The Dynamic Character of Northern Hemisphere Flow Regimes in a Near-Term Climate Change Projection

Jensen, Andrew D.; Akperov, Mirseid; Мохов, И. И.; Lupo, Anthony R.; Sun, Fengpeng

doi:10.3390/atmos9010027

Cited by 13 publications

(16 citation statements)

References 55 publications

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“…The classification scheme of reference [6] for NH flows is consistent with the idea that the NH flow has preferred observed states. This idea is not new (see reference [40] for a discussion of the history). The early work of references [52][53][54] (and others) suggested the NH flow vacillated between two quasi-stable states (zonal versus meridional), but later work suggested that the NH flow possesses multiple stable states, including those that represent blocking (e.g., references [55][56][57][58][59]).…”

Section: Discussion: Teleconnection Relationshipsmentioning

confidence: 99%

“…The North Atlantic Oscillation (NAO) (e.g., reference [36]) is a north-south pressure oscillation in the North Atlantic whose fundamental dynamics are similar to that of the Pacific North American (PNA) pattern (e.g., references [37][38][39]). The NAO also may be the regional expression of vacillation (e.g., reference [40]) in the NH flow overall. It is well known that the time series of the daily or monthly NAO index values possess interannual (e.g., references [41,42]) or interdecadal (e.g., references [43,44]) modes.…”

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confidence: 99%

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Changes in the Atmospheric Circulation Conditions and Regional Climatic Characteristics in Two Remote Regions Since the Mid-20th Century

et al. 2019

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A meridional Northern Hemisphere (NH) circulation epoch, which began in 1957, is marked by changes in the temperature and precipitation regimes over southwest Russia and central USA depending on the occurrence of NH atmospheric circulation regimes. A classification scheme proposed in 1968, and studied later put forth 13 NH circulation types, fitting more broadly into four groups, two of which are more zonal type flows and two of which are more meridional flows. Using the results of a previous study that showed four distinct sub-periods during the 1957–2017 epoch, the temperature and precipitation regimes of both regions were studied across all seasons in order to characterize modern day climate variability and their suitability for vegetation growth. Then the Hydrologic Coefficient, which combined the temperature and precipitation variables, was briefly studied. The most optimal conditions for vegetation growth, positive temperature and precipitation anomalies, were noted during the period 1970–1980 for southwest Russia, which was dominated by an increasingly more zonal flow regime in the Belgorod region and NH in general. For the central USA, the HTC showed more ideal conditions for agriculture in recent years due to favorable precipitation occurrence. In southwest Russia, variable precipitation regimes were noted during the meridional flow periods, and with the increase in temperature (since 1998), these can adversely affect the hydrothermal characteristics of the growing season. Finally, a comparison of the 13 NH circulation types with several teleconnection indexes demonstrated the robustness of the NH flow regime classification scheme used here.

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Section: Discussion: Teleconnection Relationshipsmentioning

confidence: 99%

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confidence: 99%

Changes in the Atmospheric Circulation Conditions and Regional Climatic Characteristics in Two Remote Regions Since the Mid-20th Century

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“…This is consistent with the result here, but does not suggest a cause and effect or dynamic relationship between the two. An examination of the wave dynamics would be needed and a recent study [60] suggested that the annual frequency of changes in flow regimes (here ECMs) is not changing significantly or projected to increase in the near future. Additionally, the correspondence between the future occurrence DKV46 NH flow regimes and those examined in studies such as [60] for example has not been examined as yet.…”

Section: Circulation Epochs and Information Entropymentioning

confidence: 99%

Changes in the Dynamics of the Northern Hemisphere Atmospheric Circulation and the Relationship to Surface Temperature in the 20th and 21st Centuries

Kononova

Lupo

2020

Atmosphere

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This study examines the long-term fluctuations in the Northern Hemisphere (NH) and global atmospheric circulation, teleconnections, including blocking, and surface temperature over the period 1899-2018. The teleconnection and blocking data were available from the mid-20th century. The classification of the global atmospheric circulation was developed from an early subjective categorization of atmospheric circulation conditions for the NH that considered the number, location, and amplitude of waves on the jet stream for frequently occurring circulation patterns. This work updated earlier studies that identified three circulation epochs based on the predominance of one of four different flow types that were grouped primarily based on whether the flow was zonal or meridional. This work noted a significant correlation between the early 21st century flow change toward the occurrence of more meridional flows and the increase in the occurrence of blocking as well as changes in the teleconnection indexes. The early 21st century was associated with a distinct change in the Northern Hemisphere flow entropy as measured using Information or Shannon Entropy, a change that was shown to be statistically significant. Additionally, this demonstrated that this quantity has utility as a dynamic diagnostic tool in atmospheric science. Finally, a comparison of these flow regimes to the 20th and 21st century variations in surface temperature were considered here. The global average annual surface temperature variations correlated strongly to fluctuations in the predominant atmospheric circulation type.

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“…This study is unique in that this research group is the only one that defines and examines BI across the globe. BI has been shown also to be related to dynamic quantities such as the 500 hPa height gradients [1], enstrophy, and entropy (e.g., Kolmogorov-Saini Entropy [25]). Additionally, this work will compare our results for SH blocking into the 21st century to those of [12] where appropriate.…”

Section: Introductionmentioning

confidence: 99%

Changes in Global Blocking Character in Recent Decades

et al. 2019

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A global blocking climatology published by this group for events that occurred during the late 20th century examined a comprehensive list of characteristics that included block intensity (BI). In addition to confirming the results of other published climatologies, they found that Northern Hemisphere (NH) blocking events (1968–1998) were stronger than Southern Hemisphere (SH) blocks and winter events are stronger than summer events in both hemispheres. This work also examined the interannual variability of blocking as related to El Niño and Southern Oscillation (ENSO). Since the late 20th century, there is evidence that the occurrence of blocking has increased globally. A comparison of blocking characteristics since 1998 (1998–2018 NH; 2000–2018 SH) shows that the number of blocking events and their duration have increased significantly in both hemispheres. The blocking BI has decreased by about six percent in the NH, but there was little change in the BI for the SH events. Additionally, there is little or no change in the primary genesis regions of blocking. An examination of variability related to ENSO reveals that the NH interannual-scale variations found in the earlier work has reversed in the early 21st century. This could either be the result of interdecadal variability or a change in the climate. Interdecadal variations are examined as well.

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The Dynamic Character of Northern Hemisphere Flow Regimes in a Near-Term Climate Change Projection

Cited by 13 publications

References 55 publications

Changes in the Atmospheric Circulation Conditions and Regional Climatic Characteristics in Two Remote Regions Since the Mid-20th Century

Changes in the Atmospheric Circulation Conditions and Regional Climatic Characteristics in Two Remote Regions Since the Mid-20th Century

Changes in the Dynamics of the Northern Hemisphere Atmospheric Circulation and the Relationship to Surface Temperature in the 20th and 21st Centuries

Changes in Global Blocking Character in Recent Decades

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