The study looked at how evaporation levels in Hebei Province changed from 1963 to 2003. They found that evaporation was higher in the 1960s and 1970s, but lower in the 1980s and 1990s. The biggest drop was in spring and summer. Most areas in Hebei saw a decrease in evaporation, with the south central part experiencing the largest decline. Factors like sunshine, clouds, temperature, and wind speed all play a role in evaporation levels, with solar radiation being the most important.