Analysis of the temporal variability of CO2, CH4 and CO concentrations at Lamto, West Africa

• Main Authors: Toure Dro Tiemoko, Michel Ramonet, Fidele Yoroba, Kobenan Benjamin Kouassi, Kouakou Kouadio, Victor Kazan, Claire Kaiser, François Truong, Cyrille Vuillemin, Marc Delmotte, Benoit Wastine, Phillipe Ciais
• Format: Article
• Language: English
• Published: Taylor & Francis Group 2021-01-01
• Series: Tellus: Series B, Chemical and Physical Meteorology
• Subjects: greenhouse gases; carbon dioxide; methane; carbon monoxide; lamto
• Online Access: http://dx.doi.org/10.1080/16000889.2020.1863707

The 10-year observations of the atmospheric molar fractions of CO2, CH4 and CO in West Africa were analyzed using a high precision measurement of the Lamto (LTO) station (6°31 N and 5°02 W) in Côte d’Ivoire. At daily scale, high concentrations appear at night with significant peaks around 7 a.m. local time and minimum concentrations in the afternoon for CO2 and CH4. The CO concentrations show two peaks around 8 h and 20 h corresponding to the maximum in road traffic of a northern motorway located 14 km from the station. The long-term increase rates of CH4 (∼7 ppb year−1) and CO2 (∼2.24 ppm year−1) at Lamto are very close to global trends. The variations of the concentrations of the three gases show strong seasonality with a peak in January for all gases and minima in September for CO2 and CH4, and in June for CO. The CO variation suggests a significant impact of fires on the CO, CO2 and CH4 anomalies in the Lamto region during the dry season (December to February). CO and CH4 show strong correlations (at synoptic-scale and monthly based) in January (r = 0.84), February (r = 0.90), April (r = 0.74), November (r = 0.79) and December (r = 0.72) reflecting similar sources of emission for both gases. The trajectories of polluted air masses at LTO, also indicate continental sources of emission associated with Harmattan winds.