current legislation aerosol scenario (CLE). In both cases greenhouse gas emissions follow the Representative Concentration Pathway 4.5 (RCP4.5). Under RCP4.5 with CLE aerosol the frequency of circulation patterns associated with haze events increases due to a weakening of the East Asian winter monsoon via increased sea level pressure over the North Pacific. The rapid reduction in anthropogenic aerosol and precursor emissions in MTFR further increases the frequency of circulation patterns associated with haze events, due to further increases in the sea level pressure over the North Pacific and a reduction in the intensity of the Siberian high. Even with the aggressive aerosol reductions in MTFR periods of poor visibility, represented by above-normal aerosol optical depth (AOD), still occur in conjunction with haze-favorable atmospheric circulation. However, the winter mean intensity of poor visibility decreases in MTFR, so that haze events are less dangerous in this scenario by 2050 compared to CLE and relative to the current baseline. This study reveals the competing effects of aerosol emission reductions on future haze events through their direct contribution to pollutant source and their influence on the atmospheric circulation. A compound consideration of these two impacts should be taken in future policy making.

scholarly journals Heavy thunderstorms on the Polish-German lowlands in the period 1951–2008 and their circulation conditions

2012 ◽  
Vol 31 (3) ◽  
pp. 25-32
Author(s):  
Leszek Kolendowicz
Keyword(s):  
Sea Level ◽  
Atmospheric Circulation ◽  
Atmospheric Pressure ◽  
Low Pressure ◽  
Pressure System ◽  
Sea Level Pressure ◽  
Air Masses ◽  
Atmospheric Fronts ◽  
Low Pressure System ◽  
The Impact

Abstract. The aim of the study was an analysis of the impact of atmospheric circulation over the territory of Europe on the frequency of occurrence of heavy thunderstorms on German Lowlands and on Polish Lowlands in the period 1951-2008. The atmospheric circulation in days with investigated phenomena was illustrated as the averaged image of the atmospheric pressure field over Europe (sea level pressure and 500 hPa geopotential heights). Heavy thunderstorm phenomena occur as a result of low pressure systems or low pressure troughs moving above investigated area and bringing cold air masses. Usually, the distribution of isobars at sea level indicates the occurrence of atmospheric fronts accompanying a low pressure system.

scholarly journals Variations in the Three-Dimensional Structure of the Atmospheric Circulation with Different Flavors of El Niño

2009 ◽  
Vol 22 (11) ◽  
pp. 2978-2991 ◽  
Author(s):  
Kevin E. Trenberth ◽  
Lesley Smith
Keyword(s):  
Indian Ocean ◽  
Sea Level ◽  
Atmospheric Circulation ◽  
El Niño ◽  
El Nino ◽  
Three Dimensional ◽  
Positive Sign ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The Tropics

Abstract Two rather different flavors of El Niño are revealed when the full three-dimensional spatial structure of the temperature field and atmospheric circulation monthly mean anomalies is analyzed using the Japanese Reanalysis (JRA-25) temperatures from 1979 through 2004 for a core region of the tropics from 30°N to 30°S, with results projected globally onto various other fields. The first two empirical orthogonal functions (EOFs) both have primary relationships to El Niño–Southern Oscillation (ENSO) but feature rather different vertical and spatial structures. By construction the two patterns are orthogonal, but their signatures in sea level pressure, precipitation, outgoing longwave radiation (OLR), and tropospheric diabatic heating are quite similar. Moreover, they are significantly related, with EOF-2 leading EOF-1 by about 4–6 months, indicating that they play complementary roles in the evolution of ENSO events, and with each mode playing greater or lesser roles in different events and seasons. The dominant pattern (EOF-1) in its positive sign features highly coherent zonal mean warming throughout the tropical troposphere from 30°N to 30°S that increases in magnitude with height to 200 hPa, drops to zero about 100 hPa at the tropopause, and has reverse sign to 30 hPa with peak values at 70 hPa. It correlates strongly with global mean surface temperatures. EOF-2 emphasizes off-equatorial centers of action and strong Rossby wave temperature signatures that are coherent throughout the troposphere, with the strongest values in the Pacific that extend into the extratropics and a sign reversal at and above 150 hPa. Near the surface, both patterns feature boomerang-shaped opposite temperatures in the western tropical and subtropical Pacific, with similar sea level pressure patterns, but with EOF-1 more focused in equatorial regions. Both patterns are strongest during the boreal winter half-year when anomalous precipitation in the tropics and associated latent heating drive teleconnections throughout the world. For El Niño in northern winter EOF-1 has more precipitation in the eastern tropical Pacific, while EOF-2 has much drier conditions over northern Australia and the Indian Ocean. In northern summer, the main differences are in the South Pacific and Indian Ocean. Differences in teleconnections suggest great sensitivity to small changes in forcings in association with seasonal variations in the mean state.

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