This study presents the new aerosol assimilation system, developed at the European Centre for Medium‐Range Weather Forecasts, for the Global and regional Earth‐system Monitoring using Satellite and in‐situ data (GEMS) project. The aerosol modeling and analysis system is fully integrated in the operational four‐dimensional assimilation apparatus. Its purpose is to produce aerosol forecasts and reanalyses of aerosol fields using optical depth data from satellite sensors. This paper is the second of a series which describes the GEMS aerosol effort. It focuses on the theoretical architecture and practical implementation of the aerosol assimilation system. It also provides a discussion of the background errors and observations errors for the aerosol fields, and presents a subset of results from the 2‐year reanalysis which has been run for 2003 and 2004 using data from the Moderate Resolution Imaging Spectroradiometer on the Aqua and Terra satellites. Independent data sets are used to show that despite some compromises that have been made for feasibility reasons in regards to the choice of control variable and error characteristics, the analysis is very skillful in drawing to the observations and in improving the forecasts of aerosol optical depth.
Since the first International Cooperative for Aerosol Prediction (ICAP) multi-model ensemble (MME) study, the number of ICAP global operational aerosol models has increased from five to nine. An update of the current ICAP status is provided, along with an evaluation of the performance of ICAP-MME over 2012-2017, with a focus on June 2016-May 2017. Evaluated with ground-based Aerosol Robotic Network (AERONET) aerosol optical depth (AOD) and data assimilation quality MODerate-resolution Imaging Spectroradiometer (MODIS) retrieval products, the ICAP-MME AOD consensus remains the overall top-scoring and most consistent performer among all models in terms of root-mean-square error (RMSE), bias and correlation for total, fine- and coarse-mode AODs as well as dust AOD; this is similar to the first ICAP-MME study. Further, over the years, the performance of ICAP-MME is relatively stable and reliable compared to more variability in the individual models. The extent to which the AOD forecast error of ICAP-MME can be predicted is also examined. Leading predictors are found to be the consensus mean and spread. Regression models of absolute forecast errors were built for AOD forecasts of different lengths for potential applications. ICAP-MME performance in terms of modal AOD RMSEs of the 21 regionally representative sites over 2012-2017 suggests a general tendency for model improvements in fine-mode AOD, especially over Asia. No significant improvement in coarse-mode AOD is found overall for this time period.
Biomass burning is the second largest global source of anthropogenic aerosols, and South America is one of the major source regions. In the dry season, the atmosphere of the Amazon basin features a remarkable haze, with layers containing high loadings of smoke. Aerosols with different degrees of ageing, are encountered in the boundary layer and the free troposphere. The South American Biomass Burning Analysis (SAMBBA) was an intensive observation campaign in September-October 2012 that involved measurements of the Amazonian atmosphere using the Facility for Airborne Measurements (FAAM) BAe-146 research aircraft.
Extending numerical weather forecasting with chemical weather modeling will improve prediction of aerosol extinction and direct irradiance at the surface-and thus increase reliability of solar energy.
Abstract. In the present work, atmospheric mineral dust from a MACC-II short reanalysis run for 2 years (2007–2008) has been evaluated over northern Africa and the Middle East using satellite aerosol products (from MISR, MODIS and OMI satellite sensors), ground-based AERONET data, in situ PM10 concentrations from AMMA, and extinction vertical profiles from two ground-based lidars and CALIOP satellite-based lidar. The MACC-II aerosol optical depth (AOD) spatial and temporal (seasonal and interannual) variability shows good agreement with those provided by satellite sensors. The capability of the model to reproduce the AOD, Ångström exponent (AE) and dust optical depth (DOD) from daily to seasonal time-scale is quantified over 26 AERONET stations located in eight geographically distinct regions by using statistical parameters. Overall DOD seasonal variation is fairly well simulated by MACC-II in all regions, although the correlation is significantly higher in dust transport regions than in dust source regions. The ability of MACC-II in reproducing dust vertical profiles has been assessed by comparing seasonal averaged extinction vertical profiles simulated by MACC-II under dust conditions with corresponding extinction profiles obtained with lidar instruments at M'Bour and Santa Cruz de Tenerife, and with CALIOP. We find a good agreement in dust layers structures and averaged extinction vertical profiles between MACC-II, the lidars and CALIOP above the marine boundary layer from 1 to 6 km. Surface dust daily mean concentrations from MACC-II reanalysis has been evaluated with daily averaged PM10 at three monitoring stations of the Sahelian Dust Transect. MACC-II correctly reproduces daily to interannual surface dust concentration variability, although it underestimates daily and monthly means all year long, especially in winter and early spring (dry season). MACC-II reproduces well the dust variability recorded along the station transect which reflects the variability in dust emission by different Saharan sources, but fails in reproducing the sporadic and very strong dust events associated to mesoscale convective systems during the wet season.
Abstract. A huge amount of dust is transported every year from North Africa into the Caribbean region. This paper presents an investigation of this long-range transport process based on measurements conducted during the SALTRACE campaign (June–July 2013), as well as an evaluation of the ability of the MACC global aerosol model to reproduce it and its associated features. First, the horizontal wind speed measurements obtained by the DLR airborne Doppler wind lidar (DWL) during the SALTRACE experiment are validated by means of a comparison with collocated dropsondes. The comparison indicates a systematic speed difference of 0.08 m s−1 and a standard deviation of 0.92 m s−1, while wind direction show a mean difference of 0.5° and a standard deviation between 5° and 10° depending on measurement conditions. Modelled winds in West Africa and Caribbean regions are compared to those measured by the DWL. Although a general good agreement between measurements and model is observed, some differences, particularly in the African Easterly Jet (AEJ) intensity, were noted. The observed differences between modelled and measured wind jet speeds are between 5 and 10 m s−1. The MACC model aerosol vertical distribution is compared with the CALIOP satellite extinction profiles corresponding to the campaign period. While the modelled Saharan dust plume shape shows a good agreement with the measurements, a systematic underestimation of the marine boundary layer extinction is observed. Additionally, three selected case studies covering different aspects of the Saharan dust long-range transport along the West African coast, over the North Atlantic Ocean and the Caribbean are presented. For first time, DWL measurements are used to investigate the Saharan dust long-range transport. Simultaneous wind and backscatter measurements from the DWL are used, in combination with the MACC model, to analyse different features associated with the long-range transport, including an African Easterly Wave trough, the African Easterly Jet and the Intertropical Convergence Zone.
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