Remote sensing of NO using a differential absorption lidar

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Laser Remote Sensing

Background:

• Nitric oxide (NO) is a key air pollutant with significant environmental impacts.
• Accurate measurement of atmospheric NO is crucial for air quality assessment.
• Remote sensing offers a non-invasive method for atmospheric pollutant monitoring.

Purpose of the Study:

• To demonstrate the feasibility of using differential absorption of CO2 laser radiation for atmospheric NO detection.
• To measure NO concentrations at various distances, including near a traffic source.
• To assess the impact of atmospheric water vapor absorption on remote sensing measurements.

Main Methods:

• Employed single-ended remote sensing with a frequency-doubled pulsed CO2 laser.
• Utilized differential absorption spectroscopy based on backscattered laser radiation from topographic targets.
• Measured lidar returns from targets up to 1.4 km to determine range-dependent atmospheric absorption.

Main Results:

• Successfully obtained lidar returns from targets up to 1.4 km.
• Detected significant concentrations of NO above ambient levels near a traffic roadway (0.5 km).
• Observed discrepancies between measured atmospheric differential absorption and data from transmission tapes, particularly due to water vapor absorption.

Conclusions:

• The developed laser-based differential absorption technique is effective for remote sensing of atmospheric NO.
• The study highlights the presence of elevated NO near roadways, relevant for urban air quality.
• Accurate atmospheric transmission modeling, accounting for factors like water vapor, is critical for interpreting remote sensing data.