AIM Banner


Aerosols -  small airborne particles or non cloud droplets

Climate Change - an evolution of the characteristics of the atmosphere over long time scales: years, decades or longer

Condense - the process of matter, for instance water, changing from one form to a more dense form, such as vapor to liquid or solid.

Condensation Nuclei - particles upon which water vapor condense to form cloud ice crystals

Evaporation - the process by which liquid water gains enough energy to form vapor

Ozone - an important molecule in the atmosphere consisting of three oxygen atoms

Mesosphere - the layer of the atmosphere above the stratosphere

Mesopause - the upper boundary of the mesosphere

Meteoric Dust - left from passing comets and collected as the Earth travels though their orbits

Nucleation - when a small particle serves as a "nucleus" or central core around which ice can grow from either liquid or gaseous water

Pressure - a force per unit area exerted by a fluid such as air

Saturated - when the air holds as much water vapor as it possibly can for its temperature and pressure

Stratopause - the upper boundary of the stratosphere

Stratosphere - the layer of the atmosphere above the troposphere

Thermosphere- the layer of the atmosphere above the mesosphere

Tropopause - the upper boundary of the troposphere

Troposphere - the lowermost layer of the atmosphere

Water Vapor - water molecules in the gas phase

Weather - see Weather and Climate

PBL Navigation

> PBL Scenario
> Layers of the Atmosphere
> What is a Cloud?
> Weather and Climate
> How Clouds Form, Saturation and Nucleation
> Clouds in the Lower Atmosphere
> Clouds in the Upper Atmosphere
> How Does Climate Affect the Atmosphere?
> Glossary

Teacher's Guide

I. AIM Mission Objectives
II. Key Questions for Students
III. Problem-Solving Model
IV. Materials and Procedures


A: Sample Student Activity Sheet
B: Assessment Rubric
C: National Science Education Standards

NASA's Sun-Earth Education Forum Logo

The AIM mission is a part of
NASA's Sun-Earth Connection Education Forum.

Responsible Official: James M. Russell III

Web Curator: Emily M. W. Hill
Emily Hill Designs