A stochastic model for tropical cyclone tracks based on Reanalysis data and GCM output

Thursday, 18 December 2014
Kazue Ito, Shinya Nakano and Genta Ueno, The Inst of Statistical Math, Tachikawa, Japan
In the present study, we try to express probability distribution of tropical cyclone (TC) trajectories estimated on the basis of GCM output. The TC tracks are mainly controlled by the atmospheric circulation such as the trade winds and the Westerlies as well as are influenced to move northward by the Beta effect. The TC tracks, which calculated with trajectory analysis, would thus correspond to the movement of TCs due to the atmospheric circulation. Comparing the result of the trajectory analysis from reanalysis data with the Best Track (BT) of TC in the present climate, the structure of the trajectory seems to be similar to the BT.

However, here is a significant problem for the calculation of a trajectory in the reanalysis wind field because there are many rotation elements including TCs in the reanalysis data. We assume that a TC would move along the steering current and the rotations would not have a great influence on the direction of moving. We are designing a state-space model based on the trajectory analysis and put an adjustment parameter for the moving vector. Here, a simple track generation model is developed. This model has a possibility to gain the probability distributions of calculated TC tracks by fitting to the BT using data assimilation.

This work was conducted under the framework of the “Development of Basic Technology for Risk Information on Climate Change” supported by the SOUSEI Program of the Ministry of Education, Culture, Sports, Science, and Technology.