Abstract 125

Abstract ID: 125

Study of cyclogenesis in the eastern tropical Atlantic East Atlantic with the LMDz model

Lead Author: Dame Guey
Laboratory of Electronics, Computing, Telecommunications and Renewable Energies – University Gaston Berger, Senegal

Keywords: Cyclogenesis, variability, cyclonic activity

Abstract: Tropical cyclones are among the most devastating natural disasters in the world. In the tropical Atlantic, they are responsible for more than 70% of the natural damage in the United States and they can be the cause of loss of life and property when the depressions cause them to strengthen near the coast: in August 1999, tropical storm Cindy caused the death of several dozen Senegalese fishermen. From August 23 to 31, 2005, a hurricane named Katrina, was one of the six most powerful hurricanes that the USA has ever known. More than 2000 people died from the floods caused by Katrina, the damage caused reached about 110 billion dollars and practically New Orleans and Louisiana were wiped out. However, the ability of models to reproduce these climate systems remains to be investigated. The objective of this study is to evaluate the capacity of the LMDz model to reproduce cyclogenesis, the variability of cyclonic activity, and the various processes involved in the West African coasts to the center of the tropical Atlantic basin. For this, two approaches were used in this work. In the first approach, we sought to observe the capacity of the model to represent the interannual variability of cyclonic activity in the Atlantic basin by seasonal climatological averages, and a second more descriptive approach consisting of Spatio-temporal monitoring of Hurricane Karl born near the Cape Verdean coast on September 16, 2004. This hurricane was followed by making horizontal sections of the tropospheric layers most sensitive to the cyclonic phenomenon in order to have a more exhaustive validation of the model performance. The results first showed a strong variability of cyclonic activity in the tropical Atlantic at different time scales proving the July-September period and the ITCZ band respectively as the season and the area favorable to cyclogenesis. Then, the seasonal mean conditions are identified from ERAI and NCEP reanalyses as well as the years of strong and weak cyclonic activities. Good correlations of field representation and spatial distributions between observed and simulated data were found, as well as some climatic variabilities of the monsoon in the area. Finally, the results of the follow-up of hurricane Karl are encouraging since they have demonstrated that the LMDz model is able to reproduce “fairly correctly” a hurricane in terms of intensity, spatial distribution, and trajectory followed.

Abdou Lahat DIENG (Laboratory of Physics of the Atmosphere and the Ocean-Simeon Fongang – University Cheikh Anta Diop)
Abdoulaye DEME (Laboratory of Electronics, Computing, Telecommunications and Renewable Energies – University Gaston Berger)