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ORACLES Science Team Meeting - ARC (Tentative)

Date: 
Wednesday, September 9, 2015 (All day) - Friday, September 11, 2015 (All day)

Site Visit Namibia #2

Date: 
Saturday, October 10, 2015 (All day) - Saturday, October 17, 2015 (All day)

Composite CALIPSO backscatter curtains

Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research

4STAR (Spectrometers for Sky-Scanning Sun-Tracking Atmospheric Research; Dunagan et al., 2013) is an airborne sun-sky spectrophotometer measuring direct solar irradiance and narrow field-of-view sky radiance to retrieve and remotely sense column-integrated and, in some cases, vertically resolved information on aerosols, clouds, and trace gases. The 4STAR team is a world leader in airborne sun-sky photometry, building on 4STAR’s predecessor instrument, AATS-14 (the NASA Ames Airborne Tracking Sun photometers; Matsumoto et al., 1987; Russell et al. 1999, and cited in more than 100 publication) and greatly expanding aerosol observations from the ground-based AERONET network of sun-sky photometers (Holben et al., 1998) and the Pandora network of ground-based direct-sun and sky spectrometer (e.g, Herman et al., 2009).

4STAR is used to quantify the attenuated solar light (from 350 to 1650 nm) and retrieve properties of various atmospheric constituents: spectral Aerosol Optical Depth (AOD) from ultraviolet to the shortwave infrared (e.g., LeBlanc et al., 2020, Shinozuka et al., 2013); aerosol intensive properties - Single Scattering Albedo (SSA; e.g., Pistone et al., 2019), asymmetry parameter, scattering phase function, absorption angstrom exponent, size distribution, and index of refraction; various column trace gas components (NO2, Ozone, Water Vapor; e.g., Segal-Rosenheimer et al., 2014, with potential for SO2 and CH2O); and cloud optical depth, effective radius and thermodynamic phase (e.g., LeBlanc et al., 2015).

Some examples of the science questions that 4STAR have pursued in the past and will continue to address:

  • What is the Direct Aerosol Radiative Effect on climate and its uncertainty? (1)
  • How much light is absorbed by aerosol emitted through biomass burning? (1)
  • How does heating of the atmosphere by absorbing aerosol impact large scale climate and weather patterns? (1)
  • How does the presence of aerosol impact Earth’s radiative transfer, with co-located high concentration of trace gas? (2, 4)
  • What is the impact of air quality from long-range transport of both aerosol particulates and column NO2 and Ozone, and their evolution? (2, 5)
  • What are the governing properties and spatial patterns of local and transported aerosol? (1)
  • How are cloud properties impacted near the sea-ice edge? (3)
  • In heterogeneous environments where clouds and aerosols are present, how much solar radiation is impacted by 3D radiative transfer? And how does that impact the aerosol properties? (4)

(1) ORACLES: Zuidema et al., doi:10.1175/BAMS-D-15-00082.1., 2016; LeBlanc et al., doi:10.5194/acp-20-1565-2020, 2020; Pistone et al., https://doi.org/10.5194/acp-2019-142, 2019;Cochrane et al., https://doi.org/10.5194/amt-12-6505-2019, 2019; Shinozuka et al., https://doi.org/10.5194/acp-2019-1007, In review; Shinozuka et al., https://www.atmos-chem-phys-discuss.net/acp-2019-678/, In review
(2) KORUS-AQ: Herman et al., doi:10.5194/amt-11-4583-2018, 2018
(3) ARISE: Smith et al.,
https://doi.org/10.1175/BAMS-D-14-00277.1, 2017; Segal-Rosenheimer et al., doi:10.1029/2018JD028349, 2018
(4) SEAC4RS: Song et al., doi: 10.5194/acp-16-13791-2016, 2016; Toon et al., https://doi.org/10.1002/2015JD024297, 2016
(5) TCAP: Shinozuka et al., doi:10.1002/2013JD020596, 2013; Segal-Rosenheimer et al., doi:10.1002/2013JD020884, 2014

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Research Scanning Polarimeter

In order to demonstrate the capabilities of polarimetry an instrument that can make either ground-based, or aircraft measurements, the Research Scanning Polarimeter (RSP) has been developed by SpecTIR Corporation. This instrument has similar functional capabilities to the proposed EOSP satellite instrument. The picture above shows the assembled RSP instrument with its liquid nitrogen dewar on the left side and scanner assembly on the right. Currently data acquisition is performed on a laptop, which is shown here and gives an indication of the size of the instrument. The scientific requirements for the polarimetric measurements are satisfied by the RSP through its high measurement accuracy, the wide range of viewing angles measured and by sampling of the spectrum of reflected solar radiation over most of the radiatively significant range. The RSP instrument uses a polarization compensated scan mirror assembly to scan the fields of view of six boresighted, refractive telescopes through ±60° from the normal with respect to the instrument baseplate. The refractive telescopes are paired, with each pair making measurements in three spectral bands. One telescope in each pair makes simultaneous measurements of the linear polarization components of the intensity in orthogonal planes at 0° and 90° to the meridional plane of the instrument, while the other telescope simultaneously measures equivalent intensities in orthogonal planes at 45° and 135°. This approach ensures that the polarization signal is not contaminated by uncorrelated spatial or temporal scene intensity variations during the course of the polarization measurements, which could create false polarization. These measurements in each instantaneous field of view in a scan provide the simultaneous determination of the intensity, and the degree and azimuth of linear polarization in all nine spectral bands.

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Enhanced MODIS Airborne Simulator

The Enhanced MODIS Airborne Simulator (EMAS) is a multispectral scanner configured to approximate the Moderate-Resolution Imaging Spectrometer (MODIS), an instrument orbiting on the NASA Terra and Aqua satellites. MODIS is designed to measure terrestrial and atmospheric processes. The EMAS was a joint development project of Daedalus Enterprises, Berkeley Camera Engineering, the USU Space Dynamics Laboratory, and Ames Research Center. The EMAS system acquires 50-meter spatial resolution imagery, in 38 spectral bands, of cloud and surface features from the vantage point of the NASA ER-2 high-altitude research aircraft.

Instrument Type: Multispectral Imager
Measurements: VNIR/SWIR/LWIR Imagery
 

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Solar Spectral Flux Radiometer

In early 2000, the Ames Atmospheric Radiation Group completed the design and development of an all new Solar Spectral Flux Radiometer (SSFR). The SSFR is used to measure solar spectral irradiance at moderate resolution to determine the radiative effect of clouds, aerosols, and gases on climate, and also to infer the physical properties of aerosols and clouds. Additionally, the SSFR was used to acquire water vapor spectra using the Ames 25-meter base-path multiple-reflection absorption cell in a laboratory experiment. The Solar Spectral Flux Radiometer is a moderate resolution flux (irradiance) spectrometer with 8-12 nm spectral resolution, simultaneous zenith and nadir viewing. It has a radiometric accuracy of 3% and a precision of 0.5%. The instrument is calibrated before and after every experiment, using a NIST-traceable lamp. During field experiments, the stability of the calibration is monitored before and after each flight using portable field calibrators. Each SSFR consists of 2 light collectors, which are either fix-mounted to the aircraft fuselage, or on a stabilizing platform which counteracts the movements of the aircraft. Through fiber optic cables, the light collectors are connected to 2 identical pairs of spectrometers, which cover the wavelength range from (a) 350 nm-1000 nm (Zeiss grating spectrometer with Silicon linear diode array) and (b) 950 nm - 2150 nm (Zeiss grating spectrometer with InGaAs linear diode array). Each spectrometer pair covers about 95% of the incoming solar incident irradiance spectrum.

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