The EDOP provides vertically profiled reflectivity and Doppler velocity at aircraft nadir along the flight track. The ER-2 Doppler radar (EDOP) is an X-band (9.6 GHz) Doppler radar mounted in the nose of the ER-2 aircraft. The instrument has two fixed antennas, one pointing at nadir and the second pointing approximately 33 degree ahead of nadir. The beam width of the antenna is 3 degree in the vertical and horizontal directions which, for a 20 km altitude, yields a nadir footprint at the surface of 1 km. Each Antenna measures the doppler velocity, doppler spectral width, and reflectivity factor. Doppler velocities provide a measure of the pulse volume-weighted hydrometer motion (hydrometer fallspeed + air motion.) Vertical air motion can be calculated from the nadir beam by removing the fallspeed contribution with an approximation. Along-track horizontal air motion can be calculated by combining doppler wind speeds from forward and nadir beams. The linear depolarization ratio (the ratio of the cross-polar to the co-polar reflectivites) can be measured along forward beam. EDOP is a coherent Doppler radar system at 9.6 GHz. EDOP provides measurements from a forward pointing beam that is used in combination with the nadir beam for estimating the along-track winds.