Abstract
Abstract. An accurate representation of aerosols in global numerical weather prediction (NWP) models is important to predict major air pollution events and to also understand aerosol effects on short-term weather forecasts. Recently the global aerosol forecast model at NOAA, the NOAA Environmental Modeling System (NEMS) GFS Aerosol Component (NGAC), was upgraded from its dust-only version 1 to include five species of aerosols (black carbon, organic carbon, sulfate, sea salt and dust). This latest upgrade, now called NGACv2, is an in-line aerosol forecast system providing three-dimensional aerosol mixing ratios along with aerosol optical properties, including aerosol optical thickness (AOT), every 3 h up to 5 days at global 1∘×1∘ resolution. In this paper, we evaluated nearly 1.5 years of model AOT at 550 nm with available satellite retrievals, multi-model ensembles and surface observations over different aerosol regimes. Evaluation results show that NGACv2 has high correlations and low root mean square errors associated with African dust and also accurately represented the seasonal shift in aerosol plumes from Africa. Also, the model represented southern African and Canadian forest fires, dust from Asia, and AOT within the US with some degree of success. We have identified model underestimation for some of the aerosol regimes (particularly over Asia) and will investigate this further to improve the model forecast. The addition of a data assimilation capability to NGAC in the near future is expected to provide a positive impact in aerosol forecast by the model.
Highlights
In the past 2 decades, aerosol distributions, their properties and their impact have been studied using a combination of complex numerical models and space- and groundbased monitoring programs
All this could cause the low bias in aerosol optical thickness (AOT) over India as sulfate aerosols are formed in the clouds and hygroscopic growth is most effective in high-humidity regions near clouds
These days show the progression of dust westward from the African coast with high AOT above 1 over land which gradually decreases as the dust storm crosses over the ocean
Summary
In the past 2 decades, aerosol distributions, their properties and their impact have been studied using a combination of complex numerical models and space- and groundbased monitoring programs. In contrast to climate models, global numerical weather prediction (NWP) centers have used monthly climatologies of aerosol distributions to account for aerosol effects in the past Previous studies have been done evaluating the performance of the European Centre for Medium Range Forecast (ECMWF) aerosol model by comparing model data to satellite and ground observations (Morcrette et al, 2009; Mangold et al, 2011; Cesnulyte et al, 2014) These studies focused on the comparison of monthly mean and daily aerosol quantities in both visible and UV wavelengths as well as looking into different case studies (e.g., Saharan dust event, high sea-salt aerosol load). Detailed descriptions of NGACv2 and its outputs and its operational implementation are described in Part 1 of this paper (Wang et al, 2018)
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