EGU23-13203, updated on 17 Apr 2023
https://doi.org/10.5194/egusphere-egu23-13203
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

A portable, ground-based FTS for reflected sunlight: Performance evaluation for mapping CO2 and CH4 above Los Angeles

Benedikt Hemmer1, Vincent Enders1, Frank Hase2, Ralph Kleinschek1, Julian Kostinek3, Thomas Pongetti4, Stanley Sander4, Zhao-Cheng Zeng5, and André Butz1
Benedikt Hemmer et al.
  • 1Institute of Environmental Physics, Heidelberg University, Heidelberg, Germany (benedikt.hemmer@iup.uni-heidelberg.de)
  • 2Karlsruhe Institute of Technology, IMK-ASF, Karlsruhe, Germany
  • 3School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
  • 4NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
  • 5School of Earth and Space Sciences, Peking University, Beijing, China

Precise knowledge of sources and sinks in the carbon cycle is desired to understand its sensitivity to climate change and to account and verify man-made emissions. In this context, extended sources like urban areas play an important role. While in-situ measurements of carbon dioxide (CO2) and methane (CH4) are highly accurate but localized, satellites measure column-integrated concentrations over an extended footprint. The CLARS-FTS [1, 2] stationed at the Mt. Wilson observatory looking downward into the Los Angeles basin has pioneered an innovative measurement technique that fills the sensitivity gap between in-situ and satellite measurements. The technique enables mapping the urban greenhouse gas concentration fields by collecting spectra of ground scattered sunlight and scanning through the region.

We develop a similar but portable instrument using a CLARS-FTS-like measurement geometry. It is based on the EM27/SUN FTS with a modified pointing system, increased throughput and a more sensitive detector than the standard type. The compact setup enables campaign-based observations in various source regions of interest, utilizing the increased sensitivity to boundary layer concentration by the horizontal light path component.

Here, we present the portable instrument setup and its performance. Throughout April 2022, we observed the Los Angeles basin with both the portable setup and the CLARS-FTS simultaneously. The retrieval algorithm is based on the RemoTeC software, previously employed for solar backscatter satellite measurements. From this, we evaluate the XCO2 and XCH4 precision of our setup under field conditions, and compare our instrument to the concurrent CLARS-FTS measurements.

 

References:
[1] Fu, D. et al., 2014: Near-infrared remote sensing of Los Angeles trace gas distributions from a mountaintop site, Atmos. Meas. Tech., 7, 713–729, https://doi.org/10.5194/amt-7-713-2014
[2] Wong, K. W. et al., 2015: Mapping CH4 : CO2 ratios in Los Angeles with CLARS-FTS from Mount Wilson, California, Atmos. Chem. Phys., 15, 241–252, https://doi.org/10.5194/acp-15-241-2015

How to cite: Hemmer, B., Enders, V., Hase, F., Kleinschek, R., Kostinek, J., Pongetti, T., Sander, S., Zeng, Z.-C., and Butz, A.: A portable, ground-based FTS for reflected sunlight: Performance evaluation for mapping CO2 and CH4 above Los Angeles, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13203, https://doi.org/10.5194/egusphere-egu23-13203, 2023.