[FINANCE] The role of African Easterly Wave variability and the large-scale environment on Atlantic Hurricanes: Observations and model simulations

Lead Research Organisation: University of Reading
Department Name: Meteorology


African easterly waves (AEWs) are an integral part of the West African and tropical Atlantic climate. They modulate daily rainfall over West Africa during the monsoon months (June to September) and can impact the probability of downstream tropical cyclogenesis (Hopsch et al., 2010). They are also implicated in the generation and transport of large quantities of mineral dust from North Africa across the Atlantic to the Caribbean (Jones et al., 2004) which can modify the West African monsoon circulation and also interact with the development of tropical cyclones (Jury and Santiago, 2010). Furthermore, 85% of 'major' hurricanes (i.e. those attaining category 3 or above on the Saffir Simpson scale) in the Atlantic develop from AEWs (Landsea, 1993) which in turn drive economic and insured losses on the eastern seabord of the United States (Lott and Ross, 2006). Despite their importance, the detailed aspects of AEW genesis and evolution are not well understood. In particular, our understanding of the processes that influence whether or not an AEW will develop near the west coast of Africa and spawn a tropical cyclone is poor. The aim of this project is to improve understanding of the physical processes that enhance and suppress hurricane development associated with AEWs and their interaction with the large-scale environment with a view to creating an enhanced seasonal forecast scheme for Atlantic cyclones, the results of which could be made available to the wider scientific and business community. Special emphasis will be given to the intraseasonal and interannual variability of AEWs in association with the African Easterly Jet (AEJ) and Tropical Easterly Jet, especially in the presence of dust and the role sea surface temperatures (SST) may play. The motivation for this study is two-fold. Firstly, there is a need to better understand the key atmosphere, land and ocean interactions that govern the AEW evolution over the Atlantic, as well as the interactions between dynamics and convection at intraseasonal and shorter timescales. Short timescales feedback on longer time- and larger space-scales in a continuum of process-related interactions. Therefore understanding the origin of the AEW development/decay will improve the reliability of hurricane forecasts and inform model development. Secondly, prediction, which is important for downstream cyclogenesis, requires information about the statistics of the weather systems in the Tropical Atlantic, eg. the variability of the number and intensity of AEWs. The specific science questions which will be addressed are: 1. What are the AEW spatial distributions and variability at intraseasonal and weather timescales and what AEW structures trigger cyclogenesis? Do these relate to the likelihood of a developing tropical cyclone making landfall in the Caribbean or United States? 2. What is the role of the AEJ-AEW dynamics relative to the large-scale environment for tropical cyclogenesis eg. how do dry air (mid-latitude or Saharan origin) and dust impact AEWs and tropical cyclone (TC) development? Can a better understanding of the mechanisms improve the predictability of Atlantic TCs? 3. How important are SST anomalies and associated large-scale modes of convection on intraseasonal and interannual time scales in determining the nature of the AEW variability? How does this impact the number of storms that make landfall in the Caribbean and United States? Over 3 years, the student will receive training in the science, computing and diagnostic tools for research required to support and influence crucial business decisions. They will benefit from the superb research environment at Reading with access to MSc courses and a large community of academic, research staff and PhD students working in many exciting fundamental and applied areas of meteorology, and the stimulating environment of a leading insurance house at the cutting edge of catastrophe modelling in the heart of the city of London.


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