Large Asian dust layers continuously reached North America in April 2010

The NASA space-borne Mie-lidar system CALIPSO/CALIOP revealed that multiple large Asian dust layers with a horizontal scale of 2000–3000 km reached North America, occupying the full troposphere, in April 2010. This kind of dust layer transport has not been reported before. Our analysis of CALIOP data and global aerosol model results revealed that frequent dust emissions occurred in northwestern China because of stronger-than-average near-surface winds, and that strong stable westerly winds carried the Asian dust from northwestern China to the central Pacific Ocean. A negative pressure anomaly was located in the eastern Pacific Ocean, and the main dust transport path was split into two branches: a northern path and a southern path over North America. Northern-path dust was trapped and stagnant for a longer time than southern path dust and finally subsided under a high-pressure system. Dust along the southern path reached the central US. These complex conditions resulted in a multi-layered structure of dust over North America

Numerical modeling of Asian dust emission and transport with adjoint inversion using LIDAR network observations

International audienceA four-dimensional variational (4D-Var) data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4) is applied to a heavy dust event which occurred between 20 March and 4 April 2007 over eastern Asia. The vertical profiles of the dust extinction coefficients derived from NIES LIDAR observation network are directly assimilated. We conduct two experiments to evaluate impacts of selections of observation sites: Experiment A uses five Japanese observation sites located only downwind of dust source regions; the other Experiment B uses these sites together with two other sites near source regions (China and Korea). Validations using various observation data (e.g., PM10 concentration, MODIS AOT, OMI Aerosol Index, and the dust extinction coefficient derived by space-based LIDAR NASA/CALIPSO) are demonstrated. The modeled dust extinction coefficients are improved considerably through the assimilation. Assimilation results of Experiment A are consistent with those of Experiment B, indicating that observations of Experiment A can capture the dust event correctly and include sufficient information for dust emission inversion. Time series of dust AOT calculated by modeled and LIDAR dust extinction coefficients show good agreement. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square errors of dust AOT by 31?32%. Vertical profiles of the dust layer observed by CALIPSO are also compared with assimilation results. The dense dust layer was trapped between ?=280?300 K and elevated higher toward the north; the model reproduces those characteristics well. The modeled dust AOT along the orbit paths agrees well with the CALIPSO dust AOT, OMI AI, and the coarse mode AOT retrieved from MODIS; especially the modeled dust AOT and the MODIS coarse mode AOT are consistent quantitatively. Assimilation results increase dust emissions over the Gobi Desert and Mongolia considerably; especially between 29 and 30 March, emission flux is increased by about 2?3 times. The heavy dust event is caused by the heavy dust uplift flux over the Gobi Desert and Mongolia during those days. We obtain the total optimized dust emissions of 57.9 Tg (Experiment A; 57.8% larger than before assimilation) and 56.3 Tg (Experiment B; 53.4% larger)

Adjoint inversion modeling of Asian dust emission using lidar observations

International audienceA four-dimensional variational (4D-Var) data assimilation system for a regional dust model (RAMS/CFORS-4DVAR; RC4) is applied to an adjoint inversion of a heavy dust event over eastern Asia during 20 March?4 April 2007. The vertical profiles of the dust extinction coefficients derived from NIES Lidar network are directly assimilated, with validation using observation data. Two experiments assess impacts of observation site selection: Experiment A uses five Japanese observation sites located downwind of dust source regions; Experiment B uses these and two other sites near source regions. Assimilation improves the modeled dust extinction coefficients. Experiment A and Experiment B assimilation results are mutually consistent, indicating that observations of Experiment A distributed over Japan can provide comprehensive information related to dust emission inversion. Time series data of dust AOT calculated using modeled and Lidar dust extinction coefficients improve the model results. At Seoul, Matsue, and Toyama, assimilation reduces the root mean square differences of dust AOT by 35?40%. However, at Beijing and Tsukuba, the RMS differences degrade because of fewer observations during the heavy dust event. Vertical profiles of the dust layer observed by CALIPSO are compared with assimilation results. The dense dust layer was trapped at potential temperatures (?) of 280?300 K and was higher toward the north; the model reproduces those characteristics well. Latitudinal distributions of modeled dust AOT along the CALIPSO orbit paths agree well with those of CALIPSO dust AOT, OMI AI, and MODIS coarse-mode AOT, capturing the latitude at which AOTs and AI have high values. Assimilation results show increased dust emissions over the Gobi Desert and Mongolia; especially for 29?30 March, emission flux is about 10 times greater. Strong dust uplift fluxes over the Gobi Desert and Mongolia cause the heavy dust event. Total optimized dust emissions are 57.9 Tg (Experiment A; 57.8% larger than before assimilation) and 56.3 Tg (Experiment B; 53.4% larger)

Interannual variation in the fine-mode MODIS aerosol optical depth and its relationship to the changes in sulfur dioxide emissions in China between 2000 and 2010

Anthropogenic SO<sub>2</sub> emissions increased alongside economic development in China at a rate of 12.7% yr<sup>−1</sup> from 2000 to 2005. However, under new Chinese government policy, SO<sub>2</sub> emissions declined by 3.9% yr<sup>−1</sup> between 2005 and 2009. Between 2000 and 2010, we found that the variability in the fine-mode (submicron) aerosol optical depth (AOD) over the oceans adjacent to East Asia increased by 3–8% yr<sup>−1</sup> to a peak around 2005–2006 and subsequently decreased by 2–7% yr<sup>−1</sup>, based on observations by the Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA's Terra satellite and simulations by a chemical transport model. This trend is consistent with ground-based observations of aerosol particles at a mountainous background observation site in central Japan. These fluctuations in SO<sub>2</sub> emission intensity and fine-mode AOD are thought to reflect the widespread installation of fuel-gas desulfurization (FGD) devices in power plants in China, because aerosol sulfate is a major determinant of the fine-mode AOD in East Asia. Using a chemical transport model, we confirmed that the contribution of particulate sulfate to the fine-mode AOD is more than 70% of the annual mean and that the abovementioned fluctuation in fine-mode AOD is caused mainly by changes in SO<sub>2</sub> emission rather than by other factors such as varying meteorological conditions in East Asia. A strong correlation was also found between satellite-retrieved SO<sub>2</sub> vertical column density and bottom-up SO<sub>2</sub> emissions, both of which were also consistent with observed fine-mode AOD trends. We propose a simplified approach for evaluating changes in SO<sub>2</sub> emissions in China, combining the use of modeled sensitivity coefficients that describe the variation of fine-mode AOD with changes in SO<sub>2</sub> emissions and satellite retrieval. Satellite measurements of fine-mode AOD above the Sea of Japan marked a 4.1% yr<sup>−1</sup> decline between 2007 and 2010, which corresponded to the 9% yr<sup>−1</sup> decline in SO<sub>2</sub> emissions from China during the same period

Asian dust outflow in the PBL and free atmosphere retrieved by NASA CALIPSO and an assimilated dust transport model

International audienceThree-dimensional structures of Asian dust transport in the planetary boundary layer (PBL) and free atmosphere occurring successively during the end of May 2007 were clarified using results of space-borne backscatter lidar, Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), and results simulated using a data-assimilated version of a dust transport model (RC4) based on a ground-based NIES lidar network. Assimilated results mitigated overestimation of dust concentration by reducing 17.4% of dust emissions and improved the root mean square difference (RMSD) of dust AOT between the model and NIES lidar by 31.2?66.9%. The dust layer depths, vertical and horizontal structure simulated by RC4 agreed with CALIOP from the dust source region to a long-range downwind region for which 3-D distribution of dust clouds had not been clarified previously. Based on CALIOP and RC4, two significant transport mechanisms of Asian dust in the PBL and free atmosphere were clarified: a low level dust outbreak within the dry slot region of a well developed low-pressure system, and formation of an elevated dust layer within the warm sector of a low-pressure system. Finally, the aging of pure dust particles was investigated using the particle depolarization ratio (PDR) at 532 nm and the color ratio (CR) at 1064 nm and 532 nm for the low-altitude dust transport case. Aerosols with high PDR were observed uniformly over the dust source region. As the dust cloud was transported to the eastern downwind regions, aerosols with low PDR and high CR were found in the layer of less than 1 km height, suggesting changes from the external to internal mixing state of spherical aerosols and dust in the surface layer

Western Pacific Air-Sea Interaction Study

A01: Dynamics of Atmospheric CompositionA Study on the Production and Emission of Marine-Derived Volatile Halocarbons / Y. Yokouchi, A. Ooki, S. Hashimoto and N. Itoh : 05w-pass_001.pdfMeasurements of Gaseous Peroxides in the Oceanic Lower Atmosphere / S. Hatakeyama and T. Akatsuka : 06w-pass_027.pdfPhase Partitioning of NH3 and Gas to Particle Conversion / K. Osada : 07w-pass_033.pdfNew Particle Formation of Marine Aerosols / K. Miura, H. Furutani, Y. Iwamoto, K. Nagano, H. Kobayashi, M. Mochida, H. Mukai, S. Hashimoto, M. Takami and M. Uematsu : 08w-pass_037.pdfA Study of the Chemical Processes in Aerosols and Their Impacts on the Environment Using X-ray Absorption Fine Structure Spectroscopy / Y. Takahashi, M. Higashi, T. Furukawa, T. Miyoshi, M. Fujiwara and M. Uematsu : 09w-pass_043.pdfVariability in Mineral Dust Deposition over the North Pacific and Its Potential Impact on the Ocean Productivity / H. Fukushima : 10w-pass_051.pdfAtmosphere-Ocean Interaction through Atmospheric Aerosol Particles Observed in a Single Nanoparticle Aspect / H. Furutani, J. Jinyoung and M. Uematsu : 11w-pass_061.pdfSimultaneous Measurements of Hygroscopic Property and Cloud Condensation Nucleus Activity of Aerosol Particles of Marine Biogenic Origin / M. Mochida : 12w-pass_071.pdfEruption of Mt. Kilauea Impacted Cloud Droplet and Radiation Budget over North Pacific / I. Uno, K. Eguchi and K. Yumimoto : 13w-pass_083.pdfA02: Variability of Gas Exchanges at the Air-Sea InterfaceHigh-Resolution Measurement of Volatile Organic Compounds Dissolved in Seawater Using Equilibrator Inlet-Proton Transfer Reaction-Mass Spectrometry (EI-PTR-MS) / H. Tanimoto, S. Kameyama, Y. Omori, S. Inomata and U. Tsunogai : 14w-pass_089.pdfStudy of the Production Processes of Marine Biogenic Methane and Carbonyl Sulfide Using Stable Isotope Analysis / S. Toyoda, K. Yamada, Y. Ueno, K. Koba and O. Yoshida : 15w-pass_117.pdfLong-Term Changes of Greenhouse Gases in the Ocean and Their Feedback Effects on the Climate / Y. W. Watanabe, I. Yasuda and N. Tsurushima : 16w-pass_123.pdfTemporal and Spatial Variations in Carbonate System and Air-Sea CO2 Flux in the Kuroshio and Kuroshio Extension / H. Yoshikawa-Inoue, T. Midorikawa and T. R. Takamura : 17w-pass_151.pdfA03: Dynamics of the Marine EcosystemBioavailability and Biogeochemical Processes of Trace Metals in the Surface Ocean / S. Takeda, H. Obata, A. Okubo, M. Sato and Y. Kondo : 18w-pass_163.pdfDetailed Variations in Bioactive Elements in the Surface Ocean and Their Interaction with Microbiological Processes / H. Ogawa, K. Kogure, J. Kanda, F. Hashihama and M. Suzumura : 19w-pass_177.pdfPhotoheterotrophic Process in Surface Seawater Environments / K. Hamasaki, Y. Sato-Takabe, A. Taniguchi and Y. Tada : 20w-pass_199.pdfEcological Study of Bacterial Populations Related to Biogenic Gas Transformation in Marine Environments / K. Hamasaki, R. Kaneko, A. Mouri, Y. Tada, N. Kasamatsu-Takasawa and I. Nagao : 21w-pass_203.pdfA04: Modelling of the Interaction between the Ocean and the AtmosphereModeling for Evaluation and Prediction of Effects of Short-Term Atmospheric Disturbance on Air-Sea Material Cycling / M. Fujii and A. Tanaka : 22w-pass_211.pdfRelating Phytoplankton Pnysiology to North Pacific Biogeochemistry / S. L. Smith, M. N. Aita, M. Shigemitsu and Y. Yamanaka : 23w-pass_223.pdfCoupling of Physical and Bio-Geochemical Process and Monitoring Ocean Circulation Using Data Assimilation System / Y. Ishikawa, T. Awaji, M. Ikeda and T. Toyoda : 24w-pass_237.pdfPart of "Western Pacific Air-Sea Interaction Study

Western Pacific Air-Sea Interaction Study

A01: Dynamics of Atmospheric CompositionA Study on the Production and Emission of Marine-Derived Volatile Halocarbons / Y. Yokouchi, A. Ooki, S. Hashimoto and N. Itoh : 05w-pass_001.pdfMeasurements of Gaseous Peroxides in the Oceanic Lower Atmosphere / S. Hatakeyama and T. Akatsuka : 06w-pass_027.pdfPhase Partitioning of NH3 and Gas to Particle Conversion / K. Osada : 07w-pass_033.pdfNew Particle Formation of Marine Aerosols / K. Miura, H. Furutani, Y. Iwamoto, K. Nagano, H. Kobayashi, M. Mochida, H. Mukai, S. Hashimoto, M. Takami and M. Uematsu : 08w-pass_037.pdfA Study of the Chemical Processes in Aerosols and Their Impacts on the Environment Using X-ray Absorption Fine Structure Spectroscopy / Y. Takahashi, M. Higashi, T. Furukawa, T. Miyoshi, M. Fujiwara and M. Uematsu : 09w-pass_043.pdfVariability in Mineral Dust Deposition over the North Pacific and Its Potential Impact on the Ocean Productivity / H. Fukushima : 10w-pass_051.pdfAtmosphere-Ocean Interaction through Atmospheric Aerosol Particles Observed in a Single Nanoparticle Aspect / H. Furutani, J. Jinyoung and M. Uematsu : 11w-pass_061.pdfSimultaneous Measurements of Hygroscopic Property and Cloud Condensation Nucleus Activity of Aerosol Particles of Marine Biogenic Origin / M. Mochida : 12w-pass_071.pdfEruption of Mt. Kilauea Impacted Cloud Droplet and Radiation Budget over North Pacific / I. Uno, K. Eguchi and K. Yumimoto : 13w-pass_083.pdfA02: Variability of Gas Exchanges at the Air-Sea InterfaceHigh-Resolution Measurement of Volatile Organic Compounds Dissolved in Seawater Using Equilibrator Inlet-Proton Transfer Reaction-Mass Spectrometry (EI-PTR-MS) / H. Tanimoto, S. Kameyama, Y. Omori, S. Inomata and U. Tsunogai : 14w-pass_089.pdfStudy of the Production Processes of Marine Biogenic Methane and Carbonyl Sulfide Using Stable Isotope Analysis / S. Toyoda, K. Yamada, Y. Ueno, K. Koba and O. Yoshida : 15w-pass_117.pdfLong-Term Changes of Greenhouse Gases in the Ocean and Their Feedback Effects on the Climate / Y. W. Watanabe, I. Yasuda and N. Tsurushima : 16w-pass_123.pdfTemporal and Spatial Variations in Carbonate System and Air-Sea CO2 Flux in the Kuroshio and Kuroshio Extension / H. Yoshikawa-Inoue, T. Midorikawa and T. R. Takamura : 17w-pass_151.pdfA03: Dynamics of the Marine EcosystemBioavailability and Biogeochemical Processes of Trace Metals in the Surface Ocean / S. Takeda, H. Obata, A. Okubo, M. Sato and Y. Kondo : 18w-pass_163.pdfDetailed Variations in Bioactive Elements in the Surface Ocean and Their Interaction with Microbiological Processes / H. Ogawa, K. Kogure, J. Kanda, F. Hashihama and M. Suzumura : 19w-pass_177.pdfPhotoheterotrophic Process in Surface Seawater Environments / K. Hamasaki, Y. Sato-Takabe, A. Taniguchi and Y. Tada : 20w-pass_199.pdfEcological Study of Bacterial Populations Related to Biogenic Gas Transformation in Marine Environments / K. Hamasaki, R. Kaneko, A. Mouri, Y. Tada, N. Kasamatsu-Takasawa and I. Nagao : 21w-pass_203.pdfA04: Modelling of the Interaction between the Ocean and the AtmosphereModeling for Evaluation and Prediction of Effects of Short-Term Atmospheric Disturbance on Air-Sea Material Cycling / M. Fujii and A. Tanaka : 22w-pass_211.pdfRelating Phytoplankton Pnysiology to North Pacific Biogeochemistry / S. L. Smith, M. N. Aita, M. Shigemitsu and Y. Yamanaka : 23w-pass_223.pdfCoupling of Physical and Bio-Geochemical Process and Monitoring Ocean Circulation Using Data Assimilation System / Y. Ishikawa, T. Awaji, M. Ikeda and T. Toyoda : 24w-pass_237.pdfPart of "Western Pacific Air-Sea Interaction Study

JRAero: the Japanese Reanalysis for Aerosol v1.0

A global aerosol reanalysis product named the Japanese Reanalysis for Aerosol (JRAero) was constructed by the Meteorological Research Institute (MRI) of the Japan Meteorological Agency. The reanalysis employs a global aerosol transport model developed by MRI and a two-dimensional variational data assimilation method. It assimilates maps of aerosol optical depth (AOD) from MODIS onboard the Terra and Aqua satellites every 6 h and has a TL159 horizontal resolution (approximately 1.1°  ×  1.1°). This paper describes the aerosol transport model, the data assimilation system, the observation data, and the setup of the reanalysis and examines its quality with AOD observations. Comparisons with MODIS AODs that were used for the assimilation showed that the reanalysis showed much better agreement than the free run (without assimilation) of the aerosol model and improved under- and overestimation in the free run, thus confirming the accuracy of the data assimilation system. The reanalysis had a root mean square error (RMSE) of 0.05, a correlation coefficient (R) of 0.96, a mean fractional error (MFE) of 23.7 %, a mean fractional bias (MFB) of 2.8 %, and an index of agreement (IOA) of 0.98. The better agreement of the first guess, compared to the free run, indicates that aerosol fields obtained by the reanalysis can improve short-term forecasts. AOD fields from the reanalysis also agreed well with monthly averaged global AODs obtained by the Aerosol Robotic Network (AERONET) (RMSE  =  0.08, R = 0. 90, MFE  =  28.1 %, MFB  =  0.6 %, and IOA  =  0.93). Site-by-site comparison showed that the reanalysis was considerably better than the free run; RMSE was less than 0.10 at 86.4 % of the 181 AERONET sites, R was greater than 0.90 at 40.7 % of the sites, and IOA was greater than 0.90 at 43.4 % of the sites. However, the reanalysis tended to have a negative bias at urban sites (in particular, megacities in industrializing countries) and a positive bias at mountain sites, possibly because of insufficient anthropogenic emissions data, the coarse model resolution, and the difference in representativeness between satellite and ground-based observations

The SPRINTARS version 3.80/4D-Var data assimilation system: development and inversion experiments based on the observing system simulation experiment framework

We present an aerosol data assimilation system based on a global aerosol climate model (SPRINTARS – Spectral Radiation-Transport Model for Aerosol Species) and a four-dimensional variational data assimilation method (4D-Var). Its main purposes are to optimize emission estimates, improve composites, and obtain the best estimate of the radiative effects of aerosols in conjunction with observations. To reduce the huge computational cost caused by the iterative integrations in the models, we developed an offline model and a corresponding adjoint model, which are driven by pre-calculated meteorological, land, and soil data. The offline and adjoint model shortened the computational time of the inner loop by more than 30%. By comparing the results with a 1 yr simulation from the original online model, the consistency of the offline model was verified, with correlation coefficient R > 0.97 and absolute value of normalized mean bias NMB < 7% for the natural aerosol emissions and aerosol optical thickness (AOT) of individual aerosol species. Deviations between the offline and original online models are mainly associated with the time interpolation of the input meteorological variables in the offline model; the smaller variability and difference in the wind velocity near the surface and relative humidity cause negative and positive biases in the wind-blown aerosol emissions and AOTs of hygroscopic aerosols, respectively. The feasibility and capability of the developed system for aerosol inverse modelling was demonstrated in several inversion experiments based on the observing system simulation experiment framework. In the experiments, we used the simulated observation data sets of fine- and coarse-mode AOTs from sun-synchronous polar orbits to investigate the impact of the observational frequency (number of satellites) and coverage (land and ocean), and assigned aerosol emissions to control parameters. Observations over land have a notably positive impact on the performance of inverse modelling as compared with observations over ocean, implying that reliable observational information over land is important for inverse modelling of land-born aerosols. The experimental results also indicate that information that provides differentiations between aerosol species is crucial to inverse modelling over regions where various aerosol species coexist (e.g. industrialized regions and areas downwind of them)