ALBERT

Description: Numerical simulation and validation of three-dimensional structure of atmospheric carbon dioxide (CO2) is necessary for quantification of transport model uncertainty and its role on surface flux estimation by inverse modeling. Simulations of atmospheric CO2 were performed using four transport models and two sets of surface fluxes compared with an aircraft measurement dataset of Comprehensive Observation Network for Trace gases by AIrLiner (CONTRAIL), covering various latitudes, longitudes, and heights. Under this transport model intercomparison project, spatiotemporal variations of CO2 concentration for 2006–2007 were analyzed with a three-dimensional perspective. Results show that the models reasonably simulated vertical profiles and seasonal variations not only over northern latitude areas but also over the tropics and southern latitudes. From CONTRAIL measurements and model simulations, intrusion of northern CO2 in to the Southern Hemisphere, through the upper troposphere, was confirmed. Furthermore, models well simulated the vertical propagation of seasonal variation in the northern free troposphere. However, significant model-observation discrepancies were found in Asian regions, which are attributable to uncertainty of the surface CO2 flux data. In summer season, differences in latitudinal gradients by the fluxes are comparable to or greater than model-model differences even in the free troposphere. This result suggests that active summer vertical transport sufficiently ventilates flux signals up to the free troposphere and the models could use those for inferring surface CO2 fluxes.

Description: A new aerosol chemical transport model, the Regional Air Quality Model 2 (RAQM2), was developed to simulate the Asian air quality. We implemented a simple version of a triple-moment modal aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super-μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized in which the aerosols were distributed into four categories: particles in the Aitken mode (ATK), soot-free particles in the accumulation mode (ACM), soot aggregates (AGR), and particles in the coarse mode (COR). The aerosol size distribution in each category is characterized by a single mode. The condensation, evaporation, and Brownian coagulations for each mode were solved dynamically. A regional-scale simulation (Δx = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. The modeled PM1/bulk ratios of the chemical components were consistent with observations, indicating that the simulated aerosol mixing types were consistent with those in nature. The non–sea-salt SO42− mixed with ATK + ACM was the largest at Hedo in summer, whereas the SOSO42− was substantially mixed with AGR in the cold seasons. Ninety-eight percent of the modeled NO3− was mixed with sea salt at Hedo, whereas 53.7% of the NO3− was mixed with sea salt at Gosan, which is located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean accounts for the difference in the NO3− mixing type at the two sites. Because the aerosol mixing type alters the optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

Description: We conducted a regional-scale simulation over Northeast Asia for the year 2006 using an aerosol chemical transport model, with time-varying lateral and upper boundary concentrations of gaseous species predicted by a global stratospheric and tropospheric chemistry-climate model. The present one-way nested global-through-regional-scale model is named the Meteorological Research Institute–Passive-tracers Model system for atmospheric Chemistry (MRI-PM/c). We evaluated the model's performance with respect to the major anthropogenic and natural inorganic components, SO42−, NH4+, NO3−, Na+ and Ca2+ in the air, rain and snow measured at the Acid Deposition Monitoring Network in East Asia (EANET) stations. Statistical analysis showed that approximately 40–50 % and 70–80 % of simulated concentration and wet deposition of SO42−, NH4+, NO3−and Ca2+ are within factors of 2 and 5 of the observations, respectively. The prediction of the sea-salt originated component Na+ was not successful at near-coastal stations (where the distance from the coast ranged from 150 to 700 m), because the model grid resolution (Δx=60 km) is too coarse to resolve it. The simulated Na+ in precipitation was significantly underestimated by up to a factor of 30.

Description: A continuous lacustrine sediment core obtained from the Kathmandu Valley in the Central Himalayas revealed that cyclical changes in C3/C4 vegetation corresponded to global glacial-interglacial cycles from marine isotope stages (MIS) 15 to MIS 4. The C3/C4 vegetation shifts were reconstructed from significant changes in the δ13C values of bulk organic carbon. Glacial ages were characterized by significant 13C enrichment, due to the expansion of C4 plants, attributed to an intensification of aridity. Thus, the southwest (SW) summer monsoon, which brings the majority of rainfall to the Central Himalayan southern slopes, would have been weaker. Marine sediment cores from the Indian Ocean and Arabian Sea have demonstrated a weaker SW monsoon during glacial periods, and our results confirm that arid conditions and a weak SW monsoon prevailed in the continental interior of the Central Himalayas during glacial ages. This study provides the first continuous record for the continental interior of paleoenvironmental changes directly influenced by the Indian monsoon.

Description: Atmospheric CO2 inversions estimate surface carbon fluxes from an optimal fit to atmospheric CO2 measurements, usually including prior constraints on the flux estimates. Eleven sets of carbon flux estimates are compared, generated by different inversions systems that vary in their inversions methods, choice of atmospheric data, transport model and prior information. The inversions were run for at least 5 yr in the period between 1990 and 2009. Mean fluxes for 2001–2004, seasonal cycles, interannual variability and trends are compared for the tropics and northern and southern extra-tropics, and separately for land and ocean. Some continental/basin-scale subdivisions are also considered where the atmospheric network is denser. Four-year mean fluxes are reasonably consistent across inversions at global/latitudinal scale, with a large total (land plus ocean) carbon uptake in the north (−3.3 Pg Cy−1 (±0.6 standard deviation)) nearly equally spread between land and ocean, a significant although more variable source over the tropics (1.6 ± 1.0 Pg Cy−1) and a compensatory sink of similar magnitude in the south (−1.4 ± 0.6 Pg Cy−1) corresponding mainly to an ocean sink. Largest differences across inversions occur in the balance between tropical land sources and southern land sinks. Interannual variability (IAV) in carbon fluxes is larger for land than ocean regions (standard deviation around 1.05 versus 0.34 Pg Cy−1 for the 1996–2007 period), with much higher consistency amoung the inversions for the land. While the tropical land explains most of the IAV (stdev ∼ 0.69 Pg Cy−1), the northern and southern land also contribute (stdev ∼ 0.39 Pg Cy−1). Most inversions tend to indicate an increase of the northern land carbon uptake through the 2000s (around 0.11 Pg Cy−1), shared by North America and North Asia. The mean seasonal cycle appears to be well constrained by the atmospheric data over the northern land (at the continental scale), but still highly dependent on the prior flux seasonality over the ocean. Finally we provide recommendations to interpret the regional fluxes, along with the uncertainty estimates.

Description: A new aerosol chemical transport model, Regional Air Quality Model 2 (RAQM2), was developed to simulate Asian air quality. We implemented a simple version of a modal-moment aerosol dynamics model (MADMS) and achieved a completely dynamic (non-equilibrium) solution of a gas-to-particle mass transfer over a wide range of aerosol diameters from 1 nm to super μm. To consider a variety of atmospheric aerosol properties, a category approach was utilized, in which the aerosols were distributed into 4 categories: Aitken mode (ATK), soot-free accumulation mode (ACM), soot aggregates (AGR), and coarse mode (COR). Condensation, evaporation, and Brownian coagulations for each category were solved dynamically. A regional-scale simulation (Δ x = 60 km) was performed for the entire year of 2006 covering the Northeast Asian region. Statistical analyses showed that the model reproduced the regional-scale transport and transformation of the major inorganic anthropogenic and natural air constituents within factors of 2 to 5. The modeled PM1/bulk ratios of the chemical components were consistent with the observations, indicating that the simulations of aerosol mixing types were successful. Non-sea salt SO42- mixed with ATK + ACM was the largest at Hedo in summer, whereas it mixed with AGR was substantial in cold seasons. Ninety-eight percent of the modeled NO3- was mixed with sea salt at Hedo, whereas 53.7% of the NO3- was mixed with sea salt at Gosan, located upwind toward the Asian continent. The condensation of HNO3 onto sea salt particles during transport over the ocean makes the difference in the NO3- mixing type at the two sites. Because the aerosol mixing type alters optical properties and cloud condensation nuclei activity, its accurate prediction and evaluation are indispensable for aerosol-cloud-radiation interaction studies.

Description: Atmospheric CO2 inversions estimate surface carbon fluxes from an optimal fit to atmospheric CO2 measurements, usually including prior constraints on the flux estimates. Eleven sets of carbon flux estimates are compared, generated by different inversions systems that vary in their inversions methods, choice of atmospheric data, transport model and prior information. The inversions were run for at least 5 yr in the period between 1990 and 2010. Mean fluxes for 2001–2004, seasonal cycles, interannual variability and trends are compared for the tropics and northern and southern extra-tropics, and separately for land and ocean. Some continental/basin-scale subdivisions are also considered where the atmospheric network is denser. Four-year mean fluxes are reasonably consistent across inversions at global/latitudinal scale, with a large total (land plus ocean) carbon uptake in the north (−3.4 Pg C yr−1 (±0.5 Pg C yr−1 standard deviation), with slightly more uptake over land than over ocean), a significant although more variable source over the tropics (1.6 ± 0.9 Pg C yr−1) and a compensatory sink of similar magnitude in the south (−1.4 ± 0.5 Pg C yr−1) corresponding mainly to an ocean sink. Largest differences across inversions occur in the balance between tropical land sources and southern land sinks. Interannual variability (IAV) in carbon fluxes is larger for land than ocean regions (standard deviation around 1.06 versus 0.33 Pg C yr−1 for the 1996–2007 period), with much higher consistency among the inversions for the land. While the tropical land explains most of the IAV (standard deviation ~ 0.65 Pg C yr−1), the northern and southern land also contribute (standard deviation ~ 0.39 Pg C yr−1). Most inversions tend to indicate an increase of the northern land carbon uptake from late 1990s to 2008 (around 0.1 Pg C yr−1, predominantly in North Asia. The mean seasonal cycle appears to be well constrained by the atmospheric data over the northern land (at the continental scale), but still highly dependent on the prior flux seasonality over the ocean. Finally we provide recommendations to interpret the regional fluxes, along with the uncertainty estimates.

Description: We have improved an ozone DIfferential Absorption Lidar (DIAL) system, originally developed in March 2010. The improved DIAL system consists of a Nd:YAG laser and a 2 m Raman cell filled with 8.1 × 105 Pa of CO2 gas which generate four Stokes lines (276, 287, 299, and 312 nm) of stimulated Raman scattering, and two receiving telescopes with diameters of 49 and 10 cm. Using this system, 44 ozone profiles were observed in the 1–6 km altitude range over Saga (33.24° N, 130.29° E) in 2012. High-ozone layers were observed at around 2 km altitude during April and May. Ozone column amounts within the 1–6 km altitude range were almost constant (19.1 DU on average) from January to March, and increased to 26.7 DU from late April to July. From mid-July through August, ozone column amounts decreased greatly to 14.3 DU because of exchanges of continental and maritime air masses. Then in mid-September they increased again to 22.1 DU within 1−6 km, and subsequently decreased slowly to 17.3 DU, becoming almost constant by December. The Meteorological Research Institute's chemistry–climate model version 2 (MRI-CCM2) successfully predicted most of these ozone variations with the following exceptions. MRI-CCM2 could not predict the high-ozone volume mixing ratios measured at around 2 km altitude on 5 May and 11 May, possibly in part because emissions were assumed in the model to be constant (climatological data were used). Ozone volume mixing ratios predicted by MRI-CCM2 were low in the 2–6 km range on 7 July and high in the 1–4 km range on 19 July compared with those measured by DIAL.

Description: We conducted a regional-scale simulation (with grid spacing = 60 km) over Northeast Asia for the entire year of 2006 by using an aerosol chemical transport model, the lateral and upper boundary concentrations of which we predicted with a global stratospheric and tropospheric chemistry-climate model, with a horizontal resolution of T42 (grid spacing ~300 km) and a time resolution of 1 h. The present one-way nested global-through-regional-scale model is called the Meteorological Research Institute – Passive-tracers Model system for atmospheric Chemistry (MRI-PM/c). We evaluated the model performance with respect to the major inorganic components in rain and snow measured by stations of the Acid Deposition Monitoring Network in East Asia (EANET). Through statistical analysis, we show that the model successfully reproduced the regional-scale processes of emission, transport, transformation, and wet deposition of major inorganic species derived from anthropogenic and natural sources, including SO42−, NH4+, NO3−, Na+ and Ca2+. Interestingly, the only exception was Na+ in precipitation at near-coastal stations (where the distance from the coast was from 150 to 700 m), concentrations of which were significantly underestimated by the model, by up to a factor of 30. This result suggested that the contribution of short-lived, super-large sea salt droplets (SLSD; D 〉 10–100 μm) was substantial in precipitation samples at stations near the coast of Japan; thus samples were horizontally representative only within the traveling distances of SLSD (from 1 to 10 km). Nevertheless, the calculated effect of SLSD on precipitation pH was very low, a change of about +0.014 on average, even if the ratio of SLSD to all sea salt in precipitation was assumed to be 90%.

Description: We have improved an ozone DIfferential Absorption Lidar (DIAL) system, originally developed in March 2010. The improved DIAL system consists of a Nd:YAG laser and a 2 m Raman cell filled with 8.1 × 105 Pa of CO2 gas which generate four Stokes lines (276, 287, 299, and 312 nm) of stimulated Raman scattering, and two receiving telescopes with diameters of 49 and 10 cm. Using this system, 44 ozone profiles were observed in the 1–6 km altitude range over Saga (33.24° N, 130.29° E) in 2012. High ozone concentration layers were observed at around 2 km altitude during April and May. Ozone column amounts within the 1–6 km altitude range were almost constant from January to March, and increased from late April to July. From mid-July through August, ozone column amounts decreased greatly because of exchanges of continental and maritime air masses. Then in mid-September they increased again within 1–6 km, and subsequently decreased slowly, becoming almost constant by December. The Meteorological Research Institute's Chemistry-Climate Model version 2 (MRI-CCM2) successfully predicted most of these ozone variations with the following exceptions. MRI-CCM2 could not predict the high ozone-mixing ratios measured at around 2 km altitude on 5 May and 11 May, possibly in part because emissions were assumed in the model to be constant (climatological data were used). Ozone-mixing ratios predicted by MRI-CCM2 were low in the 2–6 km range on 7 July and high in the 1–4 km range on 19 July compared with those measured by DIAL.