Researchers measure atmospheric water vapor using open-air spectroscopy

Researchers have shown that a new mid-infrared spectrometer can precisely measure the ratios of different forms of water - known as isotopologues - in atmospheric water vapor through open air in a little over 15 minutes. Isotopologue ratios, which can be affected by land-based water evaporation and plant transpiration, are used to develop models of climate change and to understand how water is transported globally in the atmosphere.

"Open-path sensing using dual frequency combs may make atmospheric water vapor isotopologue sensing simpler and easier to apply in remote environments. A broader network of isotopologue measurements will contribute to improved numerical weather modeling. The long beam paths achievable using the dual-comb technique will enable spatially resolved studies of water vapor transport over natural ecosystems as well as human-engineered ones (e.g. farms)," explained researcher Daniel Herman, National Institute of Standards and Technology (NIST).

"Future vertical column measurements using combs might also improve calibration procedures for isotopologue measurement using satellites. In addition, sensing of water vapor with dual combs can also compliment other emerging air quality applications of broadband mid-infrared spectroscopy."

Daniel Herman from NIST will present the new findings at the Optica Imaging and Applied Optics Congress, 11 - 15 July 2022. Herman's talk is scheduled for 11 July 2022, at 11:45 AM PDT.

Today, scientists rely on networks of point sensors to analyze isotopologues in atmospheric water vapor. Although these networks are expanding, they require careful calibration to maintain accuracy over time and between sites. Detecting water vapor in an open-air path may eliminate the need for calibration and make it easier to capture large-scale evaporation above reservoirs or over entire watersheds.

However, accurately detecting multiple water vapor isotopologues in the air requires a mid-infrared spectrometer with high spectral resolution, high accuracy and fast measurement rates. To accomplish this, Herman and colleagues developed a new open-path mid-infrared dual-comb spectrometer (DCS) that uses near-infrared femtosecond laser pulses and specially designed waveguides to create broadband mid-infrared pulses in a compact package.

The researchers tested the new instrument by using it to take measurements over a 760-meter path at the Platteville Atmospheric Observatory in Colorado. They found that the instrument could operate in the field for weeks at a time without requiring intervention. This allowed them to acquire several months of data during a variety of weather conditions and temperatures.

The measurements obtained using the DCS correlated well with those acquired using a point sensor network, showing the potential for open-path DCS in characterizing atmospheric water vapor.

Herman adds, "In order to expand isotopologue measurement networks, we are working to improve the accuracy of our technique by analyzing systematics in the detection setup. The sensitivity of the technique can be improved by using higher power combs to enable longer paths. Also, balanced detection technology will be implemented in the future to decrease technical noise."

The Imaging and Applied Optics Congress
The Imaging and Applied Optics Congress brings together academics, industrial and defense research perspectives to provide a comprehensive view of the latest developments in imaging and applied optical sciences. This year's meeting will be presented with the Optical Sensors and Sensing Congress 11 - 15 July 2022. The meeting will be held in a hybrid format to accommodate virtual (online) participation as well as in-person attendance at the Hyatt Regency Vancouver in British Columbia, Canada. Learn more here.

Related Links
NIST
Earth Observation News - Suppiliers, Technology and Application

Tweet

Thanks for being there;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Monthly Supporter
$5+ Billed Monthly

paypal only

SpaceDaily Contributor
$5 Billed Once

credit card or paypal

NASA aircraft conducting atmospheric studies over DC to Baltimore
Wallops Island VA (SPX) Jun 30, 2022
A NASA aircraft will fly over the I-95 corridor from Washington to Baltimore and Hampton, Virginia, in support of an atmospheric campaign in the mid-Atlantic region between July 5 and 16, 2022. The four-engine turboprop P-3 aircraft, based at NASA's Wallops Flight Facility in Virginia, will fly five days during the 12-day period at altitudes from 1,000 to 10,000 feet. Each flight during the campaign will include one low-level pass at 1,000 feet over I-95, two spiral tracks, ascending and des ... read more