Preliminary results of vertical ozone soundings at Wakkanai, Japan

In order to obtain better understanding of ozone change in northern Japan, soundings of vertical ozone profile by using an ECC type ozone sonde were conducted at Wakkanai (45.4°N, 141.7°E) in Hokkaido, the northernmost city of Japan, between 15th-24th February, 2001. Ten vertical profiles of ozone on consecutive ten days were obtained successfully. In this paper, the methods and results of the observations are shown

A comprehensive estimate of recent carbon sinks in China using both top-down and bottom-up approaches

Atmospheric inversions use measurements of atmospheric CO2 gradients to constrain regional surface fluxes. Current inversions indicate a net terrestrial CO2 sink in China between 0.16 and 0.35 PgC/yr. The uncertainty of these estimates is as large as the mean because the atmospheric network historically contained only one high altitude station in China. Here, we revisit the calculation of the terrestrial CO2 flux in China, excluding emissions from fossil fuel burning and cement production, by using two inversions with three new CO2 monitoring stations in China as well as aircraft observations over Asia. We estimate a net terrestrial CO2 uptake of 0.39-0.51 PgC/yr with a mean of 0.45 PgC/yr in 2006-2009. After considering the lateral transport of carbon in air and water and international trade, the annual mean carbon sink is adjusted to 0.35 PgC/yr. To evaluate this top-down estimate, we constructed an independent bottom-up estimate based on ecosystem data, and giving a net land sink of 0.33 PgC/yr. This demonstrates closure between the top-down and bottom-up estimates. Both top-down and bottom-up estimates give a higher carbon sink than previous estimates made for the 1980s and 1990s, suggesting a trend towards increased uptake by land ecosystems in China.</p

Simulation of CO2 concentrations at Tsukuba tall tower using WRF-CO2 tracer transport model

Simulation of carbon dioxide (CO2) at hourly/weekly intervals and fine vertical resolution at the continental or coastal sites is challenging because of coarse horizontal resolution of global transport models. Here the regional Weather Research and Forecasting (WRF) model coupled with atmospheric chemistry is adopted for simulating atmospheric CO2 (hereinafter WRF-CO2) in nonreactive chemical tracer mode. Model results at horizontal resolution of 27 × 27 km and 31 vertical levels are compared with hourly CO2 measurements from Tsukuba, Japan (36.05゜N, 140.13oE) at tower heights of 25 and 200 m for the entire year 2002. Using the wind rose analysis, we find that the fossil fuel emission signal from the megacity Tokyo dominates the diurnal, synoptic and seasonal variations observed at Tsukuba. Contribution of terrestrial biosphere fluxes is of secondary importance for CO2 concentration variability. The phase of synoptic scale variability in CO2 at both heights are remarkably well simulated the observed data (correlation coefficient >0.70) for the entire year. The simulations of monthly mean diurnal cycles are in better agreement with the measurements at lower height compared to that at the upper height. The modelled vertical CO2 gradients are generally greater than the observed vertical gradient. Sensitivity studies show that the simulation of observed vertical gradient can be improved by increasing the number of vertical levels from 31 in the model WRF to 37 (4 below 200 m) and using the Mellor-Yamada-Janjic planetary boundary scheme. These results have large implications for improving transport model simulation of CO2 over the continental sites

Bias corrections of GOSAT SWIR XCO₂ and XCH₄ with TCCON data and their evaluation using aircraft measurement data

We describe a method for removing systematic biases of column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) derived from short-wavelength infrared (SWIR) spectra of the Greenhouse gases Observing SATellite (GOSAT). We conduct correlation analyses between the GOSAT biases and simultaneously retrieved auxiliary parameters. We use these correlations to bias correct the GOSAT data, removing these spurious correlations. Data from the Total Carbon Column Observing Network (TCCON) were used as reference values for this regression analysis. To evaluate the effectiveness of this correction method, the tnzuncorrected/corrected GOSAT data were compared to independent XCO2 and XCH4 data derived from aircraft measurements taken for the Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) project, the National Oceanic and Atmospheric Administration (NOAA), the US Department of Energy (DOE), the National Institute for Environmental Studies (NIES), the Japan Meteorological Agency (JMA), the HIAPER Pole-to-Pole observations (HIPPO) program, and the GOSAT validation aircraft observation campaign over Japan. These comparisons demonstrate that the empirically derived bias correction improves the agreement between GOSAT XCO2/XCH4 and the aircraft data. Finally, we present spatial distributions and temporal variations of the derived GOSAT biases

Relative contribution of transport/surface flux to the seasonal vertical synoptic CO2 variability in the troposphere over Narita

Frequent CO2 measurements obtained by commercial aircraft provide a unique, quasi-continuous record of free-tropospheric CO2 variability. Vertically-resolved synoptic-scale fluctuations of CO2 over Narita International Airport (lat 35.8&#x00B0;N, 140.4&#x00B0;E, 43&#x2009;m above sea-level) were investigated from November 2005 to March 2009, and combined with analyses of results from a transport model simulation for the year 2007 to retrieve information on sources contributing to the observed variability. The synoptic-scale variability of the observed CO2 mixing ratio, represented by the standard deviation (SD) from the fitted curves, increased in the upper troposphere in the spring, with a noticeable increase at all altitudes in the summer. This seasonal/altitudinal change of the observed SD was shown to be statistically significant throughout the observation period, and the model result agreed with the observation except for the underestimation of the summertime SD. Tagged simulations were conducted to evaluate the relative contribution of the regional fluxes to the synoptic-scale variability over Narita. The results indicate that the major contribution to the free troposphere (FT) variability was made by the fluxes in East Asia, while the Japanese fluxes contributed mostly to the variability in the planetary boundary layer (PBL). A sensitivity analysis was performed to evaluate the relative influence of transport and of flux magnitude on the CO2 SD over Narita for 2007. It was found that a change in the surface flux magnitude could affect the altitudinal distribution of the annual SD over Narita as follows: 41 and 3% at 9&#x2009;km, 61 and 4% at 5&#x2009;km, 19 and 83% at 0.5&#x2009;km when the fossil fuel flux from East Asia and Japan was doubled, respectively. These results are qualitative in nature (since SD is a non-linear function of concentration and flux), but do indicate that the CO2 SD over Narita is more sensitive to the fluctuation in the atmospheric transport (synoptic-scale meteorological variability) in the FT, while showing much more sensitivity to the magnitude of local fluxes in the PBL. The results also point to the fact that vertical profiles of atmospheric CO2 variability at the synoptic scale could potentially provide a useful additional constraint in the inversion analysis of regional CO2 fluxes

SIZE DISTRIBUTION OF AEROSOLS AT BARROW IN ALASKA : A CASE STUDY IN SPRING

Concentration, size distribution and morphological features of aerosol particles were observed at Barrow in Alaska during the period 13-28 April 1997 together with concentrations of gaseous species (SO_2,NO and NO_2). The concentrations of gaseous species were less than 50 pptv except for locally polluted air. Aerosol size distributions suggested the occurrence of new particle formation from the gas phase in spite of very low concentrations of gaseous species, especially in the air mass from lower latitudes during the latter part of the observational period. In the air mass from higher latitudes, new particle formation was assumed to be not active. The largest maximum was found at 0.1-0.2μm radius in most of the observation periods, suggesting that the size distributions have been influenced by wellaged particles. The dominant component of aerosol particles in this size range is considered to be sulfate-containing particles. Another maximum was found occasionally at 0.02-0.05μm radius. This kind of air mass was possibly influenced by air from lower latitudes