A Comparison of Carbon Dioxide and Methane Levels at Four Tower Sites Across the United States

Looking at seasonality and overall trends for different greenhouse gases allows scientists to make predictions for the future, and also look at areas where humans can lessen the negative impacts they are having on the Earth’s atmosphere. Carbon Dioxide (CO₂) and Methane (CH₄) are greenhouse gases that have been documented to be steadily increasing over time due to anthropogenic sources. Here we present the results of an investigation of the overall temporal trends and seasonal variations of both gases using NOAA Programmable Flask Package (PFP) data. PFPs are automated sampling packages that can be sent anywhere and sampled by aircraft, towers, or mobile laboratories. All PFP air samples are analyzed at the central analytical lab at NOAA, Boulder by spectroscopy or chromatography. While PFP data has been collected at 17 tower sites since the early 2000s, this study makes use of 4 specific tower sites in the contiguous United States (see table 1, map 1). Sites were chosen in in order to sample a variety of tower environments and to ensure a healthy sampling of data from 2006/2007 to the present. Carbon dioxide and methane both show distinct seasonal trends at all locations, although methane generally shows less variability

Ozarks Isoprene Experiment (OZIE): Measurements and modeling of the "isoprene volcano''

The Ozarks Isoprene Experiment (OZIE) was conducted in July 1998 in Missouri, Illinois, Indiana, and Oklahoma. OZIE was designed to investigate the presumably high isoprene emission rates from the Missouri Ozarks due to its high density of oak trees. Ground, balloon, and aircraft measurements were taken over a three-week study period; 0-D and 3-D chemical models were subsequently used to better understand the observed isoprene emissions from the Ozarks and to investigate their potential regional-scale impacts. Leaf-level measurements for two oak tree species yielded normalized average isoprene emission factors of 66 mgC g-1 h-1, in good agreement with values used in current biogenic emissions models. However, the emission factors exhibited a temperature dependence that is not captured by currently available algorithms. Aloft isoprene mixing ratios measured using tethered balloon systems were used to estimate isoprene fluxes. These measurement-derived fluxes agreed with BEIS3 estimates within the relatively large uncertainties in the estimates. Ground level isoprene mixing ratio