Reply on RC1

Abstract

Remote sensing of surface pressure from space is critical; differential absorption LIDAR and differential absorption radar are only two kinds of remote sensing instruments with this potential. The differential absorption LIDAR works in integral path mode from the satellite in low-Earth orbit. It measures the differential optical depth of the Oxygen A-band, and the surface pressure is thereafter obtained by performing circle-iterative calculation. Performance evaluation of the differential absorption LIDAR model was conducted with respect to the advanced system parameters of the space instrument, Low echo pulse energy at ocean surface and the challenging calculation of repetitive cumulative average of echo on uneven land surface yielded random errors in surface pressure measurement. On the other hand, uncertain atmospheric temperature and water vapor mixture profiles resulted in systematic error of surface pressure. Consequently, controlling the error of surface pressure within 0.1 % proved challenging. Under a strict implementation of the error budget, the time resolution is 6.25 s and along-orbit distance resolution is 44 km, and the results showed that 765.6735/765.4637 nm is suitable as the working wavelength pair. Further, error could be expected to within 0.2–0.3 % for the cumulative average of 625 ocean surface laser pulse echoes, cumulative average of more than 144 pulse echoes on land, and observation from the 400 km orbit.