If I understood your question well, So the difference in displacement between Asce. and Desc. might be comes from the difference in the date of each pairs this is the first thing the second thing, As you know that the direction of Satellite is difference between both in Asc and Dec. path, so in case of snow monitoring might be the detected area is different and then the properties of the snow in both directions are also different.
This I explained to you before in a previous post if you remember
For more about the horizontal displacement, take a look at the landslide displacement and make change and simulation of the processing workflow.
Also take a look at this topic might be it is helpful