scholarly journals Impacts of North Pacific Subtropical and Subarctic Oceanic Frontal Zones on the Wintertime Atmospheric Large-Scale Circulations

2020 ◽  
Vol 33 (5) ◽  
pp. 1897-1914 ◽  
Author(s):  
Jing Huang ◽  
Yang Zhang ◽  
Xiu-Qun Yang ◽  
Xuejuan Ren ◽  
Haibo Hu
Keyword(s):  
High Resolution ◽  
North Pacific ◽  
Large Scale ◽  
Diabatic Heating ◽  
Climate Model ◽  
Frontal Zone ◽  
Regional Climate ◽  
Storm Track ◽  
Atmospheric Circulations ◽  
The North

AbstractAn oceanic frontal zone is a confluent region of warm and cool ocean currents, characterized by a strong meridional gradient of sea surface temperature (SST). High-resolution SST observations show that the wintertime North Pacific exhibits a unique double-oceanic-front structure, with a subtropical frontal zone (STFZ) and a subarctic frontal zone (SAFZ), whose impacts on the weather and climate over the East Asia–North Pacific–North American region need further investigation. In this study, we conduct groups of multiyear and ensemble simulations using a WRF high-resolution regional climate model, through which the different impacts of the STFZ and SAFZ on the wintertime atmospheric circulations are identified and compared. Our multiyear simulations show that the STFZ, although with weaker intensity, exerts evident and consistent impacts on the storm track and westerly jet in the North Pacific by enhancing and elongating the eddy activity, zonal wind, and Aleutian low. The SAFZ exhibits coherent impacts on the low-level atmospheric baroclinicity and storm track; however, its impacts on the upper-level storm track and atmospheric circulations are divergent, exhibiting strong year-by-year difference. Our study suggests that the SAFZ’s impacts on the atmospheric circulations strongly depend on the background mean state, which contributes to the divergent impacts of the SAFZ. Furthermore, our results highlight the role of diabatic heating for the above different impacts of the STFZ and SAFZ on the atmosphere. We argue that the much deeper diabatic heating induced by the STFZ, via affecting the baroclinicity through the whole troposphere, can exert consistent influence on eddy activities and atmospheric circulations.

scholarly journals Importance of Resolving Kuroshio Front and Eddy Influence in Simulating the North Pacific Storm Track

2017 ◽  
Vol 30 (5) ◽  
pp. 1861-1880 ◽  
Author(s):  
Xiaohui Ma ◽  
Ping Chang ◽  
R. Saravanan ◽  
Raffaele Montuoro ◽  
Hisashi Nakamura ◽  
...  
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Climate Model ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Small Scale ◽  
Low Resolution ◽  
The North ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Local and remote atmospheric responses to mesoscale SST anomalies associated with the oceanic front and eddies in the Kuroshio Extension region (KER) are studied using high- (27 km) and low-resolution (162 km) regional climate model simulations in the North Pacific. In the high-resolution simulations, removal of mesoscale SST anomalies in the KER leads to not only a local reduction in cyclogenesis but also a remote large-scale equivalent barotropic response with a southward shift of the downstream storm track and jet stream in the eastern North Pacific. In the low-resolution simulations, no such significant remote response is found when mesoscale SST anomalies are removed. The difference between the high- and low-resolution model simulated atmospheric responses is attributed to the effect of mesoscale SST variability on cyclogenesis through moist baroclinic instability. It is only when the model has sufficient resolution to resolve small-scale diabatic heating that the full effect of mesoscale SST forcing on the storm track can be correctly simulated.

Evaluating the ability of NA-CORDEX to simulate the seasonal modes of precipitation variability across the Western United States: Does resolution matter?

2021 ◽  
Author(s):  
Jonathan Meyer ◽  
Shih-Yu (Simon) Wang ◽  
Robert Gillies ◽  
Jin-Ho Yoon
Keyword(s):  
Performance Metrics ◽  
Climate Model ◽  
Regional Climate ◽  
Storm Track ◽  
Model Performance ◽  
Precipitation Variability ◽  
Future Trend ◽  
Spring Precipitation ◽  
Precipitation Patterns ◽  
The North

<p>The western U.S. precipitation climatology simulated by the NA-CORDEX regional climate model ensembles are examined to evaluate the capability of the 0.44<sup>° </sup>and 0.22<sup>° </sup>resolution<sup></sup>ensembles to reproduce 1) the annual and semi-annual precipitation cycle of several hydrologically important western U.S. regions and 2) localized seasonality in the amount and timing of precipitation. Collectively, when compared against observation-based gridded precipitation, NA-CORDEX RCMs driven by ERA-Interim reanalysis at the higher resolution 0.22<sup>° </sup>domain resolution dramatically outperformed the 0.44<sup>°</sup> ensemble over the 1950-2005 historical periods. Furthermore, the ability to capture the annual and semi-annual modes of variability was starkly improved in the higher resolution 0.22° ensemble. The higher resolution members reproduced more consistent spatial patterns of variance featuring lower errors in magnitude—especially with respect to the winter-summer and spring-fall seasonality. A great deal of spread in model performance was found for the semi-annual cycles, although the higher-resolution ensemble exhibited a more coherent clustering of performance metrics. In general, model performance was a function of which RCM was used, while future trend scenarios seem to cluster around which GCM was downscaled.</p><p><br>Future projections of precipitation patterns from the 0.22° NA-CORDEX RCMs driven by the RCP4.5 “stabilization scenario” and the RCP8.5 “high emission” scenario were analyzed to examine trends to the “end of century” (i.e. 2050-2099) precipitation patterns. Except for the Desert Southwest’s spring season, the RCP4.5 and RCP8.5 scenarios show a consensus change towards an increase in winter and spring precipitation throughout all regions of interest with the RCP8.5 scenario containing a greater number of ensemble members simulating greater wetting trends. The future winter-summer mode of variability exhibited a general consensus towards increasing variability with greatest change found over the region’s terrain suggesting a greater year-to-year variability of the region’s orographic response to the strength and location of the mid-latitude jet streams and storm track. Increasing spring-fall precipitation variability suggests an expanding influence of tropical moisture advection associated with the North American Monsoon, although we note that like many future monsoon projections, a spring “convective barrier” was also apparent in the NA-CORDEX ensembles.</p>

Dependence of benefits of convection permitting models on large-scale conditions

2020 ◽  
Author(s):  
Danijel Belusic ◽  
Petter Lind ◽  
Oskar Landgren ◽  
Dominic Matte ◽  
Rasmus Anker Pedersen ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Rapid Change ◽  
Winter Season ◽  
Storm Track ◽  
Summer Precipitation ◽  
Weather Conditions ◽  
Special Focus

<p>Current literature strongly indicates large benefits of convection permitting models for subdaily summer precipitation extremes. There has been less insight about other variables, seasons and weather conditions. We examine new climate simulations over the Nordic region, performed with the HCLIM38 regional climate model at both convection permitting and coarser scales, searching for benefits of using convection permitting resolutions. The Nordic climate is influenced by the North Atlantic storm track and characterised by large seasonal contrasts in temperature and precipitation. It is also in rapid change, most notably in the winter season when feedback processes involving retreating snow and ice lead to larger warming than in many other regions. This makes the area an ideal testbed for regional climate models. We explore the effects of higher resolution and better reproduction of convection on various aspects of the climate, such as snow in the mountains, coastal and other thermal circulations, convective storms and precipitation with a special focus on extreme events. We investigate how the benefits of convection permitting models change with different variables and seasons, and also their sensitivity to different circulation regimes.</p>

scholarly journals Modulation of Atmospheric Response to North Pacific SST Anomalies under Global Warming: A Statistical Assessment

2012 ◽  
Vol 25 (19) ◽  
pp. 6554-6566 ◽  
Author(s):  
Bolan Gan ◽  
Lixin Wu
Keyword(s):  
Global Warming ◽  
North Pacific ◽  
Climate Model ◽  
Storm Track ◽  
Early Winter ◽  
The North ◽  
Basin Scale ◽  
Climate Model Simulations ◽  
The North Pacific ◽  
Sst Anomalies

Abstract In this study the modulation of ocean-to-atmosphere feedback over the North Pacific in early winter from global warming is investigated based on both the observations and multiple climate model simulations from a statistical perspective. It is demonstrated that the basin-scale atmospheric circulation displays an equivalent barotropic ridge in response to warm SST anomalies in the Kuroshio–Oyashio Extension (KOE) region. This warm SST–ridge response in early winter can be enhanced significantly by global warming, indicating a strengthening of air–sea coupling over the North Pacific. This enhancement is likely associated with the intensification of storm tracks and, in turn, the amplification of atmospheric transient eddy feedback in a warm climate, although the secular trend of enhanced storm-track activity over the North Pacific is suggested to be biased in reanalysis product.

How uncertain are climate model projections of water availability indicators across the Middle East?

2010 ◽  
Vol 368 (1931) ◽  
pp. 5117-5135 ◽  
Author(s):  
Debbie Hemming ◽  
Carlo Buontempo ◽  
Eleanor Burke ◽  
Mat Collins ◽  
Neil Kaye
Keyword(s):  
Middle East ◽  
Water Availability ◽  
Large Scale ◽  
Drought Index ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
General Distribution ◽  
The North ◽  
Run Off

The projection of robust regional climate changes over the next 50 years presents a considerable challenge for the current generation of climate models. Water cycle changes are particularly difficult to model in this area because major uncertainties exist in the representation of processes such as large-scale and convective rainfall and their feedback with surface conditions. We present climate model projections and uncertainties in water availability indicators (precipitation, run-off and drought index) for the 1961–1990 and 2021–2050 periods. Ensembles from two global climate models (GCMs) and one regional climate model (RCM) are used to examine different elements of uncertainty. Although all three ensembles capture the general distribution of observed annual precipitation across the Middle East, the RCM is consistently wetter than observations, especially over the mountainous areas. All future projections show decreasing precipitation (ensemble median between −5 and −25%) in coastal Turkey and parts of Lebanon, Syria and Israel and consistent run-off and drought index changes. The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) GCM ensemble exhibits drying across the north of the region, whereas the Met Office Hadley Centre work Quantifying Uncertainties in Model ProjectionsAtmospheric (QUMP-A) GCM and RCM ensembles show slight drying in the north and significant wetting in the south. RCM projections also show greater sensitivity (both wetter and drier) and a wider uncertainty range than QUMP-A. The nature of these uncertainties suggests that both large-scale circulation patterns, which influence region-wide drying/wetting patterns, and regional-scale processes, which affect localized water availability, are important sources of uncertainty in these projections. To reduce large uncertainties in water availability projections, it is suggested that efforts would be well placed to focus on the understanding and modelling of both large-scale processes and their teleconnections with Middle East climate and localized processes involved in orographic precipitation.

scholarly journals Melting over the northeast Antarctic Peninsula (1999–2009): evaluation of a high-resolution regional climate model

2018 ◽  
Vol 12 (9) ◽  
pp. 2901-2922 ◽  
Author(s):  
Rajashree Tri Datta ◽  
Marco Tedesco ◽  
Cecile Agosta ◽  
Xavier Fettweis ◽  
Peter Kuipers Munneke ◽  
...  
Keyword(s):  
High Resolution ◽  
Regional Climate Model ◽  
Antarctic Peninsula ◽  
Climate Model ◽  
Regional Climate ◽  
Ocean Energy ◽  
Ice Shelf ◽  
The North ◽  
Mass Balance Models ◽  
Westerly Winds

Abstract. Surface melting over the Antarctic Peninsula (AP) may impact the stability of ice shelves and thus the rate at which grounded ice is discharged into the ocean. Energy and mass balance models are needed to understand how climatic change and atmospheric circulation variability drive current and future melting. In this study, we evaluate the regional climate model MAR over the AP at a 10 km spatial resolution between 1999 and 2009, a period when active microwave data from the QuikSCAT mission is available. This model has been validated extensively over Greenland, has is applied here to the AP at a high resolution and for a relatively long time period (full outputs are available to 2014). We find that melting in the northeastern AP, the focus area of this study, can be initiated both by sporadic westerly föhn flow over the AP mountains and by northerly winds advecting warm air from lower latitudes. A comparison of MAR with satellite and automatic weather station (AWS) data reveals that satellite estimates show greater melt frequency, a larger melt extent, and a quicker expansion to peak melt extent than MAR in the centre and east of the Larsen C ice shelf. These differences are reduced in the north and west of the ice shelf, where the comparison with satellite data suggests that MAR is accurately capturing melt produced by warm westerly winds. MAR shows an overall warm bias and a cool bias at temperatures above 0 ∘C as well as fewer warm, strong westerly winds than reported by AWS stations located on the eastern edge of the Larsen C ice shelf, suggesting that the underestimation of melt in this region may be the product of limited eastward flow. At higher resolutions (5 km), MAR shows a further increase in wind biases and a decrease in meltwater production. We conclude that non-hydrostatic models at spatial resolutions better than 5 km are needed to better-resolve the effects of föhn winds on the eastern edges of the Larsen C ice shelf.

scholarly journals Assessing the Importance of Prominent Warm SST Anomalies over the Midlatitude North Pacific in Forcing Large-Scale Atmospheric Anomalies during 2011 Summer and Autumn

2014 ◽  
Vol 27 (11) ◽  
pp. 3889-3903 ◽  
Author(s):  
Satoru Okajima ◽  
Hisashi Nakamura ◽  
Kazuaki Nishii ◽  
Takafumi Miyasaka ◽  
Akira Kuwano-Yoshida
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Large Scale ◽  
Storm Track ◽  
Anticyclonic Anomaly ◽  
The North ◽  
Basin Scale ◽  
Sst Anomaly ◽  
The North Pacific ◽  
Sst Anomalies

Abstract Sets of atmospheric general circulation model (AGCM) experiments are conducted to assess the importance of prominent positive anomalies in sea surface temperature (SST) observed over the midlatitude North Pacific in forcing a persistent basin-scale anticyclonic circulation anomaly and its downstream influence in 2011 summer and autumn. The anticyclonic anomaly observed in October is well reproduced as a robust response of an AGCM forced only with the warm SST anomaly associated with the poleward-shifted oceanic frontal zone in the midlatitude Pacific. The equivalent barotropic anticyclonic anomaly over the North Pacific is maintained under strong transient eddy feedback forcing associated with the poleward-deflected storm track. As the downstream influence of the anomaly, abnormal warmth and dryness observed over the northern United States and southern Canada in October are also reproduced to some extent. The corresponding AGCM response over the North Pacific to the tropical SST anomalies is similar but substantially weaker and less robust, suggesting the primary importance of the prominent midlatitude SST anomaly in forcing the large-scale atmospheric anomalies observed in October 2011. In contrast, the model reproduction of the atmospheric anomalies observed in summer was unsuccessful. This appears to arise from the fact that, unlike in October, the midlatitude SST anomalies accompanied reduction of heat and moisture release from the ocean, indicative of the atmospheric thermodynamic forcing on the SST anomalies. Furthermore, the distinct seasonality in the AGCM responses to the warm SST anomalies may also be contributed to by the seasonality of background westerlies and storm track.

scholarly journals Impacts of using spectral nudging on regional climate model RCA4 simulations of the Arctic

2013 ◽  
Vol 6 (3) ◽  
pp. 849-859 ◽  
Author(s):  
P. Berg ◽  
R. Döscher ◽  
T. Koenigk
Keyword(s):  
Sea Ice ◽  
Regional Climate Model ◽  
Large Scale ◽  
Climate Model ◽  
Regional Climate ◽  
Coupled System ◽  
The Arctic ◽  
Spectral Nudging ◽  
The North ◽  
Temperature And Precipitation

Abstract. The performance of the Rossby Centre regional climate model RCA4 is investigated for the Arctic CORDEX (COordinated Regional climate Downscaling EXperiment) region, with an emphasis on its suitability to be coupled to a regional ocean and sea ice model. Large biases in mean sea level pressure (MSLP) are identified, with pronounced too-high pressure centred over the North Pole in summer of over 5 hPa, and too-low pressure in winter of a similar magnitude. These lead to biases in the surface winds, which will potentially lead to strong sea ice biases in a future coupled system. The large-scale circulation is believed to be the major reason for the biases, and an implementation of spectral nudging is applied to remedy the problems by constraining the large-scale components of the driving fields within the interior domain. It is found that the spectral nudging generally corrects for the MSLP and wind biases, while not significantly affecting other variables, such as surface radiative components, two-metre temperature and precipitation.

Sign in / Sign up

Export Citation Format

Share Document