Claire Cénac

2-μm Ho emitter-based coherent DIAL for CO 2 profiling in the atmosphere

We report on the use of a thulium-fiber-pumped holmium-based emitter in a coherent differential absorption lidar (CDIAL) experiment for high time and space resolution of CO(2) absorption field in the atmosphere. The 2-μm high-power dual-wavelength single-mode Q-switched Ho:YLF oscillator delivers 10-mJ pulses with a duration of 40 ns at 2 kHz. Both short pulse duration and high repetition rate were chosen to increase the DIAL precision and time and space resolution in coherent detection. The CDIAL provides 150-m range and 15-min time-resolved CO(2) absorption coefficient with a calculated instrumental error of 0.5% at 500 m and less than 2% at 1 km. Dry-air CO(2) mixing ratio estimates from the DIAL system are compared with simultaneous in situ gas analyzer measurements during a 20-h-long experiment.

New advances in 2-?m high-power dual-frequency single-mode Q-switched Ho:YLF laser for dial and IPDA application

In the absence of climate change policies, the fossil fuel emissions are projected to increase in the next decades. Depending on how the current carbon sinks change in the future, the atmospheric CO2 concentration is predicted to be between 700–1000 ppmv by 2100, and global mean surface temperature between 1.1–6.4°C, with related changes in sea-level, extreme events and ecosystem drifts. Keeping the atmospheric CO2 concentration at a level that prevents dangerous interference with the climate system poses an unprecedent but necessary challenge to humanity. Beyond this point, global climate change would be very difficult and costly to deal with. There are two main approaches that are currently analysed: (1) to reduce emissions; (2) to capture CO2 and store it, i.e. sequestration. For these two ways, some monitoring at different scales ultimately from space would be needed. Lidar remote sensing is a powerful technique that enables measurements at various space and time resolution.