AGW Observer

Observations of anthropogenic global warming

New research – extreme weather (July 31, 2016)

Posted by Ari Jokimäki on July 31, 2016

Some of the latest papers on extreme weather are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.


Drivers of exceptionally cold North Atlantic Ocean temperatures and their link to the 2015 European heat wave (Duchez et al. 2016)

Abstract: The North Atlantic and Europe experienced two extreme climate events in 2015: exceptionally cold ocean surface temperatures and a summer heat wave ranked in the top ten over the past 65 years. Here, we show that the cold ocean temperatures were the most extreme in the modern record over much of the mid-high latitude North-East Atlantic. Further, by considering surface heat loss, ocean heat content and wind driven upwelling we explain for the first time the genesis of this cold ocean anomaly. We find that it is primarily due to extreme ocean heat loss driven by atmospheric circulation changes in the preceding two winters combined with the re-emergence of cold ocean water masses. Furthermore, we reveal that a similar cold Atlantic anomaly was also present prior to the most extreme European heat waves since the 1980s indicating that it is a common factor in the development of these events. For the specific case of 2015, we show that the ocean anomaly is linked to a stationary position of the Jet Stream that favours the development of high surface temperatures over Central Europe during the heat wave. Our study calls for an urgent assessment of the impact of ocean drivers on major European summer temperature extremes in order to provide better advance warning measures of these high societal impact events.

Predicting Atlantic seasonal hurricane activity using outgoing longwave radiation over Africa (Karnauskas & Li, 2016)

Abstract: Seasonal hurricane activity is a function of the amount of initial disturbances (e.g., easterly waves) and the background environment in which they develop into tropical storms (i.e., the main development region). Focusing on the former, a set of indices based solely upon the meridional structure of satellite-derived outgoing longwave radiation (OLR) over the African continent are shown to be capable of predicting Atlantic seasonal hurricane activity with very high rates of success. Predictions of named storms based on the July OLR field and trained only on the time period prior to the year being predicted yield a success rate of 87%, compared to the success rate of NOAA’s August outlooks of 53% over the same period and with the same average uncertainty range (±2). The resulting OLR indices are statistically robust, highly detectable, physically linked to the predictand, and may account for longer-term observed trends.

Seasonal mean temperature changes control future heat waves (Argüeso et al. 2016)

Abstract: Increased temperature will result in longer, more frequent, and more intense heat waves. Changes in temperature variability have been deemed necessary to account for future heat wave characteristics. However, this has been quantified only in Europe and North America, while the rest of the globe remains unexplored. Using late century global climate projections, we show that annual mean temperature increases is the key factor defining heat wave changes in most regions. We find that commonly studied areas are an exception rather than the standard and the mean climate change signal generally outweighs any influence from variability changes. More importantly, differences in warming across seasons are responsible for most of the heat wave changes and their consideration relegates the contribution of variability to a marginal role. This reveals that accurately capturing mean seasonal changes is crucial to estimate future heat waves and reframes our interpretation of future temperature extremes.

A Review of Drought in the Middle East and Southwest Asia (Barlow et al. 2016)

Abstract: The Middle East and Southwest Asia comprise a region that is water-stressed, societally vulnerable, and prone to severe droughts. Large-scale climate variability, particularly La Niña, appears to play an important role in region-wide drought, including the two most severe of the last fifty years—1999-2001 and 2007-2008—with implications for drought forecasting. Important dynamical factors include orography, thermodynamic influence on vertical motion, storm track changes, and moisture transport. Vegetation in the region is strongly impacted by drought and may provide an important feedback mechanism. In future projections, drying of the eastern Mediterranean is a robust feature, as are temperature increases throughout the region, which will affect evaporation and the timing and intensity of snowmelt. Vegetation feedbacks may become more important in a warming climate.

There are a wide range of outstanding issues for understanding, monitoring, and predicting drought in the region, including: dynamics of the regional storm track, the relative importance of the range of dynamical mechanisms related to drought, regional coherence of drought, the relationship between synoptic-scale mechanisms and drought, predictability of vegetation and crop yields, stability of remote influences, data uncertainty, and the role of temperature. Development of a regional framework for cooperative work and dissemination of information and existing forecasts would speed understanding and make better use of available information.

Should flood regimes change in a warming climate? The role of antecedent moisture conditions (Woldemeskel & Sharma, 2016)

Abstract: Assessing changes to flooding is important for designing new and redesigning existing infrastructure to withstand future climates. While there is speculation that floods are likely to intensify in the future, this question is often difficult to assess due to inadequate records on streamflow extremes. An alternate way of determining possible extreme flooding is through assessment of the two key factors that lead to the intensification of floods: the intensification of causative rainfall and changes in the wetness conditions prior to rainfall. This study assesses global changes in the antecedent wetness prior to extreme rainfall. Our results indicate a significant increase in the antecedent moisture in Australia and Africa over the last century; however, there was also a decrease in Eurasia and insignificant change in North America. Given the nature of changes found in this study, any future flood assessment for global warming conditions should take into account antecedent moisture conditions.

Other papers

The evolution of temperature extremes in the Gaspé Peninsula, Quebec, Canada (1974–2013) (Fortin et al. 2016)

On the emergence of rainfall extremes from ordinary events (Zorzetto et al. 2016)

Changes of extreme drought and flood events in Iran (Modarres, Sarhadi & Burn, 2016)

An integrated analysis of the March 2015 Atacama floods (Wilcox et al. 2016)

Tropical cyclones in the GISS ModelE2 (Camargo et al. 2016)

Trends and variability in extremes of precipitation in Curitiba – Southern Brazil (Pedron et al. 2016)

North Atlantic Storm Track Sensitivity to Projected Sea Surface Temperature: Local versus Remote Influences (Ciasto et al. 2016)

Observed changes in extreme temperature and precipitation over Indonesia (Supari et al. 2016)

A Modeling Study of the Causes and Predictability of the Spring 2011 Extreme US Weather Activity (Schubert et al. 2016)

A Situation-based Analysis of Flash Flood Fatalities in the United States (Terti et al. 2016)

Climatology and trend analysis of extreme precipitation in subregions of Northeast Brazil (Oliveira et al. 2016)

Can we predict seasonal changes in high impact weather in the United States? (Jung & Kirtman, 2016)

Does population affect the location of flash flood reports? (Marjerison et al. 2016)

The Physics of Drought in the U.S. Central Great Plains (Livneh & Hoerling, 2016)

Heat wave over India during summer 2015: an assessment of real time extended range forecast (Pattanaik et al. 2016)

Investigation of the 2013 Alberta flood from weather and climate perspectives (Teufel et al. 2016)

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