This truck is measuring winds around wildfires using an instrument called a Doppler lidar. This Doppler lidar uses an invisible, eye-safe laser to measure wind profiles and aerosol distribution up to 5 miles above the ground. The measurements that this truck is making will be used by scientists to study the link between local weather and the fire behavior.
The tan box in the bed of this truck contains the Doppler lidar optics which allow us to send the laser into the atmosphere and detect it. The white structure that the lidar box is mounted in actively stabilizes the lidar so we can make measurements when the truck is in motion. By putting the lidar in a pickup truck we can make measurements over large distances and move with the fire front.
The Doppler lidar system sends an invisible eye safe laser into the atmosphere and a small amount of the laser light is reflected off particles in the atmosphere and detected by the system. If the particles are moving, the wavelength or color of the light is shifted by an effect called the Doppler shift. We measure the change in wavelength of the laser and from that we can tell how fast the particles in the air are moving. The amount of time it takes for the laser light to leave the system and come back tells us how far away the particles are. These wind profiles can be used in computational models to improve weather forecasts and allow us to better understand complex weather patterns such as wildfires and hurricanes.