Airborne Lidar Measurements of XCO₂ in Synoptically Active Environment and Associated Comparisons With Numerical Simulations

Abstract

Greenhouse gases play an essential role in governing Earth's radiation budget while atmospheric CO 2 has been rising at an increasing rate (e.g., 1.50 ppm/year for 1990-1999, 1.97 ppm/year for 2000-2009, 2.40 ppm/year for 2010Peters et al., 2020). Very recently, the daily average of atmospheric CO 2 concentrations at Mauna Loa observatory in Hawaii was recorded as high as 421.21 ppm (NOAA-GML). Human activities, such as burning fossil fuels and deforestation, disturb the natural balance between CO 2 sources and sinks and are causing this increase (Salam & Noguchi, 2005;Schneider et al., 2021), making quantification of CO 2 sources and sinks essential to long term climate monitoring (Barnes et al., 2016;Masarie et al., 2014). Terrestrial ecosystem carbon fluxes are particularly uncertain, and earth system models differ vastly in their simulations of projected terrestrial CO 2 uptake in a rapidly changing climate (e.g., Keenan & Williams, 2018).An improved understanding of the spatiotemporal changes in atmospheric CO 2 due to weather systems will strengthen our ability to infer uptake and release of CO 2 from terrestrial ecosystems and the ocean through inverse methods. High-resolution observations of CO 2 vertical and spatial variability across different spatial scales (e.g.,

Atmospheric Variations in Summertime Column Integrated CO2 on Synoptic Scales Over the U.S.

“…(2020) and Walley et al. (2022) for in‐situ $${\mathrm{C}\mathrm{O}}_{2}$$ and lidar‐retrieved $${\mathrm{X}\mathrm{C}\mathrm{O}}_{2}$$, respectively. We applied this method on all the summer frontal passage cases found from 2015 to 2019 as seen from OCO‐2 over CONUS and northern Mexico (land between 20° and 55°N latitude, 50° and 140°W longitude).…”

“…We performed a sensitivity study and determined that the length of the warm and cold sectors affects the absolute value of the differences, but the choice of the length does not change the significance of the difference between the 𝐴𝐴 XCO2 frontal contrast and the associated climatology, which will be explained later in Section 3.1 (Figure 3). We define the 𝐴𝐴 ∆XCO2 frontal contrast as the warm sector mean 𝐴𝐴 XCO2 minus the cold sector mean 𝐴𝐴 XCO2 as was performed in Pal et al (2020) and Walley et al (2022) for in-situ 𝐴𝐴 CO2 and lidar-retrieved 𝐴𝐴 XCO2 , respectively. We applied this method on all the summer frontal passage cases found from 2015 to 2019 as seen from OCO-2 over CONUS and northern Mexico (land between 20° and 55°N latitude, 50° and 140°W longitude).…”

“…Recently, the Atmospheric Carbon and Transport (ACT‐America, Davis et al. (2021)) experiment targeted synoptic scale variations in $${\mathrm{C}\mathrm{O}}_{2}$$ with both in situ measurements and $${\mathrm{C}\mathrm{O}}_{2}$$ lidar observations in North America (Baier et al., 2020; Bell et al., 2020; Campbell et al., 2020; Davis et al., 2018; Sweeney et al., 2018; Walley et al., 2022; Wei et al., 2021). The overall aim of ACT‐America was to provide a “top‐down” constraint of CO 2 surface fluxes toward obtaining a more comprehensive understanding of carbon cycle features during both fair and synoptically‐active weather conditions.…”

Exploring Atmospheric Boundary Layer Depth Variability in Frontal Environments Over an Arid Region

“…In contrast, the advection due to frontal passages (i.e., fourth in the list) is primarily driven by airmass exchange across a large region, thus, inhomogeneities in the atmosphere. In essence, these advective processes are not fundamentally different from each other, as they create airmass inhomogeneities (e.g., Davis et al 2021;Walley et al 2022). However, these processes utilize different types of advective fluxes and the impact of different types of advections differ on the spatial scale.…”