The objective of this work is to advance the technology readiness
level (TRL) of lidar system to enable global Methane (CH4)
and water vapor (H2O) measurements with sufficient
coverage, sensitivity, and precision to address pressing science
questions for climate-carbon interaction. Methane (CH4) is
the second most important anthropogenic greenhouse gas with
approximately 25 times the radiative forcing of CO2 per
molecule. Natural sources of CH4 are dominated by wetland
emissions in the tropics and Arctic and sub-Arctic boreal regions,
with additional contributions from termites, ruminants, ocean biology,
and a geological source of unknown significance. Natural sources
account for about one-third of the emission total. The wetland source
is particularly variable, linked to temperature, precipitation, and
surface hydrological changes. Better characterization of the wetland
source clearly requires reliable CH4 measurements in the
often-cloudy tropics and over partially inundated land surfaces and
open water. Another important science question is in the potential
release of large amounts of stored organic carbon as CH4
and CO2 from thawing Arctic permafrost soils, which is
cause for concern as a rapid, positive greenhouse gas/climate
feedback. In addition, large but greatly uncertain amounts of
CH4 are sequestered as gas hydrates in shallow oceans and
permafrost soils, which are also subject to potential rapid release.
Although these boreal, phase-change driven sources are not yet
estimated to be large, their potential magnitude and rapid growth
dictate that measurement systems need to be put in place for early
detection. Because CH4 fluxes, as well as chemical loss,
are tightly coupled to hydrology, coordinated measurement of both
CH4 and H2O are highly desired. Precise,
seasonal measurements with coverage at high latitudes (i.e., in low
sun to dark conditions) are required. Our proposed laser remote
sensing technology will be a key step in fostering measurements of
CH4 and H2O with sufficient coverage, sampling,
and precision to address major science questions.
Our proposed laser remote sensing technology will be a key step in
fostering measurements of CH4 and H2O with
sufficient coverage, sampling, and precision to address these and
other science issues. The benefit to future Earth Science missions is
that the proposed technology enables global CH4
measurements to be made where they are really needed: in the absence
of sunlight (i.e., at night and at high latitudes in all seasons), in
the presence of scattered or optically thin clouds and aerosols, over
land and water surfaces, and with higher accuracy and precision than
currently available. These qualities are precisely those that make the
corresponding H2O measurements a valuable addition to the
current operational suite for weather and climate analysis. The
measurements will help satisfy the critical scientific need to
understand the behavior of greenhouse gases as they contribute to
climate change as well as to meet pressing national needs for
development of a national carbon monitoring system serving science,
policy-makers, and stakeholders.
The end goal of the project would be to demonstrate the readiness of
the a CH4 trace gas lidar instrument for space flight. The
target wavelengths and energies are ~1.65 µm and energy is ~500 µJ.
The specific objectives of this project are to:
Improve the tunability architecture of the seed laser(s) using two
different designs.
The first design uses a DBR laser at 1651 nm to be delivered
under an STMD Game Changing Technology program.
The second design uses a novel approach: single or dual
sideband (SSB/DSB) tuning. It has the potential to significantly
simplify the seed laser design and uses existing DFB lasers.
Demonstrate 500 µJ in Er:YGG/Er:YAG with narrow linewidth.
Reduce the size and complexity of the existing OPO
Use the tunable seed from objective 1 with the OPO and Er:YAG from
objectives 2 and 3 to demonstrate open path CH4
measurements and correlate them with an in-situ calibrated
instrument (Picarro in-situ CH4 analyzer).