A desert oasis beckons. Is it a mirage, or is that really a chairlift? Talented filmmakers Jordan Manley and Daniel Irvine has been following skiers around the globe for years for their series “A Skier’s Journey,” but in this episode, they’ve stumbled across a strange location for rippers. Ski Dubai is a small hill with a 200-foot vertical rise that’s built into a luxury shopping mall in the largest sand desert on the planet. Massive air-conditioning fans whir to cool the single slope, while temperatures outside soar above 100 degrees. But the benefits entice: a collection of quirky regulars, year-round turns and predictable conditions.