Moist air harms books, so you wish to select the site with the lower humidity. Points on this line represent times when the relative humidity at Ridgetop was exactly equal to the relative humidity at Open Lowland. At those times, the Open Lowland site would be much worse for a rare books library than the Ridgetop site. In conclusion, the Ridgetop Site seems like a better choice for a rare book library, as least as far as protecting the books from humidity is concerned. Use data from the forest to defend your answer.
Campers also care about what time of day the different weather conditions occur.
For example, cold air temperature at night, when campers can be in their tents and sleeping bags, calls for different preparation than cold air temperature during the day. We'd better bring rain gear and a weatherproof tent. The temperature fluctuated drastically between day and night. So we'd better bring our all-seasons sleeping bags. The day time temperatures are usually around 10 C, so we'll need long pants and a sweater.