scholarly journals A three-dimensional variational data assimilation system for aerosol optical properties based on WRF-Chem: design, development, and application of assimilating Himawari-8 aerosol observations

2021 ◽  
Author(s):  
Daichun Wang ◽  
Wei You ◽  
Zengliang Zang ◽  
Xiaobin Pan ◽  
Yiwen Hu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Optical Properties ◽  
Data Assimilation ◽  
North China ◽  
Model Simulation ◽  
Three Dimensional ◽  
Mie Scattering ◽  
State Variables ◽  
Aerosol Optical Properties ◽  
Optical Module

Abstract. This paper presents a three-dimensional variational (3DVAR) data assimilation (DA) system for aerosol optical properties, including aerosol optical depth (AOD) retrievals and lidar-based aerosol profiles, which was developed for the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) within the Weather Research and Forecasting model coupled to Chemistry (WRF-Chem) model. For computational efficiency, 32 model variables in the MOSAIC_4bin scheme are lumped into 20 aerosol state variables that are representative of mass concentrations in the DA system. To directly assimilate aerosol optical properties, an observation operator based on the Mie scattering theory was employed, which was obtained by simplifying the optical module in WRF-Chem. The tangent linear (TL) and adjoint (AD) operators were then established and passed the TL/AD sensitivity test. The Himawari-8 derived aerosol optical thickness (AOT) data were assimilated to validate the system and investigate the effects of assimilation on both AOT and PM2.5 simulations. Two comparative experiments were performed with a cycle of 24 h from November 23 to 29, 2018, during which a heavy air pollution event occurred in North China. The DA performances of the model simulation were evaluated against independent aerosol observations, including the Aerosol Robotic Network (AERONET) AOT and surface PM2.5 measurements. The results show that Himawari-8 AOT assimilation can significantly improve model AOT analyses and forecasts. Generally, the control experiments without assimilation seriously underestimated AOTs compared with observed values and were therefore unable to describe real aerosol pollution. The analysis fields closer to observations improved AOT simulations, indicating that the system successfully assimilated AOT observations into the model. In terms of statistical metrics, assimilating Himawari-8 AOTs only limitedly improved PM2.5 analyses in the inner simulation domain (D02); however, the positive effect can last for over 24 h. Assimilation effectively enlarged the underestimated PM2.5 concentrations to be closer to the real distribution in North China, which is of great value for studying heavy air pollution events

scholarly journals Dust aerosol optical properties over North China

2008 ◽  
Vol 8 (5) ◽  
pp. 17037-17059
Author(s):  
◽  
Keyword(s):  
Optical Properties ◽  
Seasonal Changes ◽  
North China ◽  
Particle Number ◽  
Geometric Mean ◽  
Number Concentration ◽  
Aerosol Optical Properties ◽  
Remarkable Change ◽  
Strength Change ◽  
Dust Weather

Abstract. Aerosol optical properties were obtained from ground-based sunphotometer data at nine observatories over North China during two periods of 1996–1998 and 2002–2003. The seasonal changes of aerosol optical depth (AOD) at five wavelengths were observed, with the highest value of AOD in spring, while the lowest in winter. Four patterns of AOD diurnal variation were obtained, of which the high value occurred in the morning, noon, evening and no remarkable change, respectively. Together with meteorological records, the characteristics of AOD during dust weather were analyzed, and the results show that it was more detailed and accurate to use AOD to depict the strength change of dust weather than to use surface visibility. Based on measurements by aerodynamic instrument for particle size distribution, a positive correlation between dust particle number concentration and Ångström turbidity coefficient β, and a negative correlation between aerosol geometric mean diameter (GMD) and wavelength exponent αwere revealed.

scholarly journals Improving the Model Convective Storm Quantitative Precipitation Nowcasting by Assimilating State Variables Retrieved from Multiple-Doppler Radar Observations

2014 ◽  
Vol 142 (11) ◽  
pp. 4017-4035 ◽  
Author(s):  
Yu-Chieng Liou ◽  
Jian-Luen Chiou ◽  
Wei-Hao Chen ◽  
Hsin-Yu Yu
Keyword(s):  
Data Assimilation ◽  
Doppler Radar ◽  
Scale Up ◽  
Three Dimensional ◽  
Radar Data ◽  
State Variables ◽  
Weather System ◽  
Additional Information ◽  
Convective Scale ◽  
Fine Resolution

Abstract This research combines an advanced multiple-Doppler radar synthesis technique with the thermodynamic retrieval method, originally proposed by Gal-Chen, and a moisture/temperature adjustment scheme, and formulates a sequential procedure. The focus is on applying this procedure to improve the model quantitative precipitation nowcasting (QPN) skill in the convective scale up to 3 hours. A series of (observing system simulation experiment) OSSE-type tests and a real case study are conducted to investigate the performance of this algorithm under different conditions. It is shown that by using the retrieved three-dimensional wind, thermodynamic, and microphysical parameters to reinitialize a fine-resolution numerical model, its QPN skill can be significantly improved. Since the Gal-Chen method requires the horizontal average properties of the weather system at each altitude, utilization of in situ radiosonde(s) to obtain this additional information for the retrieval is tested. When sounding data are not available, it is demonstrated that using the model results to replace the role played by observing devices is also a feasible choice. The moisture field is obtained through a simple, but effective, adjusting scheme and is found to be beneficial to the rainfall forecast within the first hour after the reinitialization of the model. Since this algorithm retrieves the unobserved state variables instantaneously from the wind measurements and directly uses them to reinitialize the model, fewer radar data and a shorter model spinup time are needed to correct the rainfall forecasts, in comparison with other data assimilation techniques such as four-dimensional variational data assimilation (4DVAR) or ensemble Kalman filter (EnKF) methods.

scholarly journals A study on the aerosol optical properties over East Asia using a combination of CMAQ-simulated aerosol optical properties and remote-sensing data via a data assimilation technique

2011 ◽  
Vol 11 (23) ◽  
pp. 12275-12296 ◽  
Author(s):  
R. S. Park ◽  
C. H. Song ◽  
K. M. Han ◽  
M. E. Park ◽  
S.-S. Lee ◽  
...  
Keyword(s):  
Optical Properties ◽  
Data Assimilation ◽  
East Asia ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Dust Particles ◽  
Aerosol Optical Properties ◽  
Fine Grid ◽  
Model Simulations ◽  
Particulate Pollution

Abstract. To more accurately estimate direct radiative forcing (DRF) by aerosols, and better investigate particulate pollution over East Asia, precise calculations of the optical properties of aerosols, such as aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol extinction coefficient (σext), are of primary importance. The aerosol optical properties over East Asia were investigated in this study, based on US EPA Models-3/CMAQ v4.5.1 model simulations. The CMAQ model simulations in this study were improved in several ways compared to those in a previous study (Song et al., 2008). Although the details of the improvements were described in the manuscript, the following points should be emphasized: (1) two data assimilation techniques were employed for producing more accurate AOD products and meteorological fields over East Asia; (2) updated/upgraded emission inventories were used in the CMAQ model simulations with a fine grid resolution of 30 × 30 km2; and (3) the 4-D particulate composition calculated from the CMAQ model simulations was converted into 3-D or 4-D aerosol optical products, using the Malm and Hand (2007) algorithm with significant further modifications. The results from the CMAQ model simulations (without assimilation) showed great improvements compared to those from a previous study. For example, in terms of the regression coefficients (R), R values were increased from 0.48–0.68 (previous study) to 0.62–0.79 (this study). The monthly-averaged CMAQ-simulated single scattering albedo (SSA) also agreed well with the AERONET SSA, with the exceptions of the Hong Kong and Taipei sites, where the air qualities were strongly influenced by active biomass burning events from January to April. There were also excellent matches between the vertical profiles of the CMAQ-simulated σext and LIDAR-retrieved σext. It was also found that the contributions of (NH4)2SO4 during summer, NH4NO3 during winter, sea-salt particles during winter and dust particles during spring to the total AOD were large over East Asia. In particular, the largest contribution of NH4NO3 to the total AOD was found over East Asia during winter. Therefore, it was suggested that this contribution of NH4NO3 should not be neglected. In order to produce more accurate AOD products, the CMAQ-simulated AODs were further assimilated with the MODIS-retrieved AODs. Both of the assimilated and AERONET AODs were better correlated with each other than the CMAQ-simulated and AERONET AODs. The obvious benefits from this study would be that with these improved aerosol optical properties, the particulate pollution (e.g. AOD can be served as a proxy to PM2.5 or PM10) and DRF by aerosols over East Asia can be more satisfactorily investigated in future.

scholarly journals Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

2011 ◽  
Vol 11 (12) ◽  
pp. 5959-5973 ◽  
Author(s):  
N. Ma ◽  
C. S. Zhao ◽  
A. Nowak ◽  
T. Müller ◽  
S. Pfeifer ◽  
...  
Keyword(s):  
Optical Properties ◽  
North China Plain ◽  
North China ◽  
Scattering Coefficient ◽  
Aerosol Optical Properties ◽  
Mean Values ◽  
The North ◽  
The North China Plain ◽  
The Mean

Abstract. The largest uncertainty in the estimation of climate forcing stems from atmospheric aerosols. In early spring and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi (Haze in China) project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties, including the scattering coefficient (σsp), the hemispheric back scattering coefficient (σbsp), the absorption coefficient (σap), as well as the single scattering albedo (ω), are presented. The diurnal and seasonal variations are analyzed together with meteorology and satellite data. The mean values of σsp, 550 nm of the dry aerosol in spring and summer are 280±253 and 379±251 Mm−1, respectively. The average σap for the two periods is respectively 47±38 and 43±27 Mm−1. The mean values of ω at the wavelength of 637 nm are 0.82±0.05 and 0.86±0.05 for spring and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional aerosol pollution in the NCP. Pronounced diurnal cycle of $σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and the accumulation of local emissions during nighttime. The pollutants transported from the southwest of the NCP are more significant than that from the two megacities, Beijing and Tianjin, in both spring and summer. An optical closure experiment is conducted to better understand the uncertainties of the measurements. Good correlations (R>0.98) are found between the values measured by the nephelometer and the values calculated with a modified Mie model. The Monte Carlo simulation shows an uncertainty of about 30 % for the calculations. Considering all possible uncertainties of measurements, calculated σsp and σbsp agree well with the measured values, indicating a stable performance of instruments and thus reliable aerosol optical data.

scholarly journals Simulation of aerosol optical properties over a tropical urban site in India using a global model and its comparison with ground measurements

2011 ◽  
Vol 29 (5) ◽  
pp. 955-963 ◽  
Author(s):  
D. Goto ◽  
K. V. S. Badarinath ◽  
T. Takemura ◽  
T. Nakajima
Keyword(s):  
Optical Properties ◽  
General Circulation ◽  
Three Dimensional ◽  
Temporal Distribution ◽  
Circulation Model ◽  
Global Model ◽  
Atmospheric Environment ◽  
Urban Site ◽  
Aerosol Optical Properties ◽  
Aerosol Emission

Abstract. Aerosols have great impacts on atmospheric environment, human health, and earth's climate. Therefore, information on their spatial and temporal distribution is of paramount importance. Despite numerous studies have examined the variation and trends of BC and AOD over India, only very few have focused on their spatial distribution or even correlating the observations with model simulations. In the present study, a three-dimensional aerosol transport-radiation model coupled with a general circulation model. SPRINTARS, simulated atmospheric aerosol distributions including BC and aerosol optical properties, i.e., aerosol optical thickness (AOT), Ångström Exponent (AE), and single scattering albedo (SSA). The simulated results are compared with both BC measurements by aethalometer and aerosol optical properties measured by ground-based skyradiometer and by satellite sensor, MODIS/Terra over Hyderabad, which is a tropical urban area of India, for the year 2008. The simulated AOT and AE in Hyderabad are found to be comparable to ground-based measured ones. The simulated SSA tends to be higher than the ground-based measurements. Both these comparisons of aerosol optical properties between the simulations with different emission inventories and the measurements indicate that, firstly the model uncertainties derived from aerosol emission inventory cannot explain the gaps between the simulations and the measurements and secondly the vertical transport of BC and the treatment of BC-containing particles can be the main issue in the global model to solve the gap.

scholarly journals A three-dimensional variational data assimilation system for multiple aerosol species with WRF/Chem and an application to PM<sub>2.5</sub> prediction

2012 ◽  
Vol 12 (5) ◽  
pp. 13515-13552 ◽  
Author(s):  
Z. Li ◽  
Z. Zang ◽  
Q. B. Li ◽  
Y. Chao ◽  
D. Chen ◽  
...  
Keyword(s):  
Los Angeles ◽  
Data Assimilation ◽  
Three Dimensional ◽  
Variational Data Assimilation ◽  
Metal Species ◽  
Individual Species ◽  
Size Distributions ◽  
State Variables ◽  
Background Error ◽  
Mass Concentrations

Abstract. A three-dimensional variational data assimilation (3-DVAR) algorithm for aerosols in a WRF/Chem model is presented. The WRF/Chem model uses the MOSAIC (Model for Simulating Aerosol Interactions and Chemistry) scheme, which explicitly treats eight major species (elemental/black carbon, organic carbon, nitrate, sulfate, chloride, ammonium, sodium, and the sum of other inorganic, inert mineral and metal species) and represents size distributions using a sectional method with four size bins. The 3-DVAR scheme is formulated to take advantage of the MOSAIC scheme in providing comprehensive analyses of specie concentrations and size distributions. To treat the large number of state variables associated with the MOSAIC scheme, this 3-DVAR algorithm first determines the analysis increments of the total mass concentrations of the eight species, defined as the sum of the mass concentrations across all size bins, and then distributes the analysis increments over four size bins according to the background error variances. The number concentrations for each size bin are adjusted based on the ratios between the mass and number concentrations of the background state. This system has been applied to the analysis and prediction of PM2.5 in the Los Angeles basin during the CalNex 2010 field experiment, with assimilation of surface PM2.5 and speciated concentration observations. The results demonstrate that the data assimilation significantly reduces the errors in comparison with a down scaling simulation and improved forecasts of the concentrations of PM2.5 as well as individual species for up to 24 h. Some implementation difficulties and limitations of the system are also discussed.

scholarly journals Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

2011 ◽  
Vol 11 (3) ◽  
pp. 9567-9605 ◽  
Author(s):  
N. Ma ◽  
C. S. Zhao ◽  
A. Nowak ◽  
T. Müller ◽  
S. Pfeifer ◽  
...  
Keyword(s):  
Optical Properties ◽  
North China Plain ◽  
North China ◽  
Aerosol Optical Properties ◽  
Mean Values ◽  
The North ◽  
The North China Plain ◽  
The Mean ◽  
Local Emissions

Abstract. The largest uncertainty in the estimation of radiative forcings on climate stems from atmospheric aerosols. In winter and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties including scattering coefficient (σsp), hemispheric back scattering coefficient (σbsp), absorption coefficient (σap, as well as single scattering albedo (ω) are presented. The characteristics of diurnal and seasonal variations are analyzed together with the meteorological and satellite data. The mean values of σsp, 550 nm of the dry aerosol in winter and summer are 280 ± 253 and 379 ± 251 Mm−1, respectively. The average σap for the two periods are respectively 47 ± 38 and 43 ± 27 Mm−1. The mean values of ω are 0.83 ± 0.05 and 0.87 ± 0.05 for winter and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional polluted aerosol of the North China Plain. Pronounced diurnal cycle of σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and accumulation of local emissions during night-time. Regional transport of pollutants from southwest in the NCP is significant both in winter and summer, while high values of σsp and σap correlate with calm winds in winter, which indicating the significant contribution of local emissions. An optical closure experiment is conducted to better understand uncertainties of the measurements. Good correlations (R>0.98) are found between values measured by nephelometer and values calculated with a modified Mie model. Monte Carlo simulations show an uncertainty of about 30% for the calculations. Considering all possible uncertainties of measurements, calculated σsp and σbsp agree well with measured values, indicating a stable performance of instruments and thus a reliable aerosol optical data.

scholarly journals A pre-operational three Dimensional variational data assimilation system in the North/Baltic Sea

Ocean Science ◽  
2011 ◽  
Vol 7 (6) ◽  
pp. 771-781 ◽  
Author(s):  
S. Y. Zhuang ◽  
W. W. Fu ◽  
J. She
Keyword(s):  
Data Assimilation ◽  
Baltic Sea ◽  
Model Simulation ◽  
Three Dimensional ◽  
Empirical Orthogonal Functions ◽  
Initial State ◽  
The North ◽  
Mean Square Errors ◽  
Data Assimilation System ◽  
Assimilation System

Abstract. This paper describes the implementation and evaluation of a pre-operational three dimensional variational (3DVAR) data assimilation system for the North/Baltic Sea. Univariate analysis for both temperature and salinity is applied in a 3DVAR scheme in which the horizontal component of the background error covariance is modeled by an isotropic recursive filter (IRF) and the vertical component is represented by dominant Empirical Orthogonal Functions (EOFs). Observations of temperature and salinity (T/S) profiles in the North/Baltic Sea are assimilated in the year of 2005. Effect of the 3DVAR scheme is assessed by a comparison between data assimilation run and control run. The statistical analysis indicates that the model simulation is significantly improved with the 3DVAR scheme. On average, the root mean square errors (RMSE) of temperature and salinity are reduced by 0.2 °C and 0.25 psu in the North/Baltic Sea. In addition, the bias of temperature and salinity is also decreased by 0.1 °C and 0.2 psu, respectively. Starting from an analyzed initial state, one month simulation without assimilation is carried out with the aim of examining the persistence of the initial impact. It is shown that the assimilated initial state can impact the model simulation for nearly two weeks. The influence on salinity is more pronounced than temperature.

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