Overview


The project Rayleigh Doppler Lidar (RDL) was taken up with Objectives of

• measurements of stratospheric and lower mesospheric mean winds

• study of role of vertically propagating waves in dynamics and energetics of middle atmosphere

Salient features

• Edge technique

• Direct Detection lidar system

• 750mm diameter telescope

• Employs Fabry Perot Interferometer as frequency discriminator

• PMT as detector

• 900m height resolution and 30 minute time resolution This complex project uses a high energy laser with 30W power @532nm and 50Hz repetition rate to get atmospheric backscattering from molecules and particles.A 750mm telescope in Newtonian configuration is used to collect the signal from athe atmosphere and a Fabry Perot Interferometer as frequency discriminator is employed to get the radial winds. A few photographs Pic 1 and 2 of the system are shown. The Project is completed and Zonal and Meridional winds are obtained between 10-50km. Sample results are shown in the Fig 1 and 2. The winds, derived from this indigenously developed system have compared well with near simultaneous GPS Radio Sonde winds. The RDL system is regularly operated. The system capability of moving the telescope in 0-360 degree azimuth and 0-45 degrees off-zenith is fully utilised to get the temperature structure as shoem in Fig 3.

Figure 1: Mean Zonal winds as measured with Doppler lidar on different days in the months of December, January February 2011, 2012.Radiosonde launch time is 1730hrs IST and lidar observation time is 2000hrs IST on 9/12/2011, 12/12/2011, 16/1/2012, 17/1/2012, 2/2/2012, 4/2/2012 respectively.

Figure 2: Mean Meridional winds as measured with Doppler lidar on different days in the months of December, January February 2011, 2012. Radiosonde launch time is 1730hrs IST and lidar observation time is 2000hrs IST on 16/1/2012, 2/2/2012, 4/2/2012, 9/2/212, 11/2/2012, 16/2/2012 respectively

Figure 3: Contours of Temperature with time on a day for 8 hours with 0-360 azimuth at 40 elevation