Influence of meteorology and interrelationship with greenhouse gases (CO<sub>2</sub> and CH<sub>4</sub>) at a sub-urban site of India

Abstract

Abstract. Atmospheric greenhouse gases (GHGs) such as carbon dioxide (CO2) and methane (CH4) are important climate forcing agents due to their significant impact on the climate system. The present study brings out first continuous measurements of atmospheric GHG's using high precision Los Gatos Research's-greenhouse gas analyser (LGR-GGA) over Shadnagar, a suburban site of Central India during the period 2014. The annual mean of CO2 and CH4 over the study region is found to be 394 ± 2.92 and 1.92 ± 0.07 ppm (mean, μ ± 1 SD, σ) respectively. CO2 and CH4 showed a significant seasonal variation during the study period with maximum (minimum) CO2 observed during Pre-monsoon (Monsoon), while CH4 recorded maximum during post-monsoon and minimum in monsoon. A consistent diurnal mixing ratio of these gases is observed with high (low) during night (afternoon) hours throughout the study period. Influences of prevailing meteorology (air temperature, wind speed, wind direction and relative humidity) on GHG's have also been investigated. CO2 and CH4 showed a strong positive correlation during winter, pre-monsoon, monsoon and post-monsoon with R equal to 0.80, 0.80, 0.61 and 0.72 respectively. It implies the seasonal variations in source-sink mechanisms of CO2 and CH4. Present study also confirms implicitly the presence OH radicals as a major sink of CH4 over the study region.

Trends and variability in methane concentrations over the Southeastern Arabian Peninsula

“…The range of XCH 4 values is ~100 ppb between 1860 and 1960 ppb, with a year-on-year increase from below 1900 ppb in 2018-2019 to an excess of 1900 ppb in 2020-2021. These XCH 4 concentrations are comparable to those measured in-situ at an urban and suburban site in India (Sreenivas et al, 2016;Metya et al, 2022). Overall, the methane concentrations are largely unchanged from 2018 to 2019 (cf.…”

“…The role of advection on the CH 4 concentration has been highlighted by Metya et al (2022), which reported on in-situ measurements collected at an urban site in western India from March 2018 to December 2020. The authors found a minimum in the CH 4 concentration in the summer season, when clean air originating from the Southern Hemisphere was transported to the site, while continental air masses in the postmonsoon and winter seasons led to higher CH 4 values, as also noted by Sreenivas et al (2016). In general, high CH 4 events co-occurred with air coming from the Indian landmass, while low CH 4 values were associated with an air mass coming from southern India and the Arabian Sea.…”

“…This may have led to a reduced advection of the CH 4 emitted by the several oil and gas platforms in the region (Bateni et al, 2022;Farahat, 2022) and by the major sources in coastal sites into the country, explaining the small changes in the XCH 4 values. The role of advection in the spatial distribution of CH 4 by both local mesoscale circulations at low-levels (Sreenivas et al, 2016;Elmi et al, 2021;Metya et al, 2022) and the background flow throughout the column (Ricaud et al, 2014) has been reported in the literature. The XCH 4 seasonal fluxes (Supplementary Figure S3) indicate that advection likely plays the largest role over the Al Hajar mountains, where there is low-level convergence of the northwesterly flow from the Arabian Gulf with the easterly flow from the Sea of Oman, in particular in the warmer months.…”

A Data-Driven Assessment of Biosphere-Atmosphere Interaction Impact on Seasonal Cycle Patterns of XCO2 Using GOSAT and MODIS Observations

“…Coincident with the maximum LST, terrestrial respiration and weakened photosynthesis could contribute to the maximum XCO 2 . As is shown in Sreenivas et al [75], XCO 2 showed a positive correlation with temperature, and soil respiration and biomass burning may be an important terrestrial carbon source contributing to the CO 2 concentration in India. To further investigate the possible influence from anthropogenic emissions on the SCA anomaly, we found that the fossil fuel emission from bottom-up estimation in CnI [76,77] (shown in Figure S4) does show a seasonal cycle, which, however, has much less consistency than LST with XCO 2 around the peaks of the XCO 2 cycle.…”