ALBERT

Description: A legacy seismic transect acquired on 30 and 31 May 2009 in the southern South China Sea (SCS) was reprocessed to reveal the thermohaline structure of the water column. In the study region, a mesoscale subsurface lens with extraordinary features was detected at 113.5° E, 11.5° N. It is centred at 450 m depth, occupies both the subsurface and intermediate water from 250 to 600 m, and has an intersection diameter of around 60 km. The simulated results from Hybrid Coordinate Ocean Model reveal an eddy-induced subsurface current running southwestward along the deep basin edge and suggest that the imaged lens is a snapshot of the subsurface current core rather than a subsurface eddy.

Description: A legacy seismic transect acquired on 30 and 31 May 2009 in the southern South China Sea (SCS) was reprocessed to reveal the thermohaline structure of the water column. In the study region, a mesoscale subsurface lens with extraordinary features was detected at (113.5° E, 11.5° N). It is centered at 45 m depth, occupies both the subsurface and intermediate water from 250 to 600 m, and has a diameter of around 60 km. The simulated results from Hybrid Coordinate Ocean Model reveal an eddy-induced subsurface current running southwestward along the deep basin edge and suggest that the imaged lens is a snapshot of the subsurface current core rather than a subsurface eddy.

Description: Variations of precipitation and temperature at Lake Qinghai, NE Tibetan Plateau on decadal scales during the past 800 years were reconstructed based on the oxygen isotope values and Li/Ca ratios from ostracod shells of the single species Eucypris inflata. Higher temperature relates to lower Li/Ca ratios; higher precipitation relates to lower δ18O values, and vice versa. The good correlation between Li/Ca ratios and δ18O values of ostracod shells indicates that temperature variations corresponded well with precipitation variations on decadal scales during the past 800 years. Variations of precipitation and temperature are synchronous with variations of solar activity reconstructed from the atmospheric 14C concentration in tree rings and the 10Be concentration in ice cores. These findings suggest that, on decadal scales solar activity may be responsible for the synchronous variations of precipitation and temperature at Lake Qinghai, NE Tibetan Plateau during the past 800 years. Keywords: Precipitation variations; Temperature variations; Eucypris inflata; Li/Ca; δ18O; Synchronous variations; Lake Qinghai; Solar activity.

Description: The impact of the East Asia monsoon on the seasonal behavior of O3 in the boundary layer of Eastern China and the west Pacific region was analyzed for 2004–2006 by means of full-year nested chemical transport model simulations and continuous observational data obtained from three inland mountain sites in central and eastern China and three oceanic sites in the west Pacific region. The basic common features of O3 seasonal behaviors over all the monitoring sites are the pre- and post-monsoon peaks with a summer trough. Such bimodal seasonal patterns of O3 are predominant over the region with strong summer monsoon penetration, and become weaker or even disappear outside the monsoon region. The seasonal/geographical distribution of the pre-defined Monsoon Index indicated that the East Asia summer monsoon is responsible for the bimodal seasonal O3 pattern, and also partly account for the differences in the O3 seasonal variations between the inland mountain and oceanic sites. Over the inland mountain sites, the O3 concentration increased gradually from the beginning of the year, reached a maximum in June, decreased rapidly to a minimum in July or August, and then peaked in September or October, thereafter decreased gradually again. Over the oceanic sites, O3 abundance showed a similar increasing trend beginning in January, but then decreased gradually from the end of March, followed by a wide trough with the minimum in July and August and a small peak in October or November. A sensitivity analysis performed by setting China-emission to zero revealed that the chemically produced O3 from China-emission contributed more than 40% of total boundary layer O3 during summertime (60–70% in June) and accounted for about 40 ppb of each peak value over the inland region. In contrast, over the oceanic region in the high monsoon index zone, the contribution of China-emission to total O3 was always less than 20% (

Description: A 3-D regional chemical transport model, the Nested Air Quality Prediction Model System (NAQPMS), with an on-line tracer tagging module was applied to study the source of the near-ground (

Description: The Canadian Centre for Climate Modelling and Analysis third generation atmospheric general circulation model (AGCM3) is described. The discussion summarizes the details of the complete physics package emphasizing the changes made relative to the second generation version of the model. AGCM3 is the underlying model for applications which include the IPCC fourth assessment, coupled atmosphere-ocean seasonal forecasting, the first generation of the CCCma earth system model (CanESM1), and middle-atmosphere chemical-climate modelling (CCM). Here we shall focus on issues related to an upwardly extended version of AGCM3, the Canadian Middle-Atmosphere Model (CMAM). The CCM version of CMAM participated in the 2006 WMO/UNEP Scientific Assessment of Ozone Depletion and issues concerning its climate such as the impact of gravity-wave drag, the modelling of a spontaneous QBO, and the seasonality of the breakdown of the Southern Hemisphere polar vortex are discussed here.

Description: The optical properties of sea-salt aerosol have been parameterized at solar and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution (and compared to AERONET results) and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both solar and longwave wavelengths. We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, such as dependence with sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both solar and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Studies of the sensitivity of forcing results to variations in effective variance show there to be minimal variation; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.ewarming) when the solar zenith angle is relatively small 30° Finally, it is found that the surface albedo significantly affects the solar radiative forcing, with the forcing diminishing to zero as the surface albedo tends to unity. We anticipate this new sea-salt optical property parameterization will be useful for GCM models due to its simplicity, computational efficiency, and that its sensitivities have been explored and summarized in this work.

Description: The impact of open crop residual burning on O3, CO, Black Carbons (BC), and Organic Carbons (OC) concentrations over Central Eastern China (CEC) during the Mount Tai Experiment 2006 (MTX2006) was evaluated using the regional chemical transport model, the Models-3 Community Multiscale Air Quality Modeling System (CMAQ). To investigate these pollutants during the MTX2006 period in June, daily gridded emissions from open crop residual burning were developed based on a bottom-up methodology and using land cover and hotspot information from satellites. This model system which involves daily emissions from open biomass burning, captured monthly-averaged observed concentrations and day-to-day variations in the patterns of O3, CO, BC, and OC with good correlation coefficients between models and observations, ranging from 0.54 to 0.66. These results were significantly improved from those using annual emissions. For monthly-averaged O3, the simulated concentration of 81.5 ppbv was close to the observed concentration (82.5 ppbv). The period of MTX2006 was roughly divided into two parts: 1) polluted days with heavy open crop residual burning in the first half of June; 2) cleaner days with negligible field burning in the latter half of June. Additionally, the first half of June was defined by two high pollution episodes during 5–7 and 12–13 June, and a relatively cleaner episode during 8–10 June between these two high pollution episodes. In the first polluted episode, this model captured high O3, CO, BC, and OC concentrations at the summit of Mount Tai which were affected by open crop residual burning in the south of CEC and northward transport. For this episode, the impacts from open crop residual burning were 12% for O3, 35% for CO, 56% for BC, and 80% for OC over CEC. The daily emissions from open crop residual burning were an essential factor to evaluate the pollutants during the MTX2006. These emissions have a large impact not only on primary pollutants but also on secondly pollutions, such as O3, in the first half of June over northeastern Asia. On the other hand, this model did not capture the second polluted episode and underestimated observed CO and BC. Improvements of both anthropogenic and open burning emissions and CO inflow from model boundary are necessary to improve both anthropogenic and open burning emissions and CO inflow to evaluate the pollutants using this model.

Description: FengYun-3C (FY-3C) is an operational polar-orbiting satellite carrying the new-generation microwave sounding instruments in China. This paper describes the assimilation of the FY-3C Microwave Temperature Sounder-2 (MWTS-2) radiances in the Global and Regional Assimilation and PrEdiction System (GRAPES) of China Meteoroligcal Administration. A quality control (QC) procedure for the assimilation of MWTS-2 radiance is proposed. Extensive monitoring before assimilation shows that MWTS-2 observations exhibit a clear striping pattern. A technique combining principal component analysis (PCA) and Ensemble Empirical Mode Decomposition (EEMD) is applied to the observations to remove the striping noise. Cloudy field-of-views (FOVs) are identified by applying the Visible and InfrarRed Radiometer (VIRR) cloud fraction threshold of 76%. Other QC steps include the following: (i) eight outmost FOVs, (ii) channel 6 if the terrain altitude is greater than 500 m, (iii) channel 5 over sea ice and land, (iv) coastal FOVs, and (v) outliers with large differences between observations and model simulations. Approximately 83%, 75%, 40% and 40% of the observations are removed by the proposed QC for channels 5-8, respectively. After QC, the global biases and standard deviations are reduced significantly. The assimilation of the MWTS-2 radiances shows a positive impact when the control experiment assimilates only conventional observations. The experiments also show that the analysis and forecast errors are slightly reduced when the striping noise is removed from the observations. The quality control scheme of extracting the striping noise may contribute to the analysis and forecast. The impact of MWTS-2 is neutral when the conventional data and other satellite data are all assimilated.

Description: Sulfate particles play a key role in the air quality and the global climate, but the heterogeneous formation mechanism of sulfates on surfaces of atmospheric particles is not well established. Carbonates, which act as a reactive component in mineral dust due to their special chemical properties, may contribute significantly to the sulfate formation by heterogeneous processes. This paper presents a study on the oxidation of SO2 by O3 on CaCO3 particles. Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), the formation of sulfite and sulfate on the surface was identified, and the roles of O3 and water in oxidation processes were determined. The results showed that in the presence of O3, SO2can be oxidized to sulfate on the surface of CaCO3 particles. The reaction is first order in SO2 and zero order in O3. The reactive uptake coefficient for SO2 [(0.6–9.8)×1014 molecule cm-3] oxidation by O3 [(1.2–12)×1014 molecule cm-3] was determined to be (1.4±0.3)×10-7 using the BET area as the reactive area and (7.7±1.6)×10-4 using the geometric area. A two-stage mechanism that involves adsorption of SO2 followed by O3 oxidation is proposed and the adsorption of SO2 on the CaCO3 surface is the rate-determining step. The proposed mechanism can well explain the experiment results. The atmospheric implications were explored based on a box model calculation. It was found that the heterogeneous reaction might be an important pathway for sulfate formation in the atmosphere.