Vim still displays the last removed character

Question

when my terminal LANG=en_US.UTF-8, my vim display is messed in that when page down or page up, the last page's conent is still displayed. or when I delete a character, for example, in "abcdef", I use x to delete character "a", the display in vim is "bcdeff", even though there is no actual 'f' at the end. I added set encoding=utf8 in .vimrc and it doesn't help. How to make vim working with terminal of locale setting like this:

LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=