Increased Arctic influence on the midlatitude flow during Scandinavian Blocking episodes

Day, Jonathan J.; Sandu, Irina; Magnusson, Linus; Rodwell, M.J.W.; Lawrence, Heather; Bormann, Niels; Jung, Thomas

doi:10.1002/qj.3673

Cited by 18 publications

(27 citation statements)

References 39 publications

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“…The microwave and conventional observations were found to be important for midlatitude forecasts in the medium range, with impacts particularly over North America and the Atlantic (stretching down to the Iberian Peninsula and North Africa at day 5) in summer and over North America and Eurasia in winter. These are likely to be regime-dependent; this has been explored in more detail for the winter season by Day et al (2019). By comparing results from Arctic OSEs to global OSEs we were also able to analyse the impacts of midlatitude observations (south of 60 • N) on medium-range weather forecasts in the Arctic (north of 60 • N).…”

Section: Discussionmentioning

confidence: 99%

“…The midlatitude summer and winter impacts shown here are likely to be regime-dependent and will be explored in further work. Indeed, an analysis for the winter season has already been carried out by Day et al (2019) and results indicate a link to Scandinavian blocking for the winter period. As well as forecast errors in the Arctic affecting midlatitudes, the reverse can also be true, with forecast errors in the midlatitudes affecting the accuracy of weather forecasts in the Arctic.…”

Section: 6mentioning

confidence: 99%

“…We focus on two recent summer and winter periods -June-September 2016 and December 2017 to March 2018 -and compare results from the Arctic OSEs to those from global OSEs run for the same period, which are also presented independently by Bormann et al (2019). A companion paper by Day et al (2019) further investigates the regime dependence of the midlatitude impacts resulting from denying observations over the polar region during winter. This paper is organised as follows.…”

Section: Introductionmentioning

confidence: 99%

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Use and impact of Arctic observations in the ECMWF Numerical Weather Prediction system

Lawrence

Bormann

Sandu

et al. 2019

Quart J Royal Meteoro Soc

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111

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This paper presents an assessment of the usage of Arctic atmospheric observations in the Numerical Weather Prediction (NWP) system of the European Centre for Medium‐Range Weather Forecasts, and of their impact on the quality of short‐ to medium‐range forecasts. The Arctic has low coverage of conventional data north of 70°N but one of the highest levels of coverage of satellite sounding data on Earth. The impact of Arctic observations on forecast skill was assessed by performing Observing System Experiments, in which different observation types were removed from the full observing system. This assessment was complemented by an analysis of Forecast Sensitivity to Observation Impact diagnostics. To our knowledge it is the first time that comprehensive numerical experimentation has been carried out to explore the role of different Arctic observations in a state‐of‐the‐art global operational NWP system. All Arctic observations were found to have a positive impact on forecast skill in the Arctic region, with the greatest tropospheric impacts on both short‐ and medium‐range forecasts due to microwave, conventional and infrared sounding observations. Results indicate the great importance of microwave sounding data and conventional data, which are found to be the key observing systems in the summer and winter seasons, respectively. These observations were found to have positive and statistically significant impacts on forecasts not only in the Arctic but also in the midlatitude regions at longer lead times. Differences between the seasons are most likely due to problems assimilating microwave sounding observations over snow and sea ice, leading to a reduced impact in winter. There is also the suggestion of increased importance of conventional data in winter, and other factors may also play a role.

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Section: Discussionmentioning

confidence: 99%

Section: 6mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Use and impact of Arctic observations in the ECMWF Numerical Weather Prediction system

Lawrence

Bormann

Sandu

et al. 2019

Quart J Royal Meteoro Soc

Self Cite

111

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“…The linkage in boreal winter is stronger than that in summer, which highlights the potential midlatitude forecast benefits from improved Arctic conditions in winter (Semmler et al, 2018). Specifically, the linkage between the Arctic and North Asia is strong during Scandinavian blocking episodes (Day et al, 2019). Moreover, the interannual variability of the Eurasian atmospheric circulation and temperature can be impacted by the Arctic troposphere via modifying large-scale atmospheric circulations, heat transport over the continent, and synoptic variations.…”

Section: Arctic Midlatitude Linkagementioning

confidence: 97%

“…The linkage between the Arctic and midlatitudes revealed by Jung et al (2014) and Semmler et al (2018) indicates that weather forecasts in the midlatitudes will be improved with more accur- ate Arctic initial conditions, especially for extreme weather events. Furthermore, Day et al (2019) demonstrated by conducting observing system experiments that weather forecasts in North Asia can benefit from accurate Arctic initial conditions. Therefore, the influence of the initial uncertainty in the Arctic on midlatitude extreme weather events forecasts may be larger and should be further discussed.…”

Section: Uncertainties In the Arctic Atmospherementioning

confidence: 99%

Influence of the Arctic on the Predictability of Eurasian Winter Extreme Weather Events

Dai

2020

Adv. Atmos. Sci.

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The linkage between the Arctic and midlatitudes has received much attention recently due to the rapidly changing climate. Many investigations have been conducted to reveal the relationship between the Arctic and Eurasian extreme events from the perspective of climatological statistics. As a prediction source for extreme events in Eurasia, Arctic conditions are crucial for extreme event predictions. Therefore, it is urgent to explore the Arctic influence on the predictability of Eurasian extreme events due to the large uncertainties in Arctic conditions. Considering the sensitivity and nonlinearity of the atmospheric circulations in midlatitude to Arctic conditions, it is necessary to investigate the Arctic influences on Eurasian extreme weather events in case studies at weather time scales. Previous studies indicate that only perturbations in specific patterns have fast growth. Thus, the conditional nonlinear optimal perturbation approach is recommended for exploring the uncertainties in Arctic initial and boundary conditions and their synergistic effect on Eurasian extreme events. Moreover, the mechanism for extreme event formation may differ in different cases. Therefore, more extreme cases should be investigated to reach robust conclusions.

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Statistical characteristics of Arctic forecast busts and their relationship to Arctic weather patterns in summer

Yamagami

Matsueda

2021

Atmospheric Science Letters

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Recently, human activity in the Arctic region, such as trans-Arctic shipping, has increased due to the reduction in Arctic sea ice. Accurate weather forecasts will become increasingly important as the level of human activity in the Arctic continues to increase. Operational numerical weather predictions (NWPs) have been improved considerably over recent decades; however, they still occasionally generate large forecast errors referred to as "forecast busts." This study investigates forecast busts over the Arctic between 2008 and 2019 using operational forecasts from five leading NWP centers. Forecasts with an anomaly correlation coefficient below its climatological 10th percentile, and a root-meansquare error above its 90th percentile at a lead time of 144 hr, are regarded as "busts." The occurrence frequency of forecast busts decreased from 2008 (13-7%) to 2012 and was between 2 and 6% for the period 2012-2019. Arctic forecast busts were most frequent in the May and July-September periods (~6 to 7%), but less frequent between December and March (~4%). The summertime forecast bust occurred more frequently when the initial pattern was the Greenland Blocking (GB) or Arctic Cyclone (AC) pattern rather than one of the other patterns. Some busts occurred without the weather pattern transition (~22 to 40%), but the others occurred with the pattern transition. These results help users to be careful when they use the forecasts initialized on GB and AC patterns.

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Increased Arctic influence on the midlatitude flow during Scandinavian Blocking episodes

Cited by 18 publications

References 39 publications

Use and impact of Arctic observations in the ECMWF Numerical Weather Prediction system

Use and impact of Arctic observations in the ECMWF Numerical Weather Prediction system

Influence of the Arctic on the Predictability of Eurasian Winter Extreme Weather Events

Statistical characteristics of Arctic forecast busts and their relationship to Arctic weather patterns in summer

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