why south east trade winds become south west monsoon

Dear student,

South east trade winds become south west monsoons or trade winds because as they (southeast trade winds) of the southern hemisphere and cross the equator , they are deflected towards the west under the influence of coriolis force and they start blowing as south west trade winds in northern hemisphere.

coriolis  force deflects the winds towards right in northern hemisphere and left in the southern hemisphere.

Regards,