Ect weather data. Trackingthe The forecasters have a lot of help! Meteorologists, or scientists who study weather, collect data from all over the world. They use automated systems at sea, on land, in the air, and in space to help track the weather. At sea, weather buoys collect data on coastal weather conditions. These data help keep people in coastal cities safe. On land, weather-monitoring stations track weather conditions in remote locations. They can send advance notice about incoming weather. Scientists also use Doppler radar towers to observe how storm clouds are moving. Weather balloons and weather satellites collect data from high above Earth’s surface. Weather satellites can track the weather over very large areas. They also help relay data from land-based tools to meteorologists around the world. Scientists launch weather balloons that carry tools, called radiosondes, into the atmosphere. A typical radiosonde measures air temperature, air pressure, and humidity. Weather satellites orbit Earth. They collect weather data, such as cloud cover, and track storms, such as hurricanes. These satellites use radio signals to transmit data back to Earth. Packets of air move across Earth’s surface. An air mass is a large body of air with the same temperature and humidity throughout. An air mass reflects the conditions of the place where it forms. Air masses that form over land are dry. Air masses that form over water are moist. Cold air masses form near the poles, and warm air masses form near the tropics. As air masses move across an area, they can collide. The boundary between two air masses is called a front. Weather changes take place at fronts. For example, as a warm front passes over an area, warm air replaces cooler air and the temperature rises. The movement of air masses and fronts explains why you might be chilly one day and warm the next. At a front, stormy conditions are common. Air masses may form over land or water. The masses that form over land near the poles will be cold and dry. The masses that form over water near the poles will be cold and moist. Which types of air masses will form near the tropics? A cold front forms where a cold air mass bumps into a warmer air mass. The denser cold air pushes the warm air up. Water vapor in the air cools, and large clouds form. Thunderstorms and heavy rain often take place. Cooler temperatures follow a cold front. A warm front forms where a warm air mass moves over a cold air mass. A warm front forms a wider area of clouds and rain than a cold front. Steady rain or snow may fall. Warmer temperatures follow a warm front.