Creating seasonal frost-pockets?

I live in a climate with fairly drastic temperature differences.  It gets quite cold winter Zone 5a (-20°F to -15°F) but as usual planting zones don't tell the whole story.  This is also a desert climate, so summer temperatures between 90°F to 100°F are typical.

My property is in the middle of a sloping plane, and that's something that I'm thinking of using to my advantage to help produce a milder climate.

Is it possible to plant some kind of deciduous hedge/windbreak on contour to trap cold air during the summer, yet allow it to flow on through in the winter?

If it's worth a try, I'd also like suggestions for good plant(s) that would:
1) drop their leaves very thoroughly to allow maximum air flow-through
2) survive in the temperature extremes of this climate -- and in a dry, low-water environment
3) hopefully provide some useful byproduct for my system (fruit, nutrient fixing, or something)