The top-ranked Swede made several long putts at the Emirates Golf Club, including a 36-foot birdie putt on the opening hole and a 60-footer on the sixth.
'The greens were my friends today,' Sorenstam said. 'I think the putt on the first was my longest birdie putt of the year. And the one on the sixth must be the longest putt of my career.'
Sorenstam had another early birdie, and four more over the last six holes for a bogey-free round.
'The greens are rolling well, but they are difficult to read because of the grains,' Sorenstam said. 'You need to know when to lag your putt or when to hit it firm. And I thought I read them pretty well today.'
Omata, who plays on the Japan Ladies PGA Tour, struggled to reach the green on the long par-4s, but her short game helped her finish with eight birdies.
English teenager Kiran Matharu, playing on a sponsor's exemption, was tied for third at 4 under with Kirsty Taylor, Sophie Sandolo and Bettina Hauert.
Matharu, a 17-year-old junior champion in England, came within a foot of double eagle on the par-5 18th.
'It is a great experience for me to play with players like Annika Sorenstam, whom I have grown up idolizing,' Matharu said. 'I hope to put up a good performance here as I intend to play full time on the Ladies European Tour next year.'
Karrie Webb was tied for 13th at 2 under, while Gwladys Nocera was at 1 under. Nocera needs to win the tournament to win the Ladies European Tour Order of Merit title.
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