星载新一代多波束测云激光雷达设计与仿真(特邀)

Design and Simulation of a Multi-Beam Cloud Lidar Based on a New Generation Polar Orbit Satellite(Invited)

针对全球云、气溶胶光学性质的量化及其对气象、气候、地球环境的影响,提出一种星载新一代多波束测云激光雷达(M^(3)CL)探测方案。该方案采用三体制、四波长、九波束的推扫测量方式形成地面九波束20 km推扫幅宽,即单激光器产生355 nm、532 nm、1064 nm和1625 nm 4个波长的激光,其中532 nm包含9个波束,波束间隔为3.05 mrad;光电接收核心波束355 nm/532 nm双波长采用高光谱探测和偏振探测,1064 nm、1625 nm为回波能量探测,另加边缘8波束532 nm能量探测。从理论上分析了探测误差限与探测信噪比的关系,并给出测云激光雷达系统参数。经过模拟仿真,给出了820 km轨道云气溶胶的散射系数探测误差分布,其契合未来极轨卫星新一代测云激光雷达的探测需求。

Objective Clouds are a crucial factor in numerical weather forecasting(NWF),significantly influencing weather-related disasters such as hail,storms,and other extreme conditions.Accurate global measurements of horizontal and vertical distributions of clouds and aerosols,as well as their optical and micro-physical properties,are necessary to assess their influence on human health,the environment,and regional climate and precipitation.The China Meteorological Administration(CMA)and the World Meteorological Organization(WMO)have outlined specific requirements for cloud phase,cloud top height,aerosol extinction coefficient,and measurement error limits.Previous payloads such as CALIPSO(NASA,operational for 17 years)and ACDL(SIOM,operational for over 2 years)have demonstrated partial cloud measurement capabilities.The EarthCARE payload,including the 355 nm HSRL scheme developed by ESA,was launched on May 29,2024.However,there remains a gap in providing certain-swath,multi-wavelength,multi-scheme,high-precision lidar measurement data.Methods To quantify the influences of clouds on precipitation,regional climate,and the global environment,we propose the concept of a multi-wavelength,multi-function,multi-beam cloud lidar(M^(3)CL)based on a polar orbit satellite.The M^(3)CL design incorporates high spectral resolution lidar(HSRL),polarization detection,and backscattering detection schemes,with four wavelengths(355,532,1064,and 1625 nm)and nine beams in a push-broom configuration,as shown in Fig.1.Fabry-Perot etalons and iodine cells are used as high spectral resolution filters for 355 and 532 nm channels,respectively.The 355 and 532 nm channels utilize polarization detection,while the remaining eight 532 nm beams are symmetrically arranged on either side of the central beam,forming a 20 km swath.We derive theoretical upper bounds for cloud and aerosol detection errors based on HSRL equations and system calibration constants.Using the parameters set in Table 1,the atmosphere/cloud mode database,and lidar equations,we simulate the SNR distribution for an 820 km polar satellite orbit.Results and Discussions We present simulation results for the relative errors upper limits of cloud and aerosol detection in Figs.2 and 3.The backscattering coefficient relative error is below 17.6%with an SNR higher than 20,and within 31.2%with an SNR higher than 10.Sensitivity simulations for different detection wavelengths in Fig.4 show that the M^(3)CL can semi-quantitatively determine particle radii ranging from 0.2 to 2μm.Figs.5 and 6 indicate that the SNR exceeds 20 under thin cloud and weak scattering conditions,while Figs.7 and 8 demonstrate that SNR remains above 20 under 2 km thick cloud,intense scattering conditions.Figs.9 and 10 indicate that aerosol detection SNR is about 10.The SNR distribution figures reveal that cloud detection SNR exceeds 20 at a 2.5 km horizontal resolution and a 200 m vertical resolution,resulting in a relative detection error within 20%.The penetration depths for thick and thin clouds are over 300 and 1000 m,respectively.Conclusions We present the concept of the M^(3)CL payload with system parameters based on a new generation polar satellite,featuring three detection schemes,four wavelengths,and nine beams.The M^(3)CL is capable of push-broom measurements with a 20 km swath,2.5 km horizontal resolution,and 200 m vertical resolution.We provide theoretical upper limits for particle backscattering coefficient detection errors based on HSRL theory,serving as a reference for evaluating HSRL detection errors.Simulation results indicate that the M^(3)CL can achieve a cloud backscattering coefficient detection relative error within 20%,calculate particle radii from 0.2 to 2μm,and penetrate thick and thin clouds to depths exceeding 300 and 1000 m,respectively.These capabilities meet the cloud detection requirements of meteorological satellites.