Source : Webster's Revised Unabridged Dictionary (1913)

Somberly \Som"ber*ly\, Sombrely \Som"bre*ly\, adv.
   In a somber manner; sombrously; gloomily; despondingly.

Source : WordNet®

somberly
     adv : in a somber manner; "`That's sure bad news,' said Dowd,
           somberly" [syn: {sombrely}]