Double-pulse 157 μm integrated path differential absorption lidar ground validation for atmospheric carbon dioxide measurement

Abstract

A ground-based double-pulse integrated path differential absorption (IPDA) instrument for carbon dioxide (CO₂) concentration measurements at 1572 nm has been developed. A ground experiment was implemented under different conditions with a known wall located about 1.17 km away acting as the scattering hard target. Off-/offline testing of a laser transmitter was conducted to estimate the instrument systematic and random errors. Results showed a differential absorption optical depth (DAOD) offset of 0.0046 existing in the instrument. On-/offline testing was done to achieve the actual DAOD resulting from the CO₂ absorption. With 18 s pulses average, it demonstrated that a CO₂ concentration measurement of 432.71±2.42 ppm with 0.56% uncertainty was achieved. The IPDA ranging led to a measurement uncertainty of 1.5 m.