Cloud Protocols W elcome Purpose Geography To observe the type and cover of clouds includ- The nature and extent of cloud cover ing contrails affects the characteristics of the physical geographic system. Overview Scientific Inquiry Abilities Students observe which of ten types of clouds Intr Use a Cloud Chart to classify cloud types. and how many of three types of contrails are visible and how much of the sky is covered by Estimate cloud cover. oduction clouds (other than contrails) and how much is Identify answerable questions. covered by contrails. Design and conduct scientific investigations. Student Outcomes Use appropriate mathematics to analyze Students learn how to make estimates from data. observations and how to categorize specific Develop descriptions and predictions clouds following general descriptions for the using evidence. categories. Recognize and analyze alternative explanations. Pr Students learn the meteorological concepts Communicate procedures, descriptions, otocols of cloud heights, types, and cloud cover and and predictions. learn the ten basic cloud types. Science Concepts Time 10 minutes Earth and Space Science Weather can be described by qualitative Level observations. All Weather changes from day to day and L earning A earning over the seasons. Frequency Weather varies on local, regional, and Daily within one hour of local solar noon global spatial scales. Clouds form by condensation of water In support of ozone and aerosol measure- vapor in the atmosphere. ments ctivities Clouds affect weather and climate. At the time of a satellite overpass The atmosphere has different properties Additional times are welcome. at different altitudes. Water vapor is added to the atmosphere Materials and Tools by evaporation from Earth’s surface and Atmosphere Investigation Data Sheet or transpiration from plants. Cloud Data Sheet A Physical Science GLOBE Cloud Chart ppendix Materials exist in different states – solid, Observing Cloud Type (in the Appendix) liquid, and gas. Prerequisites None GLOBE® 2005 Cloud Protocols - 1 Atmosphere Cloud Protocols – Ice crystals and water drops scatter light differ- ently. Thick clouds absorb more sunlight than Introduction thin ones. The types of clouds, phases of water, Clouds and the Atmosphere and amount of clouds, ice, and water drops all af- fect the amount of sunlight that comes through Water in the environment can be a solid (ice and the atmosphere to warm Earth’s surface. Clouds snow), a liquid, or a gas (water vapor). As water also affect how easily heat from the surface can moves from place to place it can melt, freeze, escape through the atmosphere back to space. evaporate, or condense. These changes happen as the water is warmed or cooled. By observing clouds, we can get information about temperature, moisture, and wind condi- Water in the atmosphere exists in all three phases tions in different places in the atmosphere. This (solid, liquid, gas) and changes phase depending information helps in predicting the weather. on temperature and pressure. Like most other Observations of clouds also help us know how gases that make up the atmosphere, water vapor is much sunlight is reaching the ground and invisible to the human eye. However, unlike most how easily heat from the ground and lower other gases in our atmosphere, under the right atmosphere can escape, and this information is conditions water vapor can change from a gas into important in understanding climate. solid particles or liquid drops. If temperatures are above freezing, the water vapor will condense into Clouds and Weather water droplets. If temperatures are below freezing, as they always are high in the atmosphere, tiny ice Which types of clouds you see often depends on crystals may form instead. When a large number the weather conditions you are experiencing or of water droplets or ice crystals are present, they will soon experience. Some clouds form only in block light enough for us to see them – they form fair weather, while others bring showers or thun- clouds. So, clouds tell us something about air derstorms. The types of clouds present provide temperature and water up in the sky. They also important information about vertical movement affect the amount of sunlight reaching the ground at different heights in the atmosphere. By paying and how far we can see. attention to the clouds, soon you will be able to use cloud formation to forecast the weather! In the troposphere, the lowest part of the atmo- sphere, temperature decreases with increasing Cloud types may indicate a trend in the weather altitude. As ice crystals form at high altitudes, they pattern. For example, altocumulus clouds are are often blown away from the region where they often the first indicator that showers may oc- formed by the strong winds of the jet streams. cur later in the day. In middle latitudes, one Through this process of formation and movement can often see the advance of a warm front by ice crystals often merge into larger crystals and then watching the cloud types change from cirrus to begin to fall. These falling or windblown crystals cirrostratus. Later on, as the front gets closer, the create streaks, which we see as wispy clouds. These clouds thicken and lower, becoming altostratus. streaks are often curved by the wind, which can As precipitation begins, the altostratus clouds blow at different velocities at different altitudes. become nimbostratus, immediately before the front passes your location. Other types of clouds are blown about by the wind, too. Updrafts help form towering clouds; down- Cloud types are an important sign of the processes drafts tend to create clear spaces between clouds. that are occurring in the atmosphere. Clouds Horizontal winds move clouds from place to place. indicate that moist air is moving upward, and Clouds that form over lakes and oceans are blown precipitation can only happen when this occurs. over the dryer land, bringing precipitation. Strong Clouds often provide the first signal that bad winds high in the atmosphere sometimes blow the weather is coming, although not all clouds are tops off clouds creating anvil shapes or carrying associated with bad weather. ice crystals far downwind to clear areas. GLOBE® 2005 Cloud Protocols - 2 Atmosphere Clouds and Climate How will cloud conditions change if Earth’s sur- W Clouds play a complex role in climate. They are the face becomes warmer on average? If the surface elcome source of precipitation, affect the amount of energy water of oceans and lakes warms, more water will from the sun that reaches Earth’s surface, and in- evaporate. This should increase the total amount sulate Earth’s surface and lower atmosphere. of water in the atmosphere and the amount of cloud cover, but what type of clouds will form? At any given time, over half of Earth’s surface is Will the increase in clouds happen mostly at high shadowed by clouds. Clouds reflect some of the altitudes or low altitudes? Clouds at all altitudes sunlight away from Earth, keeping the planet reflect sunlight helping to cool Earth’s surface, but cooler than it would be otherwise. At the same high clouds release less heat to space and thus time, clouds absorb some of the heat energy warm the surface more than low clouds. So, the Intr given off by Earth’s surface and release some of changes in surface temperatures may depend on this heat back toward the ground, keeping Earth’s how cloud conditions change. oduction surface warmer than it would be otherwise. Satel- lite measurements have shown that, on average, Many official sources of weather observations the cooling effect of clouds is larger than their are now using automated equipment to observe warming effect. Scientists calculate that if clouds clouds. These automated measurement systems never formed in Earth’s atmosphere, our planet do not take cloud type observations. This makes would be over 20˚ C warmer on average. cloud observations by GLOBE students and other amateur weather observers unique as a data Conditions on Earth affect the amount and types source. Since 1960, scientists have also used satel- of clouds that form overhead. This helps to shape lites to observe clouds. These observations began Pr local climate. For example, in rain forests, the with simple pictures of clouds, but more advanced otocols trees release large amounts of water vapor. As techniques are always being added. Scientists are daily heating causes the air to rise, clouds form working to develop automated methods to infer and intense rainstorms occur. Over three-quar- cloud types from visible and infrared weather sat- ters of the water in tropical rain forests is recycled ellite images. This task is hard, and observations in this way and cloud cover is almost complete from the ground are needed for comparison. Con- for most of the year. In contrast, in a desert there trail detection from space is especially challenging, is no surface source of moisture and clear condi- since many contrails are too narrow to see in satel- tions are typical. These clear conditions allow for L lite images. Accurate cloud type observations from A earning more heating by sunlight and larger maximum GLOBE students are an important source of these temperatures. In both cases, the local climate ground-based observations. – precipitation and temperature – is tied to cloud conditions. Human activities also can affect cloud conditions. ctivities One specific and obvious example is the formation of contrails, or condensation trails. These are the linear clouds formed when a jet aircraft passes through a portion of the atmosphere having the right combination of moisture and temperature. The jet exhaust contains some water vapor as well as small particles – aerosols – that provide A ppendix condensation nuclei that help ice crystals begin to form. In some areas, jet traffic is causing a notice- able change in cloudiness, which may affect both weather and climate.