Future Atmospheric Circulation Research Articles

Variability in Future Atmospheric Circulation Patterns in the MPI-ESM1-2-HR Model in Iran

Analyzing and classifying atmospheric circulation patterns (CPs) is useful for studying climate variability. These classifications can effectively identify the links between large-scale and regional-local scale processes. This work uses the historical (1975–2014) and projected (2015–2054) simulations of the MPI-ESM1-2-HR model to reproduce the CPs over the Middle East and Iran. Eighteen CPs were identified based on the geopotential height (GPH) of 500 hPa data from Coupled Model Intercomparison Project Phase 6 (CMIP6) in SSP1-2.6, SSP3-7.0, and SSP5-8.5. The method of principal component analysis (PCA) and k-means clustering was used. Then, the possible variability of each pattern in the surface and mid-level of the atmosphere and their expected changes in the frequency of CPs in global warming scenarios were investigated. This research showed that CPs 3, 6, and 11 happen during warm months of the year. The surface thermal low pressure is associated with the subtropical high in the atmosphere mid-level. According to the intensity of the low and the northward development, or the orbital expansion of the subtropical high, this pattern has an increasing (CPs 3 and 6) or decreasing (CP11) trend in the future period. CPs 1 and 12 occur during cold months. In CP1, dynamic high pressure prevails over Iran. However, in CP12, Iran is affected by high pressure from southeastern Europe. They will decrease in future projections. CPs 7 and 16, which often occur in the transition season (spring), show an increase in the projected patterns. CP 18 occurs throughout the year, but its highest frequency is in autumn, and the frequency of occurrence decreases. An increase in 500 hPa geopotential height over the Arabian Sea in all 18 classes and all three SSPs is predicted for future periods. Analysis of the obtained weather types indicates the identification of all effective atmospheric circulation patterns in the study area so that the behavior and frequency of each pattern explain the prevailing atmospheric phenomena in this region.

Effects of different types of heat wave days on ozone pollution over Beijing-Tianjin-Hebei and its future projection.

There are concerns that in the 21st century, global warming will lead to more frequent heat wave days (HWDs), which could amplify ozone pollution (OP). However, a recent study projected that future atmospheric circulation variations may benefit OP control in Beijing-Tianjin-Hebei (BTH). To investigate the possible reasons for this contradiction, this paper discussed the ozone amplification capacity between different HWD types and their future projections based on observations and Community Earth System Model Large Ensemble Simulations (CESM-LENS). Composite analysis shows that not all HWDs amplify the OP in BTH. The main factor determining whether HWDs aggravate OP is the accompanying circulation anomalies rather than the intensity of the HWDs. The HWDs that aggravate ozone pollution are usually accompanied by stable saddle-like circulation anomalies and atmospheric blocking (blocking HWDs), which weaken the meridional temperature gradient and strengthen atmospheric stability. In contrast, HWDs with wave-train circulation anomalies have a limited ability to exacerbate OP in BTH due to their weak atmospheric stability. We introduce the Ozone Weather Index (OWI) to discern the influence of meteorological conditions on OP and overcome the lack of ozone concentration data in CESM-LENS under RCP 8.5 scenario. The OWI shows a significant downward trend in the 21st century, which indicates that the summer mean atmospheric circulation variations are beneficial for OP control in BTH. However, the frequency of blocking HWDs, which could amplify OP, will increase significantly in the 21st century. By the end of the 21st century, the frequency of blocking HWDs will be three times more than that of the end of 20th century. These findings inform policymakers that it is imperative to consider the mean climate state and the risks associated with extreme events when formulating future ozone pollution control policies.

Atmospheric Circulation Constraints on 21st Century Seasonal Precipitation Storylines for the Southwestern United States

AbstractPrecipitation is vital for the water‐limited region of the southwestern United States. Coupled Model Intercomparison Project Phase 6 global climate models project 21st century precipitation trends of varying sign for this region, even if forced by an identical anthropogenic emissions scenario. This study investigates the role of the present‐day and future atmospheric circulation in driving the disparity in precipitation trends among models. The wettest model projections are linked to the development of an anomalous mid‐tropospheric trough over the eastern North Pacific Ocean, which depends in part on future unpredictable internal variability. By contrast, future precipitation trends are also linked to models' representation of the present‐day climatological mid‐tropospheric ridge over western North America. Models that fail to properly simulate this ridge in the present‐day climatology are responsible for the most extreme outlier precipitation scenarios for the Southwest for the 21st century: extreme drying in winter and extreme wetting in summer.

Coriolis effect recorded in Late Pleistocene Marine Isotope Stage 5e Bahamian aeolianites

Abstract The windward islands of the Lucayan Archipelago (Bahamas) form an Atlantic Ocean–facing transect spanning >950 km in length and 6° of latitude. The islands' topography is largely constructed from carbonate wind-blown dunes (i.e., aeolianites) deposited during the interglacial phases of the Late Pleistocene and Holocene. New digital elevation data from satellite radar interferometry (TanDEM-X German Earth observation satellite) enables a step change in the ability to map and quantify Bahamian aeolian landforms across the archipelago. A semi-automated mapping approach that leverages object-based image analysis yields a total aeolianite area of ~1674 km2 across Great Abaco, Eleuthera, Cat, San Salvador, Long, Crooked, Acklins, and Mayaguana islands (Bahamas) and the Turks and Caicos Islands. Longitudinal axis measurements from 747 Pleistocene parabolic dunes record increasing consistency of east-west orientation with decreasing latitude. Three U.S. National Data Buoy Center data buoys provided modern wind direction and velocity measurements (n = 730,933 of each) along this transect. Analysis of wind vectors (>P90 [90th percentile], n = 70,095) demonstrates increasing organization of easterlies at southern latitudes and an offset in directionality compared to formational winds of Pleistocene Marine Isotope Stage (MIS) 5e deposits. Southward trends of increasing wind strength and consistency reflect geostrophic flow driven by atmospheric circulation within the Hadley cell and right-hand deflection of the Coriolis effect in the Northern Hemisphere. We propose that the offset in directionality between dune axes and modern wind vectors is related to changes in latitudinal width of the Hadley cell from the Late Pleistocene (MIS 5e) to today. This data set is robust enough to serve as a benchmark against which future atmospheric circulation models can be compared.

A regime view of future atmospheric circulation changes in northern mid-latitudes

Abstract. Future wintertime atmospheric circulation changes in the Euro–Atlantic (EAT) and Pacific–North American (PAC) sectors are studied from a weather regimes perspective. The Coupled Model Intercomparison Project phases 5 and 6 (CMIP5 and CMIP6) historical simulation performance in reproducing the observed regimes is first evaluated, showing a general improvement in the CMIP6 models, which is more evident for EAT. The circulation changes projected by CMIP5 and CMIP6 scenario simulations are analysed in terms of the change in the frequency and persistence of the regimes. In the EAT sector, significant positive trends are found for the frequency and persistence of NAO+ (North Atlantic Oscillation) for SSP2–4.5, SSP3–7.0 and SSP5–8.5 scenarios with a concomitant decrease in the frequency of the Scandinavian blocking and Atlantic Ridge regimes. For PAC, the Pacific Trough regime shows a significant increase, while the Bering Ridge is predicted to decrease in all scenarios analysed. The spread among the model responses is linked to different levels of warming in the polar stratosphere, the tropical upper troposphere, the North Atlantic and the Arctic.

Atmospheric Dynamics is the Largest Source of Uncertainty in Future Winter European Rainfall

Abstract The IPCC Fifth Assessment Report highlighted large uncertainty in European precipitation changes in the coming century. This paper investigates the sources of intermodel differences using CMIP5 model European precipitation data. The contribution of atmospheric circulation to differences in precipitation trends is investigated by applying cluster analysis to daily mean sea level pressure (MSLP) data. The resulting classification is used to reconstruct monthly precipitation time series, thereby isolating the component of precipitation variability directly related to atmospheric circulation. Reconstructed observed precipitation and reconstructions of simulated historical and projection data are well correlated with the original precipitation series, showing that circulation variability accounts for a substantial fraction of European precipitation variability. Removing the reconstructed precipitation from the original precipitation leaves a residual component related to noncirculation effects (and any small remaining circulation effects). Intermodel spread in residual future European precipitation trends is substantially reduced compared to the spread of the original precipitation trends. Uncertainty in future atmospheric circulation accounts for more than half of the intermodel variance in twenty-first-century precipitation trends for winter months for both northern and southern Europe. Furthermore, a substantial part of this variance is related to different forced dynamical responses in different models and is therefore potentially reducible. These results highlight the importance of understanding future changes in atmospheric dynamics in achieving more robust projections of regional climate change. Finally, the possible dynamical mechanisms that may drive the future differences in regional circulation and precipitation are illustrated by examining simulated teleconnections with tropical precipitation.

Atmospheric drivers of Greenland surface melt revealed by self‐organizing maps

AbstractRecent acceleration in surface melt on the Greenland ice sheet (GrIS) has occurred concurrently with a rapidly warming Arctic and has been connected to persistent, anomalous atmospheric circulation patterns over Greenland. To identify synoptic setups favoring enhanced GrIS surface melt and their decadal changes, we develop a summer Arctic synoptic climatology by employing self‐organizing maps. These are applied to daily 500 hPa geopotential height fields obtained from the Modern Era Retrospective Analysis for Research and Applications reanalysis, 1979–2014. Particular circulation regimes are related to meteorological conditions and GrIS surface melt estimated with outputs from the Modèle Atmosphérique Régional. Our results demonstrate that the largest positive melt anomalies occur in concert with positive height anomalies near Greenland associated with wind, temperature, and humidity patterns indicative of strong meridional transport of heat and moisture. We find an increased frequency in a 500 hPa ridge over Greenland coinciding with a 63% increase in GrIS melt between the 1979–1988 and 2005–2014 periods, with 75.0% of surface melt changes attributed to thermodynamics, 17% to dynamics, and 8.0% to a combination. We also confirm that the 2007–2012 time period has the largest dynamic forcing relative of any period but also demonstrate that increased surface energy fluxes, temperature, and moisture separate from dynamic changes contributed more to melt even during this period. This implies that GrIS surface melt is likely to continue to increase in response to an ever warmer future Arctic, regardless of future atmospheric circulation patterns.

Current and future atmospheric circulation at 500 hPa over Greenland simulated by the CMIP3 and CMIP5 global models

The Greenland ice sheet is projected to be strongly affected by global warming. These projections are either issued from downscaling methods (such as Regional Climate Models) or they come directly from General Circulation Models (GCMs). In this context, it is necessary to evaluate the accuracy of the daily atmospheric circulation simulated by the GCMs, since it is used as forcing for downscaling methods. Thus, we use an automatic circulation type classification based on two indices (Euclidean distance and Spearman rank correlation using the daily 500 hPa geopotential height) to evaluate the ability of the GCMs from both CMIP3 and CMIP5 databases to simulate the main circulation types over Greenland during summer. For each circulation type, the GCMs are compared to three reanalysis datasets on the basis of their frequency and persistence differences. For the current climate (1961–1990), we show that most of the GCMs do not reproduce the expected frequency and the persistence of the circulation types and that they simulate poorly the observed daily variability of the general circulation. Only a few GCMs can be used as reliable forcings for downscaling methods over Greenland. Finally, when applying the same approach to the future projections of the GCMs, no significant change in the atmospheric circulation over Greenland is detected, besides a generalised increase of the geopotential height due to a uniform warming of the atmosphere.

Present and future climates of the Greenland ice sheet according to the IPCC AR4 models

The atmosphere–ocean general circulation models (AOGCMs) used for the IPCC 4th Assessment Report (IPCC AR4) are evaluated for the Greenland ice sheet (GrIS) current climate modelling. The most suited AOGCMs for Greenland climate simulation are then selected on the basis of comparison between the 1970–1999 outputs of the Climate of the twentieth Century experiment (20C3M) and reanalyses (ECMWF, NCEP/NCAR). This comparison indicates that the representation quality of surface parameters such as temperature and precipitation are highly correlated to the atmospheric circulation (500 hPa geopotential height) and its interannual variability (North Atlantic oscillation). The outputs of the three most suitable AOGCMs for present-day climate simulation are then used to assess the changes estimated by three IPCC greenhouse gas emissions scenarios (SRES) over the GrIS for the 2070–2099 period. Future atmospheric circulation changes are projected to dampen the zonal flow, enhance the meridional fluxes and therefore provide additional heat and moisture to the GrIS, increasing temperature over the whole ice sheet and precipitation over its northeastern area. We also show that the GrIS surface mass balance anomalies from the SRES A1B scenario amount to −300 km3/year with respect to the 1970–1999 period, leading to a global sea-level rise of 5 cm by the end of the 21st century. This work can help to select the boundaries conditions for AOGCMs-based downscaled future projections.

The influence of climate on air and precipitation chemistry over Europe, and downscaling applications to future acidic deposition

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 14:7-24 (2000) - doi:10.3354/cr014007 The influence of climate on air and precipitation chemistry over Europe and downscaling applications to future acidic deposition Julie M. Jones1,*, Trevor D. Davies2 1Institute of Hydrophysics, GKSS, Max-Planck-Strasse, 21502 Geesthacht, Germany 2School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom *E-mail: jones@gkss.de ABSTRACT: Atmospheric circulations, and related climate conditions, exert a strong influence on the transport and ultimate deposition of atmospheric pollutants. One potential outcome of climate change is alteration of atmospheric circulation patterns. The first stage in the development of a downscaling methodology to assess the influence of these possible future atmospheric circulation changes on transport and deposition of atmospheric pollutants over Europe is described. Firstly, the main modes of regional-scale circulation over a domain covering the North Atlantic and Europe are determined using principal components analysis of sea level pressure patterns. To determine whether the principal components represent circulation types found in reality, and show realistic relationships with surface temperature and precipitation amount, they are compared to the Lamb Weather Types, Central England Temperature, and England and Wales Rainfall. There are statistically significant relationships between some of the principal components and aqueous and ambient pollutant concentrations at 5 selected stations from the European Monitoring and Evaluation Programme monitoring network. Although, for any one combination of principal component and pollutant variable, the level of explanation can be quite small, notwithstanding some levels of variance explained for individual combinations being up to 69% (45% for the winter season, described in detail here). Because the pollution climate at any one location is a function of many combinations of circulation/pollution relationships, despite the relatively small magnitude of variance explained for individual combinations in this study, the results confirm the utility of atmospheric circulation principal components in deriving downscaling relationships for surface pollution behaviour (via eventual multiple regressions, not reported in this paper), as well as giving further insight into the climatic influences on air and precipitation chemistry over Europe. KEY WORDS: Acidic deposition · Air pollution · Downscaling · Synoptic climatology · Principal components analysis · Climate change Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 14, No. 1. Online publication date: January 24, 2000 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 2000 Inter-Research.

Relations between winter precipitation and atmospheric circulation simulated by the geophysical fluid dynamics laboratory general circulation model

AbstractGeneral circulation model (GCM) simulations of atmospheric circulation are more reliable than GCM simulations of temperature and precipitation. Thus, some researchers are developing empirical relations between observed atmospheric circulation and observed temperature and precipitation to translate GCM estimates of future atmospheric circulation into estimates of future regional temperature and precipitation. Developing climate‐change scenarios in this manner assumes, at least, that relationships between atmospheric circulation and surface climate variables, such as temperature and precipitation, are properly simulated by GCMs.In this study, temporal correlations between 700 hPa height anomalies (700 hPa anomalies) over North America simulated by the Geophysical Fluid Dynamics Laboratory (GFDL) GCM and GFDL‐GCM‐simulated (GFDL‐simulated) winter precipitation at eight locations in the conterminous United States are compared with corresponding correlations in observations. The objectives are to (i) characterize the relations between atmospheric circulation and winter precipitation simulated by the GFDL GCM for selected locations in the conterminous USA, (ii) determine whether these relations are similar to those found in observations of the actual climate system, and (iii) determine if GFDL‐simulated precipitation is forced by the same circulation patterns as in the real atmosphere.Results indicate that the GFDL GCM simulates relations between 700 hPa anomalies and local winter precipitation that are similar to relations found in observed data for most of the locations analysed in this study. Results also indicate that at regional scales GFDL GCM simulations of the relations between 700 hPa anomalies and winter precipitation are most similar to observed relations for locations near oceanic sources of atmospheric moisture. These results suggest that the GFDL GCM may not adequately simulate variations in advection of atmospheric moisture into the interior parts of the USA and/or that this moisture is not adequately converted into precipitation in the interior parts of the country. This problem may be due, in part, to (i) the inadequate representation of topography in the GFDL GCM, (ii) stronger‐than‐observed mean winter zonal winds simulated by the GFDL GCM and the consequent more west‐to‐east paths of air flow and storm systems across North America, (iii) the relative weakness of important synoptic patterns in GFDL simulations, such as the Pacific North American circulation pattern, and (iv) the occurrence of ‘spectral rain’.In addition, for some locations, the GFDL‐simulated relationships between precipitation and 700 hPa anomalies can be quite different from observed relations. The differing relationships suggest that GFDL‐simulated changes in regional precipitation in response to changes in atmospheric circulation could differ from changes that would occur in the actual climate system.