climatologic "India-Burma Trough Index" defined by vorticity. Unit: s-1 Jan~Dec
-3.5109e-06
-3.45906e-06
-5.66606e-06
-6.98812e-06
-2.2735e-06
3.83292e-06
6.08671e-06
7.96125e-06
3.4065e-06
-1.28085e-06
-3.08159e-06
-3.2888e-06