Surface weather observation

People watch the weather to stay safe.

They can use tools or computers. Some people watch the weather at airports. This helps planes land safely.

They check how hot or cold it is. They also check the wind. They look at how much rain falls.

They even check the air pressure. This is how heavy the air feels. They use these facts to make maps. These maps help us see the weather. It is a very busy job.

People study the weather to keep everyone safe.

They can take notes by hand. They can also use automated stations. These use computers to collect data.

Observers look at many things. They check the air temperature. This is how hot or cold the air is. They also find the dew point. This is the temperature where water turns into dew.

They use tools to measure the wind. An anemometer measures wind speed. A wind vane shows the direction. They also check the air pressure. This is how heavy the air feels. To make maps, they use sea level pressure. This helps everyone compare weather in different places.

Airports are very important for this work. Pilots need to know the weather to land safely. They look for things like snow or fog. They also watch for heavy rain. Heavy rain can make it hard to see. It can even put ice on plane wings. This is why weather data is so vital for flight.

Weather observers collect important data to keep people safe. This information helps experts forecast the weather and issue warnings. People can take these notes by hand. They can also use automated weather stations with computers. Some stations use both people and computers together. These observations are very important for planning and safety.

There are many ways to measure the air. Observers check the temperature to see how much heat is moving. They also find the dew point. This is the temperature where water vapor turns into liquid dew.

They use tools like anemometers to find wind speed. Wind vanes show which direction the wind is blowing. They also measure air pressure to see how heavy the air feels. To make maps, they use sea level pressure. This makes sure the numbers are easy to compare everywhere.

People have been watching the weather for a long time. Reverend John Campanius Holm took the first systematic notes in Colonial America. He lived in a Swedish colony near the Delaware River. He recorded the weather every day in 1644 and 1645. He did not even use tools to do this! Later, President George Washington kept a weather diary at Mount Vernon. In 1807, Dr. B. S. Barton asked people to use tools to track weather history.

Weather stations have changed a lot over the years. In the early 1900s, many stations moved from farms into towns. By 1926, there were over 5,000 locations in the U.S. and the Caribbean. In 1939, the U.S. Navy began making automated stations. Today, airports use special codes called METAR to send data worldwide. Each code has a station identifier with four characters. For example, the letter "P" stands for the Pacific Ocean area. The letter "E" stands for Europe.

Watching the weather is vital for pilots at airports. They must know if there is heavy rain or snow. Heavy rain can make it hard to see the runway. Freezing rain is also a big danger for flying. It can leave ice on the wings of an airplane. Observers also watch for things like dust storms or volcanic ash. These reports help everyone stay safe during takeoffs and landings.

Surface weather observation is the systematic collection of data about the atmosphere near the Earth's surface. This data is essential for forecasting weather patterns and issuing safety warnings worldwide. Observers can gather this information manually by hand. They can also use automated weather stations that rely on computers. Some locations use a hybrid scheme. In these cases, human observers work alongside automated systems to improve accuracy. This constant stream of data helps meteorologists understand how the atmosphere behaves.

To make data useful, scientists use the International Standard Atmosphere, or ISA. The ICAO defines this as a model of how pressure, temperature, density, and viscosity change with altitude. This model helps experts reduce a station's local pressure to sea level pressure, known as SLP.

Reducing pressure to a sea level standard allows different locations to be compared easily on weather maps. Without this calibration, high and low pressure areas would depend on local geography rather than actual weather systems. This standardization is also vital for designing aircraft and calibrating flight instruments.

Weather observations include several specific physical measurements. Temperature measures the kinetic energy of matter and determines how heat flows between objects. In meteorology, thermometers are kept in the air but sheltered from direct sunlight. Most of the world uses the Celsius scale, though the United States often uses Fahrenheit. Another key metric is the dew point. This is the temperature at which air must cool for water vapor to condense into liquid dew. If the dew point is below freezing, it is called the frost point, where water vapor creates frost instead.

Wind and pressure are also critical components of a report. Wind speed is measured using anemometers, while direction is tracked with wind vanes or aerovanes. In the United States, average wind speed is a two-minute average, while other regions use a 10-minute average. Wind direction is measured in degrees, starting at 0 or 360 for North and increasing clockwise. For aviation, the altimeter setting is used. This is the local air pressure at mean sea level, which helps pilots calibrate their altimeters to show height above the ground.

History shows that weather recording has evolved from simple notes to complex technology. Reverend John Campanius Holm is credited with the first systematic observations in Colonial America. In 1644 and 1645, he recorded daily weather at a Swedish colony near the Delaware River without any instruments. Later, President George Washington kept a detailed weather diary at Mount Vernon during the late 1700s. In 1807, Dr. B. S. Barton requested that the Linnaean Society of Philadelphia maintain instrumented sites to build a climatological history. By 1926, the United States and the Caribbean had over 5,000 observing locations. The U.S. Navy began developing automated stations in 1939.

Modern aviation relies heavily on specialized reporting codes. Airports often use the METAR observing code to transmit data globally.

METAR reports are usually generated once every hour. However, if weather conditions change suddenly, they issue special reports called SPECIs. Each METAR report includes a four-character station identifier. The first letter indicates the region; for example, "P" is for the Pacific and "E" is for Europe. The second character often represents a country or state. In the U.S., the letters "C" or "K" are used to represent specific regions. This coding allows pilots to receive rapid, standardized updates on visibility and hazards.

Safety is the primary reason for detailed surface observations at airports. Pilots must monitor present weather, such as precipitation, squalls, or volcanic ash. Heavy precipitation can limit visibility during critical takeoff and landing phases. Freezing rain is particularly dangerous because it can deposit ice on aircraft wings. Observers also track snow depth and snowfall amounts. For airport technicians, hourly snowfall reports help determine how often runways must be plowed. By monitoring these variables, weather observation systems protect lives and ensure the smooth operation of global transportation networks.