Effects of subseasonal basic state changes on Rossby wave propagation during northern summer

Yun, Kyung-Sook; Kim, Seong-Yeol; Ha, Kyung‐Ja

doi:10.1029/2011jd016258

Cited by 8 publications

(7 citation statements)

References 26 publications

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“…The lack of skillful predictions based on tropical indices is consistent with minimal tropical influence on the Northern Hemisphere mid-latitudes during summer 23 . Whereas a causal relationship between tropical Pacific sea surface temperature anomalies and Northern Hemisphere weather is well established for winter conditions 24,25 , the lack of a similar relationship for summer 26,27 can be understood from seasonal differences in both the magnitude of tropical anomalies and the mean atmospheric circulation 28,29 .…”

Section: Comparison To Other Predictorssupporting

confidence: 58%

Long-lead predictions of eastern United States hot days from Pacific sea surface temperatures

et al. 2016

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Seasonal forecast models exhibit only modest skill in predicting extreme summer temperatures across the eastern US. Anomalies in sea surface temperature and monthly-resolution rainfall have, however, been correlated with hot days in the US, and seasonal persistence of these anomalies suggests potential for long-lead predictability. Here we present a clustering analysis of daily maximum summer temperatures from US weather stations between 1982-2015 and identify a region spanning most of the eastern US where hot weather events tend to occur synchronously. We then show that an evolving pattern of sea surface temperature anomalies, termed the Pacific Extreme Pattern, provides for skillful prediction of hot weather within this region as much as 50 days in advance. Skill is demonstrated using out-of-sample predictions between 1950 and 2015. Rainfall deficits over the eastern US are also associated with the occurrence of the Pacific Extreme Pattern and are demonstrated to o er complementary skill in predicting high temperatures. The Pacific Extreme Pattern appears to provide a cohesive framework for improving seasonal prediction of summer precipitation deficits and high temperature anomalies in the eastern US.T he twenty-first century has already featured a number of costly 1 and ill-predicted 2 heat waves with negative impacts on crop production 3 and human health 4 . Climate change has the potential to increase the frequency and magnitude of heat waves 5 , underscoring the importance of skillful seasonal and subseasonal forecasts 6 . Present seasonal forecast models have modest skill in predicting summer temperature across the eastern US (ref. 7) but tend to underestimate the probability of extremes at lead times longer than a week 8 . A complementary approach is to take advantage of certain mid-latitude conditions that may precede hot weather. Monthly-resolution precipitation deficits have been correlated with high temperatures in the following month 9 and anomalous mid-latitude sea surface temperature (SST) patterns have been highlighted as preceding heatwave episodes 10-13 . In the following we further explore and quantify the degree to which precipitation and sea surface temperatures provide for skillful prediction of high summer temperatures. Defining hot weatherOur focus is on hindcasting the occurrence of high temperature anomalies during the 60 hottest days of summer (hereafter simply summer) recorded in the Global Historical Climatology Network 14 . We identify regions that tend to experience hot days synchronously through a clustering algorithm that groups stations together on the basis of simultaneously recording temperature anomalies above the 95th percentile during summer (see Methods). Clustering stations into five regions results in interpretable climate zones: the maritime west coast, the arid interior west, the semiarid and subtropical southwest, tropical Florida, and the humid and continental eastern US ( Supplementary Fig. 1a). We focus on the eastern US cluster, comprising 1,613 stations, because i...

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Section: Comparison To Other Predictorssupporting

confidence: 58%

Long-lead predictions of eastern United States hot days from Pacific sea surface temperatures

et al. 2016

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“…Various studies documented that the ISM affected the summer climate in East Asia through a midlatitude wave train along the East Asian upper tropospheric westerly jet stream, causing differences in atmospheric circulation and water vapor transport [18,19]. e results further revealed that an enhanced ISM could generate anomalous cyclonic circulation over the Mediterranean Sea in the upper layer [20,21] and stimulated a continuous downstream air flow, i.e., a silk road pattern [22], with a barotropic anticyclonic anomaly over East Asia, leading to more water vapor being transported northward along the western periphery of the WPSH [23]. However, the position and intensity of the ISM, which lead to precipitation over NC, exhibit large variabilities in addition to land-sea thermal contrasts and are affected by atmospheric internal dynamic processes [24] and El Niño-Southern Oscillations (ENSO) [25].…”

Section: Introductionmentioning

confidence: 91%

Synergy Effects of the Indian Summer Monsoon and the Tibetan Plateau Heating on Summer Rainfall over North China

Zhao

Zhang

2020

Advances in Meteorology

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An analysis based on July-August precipitation reveals that there is a tripole pattern of the precipitation distribution, that is, significantly increased rainfall over North China (NC) is related to the increased rainfall over the Indian subcontinent (IS) and the decreased rainfall over the southeastern Tibetan Plateau (TP) and vice versa, that corresponds to the Indian summer monsoon (ISM) and TP heating pattern, which are interactive. Therefore, it is necessary to investigate the effect of NC rainfall-related atmospheric circulation and the physical linkage with the two thermal forcings together. The linear baroclinic model (LBM) is applied to determine the dynamics of the process. The results show that an enhanced ISM is accompanied by reduced TP heating, favors convection and easterly anomaly over the IS, and produces a Gill-type Rossby wave that affects the vorticity over North Africa. Meanwhile, there is another Rossby wave originating in North Africa and moving eastward to the Pacific Ocean, which interferes with circulation at mid- to high-latitudes, i.e., it strengthens the cyclone over the Baikal region and stretches the western Pacific subtropical high (WPSH) northward to northeastern Asia, and results in abundant water vapor transported to NC. Furthermore, the strong convection over the IS excites the Kelvin waves over the equatorial region, which moves eastward and generates anticyclones over Philippines, consequently leading to the Pacific-Japan (PJ) pattern. The PJ pattern cooperates with the wave train at midlatitudes, resulting in abundant water vapor being transported to NC. The summer rainfall over NC is therefore modulated by synergistic effect of both the ISM and TP heating.

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“…4c). Yun et al (2011) describes that this NPH in August is accompanied by the northward shift of the Asian jet induced blocking by Rossby wave. The structure of anticyclonic anomalies in July, which appear to be as strong as the anticyclonic anomaly pattern in August, leads to the following conclusion.…”

Section: Large-scale Circulation With Blockingmentioning

confidence: 98%

What Caused the Extraordinarily Hot 2018 Summer in Korea?

Yeo

Seo

et al. 2020

Journal of the Meteorological Society of Japan

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In 2018, heatwaves (HWs), which are defined as period of abnormally hot weather with the daily maximum temperature (T_Max) exceeding its 95th percentile threshold for at least three consecutive days, were prevalent during June to August, and temperature records were broken in many countries over East Asia (EA) including China (CH), Japan (JP), and the Korean Peninsula (KP). In particular, extreme HWs through July to August lasted for the longest duration with 21.3 days with T_Max reaching 36.9°C. The highest T_Max, recorded since 1907, exceeded to 41°C in Hongcheon, located east of Seoul in the KP. Here, we examine the factors that influenced the 2018 HW, and how these relate to the 1994 HW, which was second longest HW recorded in the KP. The results show that abnormally strong and northwestward extended anticyclone features observed in July 2018 lasted as a persistent North Pacific anticyclone anomaly until August 2018 centered at the northern KP. These anticyclone features subsequently formed as a modon-like blocking with a cyclonic anomaly in the East China Sea. Meanwhile, in August 1994, the North Pacific High (NPH) extended to eastern EA, which broked the meridional dipole structure and HWs do not persist. The NPH, which persisted till August 2018, was accompanied by a sinking motion, suppression of precipitation, anomalous maximum temperature, weakening of the westerly jet stream, and increased insolation due to clear sky. We find that the prolonged and northwestward-shifted NPH including the KP drove the extraordinarily hot 2018 summer in Korea. In addition, low precipitation and massive evapotranspiration with the persistent insolation in July 2018 influenced the dry condition at the surface. We suggest that the predictions for the location and duration of the NPH associated with the HWs are required to reduce heat-related mortality and the impact on agriculture due to excessive evapotranspiration.

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Effects of subseasonal basic state changes on Rossby wave propagation during northern summer

Cited by 8 publications

References 26 publications

Long-lead predictions of eastern United States hot days from Pacific sea surface temperatures

Long-lead predictions of eastern United States hot days from Pacific sea surface temperatures

Synergy Effects of the Indian Summer Monsoon and the Tibetan Plateau Heating on Summer Rainfall over North China

What Caused the Extraordinarily Hot 2018 Summer in Korea?

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