Tropical Cyclone Rainfall in the Observations, Reanalysis and ARPEGE Simulations in the North Atlantic Basin
Daloz, A. S. ; Chauvin, F. ; Roux, F.
In this chapter, we performed a climatological study of the tropical cyclone (TC) precipitation in the satellite observations and the reanalysis from the ECMWF and NCEP/NCAR centers over the North Atlantic (NATL) basin. Using the recently developed best track IBTrACS (Kruk et al. 2009; Knapp et al. 2009) we derived the mean daily TCs rainfall within 10°×10° box around the center of the TCs, the fraction of TCs rainfall to total rainfall and the TCs precipitation efficiency (TCPE). These variables were used to assess the ability of the reanalysis to represent the impact of TCs in altering the total rainfall over the North Atlantic basin. The main results show that : - The maximum of cyclonic precipitation is located in the Caribbean Sea and the Gulf of Mexico, for the observation and the reanalysis. - TCs contribute to a maximum of precipitation (between 15° and 25°N) over the Southern Gulf of Mexico, the Caribbean Sea and the West Atlantic Ocean for the observation and the reanalysis. - The most efficient TCs are located in the Gulf of Mexico, the Caribbean Sea and the West Atlantic Ocean for the observation and the reanalysis. We used a high resolution (0.5°) stretched atmospheric global climate model (GCM) ARPEGE to simulate the present and future TCs rainfall.The tracking of TCs was realized with the method of Chauvin et al. (2006). With the present integration, we assessed the ability of ARPEGE in simulating the TCs rainfall and the fraction and the efficiency of TCs rainfall. Future simulation has also been produced to study the possible evolution of those variables. The main results for the present and future simulations over the North Atlantic basin indicate that : - ARPEGE detects the maxima obtained by the observations and the reanalysis for the TCs rainfall and the fraction. However, it overestimates them. - ARPEGE obtains sparser results than the observations and the reanalysis for the efficiency of TCs, but detects the maxima over the West and East NATL Ocean. - ARPEGE presents a sensitivity to the time period, consistent with the real variation of TCs activity. - The difference between the future and present integration shows a decreasing contribution of the TCs rainfall and an increasing efficiency of TCs.
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