Actually, the pic in question seems to have its bump-ness reducing as it fades up. For that effect, I'd load in an inverted leather seamless bumpmap to an alpha channel, then apply a gradient to it of black fading to transparentstraight down so the top becomes gradually darker (or jump into quick mask mode in the channel, apply a gradient to make a gadiated selection, then adjust levels so the contrast reduces and the image gets darker near the top).

Use this as the lighting effects texture channel. Then it might be possible to simply use a copy of this channel as the layer mask on the effect itself -- if not, use a plain gradient like mentioned above.