Atmospheric CO₂ in situ measurements: Two examples of Crown Design flights in NE Spain

Abstract

The new “Crown” aircraft sampling (CAS) approach integrates CO2 data obtained through horizontal transects and vertical profiles, sampling a specific volume of air at different atmospheric sections: 600 m, 1200 m, and 2500 m above the sea level (masl). This approach provides new tools to model fluxes in relation with meteorological conditions. It has been applied over a plain in the basin of the river called Ebre in the North East of Spain, with a triangular section defined by Linyola, Mequinensa's dam and Binèfar, taking up 1500 km2. The main human activity is agriculture, either irrigated or dry land. Horizontal transects at 600 and 1200 masl were sampled for CO2, with vertical profiles at the vertexes from 600 to 2500 masl (ground level is around 400 masl). The three‐dimensional configuration of the CAS Design enables the study of the CO2 fluxes between sections. Data have been obtained on a monthly basis since February 2006 until nowadays. In order to study the influence of forced turbulence in the atmospheric CO2 spatial distribution, two data sets are examined: the flight of 7 February 2006, performed under stable anticyclonic weather conditions; and the 6 March 2006 flight, characterized by strong northerly winds. The presence of stable/unstable layers in the February flight resulted in a stepwise vertical distribution of CO2 (with an increase from the free troposphere, 383 ppmv, to 400 ppmv close to the ground) whereas the unstable low troposphere sampled in March 2006 provided flat CO2 vertical profiles (concentrations ranging from 385 to 387 ppmv). In regard to the variability in the horizontal sections, the calculation of the Hurst exponents (H) provides a way to measure the persistence of vertical transport along the horizontal transects. In the February flight, CO2 concentration in transects shows the imprint of a spreading vertical transport from land (H > 0.90) but it is partially wiped away by high turbulence levels in the March flight (H = 0.79). From these results we expect CAS Design to provide better estimates of CO2 fluxes in the future.

Daytime CO2 urban surface fluxes from airborne measurements, eddy-covariance observations and emissions inventory in Greater London

“…The plane instrumented with an AIMMS-20 Air Data Probe (Aventech Research Inc.) measured temperature, barometric pressure, three components of wind speed and horizontal wind direction, with an instrument accuracy of 0.05 C (temperature), 0.1 kPa (pressure), 0.5 m s À1 (horizontal wind) and 0.75 m s À1 (vertical wind) (Beswick et al, 2008). Atmospheric CO 2 dry mole fractions were measured with a non-dispersive infrared (NDIR) portable instrument, the CO 2 Airborne Analyzer System AOS Inc., at a frequency of 0.5 Hz with a mean precision and accuracy of ±0.23 ppm and ±0.28 ppm, respectively (Font et al, 2008 provide further details). CO 2 concentrations were traceable to the International Standards (WMO-X2007 scale).…”

Physical atmospheric structure and tropospheric mixing information in vertical profiles of atmospheric CO2 mixing ratios

“…Under flight conditions, the mean precision is estimated at σ = ± 0.23 ppmv. For further details of the experimental procedure see Font et al [2008].…”

Multiyear average characteristics of CO2 variations in the free atmosphere over Colorado (40° N, 104° W)

“…Until recently, the majority of CO 2 monitoring stations have employed the flask sampling method of CO 2 mole fraction determination at the Earth's surface (Conway et al, 2003) or in the troposphere using aircraft. Extensive results of multiyear CO 2 measurements in the tropo-stratosphere with scientific and commercial aircrafts were published previously (Pearman and Beardsmore, 1984;Matsueda et al, 2002;Levin et al, 2002;Gerbig et al, 2003;Font et al, 2008;Sawa et al, 2012, etc.). Most of these studies were concentrated on studies of horizontal CO 2 structures at several selected levels in the tropo-stratosphere.…”