Dimitri Edouart

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.

An a Posteriori method based on photo-acoustic cell information to correct for lidar transmitter spectral shift : Application to atmospheric CO2 differential absorption lidar measurements

An a posteriori corrective method based on photo-acoustic cell (PAC) information is proposed to correct for laser transmitter spectral shift during atmospheric CO2 measurements by 2 μm heterodyne differential absorption lidar (HDIAL) technique. The method for using the PAC signal to retrieve the actual atmospheric CO2 absorption is presented in detail. This issue is tackled using a weighting function. The performance of the proposed corrective method is discussed and the various sources of error associated with the PAC signal are investigated. For 300 shots averaged and a frequency shift (from the CO2 absorption line center) lower than the CO2 absorption line half-width, the relative error on HDIAL CO2 mixing ratio measurements is lower than 1.3%. The corrective method is validated in absolute value by comparison between HDIAL and in situ sensor measurements of CO2.

High Brightness 2 µm Source Based on A Type II Doubly Resonant ECOPO

For CO2 DIAL, the single mode output of a type II PPLN, entangled-cavity nanosecond OPO is amplified to 11 mJ at 2.05 µm, with 3MHz frequency stability and a M2quality factor better than 1.9.

Error budget of the MEthane Remote LIdar missioN (MERLIN) and its impact on the uncertainties of the global methane budget.

MEthane Remote LIdar missioN (MERLIN) is a German-French space mission, scheduled for launch in 2024 and built around an innovative light detecting and ranging instrument that will retrieve methane atmospheric weighted columns. MERLIN products will be assimilated into chemistry transport models to infer methane emissions and sinks. Here the expected performance of MERLIN to reduce uncertainties on methane emissions is estimated. A first complete error budget of the mission is proposed based on an analysis of the plausible causes of random and systematic errors. Systematic errors are spatially and temporally distributed on geophysical variables and then aggregated into an ensemble of 32 scenarios. Observing System Simulation Experiments are conducted, originally carrying both random and systematic errors. Although relatively small (±2.9 ppb), systematic errors are found to have a larger influence on MERLIN performances than random errors. The expected global mean uncertainty reduction on methane emissions compared to the prior knowledge is found to be 32%, limited by the impact of systematic errors. The uncertainty reduction over land reaches 60% when the largest desert regions are removed. At the latitudinal scale, the largest uncertainty reductions are achieved for temperate regions (84%) and then tropics (56%) and high latitudes (53%). Similar Observing System Simulation Experiments based on error scenarios for Greenhouse Gases Observing SATellite reveal that MERLIN should perform better than Greenhouse Gases Observing SATellite for most continental regions. The integration of error scenarios for MERLIN in another inversion system suggests similar results, albeit more optimistic in terms of uncertainty reduction.

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.