The Spaniard is second in the drivers' championship going into Sunday's race but trails Sebastian Vettel by 60 points with six races left and has not won a grand prix since his home GP in May.
"I am not surprised at the outcome of this qualifying session because in terms of pure performance, Saturday is always difficult for us and will continue to be so until the end of the season," said a clearly downcast Alonso, a two-time world champion.
"This weekend seems harder than usual because while up until now we have always had a good race pace, both yesterday and today we suffered on the long runs and that means we must absolutely improve for tomorrow," added Alonso, who will start fifth on the grid because of a penalty for Mark Webber.
"We have a few problems with the tyres which we are unable to manage as well as the others: there's a lot of graining and if you push very hard in the first sector you almost risk being unable to finish the lap.
There is a chance of rain at the Yeongam circuit on race day and Alonso admitted that may be no bad thing if he is to stand any chance of chasing down pole-sitter Vettel.
"Given how we look in the dry, the rain could mix things up and in fact we have nothing to lose and even if there will be little time to adapt to it, we must be ready for this eventuality," he said.