Weather satellites measure a growing array of environmental information that helps agencies like NOAA create daily forecasts and predict and monitor dangerous weather events.
A satellite is any manmade or natural object that orbits another larger object, such as a planet, moon or star. The Earth is a satellite of the sun.
Polar-Orbiting Satellites
A polar-orbiting satellite is one that orbits the Earth in an almost north-south path, passing close to each of the planet’s poles many times per day. In contrast to geostationary and geosynchronous satellites, polar-orbiting satellites stay closer to the ground and provide high resolution measurements of weather conditions.
The most well-known polar-orbiting satellite is the National Oceanic and Atmospheric Administration’s (NOAA) Global Change and Operational Environmental Satellite System, better known as GOES-I through M series. These satellites use advanced sensors to monitor critical weather conditions and improve forecasting for the nation’s weather service.
GOES satellites are designed to provide a high-resolution view of the entire planet in order to help predict weather events. They observe and record the Earth’s temperature and moisture levels and use microwave imagery to see through clouds.
In addition, GOES satellites can track and relay wind information in the upper atmosphere. These wind sensors can provide the data needed to identify and track tropical cyclones as they form. They also use microwave technology to see through clouds, making them the ideal instrument for monitoring hurricanes and other storm systems in the water.
Because GOES satellites are so high, they are able to see much more detail than their geostationary counterparts. In fact, they can see up to 15 different temperature and moisture readings for every point on the Earth.
They also measure incoming solar protons, positive ions, and electron-flux density at their altitude. This is a significant improvement over GOES’s early-generation instruments.
Another advantage of GOES is that it passes over all points on the Earth twice each day in a sun-synchronous orbit. This allows it to see each location twice with the same general lighting conditions, which is important for a variety of applications.
For example, it can help scientists determine whether the earth is covered with snow or ice. It can also provide vital data for detecting oil spills and locating illegal construction.
In addition to the GOES-I through M series, NOAA operates a number of other polar-orbiting satellites. These include the polar-orbiting satellites of the Joint Polar Satellite System, NOAA-20 and NOAA/NASA Suomi-NPP. These satellites carry a number of instruments that cannot be found on the GOES-I through M series, including microwave and day-night bands, which allow forecasters to see cloud patterns in the night.
Geostationary Satellites
Weather satellites provide a reliable, global view of Earth’s weather systems. They monitor temperature, moisture, cloud cover and other important meteorological data that help forecasters predict weather patterns.
There are two basic types of weather satellites: geostationary and polar. The orbits of these two types are different and each has its advantages and disadvantages.
Geostationary satellites circle the Earth above the equator from west to east and travel at the same speed as the planet itself. This allows them to measure the same regions on the earth all the time.
These satellites are at an altitude of about 35,786 km (22,236 miles) above the surface of the earth. This is much farther than a satellite can get from the ground and means that it takes about one day for each satellite to circle the Earth once.
In addition to monitoring weather conditions, these satellites can also be used for many other purposes. For example, they can be used to detect fires and floods.
They can also be used to take atmospheric profiles and measurements of the Earth’s surface. The images they produce can be used for analyzing the effects of climate change, such as how the oceans are warming and cooling, and how that affects vegetation growth and land use.
As of 2016, there are eight GOES satellites operating over the United States and other parts of the world. They can be commanded to monitor different regions of the globe at different times and can also focus in on particular areas that are impacted by severe weather.
During an outbreak of severe weather, the US GOES satellites can be commanded to scan the Western Hemisphere every 15 minutes and the Continental United States every five minutes. They can also be commanded to focus on areas of intense storms, like hurricanes and tornadoes.
The GOES satellites can also be commanded to focus on a particular area in the atmosphere and send pictures back to the control center. This is called “nowcasting” and is used to predict the future evolution of severe weather to keep people safe.
Satellite Imagery
Satellite imagery is a form of Earth observation used to monitor the physical environment (air, water, land, vegetation) and human activity across the globe. It is a powerful tool and has many applications, from meteorology and weather forecasting to fishing, oceanography, agriculture, conservation, forestry, landscape analysis, geology, mapping, regional planning, environmental assessment, intelligence, warfare and education.
There are different types of satellites that can produce images, each with its own unique advantages and disadvantages. These include visible and infrared imaging, spectral data, revisit rates, and cloud cover.
Visible satellite images are useful for observing the Earth during daylight hours. They are also useful for monitoring storms and precipitation.
Infrared satellites can capture heat energy from the atmosphere. This information is especially helpful for determining the temperature and water vapor content of clouds at various heights.
The information is important for predicting weather conditions because clouds emit more infrared radiation than they do visible light. This enables satellites to measure the temperature of cloud tops and help predict when and where rain is likely to occur.
These IR images are also useful for identifying ocean surface features, such as eddies or currents. These can be valuable to shipping companies and other businesses that rely on sea transport.
Some IR satellites also have sensors that capture thermal or infrared energy from the ground as well as from the surface of the Earth. This can be helpful for detecting tropical cyclones with their warm eye patterns.
Other IR satellites capture information about water vapor and air temperature, and this can be useful for determining the amount of precipitation that is falling from the sky.
This information is especially important for assessing the potential impact of climate change on the Earth. It can also be used for identifying the extent of glacial retreat in the Antarctic and Greenland.
Another advantage of IR satellites is that they are able to monitor the ozone layer. This can be particularly helpful for preventing and treating ozone depletion, which has a significant impact on global warming.
A common type of satellite is the sun-synchronous orbit (SSO). This orbit allows the satellite to pass over the same part of the Earth every day, and the consistent lighting is important for comparing imagery from multiple dates to see if any changes are occurring.
Cloud Movement
Satellites that monitor weather conditions, including cloud movement, help meteorologists make more accurate forecasts of severe storms and other climate-related events. These satellites can observe clouds and water vapour in a way that cannot be done from the ground, giving us a unique perspective on weather.
Wind, altitude and the temperature of the air play an important role in determining the shape of clouds. Higher winds move faster than lower ones and can cause them to shift horizontally across the sky, often forming large circular cirrus clouds.
Some clouds are also shaped by their density, or the amount of moisture in them. If the clouds are dense and have a lot of water droplets and ice crystals, they can withstand strong winds. However, if the cloud is thin and wispy, the winds can break it apart.
Another way that wind affects clouds is by creating wind shear. The wind shear creates small gaps in a cloud that are more likely to form. This allows the clouds to move slightly more quickly than they would without the shear.
The speed of these cloud shears can vary from a few miles per hour to more than 100 miles per hour depending on the type of clouds and their size. This shear can make it harder for people to see things at low levels, but can allow people to see higher-level details.
During a hurricane, a strong hurricane wind can force clouds to move vertically, causing them to rise above the hurricane and reach a higher altitude in the sky. This is called convection, and it can be the cause of some heavy rainfall, particularly in coastal regions.
These high-altitude clouds are known as cirrus, and they tend to be more numerous than the mid-level clouds. There are other types of clouds, though, and some of them are categorized by their base altitudes, which can range from 2,000 to 6,000 meters (6,500 to 20,000 feet) above the Earth.
A key part of how environmental satellites monitor the weather is by observing and collecting data on the cloud fraction, or how much of the Earth is covered with clouds. These data are then used by NWP models to predict the weather ahead of severe storms and other events.