GPU implementation of local ensemble transform Kalman filter (LETKF) with two-dimensional lattice Boltzmann method

Hasegawa, Yuta   ; Onodera, Naoyuki   ; Asahi, Yuichi   ; Idomura, Yasuhiro   

We developed GPU implementation of ensemble data assimilation (DA) using the local ensemble transform Kalman filter (LETKF) with the lattice Boltzmann method (LBM). The performance test was carried out upto 32 ensembles of two-dimensional isotropic turbulence simulations using the D2Q9 LBM. The computational cost of the LETKF was less than or nearly equal to that of the LBM upto eight ensembles, while the former exceeded the latter at larger ensembles. At 32 ensembles, their computational costs per cycle were respectively 28.3 msec and 5.39 msec. These results suggested that further speedup of the LETKF is needed for practical 3D LBM simulations.