Evaluating the Potential for Retrieving Aerosol Optical Depth over Land from AVHRR Pathfinder Atmosphere Data

Abstract

In spite of numerous studies on the remote sensing of aerosols from satellite, the magnitude of aerosol climate forcing remains uncertain. However, data from the Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmosphere (PATMOS) data set-a statistical reduction of more than19 years of AVHRR data (1981-2000)-could provide nearly 20 years of aerosol history. PATMOS data has a daily 110×110 km 2 equal-area grid that contains means and standard deviations of AVHRR observations within each grid cell. This research is a first step toward understanding aerosols over land with PATMOS data. Herein, the aerosol optical depth is retrieved over land at numerous aerosol robotic network (AERONET) sites around the globe using PATMOS cloud-free reflectances. First, the surface bidirectional reflectance distribution function (BRDF) is retrieved using a look-up table created with a radiative transfer model and the Rahman BRDF. Aerosol optical depths are then retrieved using the retrieved BRDF parameters and the PATMOS reflectances assuming a globally constant aerosol model. This method is applied to locations with ground truth measurements, where comparisons show that the best retrievals are made by estimating the surface reflectance using observations grouped by month. Random errors (i.e., correlation coefficients and standard error of estimate) in this case are lower than those where the surface BRDF is allowed a year-to-year variations. By grouping the comparison results by land cover type, it was found that less noise is expected over forested regions, with a significant potential for retrieval for 80% of all land surfaces. These results and analyses suggest that the PATMOS data can provide valuable information on aerosols over land.

Validation of a modified AVHRR aerosol optical depth retrieval algorithm over Central Europe

“…Remote sensing of aerosol properties with the Advanced Very High Resolution Radiometer (AVHRR) has a long tradition (Knapp and Stowe, 2002), even though aerosol detection was not the initial aim of this instrument. Nonetheless, the AVHRR, carried on board the National Oceanic and Atmospheric Administration (NOAA) and the Meteorological Operational Satellite (MetOp) polar orbiting satellites, is the only instrument offering the opportunity to analyse more than 25 years of satellite data in moderate Published by Copernicus Publications on behalf of the European Geosciences Union.…”

“…The retrieval over brighter and heterogeneous land surfaces is more complicated and prone to introduce larger errors due to reduced aerosol signal and temporally unstable surface reflectance. Knapp and Stowe (2002) derived τ a from the reduced resolution (110 × 110 km 2 ) Pathfinder-Atmosphere (PATMOS) data set using also bright surface targets. Hauser et al (2005a) applied a similar technique to derive τ a at full resolution (1.1 × 1.1 km 2 ) for Central Europe using NOAA-16 AVHRR and they further qualitatively compared monthly and seasonal means from this product with MODIS collection 004 data (Hauser et al, 2005b).…”

A comparison of different optimization algorithms for retrieving aerosol optical depths from satellite data: an example of using a dual-angle algorithm

“…In the literature, the traditional optimization inversion method and the lookup table method are widely used to estimate AOD from satellite data, such as AVHRR (advanced very high resolution radiometer) (Knapp and Stowe 2002), MERIS (medium resolution imaging spectrometer) (Santer et al 1999, Santer 2000, Von Hoyningen-Huene et al 2003, SCIAMACHY (scanning imaging absorption spectrometer for atmospheric cartography) (Di Nicolantonio et al 2006), GOME (global ozone monitoring experiment) (Veefkind et al 2000), ATSR-2 (along track scanning radiometer-2) (North et al 1999), AATSR (advanced along track scanning radiometer) (Grey et al 2006) and the polarizing remote sensor POLDER (polarization and directionality of the earth's reflectances) (Sano and Mukai 2000).…”

Retrieval of aerosol optical thickness over land surfaces from top‐of‐atmosphere radiance

“…Recently also studies are made to use AVHRR data together with a detailed surface reflectance database [cf. Knapp and Stowe, 2002]. Also modern multichannel space-borne radiometers such as SeaWiFS, MODIS, MISR, MERIS, SCIAMACHY and AATSR provide sufficient spectral information in the short-wave range (<0.55 mm) to enable the separation of land surface and aerosol scattering also for nadir scanning instruments.…”