The Collaborative International Dictionary of English v.0.48:
Somberly \Som"ber*ly\, Sombrely \Som"bre*ly\, adv. In a somber manner; sombrously; gloomily; despondingly. [1913 Webster] SombernessWordNet (r) 3.0 (2006):
somberly adv 1: in a somber manner; "`That's sure bad news,' said Dowd, somberly" [syn: somberly, sombrely]