Sunrise
From FIS Freestyle wiki
The daily appearance of the sun on the eastern horizon as a result of the earth's rotation. In the United States, it is considered as that instant when the upper edge of the sun appears on the sea level horizon. In Great Britain, the center of the sun's disk is used instead. Time of sunrise is calculated for mean sea level.
Also See
Return to Snow and Weather Glossary, Working with Snow, Freestyle Skiing