The duration and the thickness of the radiation fog depends on the local conditions as well as the solar heating. The fog is thick and persistent in low-lying areas such as river valleys, valley fog , and in the presence of weak rays of sun during late autumn and early winter.
Upslope fog: a ground-level cloud induced by expansional cooling. It forms when moist air flows upon windward side of hillsides or mountain slopes. It can persist for many days over an extensive area. Advection fog: a ground-level cloud induced by advective cooling.
It forms when relatively warm air is chilled to saturation by over-running a sufficiently cool surface. Advection fog is usually thicker tens of meters deep and lasts longer than the radiation fog. It is more common for the following three conditions: i when mild, humid air flows over relatively cold, snow-covered ground in early spring, if the ground is extremely cold, ice crystals form, ice fog. Evaporation Steam fog: a ground-level cloud induced by mixing.
It occurs when cold, dry air comes in contact with the relatively warm water. Over the ocean in polar regions where the air is extremely cold during winter, stream fog is referred to as arctic sea smoke.
Stream fog also develops on a cold day over a heated outdoor swimming pool or over a warm lake in early autumn. In general, fog creates pollution, health, and transport problems. The foggiest place near sea level in the United States is Cape Disappointment, Washington, which has an average of foggy days per year.
Cloud: a visible aggregate of tiny water droplets or ice crystals or a mixture of both suspended in the air. Within the atmosphere, at most, only a slight supersaturation conditions are necessary for cloud development. Curvature effect: At a given temperature, the saturation vapor pressure is higher in the air surrounding a spherical water droplet than in the air over a flat surface. As water surface increases its curvature, more water molecules evaporate.
Water molecules that form a curved surface have fewer neighboring molecules and hence, they are weakly bound than the molecules over a flat surface. The curvature effect increases with decreasing radius of a water droplet. Thus, water molecules are more readily escape small droplets than large droplets. The saturation vapor pressure and the degree of supersaturation needed for cloud development increases rapidly as the radius of the droplet decreases.
Nuclei: tiny solid and liquid particles of matter on which condensation or deposition of water vapor takes place. They are products of both human and natural activity such as forest fires, volcanic eruptions, soil erosions, saltwater spray and the discharge from domestic and industrial chimneys.
There are typically about 10, nuclei per cm3 of air. Cloud condensation nuclei CCN : tiny particles that promote the formation of water droplets. CCN are active at temperatures both above and below freezing. Ice-forming nuclei IN : tiny particles that promote the formation of ice crystals. They are much less abundant than CCN and become active only at temperatures well below freezing. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.
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It differs from climate, which is all weather conditions for a particular location averaged over about 30 years. Weather is influenced by latitude, altitude, and local and regional geography.
It impacts the way people dress each day and the types of structures built. Explore weather and its impacts with this curated collection of classroom resources.
Humidity, or the amount of moisture in the air, changes based on air temperature, warm bodies of water, and air movement. The water cycle describes how water is exchanged cycled through Earth's land, ocean, and atmosphere. Join our community of educators and receive the latest information on National Geographic's resources for you and your students.
Skip to content. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Dew is the moisture that forms as a result of condensation. Condensation is the process a material undergoes as it changes from a gas to a liquid.
Dew is the result of water changing from a vapor to a liquid. Dew forms as temperatures drop and objects cool down. Precipitation does not fall in the same amounts throughout the world, in a country, or even in a city. Here in Georgia, USA, it rains fairly evenly all during the year, around inches centimeters cm per year. Summer thunderstorms may deliver an inch or more of rain on one suburb while leaving another area dry a few miles away. But, the rain amount that Georgia gets in one month is often more than Las Vegas, Nevada observes all year.
The world's record for average-annual rainfall belongs to Mt. Waialeale, Hawaii, where it averages about inches 1, cm per year. A remarkable inches 1, cm was reported there during one twelve-month period that's almost 2 inches 5 cm every day! Is this the world record for the most rain in a year? No, that was recorded at Cherrapunji, India, where it rained inches 2, cm in Contrast those excessive precipitation amounts to Arica, Chile, where no rain fell for 14 years, and in Bagdad, California, where precipitation was absent for consecutive days from October to November The map below shows average annual precipitation, in millimeters and inches, for the world.
The light green areas can be considered "deserts". You might expect the Sahara area in Africa to be a desert, but did you think that much of Greenland and Antarctica are deserts? On average, the 48 continental United States receives enough precipitation in one year to cover the land to a depth of 30 inches 0. Have you ever watched a raindrop hit the ground during a large rainstorm and wondered how big the drop is and how fast it is falling?
Or maybe you've wondered how small fog particles are and how they manage to float in the air. Source: Lull, H. Publication No. Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over millions of years. Rain and snow are key elements in the Earth's water cycle, which is vital to all life on Earth.
Rainfall is the main way that the water in the skies comes down to Earth, where it fills our lakes and rivers, recharges the underground aquifers, and provides drinks to plants and animals. For the water cycle to work, water has to get from the Earth's surface back up into the skies so it can rain back down and ruin your parade or water your crops or yard. It is the invisible process of evaporation that changes liquid and frozen water into water-vapor gas, which then floats up into the skies to become clouds.
The air is full of water, as water vapor, even if you can't see it. Condensation is the process of water vapor turning back into liquid water, with the best example being those big, fluffy clouds floating over your head. And when the water droplets in clouds combine, they become heavy enough to form raindrops to rain down onto your head.
You can't see it, but a large portion of the world's freshwater lies underground. It may all start as precipitation, but through infiltration and seepage, water soaks into the ground in vast amounts.
Water in the ground keeps all plant life alive and serves peoples' needs, too. Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human Ice and glaciers are part of the water cycle, even though the water in them moves very slowly.
Ice caps influence the weather, too. The color white reflects sunlight heat more than darker colors, and as ice is so white, sunlight is reflected back out to the sky, which helps to create weather patterns.
Read on to learn how glaciers and ice caps are part of the water cycle. Yes, water below your feet is moving all the time, but, no, if you have heard there are rivers flowing below ground, that is not true. Water moves underground downward and sideways, in great quantities, due to gravity and pressure. Eventually it emerges back to the land surface, into rivers, and into the oceans to keep the water cycle going. Evapotranspiration can be defined as the sum of all forms of evaporation plus transpiration, but here at the Water Science School, we'll be defining it as the sum of evaporation from the land surface plus transpiration from plants.
Freshwater on the land surface is a vital part of the water cycle for everyday human life. On the landscape, freshwater is stored in rivers, lakes, reservoirs, and creeks and streams. Most of the water people use everyday comes from these sources of water on the land surface.
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