Doppler lidar atmospheric wind sensor: reevaluation of a 355-nm incoherent Doppler lidar

Abstract

We reevaluate the performance of an incoherent Doppler lidar system operating at 354.7 nm, based on recent but well-proven Nd:YAG laser technology and currently available optical sensors. For measurements in the lower troposphere, up to ~5 km altitude, and also in the Junge-layer of the lower stratosphere, a wind component accuracy of +/- 2 m/s and a vertical resolution of 1 km should be obtained with a single pulse from a 1-J laser, operating at Polar Platform altitudes (700-850 km) and high scan angles (55 degrees ). For wind measurements in the upper troposphere (above ~5 km altitude) and stratosphere (above and below the Junge layer) the concentration of scatterers is much lower and higher energies would be required to maintain +/-2m/s accuracy and 1 km vertical resolution, using single laser pulses. Except for the region in the vicinity of the tropopause (10 km altitude), a 5-J pulse would be appropriate to make measurements in these regions. The worst case is encountered near 10 km altitude, where we calculate that a 15-J pulse would be required. To reduce this energy requirement, we would propose to degrade the altitude resolution from 1 km to 2-3 km, and also to consider averaging multiple pulses. Degrading the vertical and horizontal resolution could provide an acceptable method of obtaining the required wind accuracy without the penalty of using a laser of higher output power. We believe that a Doppler lidar system, employing a near ultraviolet laser with a pulse energy of 5 J, could achieve the performance objectives required by the major potential users of a global space-borne wind observing system.