Effects of Large-scale Modes of Atmospheric Circulation on the Regimes of Temperature and Precipitation in the Arctic (original) (raw)
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International Journal of Climatology, 2017
The increased extreme warm and decreased extreme cold temperature events across the Arctic strongly influence the natural environment as well as the societal activities. This study investigates temporal and spatial variability of wintertime extreme high and low temperature events defined by the 95 and 5% percentiles across the Arctic and subarctic regions, respectively (north of 60 ∘ N) using data from 238 stations in the Global Summary of the Day for the period 1979-2016. Empirical orthogonal function analyses indicate that the first modes (which account for 30-35% of the total variance) are out-of-phase between northern Europe, western and central Russia, and northeastern North America, and that this appears to be related to the Arctic Oscillation (AO) and the Northern Atlantic Oscillation. The second modes explain about 8% of the total variance. During the positive phase of the first and second modes the anomalous northeasterly and northerly winds decrease Arctic extreme high and increase extreme low temperature occurrences; while the anomalous southerly and southwesterly winds have the opposite effect. Symmetric and asymmetric effects of the AO index on extreme temperature events refer to the difference and sum between the composite of its positive and negative phases. The symmetric components of the spatial patterns are similar to those of the first modes. The asymmetric components occur mainly over western and central Russia for extreme high and low temperatures, respectively. In addition the impacts of six other large-scale climate modes are also explored. KEY WORDS Arctic extreme temperature events; Arctic Oscillation; Pacific North America pattern; asymmetric impact
On the interaction of atmospheric dynamics Arctic and mid-latitudes under climate change
IOP Conference Series: Earth and Environmental Science, 2018
The article discusses some aspects of interaction between atmospheric dynamics processes in the Arctic and the mid-latitudes under conditions of global climate change and rapid warming in the Arctic in the lower layer of the troposphere (due to a mechanism of positive feedbacks, enhancement of atmospheric heat and moisture fluxes to the Arctic and heat transfer by currents in the ocean). This is a difficult task, given the fact that the observation of this phenomenon is relatively short. One of the plausible physical hypotheses of the effect of warming in the Arctic on the dynamics of the atmosphere in the mid-and high latitudes is that the reduction of sea ice and snow cover anomalies caused by this warming can lead to changes in the frequency and intensity of the extreme weather events and largescale circulation in the mid-latitudes and in the Arctic region. Polar cyclones, stratospheric vortex, jet streams, North Atlantic oscillations-these objects of atmospheric dynamics are the subject of discussion in this article. The paper also presents the results of a study of the sensitivity of the Arctic Ocean and the sea ice to variability of atmospheric circulation, taking into account the dynamics of the NAO/AO. Special attention is paid to the circulation over the Norwegian and Greenland Seas, which are the area of formation of the initial trajectory of distribution of Atlantic waters in the Arctic Ocean.
Journal of Climate
This study gives a comprehensive picture on how atmospheric large-scale circulation is related to moisture transport, and to distributions of moisture, clouds and surface downward longwave radiation in the Arctic in winter. Anomaly distributions of above-mentioned variables are compared in 30 characteristic wintertime atmospheric circulation regimes, which are allocated from 15 years (2003–2017) of mean sea-level pressure (MSLP) data of ERA-Interim reanalysis applying the Self-Organizing Map (SOM) method. The characteristic circulation regimes are further related to known climate indices: the North Atlantic Oscillation (NAO), the Arctic Oscillation (AO), and Greenland Blocking Index (GBI), as well as to a frequent high-pressure pattern across the Arctic Ocean from Siberia to North America, called here as the Arctic Bridge. Effects of large-scale circulation on moisture, cloud and longwave radiation are to a large extent occurring through the impact of horizontal moisture transport. ...
Nonlinear impact of the Arctic Oscillation on extratropical surface air temperature
2012
1] The Arctic Oscillation (AO) is the leading climate mode of sea level pressure (SLP) anomalies during cold season in the Northern Hemisphere. To a large extent, the atmospheric climate anomalies associated with positive and negative phases of the AO are opposite to each other, indicating linear impact. However, there is also significant nonlinear relationship between the AO and other winter climate variability. We investigate nonlinear impacts of the AO on surface air temperature (SAT) using reanalysis data and a multimillennial long climate simulation. It is found that SAT response to the AO, in terms of both spatial pattern and magnitude, is almost linear when the amplitude of the AO is moderate. However, the response becomes quite nonlinear as the amplitude of the AO becomes stronger. First, the pattern shift in SAT depends on AO phase and magnitude, and second, the SAT magnitude depends on AO phase. In particular, these nonlinearities are distinct over the North America and Eurasian Continent. Based on the analyses of model output, we suggest that the nonlinear zonal advection term is one of the critical components in generating nonlinear SAT response, particularly over the North America.
THE ARCTIC REGIONAL CLIMATE SYSTEM MODEL: CURRENT STATUS AND RECENT RESULTS
2000
Conceptual models of the global general circulation typically have not included a separate high latitude frontal zone. As noted by Serreze et al. (2000), the notion of a region of frequent mesoscale frontal activity in northern high latitudes emerging as distinct from frontal activity in middle latitudes can be traced back to the early work of Dzerdzeevskii (1945). Reed and
Regional climate model of the Arctic atmosphere
Journal of Geophysical Research, 1996
A regional climate model of the whole Arctic using the dynamical package of the High-Resolution Limited Area Model (HIRLAM) and the physical parameterizations of the Hamburg General Circulation Model (ECHAM3) has been applied to simulate the climate of the Arctic north of 65 øN at a 50-km horizontal resolution. The model has been forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses at the lateral boundaries and with climatological or actual observed sea surface temperatures and sea ice cover at the lower boundary. The results of simulating the Arctic climate of the troposphere and lower stratosphere for January 1991 and July 1990 have been described. In both months the model rather closely reproduces the observed monthly mean circulation. While the general spatial patterns of surface air temperature, mean sea level pressure, and geopotential are consistent with the ECMWF analyses, the model shows biases when the results are examined in detail. The largest biases appear during winter in the planetary boundary layer and at the surface. The underestimated vertical heat and humidity transport in the model indicates the necessity of improvements in the parameterizations of vertical transfer due to boundary layer processes. The tropospheric differences between model simulations and analyses decrease with increasing height. The temperature bias in the planetary boundary layer can be reduced by increasing the model sea ice thickness. The use of actual observed sea surface temperatures and sea ice cover leads only to small improvements of the model bias in comparison with climatological sea surface temperatures and sea ice cover. The validation of model computed geopotential, radiative fluxes, surface sensible and latent heat fluxes and clouds against selected station data shows deviations between model simulations and observations due to shortcomings of the model. This first validation indicates that improvements in the physical parameterization packages of radiation and in the description of sea ice thickness and sea ice fraction are necessary to reduce the model bias.
A difficult Arctic science issue: Midlatitude weather linkages
Polar Science, 2016
There is at present unresolved uncertainty whether Arctic amplification (increased air temperatures and loss of sea ice) impacts the location and intensities of recent major weather events in midlatitudes. There are three major impediments. The first is the null hypothesis where the shortness of time series since major amplification (~15 years) is dominated by the variance of the physical process in the attribution calculation. This makes it impossible to robustly distinguish the influence of Arctic forcing of regional circulation from random events. The second is the large chaotic jet stream variability at midlatitudes producing a small Arctic forcing signal-to-noise ratio. Third, there are other potential external forcings of hemispheric circulation, such as teleconnections driven by tropical and midlatitude sea surface temperature anomalies. It is, however, important to note and understand recent emerging case studies. There is evidence for a causal connection of Barents-Kara sea ice loss, a stronger Siberian High, and cold air outbreaks into eastern Asia. Recent cold air penetrating into the southeastern United States was related to a shift in the long-wave atmospheric wind pattern and reinforced by warmer temperatures west of Greenland. Arctic Linkages is a major research challenge that benefits from an international focus on the topic.
Regional Variation of Winter Temperatures in the Arctic
Journal of Climate, 1997
The surface temperature field in the Arctic winter is primarily controlled by downward longwave radiation, which is determined by local atmospheric temperature and humidity profiles and the presence of clouds. The authors show that regional differences in the atmospheric thermal energy budget are related to the tropospheric circulation in the Arctic. Data sources include several gridded meteorological datasets and surface and rawinsonde observational data. Four independent climatologies of mean January surface temperature show consistent spatial patterns: coldest temperatures in the western Arctic north of Canada and warmer regions in the Chukchi, Greenland, and Barents Seas. Data from the five winters of 1986-90 illustrate the coupling between the surface temperature, the downward longwave radiative fields, and the tropospheric temperature and humidity fields, with monthly surface-upper-air correlations on the order of 0.6. Upper-level circulation patterns reveal features similar to the surface temperature fields, notably a persistent low center located over northern Canada; the cyclonic flow around the low is a tropospheric extension of the polar vortex. Colder and drier conditions are maintained within the vortex and communicated to the surface through radiative processes. The polar vortex also steers transient weather systems, the most important mechanism for horizontal heat transport, into the eastern Arctic, which results in as much as 25 W m Ϫ2 more heat flux into the eastern Arctic than the western Arctic. A reason for the colder temperatures in the western Arctic is that the polar vortex tends to be situated downstream of the northern Rocky Mountains; this preferred location is related to orographic forcing of planetary waves. Monthly and interannual variability of winter temperatures is conditioned by the interaction of the Arctic and midlatitude circulations through the strength and position of the polar vortex.
Intercomparison of Arctic regional climate simulations: Case studies of January and June 1990
Journal of Geophysical Research, 2000
Advances in regional climate modeling must be strongly based on analysis of physical processes in comparison with data. In a data-poor region such as the Arctic; this procedure may be enhanced by a community-based approach, i.e., through collaborative analysis by several research groups. To illustrate this approach, simulations were performed with two regional climate models, HIRHAM and ARCSyM, over the Arctic basin to 65øN, laterally driven at the boundaries by observational analyses. It was found that both models are able to reproduce reasonably the main features of the large-scale flow and the surface parameters in the Arctic. Distinct differences in the simulations can be attributed to specific characteristics of the boundary layer and surface parameterizations, which result in surface flux differences, and to the lateral moisture forcing, both of which affect moisture availability in the atmosphere. Further disparities are associated with the additional degrees of freedom allowed in the coupled model ARCSyM. Issues of model configuration and experimental design are discussed, including domain size, grid spacing, boundary formulations, model initialization and spin-up, and ensemble approaches. In order to reach definitive conclusions in a regional climate model intercomparison, ensemble simulations with adequate spin-up and equivalent initialization of surface fields will be required. 1998], MERCURE project, PIRCS project [Arritt et al., 1999; Takle et al., 1999]) provide examples for frameworks which eval-uate the strengths and weaknesses of RCMs and their component parameterizations through systematic, comparative simulations.