A novel variable resolution global spectral method on the sphere

► HTBT is a re-parametrization map on the sphere, preserves differential operators. ► Variable resolution global spectral method is generated through re-parametrization. ► Resolution is finer over the tropics and decreases smoothly away from it. ► Spectral coefficients are computed through FFT and Gaussian quadrature methods. ► Boyd-Vandeven filter helps to retain the higher order accuracy of the method.