The Algorithm For Retrieval Of Middle Atmospheric Temperature Using Rayleigh Lidar

Rayleigh lidar is an active atmospheric remote sensing instrument which has the capacity of continuous detection with high spatial and temporal resolution.It is an important equipment to measure temperature in the mesosphere and can detect the temperature for the range of 30-80 km accurately.The Rayleigh lidar located in Yanqing,Beijing(40.3°N,116.2°E)consists of a 532 nm channel and a 589 nm channel.The 532 nm channel is used for calculating temperature for the range of 60-90 km and the 589 nm channel is used for calculating temperature for the range of 35-70 km and density of Na for the range of 80-110 km.The Chanin-Haunchecorne method is used to calculate temperature in the mesosphere.It is supposed that middle atmosphere should obey the perfect gas law and should be in hydrostatic equilibrium.Initial temperature of the upper detection limit is obtained by looking up the NRLMSISE-00 atmospheric model which is inaccuracy,so it is necessary to abandon the 10 km temperature below the upper detection limit.To make the utmost of the original data obtained by Rayleigh lidar,initial temperatures based on uniform distribution are used for calculating atmospheric temperature,which improves the conventional Chanin-Haunchecorne method.The Rayleigh lidar located in Yanqing,Beijing(40.3°N,116.2°E)consists of a 589 nm channel and a 532 nm channel.The 589 nm channel is used for calculating atmospheric temperature and the 532 nm channel is taken as reference.Multiple initial temperatures are chosen in [150,250] at regular intervals to calculate temperature profiles and the corresponding density profiles of the 589 nm channel.Initial interval is narrowed continually so that the accurate initial temperature and the corresponding temperature profile can be obtained according to the reference density profile.This accurate temperature profile is compared with 532 nm channel to demonstrate that the method is reliable and they are show good agreement with each other.This improved method makes the most of optical signals with poor signal-to-noise ratio and extends the upper detection limit of atmospheric temperature with 589 nm channel from 60 km to 70 km.The Levenberg-Marquardt algorithm combining with SABER satellite is used for calculating the section functions of temperature profiles for the range of 60-90 km.Taking July 14,2012 as an example,a density profile for the range of 60-90 km from the 532 nm channel is calculated and taken as an accurate profile.The initial temperature expressions are obtained by observing SABER datum and their coefficients are optimized by the Levenberg-Marquardt algorithm.The temperature profile of 532 nm channel is compared with SABER datum to demonstrate that the method is reliable and they show good agreement with each other.This improved method makes the most of optical signals with poor signal-to-noise ratio and extends the upper detection limit of atmospheric temperature with 532 nm channel from 80 km to 90 km.