The TVTropes Trope Finder is where you can come to ask questions like "Do we have this one?" and "What's the trope about...?" Trying to rediscover a long lost show or other medium but need a little help? Head to Media Finder and try your luck there. Want to propose a new trope? You should be over at You Know, That Thing Where.
I'd probably just call that comedic irony.
If it were something more like depicting a sunny beach that in reality is strewn with garbage and industrial pollutants, that would be Very False Advertising.
To get specific on the type of irony, that sort falls between situational irony (someone's expectations vs reality) and cosmic irony (the characters begin to suspect the universe/the author is screwing with them)
A person sees an advertisement for Los Angeles, California. The tourist brochure shows a beach and a sun beaming in the sky and the headline is "Land of Eternal Sunshine". They arrive in Los Angeles by train while a rainstorm of Biblical proportions is underway. What trope is this?