How are supercell and landspout tornadoes detected?

Supercell tornadoes are easier to detect. They arise from the larger circulation of the mesocyclone or rotating updraft of a supercell. This rotation can be detected by doppler radar, which can measure wind speed from a distance. In somce cases the rotation of the tornado itself may be detected. This is more difficult for landspouts, which tend to be smaller, and do not arise from a larger mesocyclone. Since radar cannot scan ground level winds, visual confirmation is often used to determine if a tornado has touched down. There are people, called spotters, who are trained to identify and report tornadoes and other weather hazards. A new advancement in doppler radar, called dual polarization has futher improved tornado detection. Before this development, radar could detect material in the air, but could not actually tell the difference between raidrops, hailstones, and other objects such as tornadic debris. If a dual polarized radar picks up on debris, that's a good sign that a tornado has touched down.