空はからっと晴れていて、百舌鳥の声がきんきん、響いていました。
(Sora wa karatto hareteite, mozu tori no koe ga kinkin hibiite imashita.)
I think it means something like, 'when the sky cleared up, the sound of the mozu bird rang out', or 'the sky was clear and the sound of the mozu bird was ringing out.'
But what does 'karatto' mean? I can't seem to find it in any dictionary, although when I google it, it looks like you can say it with kanji, thus: 空土