Southern California hotels were noticeably absent from TripAdvisor’s annual ranking of top U.S. lodging destinations released last week, although San Diego’s Fairmont Grand Del Mar made it onto the list of the most beloved luxury properties.

TripAdvisor’s Travelers’ Choice Awards, based on millions of reviews of users worldwide over the past year, are the first of several hospitality rankings to be released in the coming months — some considered more prestigious than others.

Unlike some of the rankings, which are determined following formal inspections of the properties, TripAdvisor’s selections are based solely on online reviews, which explains why some winners vary markedly from year to year.

The Fairmont, for example, was ranked No. 1 luxury hotel in the nation last year, but in the newest rankings, it is now 13th. And in the narrower category of family hotels, the Legoland California hotel in Carlsbad is ranked No. 3 this year where a year earlier it was 16th.

“This is the 16th year of the Traveler’s Choice awards, and it’s always interesting to see how the lists turn out,” said spokeswoman Elizabeth Monahan. “If you go to TripAdvisor and search San Diego hotels, you’ll see the rankings change every day or even a couple times a day based on people reviewing the hotel. But for these awards, rather than look at one person’s review for a week or month, they take into consideration a full year of traveler reviews from all around the world.

“The awards do rely on the quantity and quality of traveler reviews, so if there’s been a renovation or new features, that helps the brand but it’s hard to nail down why there are changes in the rankings.”

Rancho Valencia Resort & Spa ranked 17th in last year’s awards but was not among the top 25 this year. La Maison hotel in Palm Springs was the only other Southern California property to join Fairmont in the top luxury hotels.

Said Grand Del Mar General Manager Dennis Clark, “As the only property in San Diego to be included, we are thrilled to represent our city and look forward to continuing to provide exceptional service, luxurious accommodations and experiences for our guests.”