In:
Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 22, No. 22 ( 2022-11-18), p. 14657-14692
Abstract:
Abstract. The Copernicus Atmosphere Monitoring Service (CAMS)
provides near-real-time forecast and reanalysis of aerosols using the ECMWF
Integrated Forecasting System with atmospheric composition extension,
constrained by the assimilation of MODIS and the Polar Multi-Sensor Aerosol
Optical Properties (PMAp) aerosol optical depth (AOD). The objective of this
work is to evaluate two new near-real-time AOD products to prepare for their
assimilation into CAMS, namely the Copernicus AOD (collection 1) from the Sea
and Land Surface Temperature Radiometer (SLSTR) on board Sentinel 3-A/B
over ocean and the NOAA EPS AOD (v2.r1) from VIIRS on board S-NPP and
NOAA20 over both land and ocean. The differences between MODIS (C6.1), PMAp
(v2.1), VIIRS (v2.r1), and SLSTR (C1) AOD as well as their departure from the
modeled AOD were assessed at the model grid resolution (i.e., level-3)
using the 3-month AOD average (December 2019–February 2020 and March–May 2020). VIIRS and MODIS show the best consistency across the products, which is
explained by instrument and retrieval algorithm similarities. VIIRS AOD is
frequently lower over the ocean background and higher over biomass burning
and dust source land regions compared to MODIS. VIIRS shows larger spatial
coverage over land and resolves finer spatial structures such as the
transport of Australian biomass burning smoke over the Pacific, which can be
explained by the use of a heavy aerosol detection test in the retrieval
algorithm. Our results confirm the positive offset over ocean (i) between
Terra/MODIS and Aqua/MODIS due to the non-corrected radiometric calibration
degradation of Terra/MODIS in the Dark Target algorithm and (ii) between
SNPP/VIIRS and NOAA20/VIIRS due to the positive bias in the solar reflective
bands of SNPP/VIIRS. SLSTR AOD shows much smaller level-3 values than the
rest of the products, which is mainly related to differences in spatial
representativity at the IFS grid spatial resolution due to the stringent
cloud filtering applied to the SLSTR radiances. Finally, the geometry
characteristics of the instrument, which drive the range of scattering
angles sampled by the instrument, can explain a large part of the
differences between retrievals such as the positive offset between PMAp datasets from MetOp-B and MetOp-A.
Type of Medium:
Online Resource
ISSN:
1680-7324
DOI:
10.5194/acp-22-14657-2022
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2022
detail.hit.zdb_id:
2092549-9
detail.hit.zdb_id:
2069847-1