Taylor Swift's New York love affair

Taylor Swift is enjoying her ninth week at the top of Billboard Artist 100 chart. But her popular track, "Welcome to New York," which kicks off the album isn't just another example of her foray into more pop-sounding music. It's actually part of a partnership with New York City's official marketing and tourism group.

As part of the cooperation with NYC & Company—the city's official marketing and tourism body—New York has paid for outdoor advertisements in cities along the East Coast, as well as international hubs in Spain and Italy. In addition, NYC tourist-themed video ads have also been placed in taxis and through social media, encouraging visitors to use #W2NY.

"It's all about capitalizing on the starry-eyed optimism that you get when you come to New York City," Chris Heywood, senior vice president of global communications for NYC & Company told CNBC. "And this genuine excitement you get, the electricity, the energy and vibrancy."

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Ambassador Swift?

Since being named the city's "Global Welcome Ambassador," the campaign is getting a boost from Swift herself. The pop diva's social media channels do massive traffic, according to Starcount, a company that tracks data across 12 social networks. Those figures show Swift is currently the No. 1 celebrity in terms of follower numbers and YouTube views.

The social media exposure, combined with Swift's chart-topping popularity, was a big reason behind why New York selected her to represent the city.

"We listened to the song and it was on brand for us," Heywood said. "It becomes a pop culture reference point and it's a wave we're very fortunate to ride. We're so grateful we could use her popularity to promote New York and think it'll resonate with a number of demographics around the world."

NYC & Company, which has an annual budget of $36 million, says there was no exchange of money for Swift to be the global ambassador. However, officials said there were modest promotional expenses around "Welcome to New York" that could not be discussed.

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A representative from Swift declined to elaborate, and referred CNBC back to NYC & Company for comment.

One reason why the marketing team wanted Swift, was for how nicely they thought she'd align with their objective of appealing to millennials, the hotly coveted below-30 age group.

"It's an influential group of travelers and the next generation of travel. There's no one better than Taylor Swift to speak to that audience around the world," said Heywood.

"Her image is exactly what we want to leverage in a way that communicates the vibrancy, excitement and optimism of New York City," he added.