upslope vs upward

upslope

adj
  • in a direction up a slope 

noun
  • an upward slope 

adv
  • up a slope 

upward

adj
  • Directed toward a higher place. 

adv
  • In a direction from lower to higher; toward a higher place; in a course toward the source or origin 

  • Yet more; indefinitely more; above; over. 

  • In the upper parts; above. 

How often have the words upslope and upward occurred in a corpus of books? (source: Google Ngram Viewer )