Integrated Regional Enstrophy and Block Intensity as a Measure of Kolmogorov Entropy

Proceedings of the 2nd International Electronic Conference on Atmospheric Sciences

Jensen

et al. 2017

Some weather extremes can be the result of atmospheric blocking, which can be responsible for the stagnation of weather patterns. These large-scale quasi-stationary mid-latitude flow regimes can result in significant temperature and precipitation anomalies in the regions that the blocking event impacts. The ability to predict periods of anomalous weather conditions due to atmospheric blocking is a major problem for medium-range forecasting. Analyzing the NCEP Ensemble 500-mb pressure heights (240 h) ten-day forecasts, and using the University of Missouri blocking archive to identify blocking event, the forecasted duration and intensity of model blocking events are compared to observed blocks. Comparing these differences using four case studies occurring over a one-year period across the Northern Hemisphere has shown the continued need for improvement of the duration and intensity of blocking events. Additionally, a comparison of the block intensity to a diagnostic known as the Integrated Regional Enstrophy (IRE) was performed in order to determine if there is a correlation between these quantities. Having a better understanding of knowing how long each block will last and their associated anomalies can help society prepare for the damage they can cause. Simulating and identifying blocks correctly is important in improving forecast issues.

Section: Discussionsupporting

confidence: 87%

“…To test this proposal correlation was performed with and without a time lag of each variable up to 72 h as in [34]. There were no positive correlations when BI led IRE.…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…Here we used the 500-hPa heights and the [20] criterion to identify blocking and calculate intensity. Additionally, the IRE was calculated and compared to the BI following [34].…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

The Predictability of Northern Hemispheric Blocking Using an Ensemble Mean Forecast System

Reynolds

Proceedings of the 2nd International Electronic Conference on Atmospheric Sciences

Jensen

et al. 2017

“…Many studies (e.g., [19][20][21]) also demonstrate that such flow regime behavior occurs independently in each of the major NH ocean basins. Additionally, Jensen et al [22] (and references therein) demonstrated that quantities such as enstrophy (specifically the measure developed by [23] called area integrated enstrophy-IE) can be utilized to identify the transitions between hemispheric or regional flow regimes. They [22] showed a correspondence between IE and entropy (Kolmogorov-Saini or metric entropy), which is related to flow predictability and stability, as well as block intensity (BI-as in [22]).…”

Section: Introductionmentioning

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

2020

Atmosphere

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.

The relationship between atmospheric blocking and temperature anomalies in Turkey between 1977 and 2016

Efe

Sezen

Intl Journal of Climatology

et al. 2019

The relationship between the character of atmospheric blocking and surface temperature has not been studied in depth for Turkey. Here, these relationships are investigated for the period 1977–2016. The seasonal mean temperature anomalies for all stations during blocked days varies between −2.1 and 0.8°C. There are four main patterns representing the mean seasonal temperature anomalies for all stations during blocked and non‐blocked days. The annual cycle for each group is nearly opposite, and this indicates the impact of blocking on observed temperature, as blocked days comprised 30% of the study period. When focusing on the spatial distribution of mean seasonal anomalies, the winter and fall seasons show that, almost all stations have negative temperature anomalies although anomalies are close to zero during warm seasons (spring and summer). The composite analysis shows that the western part of the country is strongly affected by cold air advection during upstream blocking events and the eastern part of the country is affected by warm temperature advection for downstream blocking events. There is a statistically significant (95% confidence level) negative correlation between blocking intensity and temperature anomalies in all seasons except spring. There is no relationship between both blocking duration and longitudinal extent and the seasonal mean temperature anomaly except during winter, which has a significant negative correlation. The temperature anomaly distribution stratified by season shows that strong positive anomalies are rarely observed in all seasons. Only winter and spring were associated with very strong positive anomalies and only at a few stations. Rex‐type atmospheric blocking events are observed during the period of not only the maximum temperature anomaly but also for minimum anomalies. However, the location of the blocking event differed from the typical situation above, with the cold and warm events being located downstream and upstream of Turkey, respectively.