Create a new layer and place it above all the previous layers. Paint it in black color with Paint Bucket Tool and apply the filter that is shown here: Filter - Noise - Add Noise.

fairy tale - rainy day - 
photo effects

Selecting the Motion Blur, it's possible to blur out this layer:

fairy tale - rainy day - 
photo effects

Change the layer's type on Screen and make the appropriate
 
corrections on its brightness and on its contrast (ctrl+L).

fairy tale - rainy day - 
photo effects

Blur it out also with Filter - Blur - Gaussian Blur.

fairy tale - rainy day - 
photo effects

Select the Layer Mask and Gradient Tool to hide the lowest part of the layer.

fairy tale - rainy day - 
photo effects