James T. Peterson

Atmospheric CO2 variations at Barrow, Alaska, 1973–1982

The first 10 years (1973–1982) of atmospheric CO2 measurements at Barrow, Alaska, by the NOAA/GMCC program are described. The paper updates and extends the Barrow CO2 record presented in Tellus (1982). The data are given in final form, based on recent calibrations of the Scripps Institution of Oceanography, with selected values identified as representative of large, spacescale conditions. Analyses of the data show: (1) a long-term CO2 average increase of 1.3 ppm per year, but with large year-to-year variations in that growth rate; (2) a suggestion, not statistically significant, of a secular increase in the amplitude of the annual cycle, presumably a reflection of global-scale biospheric variability; and (3) good absolute agreement between the Barrow results and those from four neighboring high latitude sites between 50 and 82°N.

On the variability of atmospheric carbon dioxide concentration at Barrow, Alaska during summer

Abstract Atmospheric carbon dioxide data obtained at Barrow, Alaska for the May–September period of 1978 were studied to understand the causes of the day-to-day and within-day variations. Sixteen instances of 24-h change in average CO 2 concentration of from 15 to 50% of the annual range (approx. 14 ppm) were identified. Within-day variations of up to 50% of the annual range were noted. The variations were found to be related to local and synoptic scale meteorology interacting with local and regional sources and sinks of CO 2 . The results are consistent with an overall source of CO 2 in the tundra of the Alaskan North Slope and a significant sink for CO 2 in the ice-free areas of the seas bordering Alaska. The analysis provides an interpretation of the Barrow CO 2 record which can be used in the selection of representative data for studying large scale trends.

On the Influence of Pacific Ocean Temperatures on Atmospheric Carbon Dioxide Concentration at Ocean Weather Station P

Abstract The study presents an analysis of atmospheric CO2 measurements at Ocean Weather Station P (50°N, 145°W) and sea surface temperatures over the North Pacific for the period 1974–78. The results show that during 1976 and 1977 sea surface temperatures over the Northwest Pacific were significantly below normal and, coincidentally, atmospheric CO2 levels at Station P also were lower than expected. This indirect evidence does not prove but suggests that the Northwest Pacific (40–45°N) may have been a major sink for atmospheric CO2 during 1976 and 1977. However, a specific mechanism for this sink is not established. Broecker et al. (1979) presented direct evidence of a C02 sink at 40°N, 180°W in late 1973 and early 1974. In the future direct observations of pertinent parameters obtained at appropriate times could establish the significance of the North Pacific as a sink for atmospheric C02 and lead to studies of the mechanism for such a sink.

Dependence of the NO2 photodissociation rate constant on altitude

Abstract An important parameter of photochemical diffusion models is the rate constant ( k ) for the photodissociation of NO 2 . Theoretical values of k were determined as a function of altitude (surface to 4.2 km) and solar zenith angle (0°–86°), based on calculations of solar actinic flux for average atmospheric conditions. Between the surface and an altitude of 1.0 km, for example, k increases by 21%–70%, depending on solar zenith angle. The effect of greater than average aerosol loadings on the change of k with height was also estimated. As low-level aerosol concentrations increase, so does the vertical gradient of k . The theoretical calculations were compared to measurements of incident ultraviolet radiation made at an urban and at a nearby mountain-top (1.82 km) site near Los Angeles. For similar aerosol optical thicknesses, the changes with altitude of empirical and theoretical downward radiative fluxes were similar.

The Global Atmospheric CO2 Distribution 1968–1983: Interpretation of the Results of the NOAA/GMCC Measurement Program

The modern period of precise atmospheric CO2 measurements began with Keeling’s pioneering determinations at Mauna Loa, Hawaii, and the South Pole during the International Geophysical Year. The Mauna Loa record (e.g., Keeling 1983) remains the single most valuable CO2 time series for carbon cycle model verification. For very recent interpretations of atmospheric CO2 measurements and carbon cycle relationships, the reader is referred to Cleveland et al. (1983), Keeling (1983), Machta (1983), Mook et al. (1983), Pearman et al. (1983), Keeling et al. (1984), Wong et al. (1984), Bacastow et al. (1985), Komhyr et al. (1985), and Fraser et al. (this volume). In this chapter, the global atmospheric CO2 records, particularly of the NOAA/GMCC (National Oceanic and Atmospheric Administration/Geophysical Monitoring for Climatic Change) program, are summarized for the period 1968 through 1983, with emphasis on the mean properties of the global carbon cycle as viewed from the atmosphere (i.e., global mean CO2 concentration, latitude dependence of concentration and seasonal amplitude, airborne fraction, etc.).

Visibility-atmospheric turbidity dependence at Raleigh, North Carolina

Abstract Six years of turbidity measurements and visibility observations from rural Raleigh, North Carolina are analyzed to determine their interdependence. Exponential least squares regression equations were computed by month for all data and for three stratifications by relative humidity. Regression results showed a distinct seasonal dependence with the best results (i.e. greatest explained variance) in summer and poorest in winter. Stratification of the data by relative humidity improved the results for all months. During summer best results were obtained with lowest relative humidities. Under these conditions there is a significant dependence of visibility on atmospheric turbidity; the explained variance exceeded 66% during June to September.