Meteorologists studying the change in a region's precipitation over a 20-year period are studying the region's

Climate

Climate is a term used to the weather conditions prevailing in an area for longer period of time. Its a record of the weather conditions of that area. Generally, its the record of many years. A particular area has its own specific climatic conditions. Factors being studied are temperature, humidity, precipitation, pressure of the atmosphere, wind speed.

The term weather is used when these factors are studied for a shorter period of time. This is how its different from climate.

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom

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