这两个词的区别在于当副词的时候
两者区别是：当它们都作副词用时,close是距离上的接近,而closely是感情关系上的亲近.close表示“靠近”、“紧紧地”,closely则表示“紧密地”、“严密地”、“密切地”.如：
I went closer,and saw clearly a tall man in the moonlight．
Come close,I want to tell you something important．
The policeman followed the strange man closely．
The scientists got closely in touch with the astronauts