降 - COME DOWN, from the Hill or from the Sky

Readings & Meanings:

こう

ふ（る）

お（りる）

to fall (rain, snow)

to get off, to come down

Common Usage:

降る

降雨

降参

Examples:

昨日から雪が降っている。

明日の降雨率は５０パーセントだ。

降参の印に白いハンカチを振った。

Translations:

It's been snowing since yesterday.

There is a 50% chance of rain tomorrow.

In a sign of surrender, they waved a white handkerchief.

Radical:

It's a good time to address Kozato, the 阝 radical.

That is, 阝 is called Kozato only when it's on the left. When it's on the left, it's an abbreviated form of 阜, which means piled earth, mound, or hill.

(But, when 阝 is on the right (see 京都), it's called Oozato and is an abbreviated form of 邑, for town. Sometimes simplification makes things harder.)

On the right is 夅. 夅 was how this kanji appeared in the earliest records of Chinese calligraphy (before 1000 BC). 夅 is a pictograph of feet that are pointing down.

The earliest meaning of 阝+ 夅 was to descend a high hill or descend from something higher. Later, the meaning was extended to "defeat," "give up," "rain," and even "abort."

References:

http://www.thejapanesepage.com/node/kanji/ka.htm
http://www.thejapanesepage.com/node/kanji/o.htm