Do raindrops get bigger as they fall from the sky?

This excellent question came from a second grader while learning about condensation in The Weather Program taught by Catch the Science Bug.   He wanted to know if more and more water vapor molecules stuck to the water drop as it fell and  if that is why the amount of rain falling can change from a drizzle to rain to a down pour.

Yes! After checking with the National Weather Service, water vapor can attach to raindrops as they fall and increase the size of the falling drop, thus increasing the amount of rain falling. The United States Geological Survey also informed us that raindrops can bump into each other and become one drop as they are falling as well.  This process is called coalescence. Once a drop reaches 4 millimeters in size, it usually splits into two drops.

Additionally when a different cloud moves overhead, the amount of rain and the intensity of rain may also change. So this is another reason why, we can change from a drizzle to rain.  Rain is usually from a cloud higher in our atmosphere and drizzle from a lower cloud.

In case you are wondering…..How do raindrops form?

Raindrops form when water vapor molecules bump into a dust particle in a cloud and condense around it becoming a droplet (smaller than a drop). Condense means that the water vapor (water in gas form) changes to water in liquid form around the dust particle. Wow- a good thing about dust! The size of the dust particle will affect the size of the droplet. A bigger particle of dusts results in a bigger droplet. The droplets must coalesce (bump and become one) with other droplets to become heavy enough to fall from the cloud.

Answers to Weather Challenge I

This is for you GRADE 4 of the Clara Barton Elementary School in Oxford, MA! You all did a great job in class this week and since I am not at your school today, I am watching the tsunami unfold on TV!

Hope you all have a great day!

1. c                                    

2. e

3. b

4. j

5. d

6. f

7. g

8. i

9. a

10. h

Weather Challenge I

This is a quiz that I give to the kids who I teach in school! It’s tough. You may need to look some of these up on the web or team up with a friend….preffeably one who knows a lot about the weather!

1. A river of wind made by the meeting of massive air masses high up in the atmosphere

 2. A relative air pressure difference that usually brings good weather and characterized by descending air that warms

 3. An especially fast moving area of wind in the great river of wind associated storms

 4. The temperature at which the air needs to be cooled to in order for clouds, fog, and moisture drops to form

 5. A relative air pressure difference that brings stormy weather and is characterized by rising, cooling air

 6.   

 7.   

8. A combination of wind speed and temperature help determine this value that let’s you know how long skin can be exposed to the cold before it freezes

 9.  The amount of water vapor in the air relative to the amount of water vapor the air can hold at the current temperature and pressure

 10. To measure this, you would use a barometer

Choices

a. Humidity

b. Jet streak

c. Jet stream

d. Low pressure

e. High pressure

f. Warm front

g. Cold front

h. Pressure

i. Wind chill factor

j. Dew point

Roadside Snow

As the big melt down begins this winter, I was curious about the dirt content of the snow on the side of the road.  To further investigate, I took some snow from the side of the road.  It did not look that dirty compared to the really black snow along the sides of the highways.

Container of roadside snow

Now here is what the melted snow looked like….

After forgetting about this in my garage for a few weeks I found that the dirt had settled to the bottom and that the water became clear.  

Dirt has settled to the bottom

In real life this happens when our wastewater is left to sit in big tanks.  Much of the solid waste is pulled to the bottom of the tank by gravity. See our Wastewater Investigation File under the Science Files to learn more!

Man-made vs. Nature-made Snow

Thankfully, I snowboarded a few days this year.  As our natural snow began to melt, Mt. Wachusett  gave Mother Nature some help and made more snow for the trails.  I noticed that this snow was a lot heavier. My friend Jeff suggested we look at the difference in water content in natural snow vs. man-made snow.  So I took my grandfather’s old graduated cylinder, and filled it with equal amounts of  newly fallen snow and then with man-made snow from Mt. Wachusett!  I only took these pictures after the snow began to melt. Please note that  both times the graduated cylinder was filled with snow up to the 32 oz mark!

Newly fallen snow

Man-made snow

Being that the newly fallen snow was heavy, this told me that the water content of the snow would be more than a lighter, fluffier snow.  When 4 cups (32 oz) of the newly fallen snow melted, I was left with a tad over a half cup of water (4.5 oz). When the man-made snow melted…. WOW!

Water content in newly fallen snow = 4.5 oz

Water content in man-made snow = 19.5 oz

The man-made snow had a little over 4 times the amount of water as the newly fallen snow! 

Try this at home with snow from different storms OR snow that has laid on the ground for a while vs. newly fallen snow. And if you ski or snowboard, melt some mountain snow to see the water content of your mountain’s man-made snow! 

Snow Making at Mt. Wachusett

We have had plenty of snow in Princeton, MA this year but when there is not enough snow for skiing or riding  check out how Mt. Wachusett lends Mother Nature a hand!