https://horizon.documentation.ird.fr/exl-doc/pleins_textes/pleins_textes_7/b_fdi_51-52/010019285.pdf

AERONET-a federated instrument network and data archive for aerosol Characterization

Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates, oceanic sites, desert sites, and background sites. Seasonal trends for each of these nine sites are discussed and climatic averages presented.

/pdf/an-emerging-ground-based-aerosol-climatology-aerosol-optical-5e0rm6d06m.pdf

An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET

Imaging Spectroscopy and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

Validation of the land-surface temperature products retrieved from Terra Moderate Resolution Imaging Spectroradiometer data

 The Aerosol Robotic Network (AERONET) has provided highly
accurate, ground-truth measurements of the aerosol optical depth (AOD) using
Cimel Electronique Sun–sky radiometers for more than 25 years In Version 2 (V2)
of the AERONET database, the near-real-time AOD was semiautomatically
quality controlled utilizing mainly cloud-screening methodology, while
additional AOD data contaminated by clouds or affected by instrument
anomalies were removed manually before attaining quality-assured status
(Level 20) The large growth in the number of AERONET sites over the past
25 years resulted in significant burden to the manual quality control of millions
of measurements in a consistent manner The AERONET Version 3 (V3) algorithm
provides fully automatic cloud screening and instrument anomaly quality
controls All of these new algorithm updates apply to near-real-time data as
well as post-field-deployment processed data, and AERONET reprocessed the
database in 2018 A full algorithm redevelopment provided the opportunity to
improve data inputs and corrections such as unique filter-specific
temperature characterizations for all visible and near-infrared wavelengths,
updated gaseous and water vapor absorption coefficients, and ancillary data
sets The Level 20 AOD quality-assured data set is now available within a
month after post-field calibration, reducing the lag time from up to several
months Near-real-time estimated uncertainty is determined using data
qualified as V3 Level 20 AOD and considering the difference between the AOD
computed with the pre-field calibration and AOD computed with pre-field and
post-field calibration This assessment provides a near-real-time
uncertainty estimate for which average differences of AOD suggest a +002  bias
and one sigma uncertainty of 002, spectrally, but the bias and uncertainty
can be significantly larger for specific instrument deployments Long-term
monthly averages analyzed for the entire V3 and V2 databases produced
average differences (V3–V2) of  + 0002 with a ± 002 SD (standard
deviation), yet monthly averages calculated using time-matched observations
in both databases were analyzed to compute an average difference of  −0002 
with a ±0004  SD The high statistical agreement in
multiyear monthly averaged AOD validates the advanced automatic data
quality control algorithms and suggests that migrating research to the
V3 database will corroborate most V2 research conclusions and likely lead to
more accurate results in some cases

/pdf/advancements-in-the-aerosol-robotic-network-aeronet-version-uve5u95xm4.pdf

Advancements in the Aerosol Robotic Network (AERONET) Version 3 database – automated near-real-time quality control algorithm with improved cloud screening for Sun photometer aerosol optical depth (AOD) measurements

A variation of the modified Langley plot algorithm is reported here and applied to the retrieval of atmospheric water column abundance from a filtered sunphotometer. In this new methodology an absorption data base (LOWTRAN 7) is used to compute a water abundance versus transmittance curve of growth, rather than the square-root dependence previously assumed. Validation of the technique is provided from an uncertainty analysis, and plans to further validate using Fourier transform spectrometers are detailed. The new sunphotometer technique is used to report local column water vapor during the First ISLSCP Field Experiment (FIFE), and comparisons are made with abundances retrieved via FIFE radiosonde observations. The sunphotometer data can best be utilized, however, to in turn validate data from airborne or in-orbit measurements of water vapor. With these flight sensors, horizontal and topographic variability within the scene can be viewed. An example of the airborne data set is given using an image from the airborne visible infrared imaging spectrometer, as acquired on August 31, 1990.

Water vapor column abundance retrievals during FIFE

A comparison is made between two ground-based atmospheric water-vapor measurement techniques, each of which uses data from a solar-pointing radiometer. One technique uses visible wavelength channels to retrieve aerosol loading, surface pressure readings for Rayleigh scattering analyses, and the 0.94 micron channel to extract water vapor from the residual of total versus scattering opacity. The other technique requires only the ratio of channels centered at 0.94 and 0.87 micron. Results are given for the April 13, 1989 AVIRIS in-flight calibration.

In-situ atmospheric water-vapor retrieval in support of AVIRIS validation

This overview paper describes the system design of the structurally-connected interferometer (SCI) concept studied for the Terrestrial Planet Finder (TPF) project. This paper covers progress since August 2003 and serves as an update to a paper presented at that month's SPIE conference, "Techniques and Instrumentation for Detection of Exoplanets". SCI trade studies conducted since mid-2003 have focused on key factors driving overall flight segment mass and performance, including launch vehicle packaging, structural design, and instrument layout. This paper summarizes the results of the recent design trades, with discussion of the primary requirements that drive the baseline design concept.

Ronald G. Holm

Papers

Water vapor column abundance retrievals during FIFE

In-situ atmospheric water-vapor retrieval in support of AVIRIS validation

Current status of the Terrestrial Planet Finder structurally connected interferometer concept