A comparison of CMAQ‐based aerosol properties with IMPROVE, MODIS, and AERONET data

Abstract

[1] Evaluation of concentrations predicted by air quality models is needed to ensure that model results are compatible with observations. In this study aerosol properties derived from the Community Multiscale Air Quality (CMAQ) model-simulated aerosol mass concentrations are compared with routine data from NASA satellite-borne Moderate Resolution Imaging Spectroradiometer (MODIS) sensor aboard the Sun-synchronous Terra satellite, NASA's ground-based Aerosol Robotic Network (AERONET), and the ground-based Interagency Monitoring of Protected Visual Environment (IMPROVE) network. The motivation for this analysis is to determine how best to use these parameters in evaluating model-predicted PM 2.5 concentrations. CMAQ surface extinction estimates due to scattering at 550 nm wavelength are compared with the IMPROVE nephelometer data obtained from 25 sites within the United States. It is found that model-predicted surface extinctions bear high correlations with nephelometer measured data. Sulfate fractional aerosol optical depth (AOD) is found to dominate in the northeastern part of the United States; hence ground-based measurement of sulfate concentrations have been compared with time series of columnar AOD as observed by the MODIS instrument and also with the CMAQ-predicted tropospheric column values obtained during the JuneAugust period of 2001. CMAQ surface extinctions are found to be relatively higher than the IMPROVE nephelometer observations; however, there is a good agreement between CMAQ AOD trends and AERONET and MODIS data, obtained at the seven AERONET sites located in the eastern United States. CMAQ is also found to capture the day-to-day variability in the spatial AOD patterns. Monthly average satellite AOD estimates are found to be higher than the AOD data obtained using the CMAQ-predicted aerosol concentrations. Seasonal variation of satellite-measured aerosol intensive property ''Angstrom exponent'' (a gross indicator of the aerosol size distribution) is presented for four selected sites: one each in the eastern and central parts, and two in the western part of the continental United States. Variability of Angstrom exponent at these four selected sites is analyzed in conjunction with the variation of summertime AOD (observed and modeled), mass concentration (observed and modeled) and modeled SO 4 average concentrations during the summer (June-August) period of the year 2001. Annual time series of Angstrom exponent data at the four selected sites show a large east-west variation.

Aerosol loading in the Southeastern United States: reconciling surface and satellite observations

“…AOD from MODIS is retrieved separately over the ocean and land to account for differences in surface properties (e.g., Remer et al, 2005). While some studies have found a high AOD bias in the Western US due to the use of an estimated surface reflectance over the bright land surface , the SEUS has dense vegetation that provides good dark targets and greater confidence in the MODIS aerosol retrieval (Roy et al, 2007). For this work, we use Collection 5 Level 3 daily measurements and combine land and ocean optical depth retrievals.…”

Application of WRF/Chem-MADRID and WRF/Polyphemus in Europe – Part 1: Model description, evaluation of meteorological predictions, and aerosol–meteorology interactions

“…The variables evaluated column concentrations of tropospheric CO and NO 2 , tropospheric O 3 residual (TOR), and aerosol optical depth (AOD). To evaluate all observations related to MODIS, the monthly-mean AOD predictions are calculated as an average of column-integrated values during 15:00-20:00 UTC when the Terra satellite passes over Europe, following Roy et al (2007).…”

Modelling Saharan dust transport into the Mediterranean basin with CMAQ

“…9d). Underestimations of CMAQ-derived AOT values have been reported by several authors before (Roy et al, 2007;Park et al, 2011).…”

“…Many authors have looked into tometers that measures the optical properties of aerosols (Holben possible ways to use satellite or ground-based vertical observations of et al, 1998). The data obtained from AERONET consisted in the the atmosphere to assess air quality models such as CMAQ in a more daily average AOT level 2.0 at 440 nm (cloud-screened) for the consistent way (Roy et al, 2007). Although remote sensing data may entire month of July.…”