Climate variability as reflected in a regional atmospheric CO₂ record

Abstract

A B S T R A C T This paper analyses a 15-year long atmospheric CO 2 mixing ratio record measured at a mid-continental, low-elevation station (Hegyhátsál, Hungary) to reveal the effect of regional climate variability. While the long-term trend and the temporal fluctuation of the growth rate of CO 2 mixing ratio follow the global tendencies to a large extent, the shorter-term variations show special features. We present the distorted seasonal cycle caused by the seasonality in the atmospheric vertical mixing and the tendentious change in its shape, which can be attributed to the gradual warming and to the resulted prolongation of the growing season. The decreasing summer diurnal amplitude and the decreasing seasonal amplitude in the mixing ratio, furthermore the higher than average summer CO 2 mixing ratio growth rate in the first period of the measurements (1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) with generally rising temperature and decreasing precipitation are explained as the consequence of the reduced activity of the biosphere in the influence area of the station and that of the reduced biomass under environmental conditions getting increasingly unfavourable. The explanation is supported by the colocated tall tower surface-atmosphere CO 2 exchange measurements and by the crop yield statistics of the dominantly agricultural region around the station.

Differences between carbon dioxide levels over suburban and rural sites in Northern Spain

“…The maximum average CO 2 level for each hour was lower, around 406 ppm, and was obtained earlier from 0300 to 0500 GMT. The daily amplitude is 2.3 ppm lower than that obtained in the suburban site and much higher than other rural locations (Reid and Steyn 1997;Haszpra and Barcza 2010). The minimum values obtained during the day remained steady over longer periods; from 1100 to 1600 GMT, the mean concentration being 383.9 ppm, in contrast to the results obtained for the other location, from 1300 to 1600 GMT and a mean value 3.0 ppm higher.…”

Multi-decadal atmospheric carbon dioxide measurements in Central Europe, Hungary

“…This process overcompensates the contribution of the surface that is still a net CO2 source at that time of the year. A simple box model used in our earlier work (Haszpra and Barcza, 2010) proved that the changing vertical mixing can result in the observed reduction in the late winter/early spring surface layer concentrations. Concentration maximums preceding the net uptake period of the regional vegetation are also be observed at other monitoring sites (Levin et al, 1995;Davis et al, 2003;Kozlova et al, 2008;Popa et al, 2010;Schmidt et al, 2014;-Belikov et al, 2019;Conil et al, 2019;Curcoll et al, 2019; https://doi.org/10.5194/amt-2024-29 Preprint.…”

Signs of reduced biospheric activity with progressing global warming: evidence from long-term records of atmospheric CO<sub>2</sub> mixing ratios in Central-Eastern Europe

“…Measurements of CO2 mixing ratio profiles, temperature, humidity and wind profiles began in September 1994. The Hegyhatsal tower is also a NOAA/CMDL global air sampling network site and part of the Global Atmosphere Watch programme (https://gaw.kishou.go.jp/search/station; Haszpra et al 2010; https://www.esrl.noaa.gov/gmd/dv/site/; Dlugokencky et al 2018).…”

“…Both Hegyhatsal and Mace Head are also measuring CO2 using the state of the art techniques and report mixing ratios directly calibrated against WMO-CO2-X2007 scales. Information on their specific instrument set and calibration techniques can be found in Haszpra et al 2010 andDlugokencky et al, 2018. The data for both stations were retrieved from the GLOBALVIEW-CO2 NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network (http://www.esrl.noaa.gov/gmd/dv/data/ -Dlugokencky et al, 2018).…”