Impact of solar background radiation on the accuracy of wind observations of spaceborne Doppler wind lidars based on their orbits and optical parameters.

Due to the quantum properties of light, solar background radiation (SBR) is the main source of noise in daytime wind observations of spaceborne Doppler wind lidars (DWLs). In previous works, the impact of SBR on the observation accuracy of spaceborne lidars was assessed mainly using the default or worst-case scenarios. We assessed the impact of SBR on the observations of spaceborne DWLs using the global distributions of SBR in summer and winter, which were obtained based on their orbit parameters, view geometry and optical parameters. Three experiments illustrate that the uncertainty in wind observations increases with an increase in the quantiles of SBR. The uncertainties of the whole profiles of wind are greater than 2 m s-1 in the troposphere and 3 m s-1 in the stratosphere when the quantile of the SBR is greater than 85% in summer and 95% in winter, which do not satisfy the accuracy expectations of the European Space Agency (ESA) for spaceborne DWLs. The facts indicate that the impact of SBR cannot be negligible for the observations of spaceborne DWLs. Based on the orbit parameters, view geometry, and optical parameters of new spaceborne DWLs, engineers can assess the impact of SBR on the accuracy of wind observations from a global perspective using the method proposed in this paper.

Simulation and assessment of solar background noise for spaceborne lidar.

The properties for six typical land cover types and three sky conditions were derived in this paper, which allows to make seasonal upper estimations of solar background radiation for a given atmospheric scenario. Solar background noise can be derived from the estimations for a spaceborne lidar based on optical parameters. Comparisons among simulated solar background noise and measurements of Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and a Moderate Resolution Imaging Spectroradiometer (MODIS) demonstrate the feasibility of this method. The upper estimates of solar background radiation can be used for lidar engineers to assess the upper estimates of solar background noise for given atmospheric scenarios, which would be a step forward in comparison with using the worst-case scenario everywhere.