Well your deck in definitely pressure treated.......and very dry. Steps to take to get the job done would be a deck cleaner, either Cabots problem solver or other. Let the deck dry for at least 24 hours before staining. For a semi tran deck stain I have heard good reports about SW deckscapes, Cabots is a decent product as well as Ben Moore. Another product to consider would be Sikkens semi-trans. We have had rave reviews of this product. But, now the but, horizontal surfaces are very difficult to keep a finish on especially when dealing with PT. So good luck..........