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Global high‐precision atmospheric Δ14CO2 records covering the last two decades are presented, and evaluated in terms of changing (radio)carbon sources and sinks, using the coarse‐grid carbon cycle model GRACE. Dedicated simulations of global trends and interhemispheric differences with respect to atmospheric CO2 as well as δ13CO2 and Δ14CO2, are shown to be in good agreement with the available observations...
This study simulates optical depth of marine warm clouds for year 2001 based on interactively predicted aerosol concentrations with a global chemical transport model (CTM) driven by the ERA‐40 re‐analysis meteorological data. The simulated aerosol and cloud droplet number concentrations (CDNC) largely reproduce the variations between polluted and pristine marine environment as revealed by surface...
Characterizing the capacity of the terrestrial biome to absorb CO2 is one of the most pressing topics in climate science. One of the key players in this arena is also one of the most poorly understood: the role of nitrogen deposition. While N deposition seems to fertilize some forests, in others it has been blamed for forest decline and tree mortality. In order to further understand the role of N...
This paper uses a refined soil gradient method to estimate soil CO2 efflux. Six different models are used to determine the relative gas diffusion coefficient (ξ). A weighted harmonic averaging is used to estimate the soil CO2 diffusion coefficient, yielding a better estimate of soil CO2 efflux. The resulting soil CO2 efflux results are then compared to the soil CO2 efflux measured with a soil chamber...
In this issue, Ramonet et al. revealed a positive trend in European, atmospheric CO2 concentrations relative to a marine, North Atlantic reference baseline, for the years 2001–2006. The observed build up mainly occurred during the cold season where it reaches a 0.8 ppm yr−1 at low‐altitude stations to a 0.3 ppm yr−1 at mid‐altitude stations. We explore the cause of this build‐up using the mesoscale...
We analysed interannual and decadal changes in the atmospheric CO2 concentration gradient (ΔCO2) between Europe and the Atlantic Ocean over the period 1995–2007. Fourteen measurement stations are used, with Mace‐Head being used to define background conditions. The variability of ΔCO2 reflects fossil fuel emissions and natural sinks activity over Europe, as well as atmospheric transport variability...
Four years measurements of broadband global solar radiation (RS) and total ultraviolet (UV) radiation (the sum of UV‐A and UV‐B) were conducted from 2005 to 2008 in Beijing. These data were used to determine the temporal variability of UV/RS and its dependence on water vapour content and clearness index. A simple, efficient and empirically derived all‐weather model is proposed to estimate UV from...
Remote sensors designed specifically for studying the atmosphere have been widely used to derive timely information on air pollution at various scales. Whether the satellite‐generated aerosol optical thickness (AOT) data can be used to monitor air pollution, however, is subject to the effect of a number of meteorological parameters. This study analyses the influence of four meteorological parameters...
A new observational approach is presented to approximate the uncertainty (scatter or error variance) in 1‐h averaged turbulence fluxes from eddy‐covariance measurements. The uncertainty includes potential contributions from instrument problems, heterogeneity and non‐stationarity in addition to classical random sampling error. The daytime relative flux uncertainty (RFE) is half as large (20%) at a...
Based on AErosol RObotic NETwork and Chinese Sun Hazemeter Network data, the Multi‐angle Imaging SpectroRadiometer (MISR) level 2 aerosol optical depth (AOD) products are evaluated in China. The MISR retrievals depict well the temporal aerosol trend in China with correlation coefficients exceeding 0.8 except for stations located in northeast China and at the Lanzhou site. In general, the MISR AOD...
A systematic 1‐yr chemical data for the fine mode (PM2.5) air‐borne particulate matter, collected from a high‐altitude site (Mt. Abu, 22.7°N, 74.6°E, 1680 m asl) in a semi‐arid region of western India, reveal characteristic temporal variability in the abundance of mineral dust and fractional solubility of aerosol Fe (referred as water‐soluble Fe). A notable feature of the data is seen from an inverse...
We use 6 yr of multisensor radiometric data (1998–2003) from the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program to provide an observational quantification of the short‐wave aerosol first indirect effect in the Arctic. Combined with the previously determined long‐wave indirect effect, the total (short‐wave and long‐wave) first indirect effect in the high Arctic is found to...
Regional aerosol concentrations are governed by an evolving balance between aerosol sources and sinks. Here, a simple technique is described for making estimates of the extent to which seasonal aerosol variability is controlled by wet scavenging rather than the efficiency of transport from pollution source regions. Carbon monoxide (CO) is employed as an assumed passive tracer of pollution transport...
In this paper, we provide the concentrations and fluxes of dust particles (1–30 μm diameter), quantitatively calculated, in several shallow ice cores recovered from the northern (Dunde), western (Muztagata), central (Tanggula) and southern (Dasuopu and Everest) parts of the Tibetan Plateau over the past few decades. Dust concentrations from the northern and western Tibetan Plateau are 2–10 times higher,...
The vertical structure of gas‐phase dimethyl sulphide [DMS(g)] in the high Arctic atmosphere is investigated during a summer season. The model results show that the near‐surface DMS(g) concentration over open ocean is very variable both in time and space, depending on the local atmospheric conditions. Profiles over ocean have typically highest concentration near the surface and decrease exponentially...
The variations of soil water content (SWC) and its influences on the carbon (C) cycle in Canada's forests and wetlands were studied through model simulations using the Integrated Terrestrial Ecosystem Carbon (InTEC) model. It shows that Canada's forests and wetlands experienced spatially and temporally heterogeneous changes in SWC from 1901 to 2000. SWC changes caused average NPP to decrease 40.8...
Peatlands are one of the major natural sources of methane (CH4), but the quantification of efflux is uncertain especially during winter, fall and the highly dynamic spring thaw period. Here, we report pronounced diurnal variations in CH4 fluxes (FCH4), measured using the eddy‐covariance technique during the snow‐thawing period at a boreal peatland in north‐western Russia. Following the background...
Particulate matter (PM) levels show significant seasonal variability and this can influence the neutralization of rainwater acidity. Months were grouped in two periods: monsoon (July to October) and non‐monsoon (November to June) for studying the seasonal variability in PM and rainwater composition. To clearly establish the cause effect relationship of acid rain neutralization, a two tier model was...
The remote marine aerosol and the cloud droplet number concentration (CDNC) are examined with an aerosol microphysics box model in an attempt to better understand the processes involved in the formation and transformation of the marine aerosol. Emission of submicrometre sea‐salt and dimethylsulfide (DMS) have been included together with aerosol dynamics, gas and liquid phase chemistry and cloud processing...
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