Surface shortwave aerosol radiative forcing during the Atmospheric Radiation Measurement Mobile Facility deployment in Niamey, Niger

Journal Article · Wed Mar 18 04:00:00 EDT 2009 · Journal of Geophysical Research. D. (Atmospheres), 114:Art. No. D00E06

DOI:https://doi.org/10.1029/2008JD010491· OSTI ID:951034

McFarlane, Sally A; Kassianov, Evgueni I; Barnard, James C; Flynn, Connor J; Ackerman, Thomas P

This study presents ground-based remote sensing measurements of aerosol optical properties and corresponding shortwave surface radiative effect calculations for the deployment of the Atmospheric Radiation Measurement (ARM) Program’s Mobile Facility (AMF) to Niamey, Niger during 2006. Aerosol optical properties including aerosol optical depth (AOD), single scattering albedo (SSA), and asymmetry parameter (AP) were derived from multi-filter rotating shadowband radiometer (MFRSR) measurements during the two dry seasons (Jan-Apr and Oct-Dec) at Niamey. The vertical distribution of aerosol extinction was derived from the collocated micropulse lidar (MPL). The aerosol optical properties and vertical distribution of extinction varied significantly throughout the year, with higher AOD, lower SSA, and deeper aerosol layers during the Jan-Apr time period, when biomass burning aerosol layers were more frequent. Using the retrieved aerosol properties and vertical extinction profiles, broadband shortwave surface fluxes and atmospheric heating rate profiles were calculated. Corresponding calculations with no aerosol were used to estimate the aerosol direct radiative effect at the surface. Comparison of the calculated surface fluxes to observed fluxes for non-cloudy periods indicated that the remote sensing retrievals provided a reasonable estimation of the optical properties, with mean differences between calculated and observed fluxes of less than 5 W/m2 and RMS differences less than 25 W/m2. Sensitivity tests for a particular case study showed that the observed fluxes could be matched with variations of < 10% in the inputs to the radiative transfer model. We estimated the daily-averaged aerosol radiative effect at the surface by subtracting the clear calculations from the aerosol calculations. The average daily SW aerosol radiative effect over the study period was -27 W/m2, which is comparable to values estimated from satellite data and from climate models with sophisticated dust parameterizations.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 951034
• Report Number(s): PNNL-SA-60673; KP1701000
• Journal Information: Journal of Geophysical Research. D. (Atmospheres), 114:Art. No. D00E06, Journal Name: Journal of Geophysical Research. D. (Atmospheres), 114:Art. No. D00E06 Vol. 114; ISSN 0747-7309
• Country of Publication: United States
• Language: English

Related Subjects

09 BIOMASS FUELS
AEROSOLS
ALBEDO
ASYMMETRY
BIOMASS
CLIMATE MODELS
DISTRIBUTION
DUSTS
HEATING RATE
NIGER
OPTICAL PROPERTIES
OPTICAL RADAR
RADIANT HEAT TRANSFER
RADIATIONS
RADIOMETERS
REMOTE SENSING
SCATTERING
SEASONS
SENSITIVITY