NARRATOR：

Listen to a conversation between a student and his geography professor.

MALE STUDENT：

Hi, Professor Brown.

FEMALE PROFESSOR：

Hi, Paul. What can I do for you?

MALE STUDENT：

I have a question about the final exam … I mean, will it cover everything we’ve done all term, or just what we’ve been doing since the midterm exam?

FEMALE PROFESSOR：

Everything we’ve done all term.

MALE STUDENT：

[Not very happy about that]Oh, boy. You know, I’m still not too clear about the hydrologic cycle, um … the transfer of water back and forth between the Earth and the atmosphere …

I really blew the question about it on the midterm exam. I wanna do better on the final exam, but I’m still having trouble with it.

FEMALE PROFESSOR：

[Sympathetic]Well—um, have you been to the tutoring center?

MALE STUDENT：

No, not for geography anyway. Isn’t that just for when you need help with writing … like an essay or a research paper?

FEMALE PROFESSOR：

Oh, no. You can get tutoring in a lot of subjects. Some graduate students from this department tutor there.

MALE STUDENT：

Um, that’s good to know, but I hardly go there because I have a part-time job. I never seem to be free when they’re open.

FEMALE PROFESSOR：

Well, they’ll be extending their hours when final exams begin—you might try then.

But um…Well since you’re here now, can I help you with something?

MALE STUDENT：

Well, the hydrologic cycle …

I remember we went over a diagram in class … and from what I remember … water changes back and forth from water in lakes and oceans to vapor, and then back to water again when it falls as rain or snow … as precipitation.

It’s constantly being recycled, through evaporation and condensation.

FEMALE PROFESSOR：

[Not sure what the problem is]That’s it, basically. Umm … so exactly what is it you don’t understand?

MALE STUDENT：

[Realizing he has to ask a more specific question] OK. I guess what I’m really confused about is how the topography of the land —the mountains and valleys and stuff—affect precipitation.

FEMALE PROFESSOR：

OK, good question … Precipitation is influenced by topography, among other things. Uhh, why don’t we talk about lake-effect snow...

It’s a phenomenon that occurs anywhere you have a large lake that doesn’t freeze, and has cold air flowing over it.

Mostly in the Northern Hemisphere.

MALE STUDENT：

Like the Great Lakes in the United States?

FEMALE PROFESSOR：

Yes. What happens is that the cold, arctic air blows across the lake from the north in winter, and as the air crosses the lake, the lower layer is warmed by the lake water, which is much warmer than the arctic air.

And as this layer is warmed and picks up moisture, it becomes lighter than the air above it …

MALE STUDENT：

So it starts to rise, right?

FEMALE PROFESSOR：

Yes. And clouds begin to form.

When the air gets close to the shore, it’s slowed down by the land, and starts to pile up.

So it rises even faster, because it has nowhere else to go.

That’s where topography comes into the picture.

MALE STUDENT：

[Happy he knows the answer]And then it snows because as the air rises, it cools off and loses its capacity to hold water vapor.

FEMALE PROFESSOR：

That’s right.

MALE STUDENT：

OK, thanks. Any chance you’ll ask this question on the final?

FEMALE PROFESSOR：

[Laughing] I don’t know yet … but you seem to have a handle on it.