Quiz 11 Solutions

1.) Water vapor is partially responsible for the shape of ice crystals. What meteorological variable largely determines crystal shape, according to the reading.

Water vaport determines how much "stuff" is available to form ice crystals. The other important variable is temperature. Generally, temperature helps determine the shape of the ice crystal.

2.) From the notes last week, what are two items which cause Numerical Weather Prediction to be less than perfect.

Any two of these are valid. Bad data (the sensor is messed up), data is not representative of surroundings (a mountain ob doesn't represent what is going on in the valley), gaps in available data (over oceans), equations are not perfect (attempt at describing how atmosphere works is not perfect), assumptions are made (such as the physics inside clouds, which are not fully understood), and chaos theory (there are so many small scale factors involved, you can't keep track of all of them)

3.) Define, in your own words, what is meant by model initialization. You can be brief. This is not Dr. Carr's OBAN class. ;)

Initialization is the initial start-up conditions of the model. This is often called the starting analysis for the model. If the initialization is bad, the model probably will not generate a worthwhile forecast.

4.) From the notes, which model would be best for continuous short-term forecasts (ie: it updates every 3 hours publicly and forecasts out 12 hours)?

The RUC model.

5.) What is the difference between hail and ice pellets (also called sleet in the US), according to the reading?

Hail is created from water freezing and then being caught in an updraft and having supercooled water or ice stick to it. (This is called riming.) Ice pellets generally freeze fall through a warm layer, and then refreeze before reaching the surface. Generally, ice pellets are not caught in updrafts and continue to grow.