Associated content: 
ARCSIX

High Altitude Lidar Observatory

The NASA Langley High Altitude Lidar Observatory (HALO) is used to characterize distributions of greenhouse gasses, and clouds and small particles in the atmosphere, called aerosols. From an airborne platform, the HALO instrument provides nadir-viewing profiles of water vapor, methane columns, and profiles of aerosol and cloud optical properties, which are used to study aerosol impacts on radiation, clouds, air quality, and methane emissions.  When the water vapor, aerosol and cloud products are combined it provides one of the most comprehensive data sets available to study aerosol cloud interactions.  HALO is also configured to provide in the future measurements of the near-surface ocean, including depth-resolved subsurface backscatter and attenuation.
 

Instrument Type: 
Lidar
Measurements: 
water vapor profiles, methane columns and profiles, Aerosol Depolarization Ratio, Aerosol Scattering Ratio, Aerosol Backscattering, Aerosol Extinction
Aircraft: 
DC-8- AFRC, C-130- WFF, P-3 Orion - WFF, B200 - LARC, B-200 (UC-12B) - LARC, DC-8 - AFRC, Gulfstream V - JSC, Gulfstream III - LaRC
Point(s) of Contact: 
Amin R. Nehrir (PI)

Research Scanning Polarimeter

The NASA GISS Research Scanning Polarimeter (RSP) is a passive, downward-facing polarimeter that makes total radiance and linear polarization measurements in nine spectral bands ranging from the visible/near-infrared (VNIR) to the shortwave infrared (SWIR). The band centers are: 410 (30), 470 (20), 550 (20), 670 (20), 865 (20), 960 (20), 1590 (60), 1880 (90) and 2250 (130) nm where the full width at half maximum (FWHM) bandwidths of each channel is shown in parenthesis. Noise is minimized in the SWIR channels by cooling the detectors to less than 165K using a dewar of liquid nitrogen. The RSP measures the degree of linear polarization (DoLP) with an uncertainty of <0.2%. The polarimetric and radiometric intensity measurement uncertainties are each <3%. A full set of RSP’s design parameters are shown in Table 1 and more details on design and calibration can be found in Cairns et al. (1999) and Cairns et al. (2003).
 
The RSP is an along track scanning instrument that can make up to 152 measurements sweeping ± 60° from nadir along the aircraft's track every 0.8 seconds with each measurement having a 14 mrad (~0.8°) field-of-view. Each scan includes stability, dark reference and calibration checks. As the RSP travels aboard an aircraft, the same nadir footprint is viewed from multiple angles. Consecutive scans are aggregated into virtual scans that are reflectances of a single nadir footprint from multiple viewing angles. This format comprises the RSP’s Level 1C data.
 
RSP’s high-angular resolution and polarimetric accuracy enables numerous aerosol, cloud and ocean properties to be retrieved. These are Level 2 data products. A summary of the primary L2 aerosol, cloud and ocean data products retrieved by the RSP are shown in Table 3.
 
The RSP’s data archive is publicly available and organized by air campaign, each of which contain ReadMe files provided by the RSP team for their Level 1C and Level 2 data products, including important details about biases and uncertainties that data users should consult.

The RSP data archive is available at: https://data.giss.nasa.gov/pub/rsp/
 
A visualizer showing the times and locations of NASA Airborne Campaigns the RSP has taken part in is available at: http://rsp.apam.columbia.edu:3000
 

Table 1: RSP Design Parameters
Parameter Performance
Degree of Linear Polarization Uncertainty (%) <0.2
Polarization Uncertainty (%) <3.0
Radiometric Uncertainty (%) <3.0
Dynamic Range >104
Signal-to-Noise Ratio >2000 (with R=0.3)
Spectral Characteristics See table
Field of View >90o
Instantaneous FOV 14 mrad
Photodiode Detector Type:
·       Visible/NIR
·       Shortwave IR (temperature)		  
Silicon
HgCdTe (165K)
SWIR Detector Cooling LN2 dewar
Data Rate <20 kbytes/sec
Size, W x L x H (cm) 40 x 64 x 34
Mass (kg) <20
Power (watts) <20 w/o heaters

 

Table 2: RSP Spectral Channels
Band ID λc (nm) Δλ (nm) Wavelength Type
V1 410 27 Visible
V2 470 20 Visible
V3 555 20 Visible
V4 670 20 Visible
V5 865 20 Near-IR
V6 960 20 Near-IR
S1 1590 60 Shortwave-IR
S2 1880 90 Shortwave-IR
S3 2250 130 Shortwave-IR

 

Table 3: Summary of L2 Data Products
Property Type Property Uncertainty Reference
Aerosol Aerosol Optical Depth for fine & coarse modes (column) 0.02/7% Stamnes et al., 2018
Aerosol Aerosol Size: effective radius for fine and coarse modes (column) 0.05 µm/10% Stamnes et al., 2018
Aerosol Aerosol Size: effective variance for fine and coarse modes (column) 0.3/50% Stamnes et al., 2018
Aerosol Aerosol Single Scatter Albedo (column) 0.03 Stamnes et al., 2018
Aerosol Aerosol Refractive Index (column) 0.02 Stamnes et al., 2018
Aerosol Aerosol Number Concentration 50% Schlosser et al., 2022
Aerosol Aerosol Top Height < 1 km Wu et al., 2016
Aerosol Surface Wind Speed 0.5 m s-1 Stamnes et al., 2018
Ocean Chlorophyll-A Concentration 0.7 mg m-3 Stamnes et al., 2018
Ocean Ocean diffuse attenuation coefficient 40% Stamnes et al., 2018
Ocean Ocean hemispherical backscatter coefficient 10% Stamnes et al., 2018
Cloud Cloud Flag 10%  
Cloud Cloud Albedo 10%  
Cloud Cloud Top Phase Index 10% van Diedenhoven et al., 2012
Cloud Cloud Top Effective Radius 1 um/10% Alexandrov et al., 2012a/b
Cloud Cloud Top Effective Variance 0.05/50% Alexandrov et al., 2012a/b
Cloud Cloud Mean Effective Radius 20% Alexandrov et al., 2012a/b
Cloud Cloud Optical Depth 10% Nakajima & King, 1990
Cloud Liquid Water Path 25% Sinclair et al., 2021
Cloud Columnar Water Vapor (Above Surface or Cloud) 10% Nielsen et al., 2023 (to be submitted)
Cloud Cloud Top Height 15% Sinclair et al., 2017
Cloud Cloud Droplet Number Concentration 25% Sinclair et al., 2021; Sinclair et al., 2019

 

Table 4: References
Alexandrov, M. D., Cairns, B., & Mishchenko, M. I. (2012). Rainbow fourier transform. Journal of Quantitative Spectroscopy and Radiative Transfer, 113(18), 2521-2535.
Alexandrov, M. D., Cairns, B., Emde, C., Ackerman, A. S., & van Diedenhoven, B. (2012). Accuracy assessments of cloud droplet size retrievals from polarized reflectance measurements by the research scanning polarimeter. Remote Sensing of Environment, 125, 92-111.
Cairns, B., E.E. Russell, and L.D. Travis, 1999: The Research Scanning Polarimeter: Calibration and ground-based measurements. In Polarization: Measurement, Analysis, and Remote Sensing II, 18 Jul. 1999, Denver, Col., Proc. SPIE, vol. 3754, pp. 186, doi:10.1117/12.366329.
Cairns, B., E.E. Russell, J.D. LaVeigne, and P.M.W. Tennant, 2003: Research scanning polarimeter and airborne usage for remote sensing of aerosols. In Polarization Science and Remote Sensing, 3 Aug. 2003, San Diego, Cal., Proc. SPIE, vol. 5158, pp. 33, doi:10.1117/12.518320.
Nakajima, T., & King, M. D. (1990). Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. Part I: Theory. Journal of Atmospheric Sciences, 47(15), 1878-1893.
Schlosser, J. S., Stamnes, S., Burton, S. P., Cairns, B., Crosbie, E., Van Diedenhoven, B., ... & Sorooshian, A. (2022). Polarimeter+ lidar derived aerosol particle number concentration. CHARACTERIZATION OF REMOTELY SENSED, MODELED, AND IN-SITU DERIVED AMBIENT AEROSOL PROPERTIES.
Sinclair, K., Van Diedenhoven, B., Cairns, B., Yorks, J., Wasilewski, A., & McGill, M. (2017). Remote sensing of multiple cloud layer heights using multi-angular measurements. Atmospheric Measurement Techniques, 10(6), 2361-2375.
Sinclair, K., Van Diedenhoven, B., Cairns, B., Alexandrov, M., Moore, R., Crosbie, E., & Ziemba, L. (2019). Polarimetric retrievals of cloud droplet number concentrations. Remote Sensing of Environment, 228, 227-240.
Sinclair, K., van Diedenhoven, B., Cairns, B., Alexandrov, M., Dzambo, A. M., & L'Ecuyer, T. (2021). Inference of precipitation in warm stratiform clouds using remotely sensed observations of the cloud top droplet size distribution. Geophysical Research Letters, 48(10), e2021GL092547.
Stamnes, S., et al. "Simultaneous polarimeter retrievals of microphysical aerosol and ocean color parameters from the “MAPP” algorithm with comparison to high-spectral-resolution lidar aerosol and ocean products." Applied optics 57.10 (2018): 2394-2413.
van Diedenhoven, B., Fridlind, A. M., Ackerman, A. S., & Cairns, B. (2012). Evaluation of hydrometeor phase and ice properties in cloud-resolving model simulations of tropical deep convection using radiance and polarization measurements. Journal of the Atmospheric Sciences, 69(11), 3290-3314.
Wu, L., Hasekamp, O., van Diedenhoven, B., Cairns, B., Yorks, J. E., & Chowdhary, J. (2016). Passive remote sensing of aerosol layer height using near‐UV multiangle polarization measurements. Geophysical research letters, 43(16), 8783-8790.
Instrument Type: 
Polarimeter
Measurements: 
Imagery
Aircraft: 
ER-2 - AFRC, P-3 Orion - WFF, C-130- WFF, King Air B-200 - LaRC, J-31
Point(s) of Contact: 
Brian Cairns (PI)

Diode Laser Hygrometer

The DLH has been successfully flown during many previous field campaigns on several aircraft, most recently ACTIVATE (Falcon); FIREX-AQ, ATom, KORUS-AQ, and SEAC4RS (DC-8); POSIDON (WB-57); CARAFE (Sherpa); CAMP2Ex and DISCOVER-AQ (P-3); and ATTREX (Global Hawk). This sensor measures water vapor (H2O(v)) via absorption by one of three strong, isolated spectral lines near 1.4 μm and is comprised of a compact laser transceiver and a sheet of high grade retroflecting road sign material to form the optical path. Optical sampling geometry is aircraft-dependent, as each DLH instrument is custom-built to conform to aircraft geometric constraints. Using differential absorption detection techniques, H2O(v) is sensed along the external path negating any potential wall or inlet effects inherent in extractive sampling techniques. A laser power normalization scheme enables the sensor to accurately measure water vapor even when flying through clouds. An algorithm calculates H2O(v) concentration based on the differential absorption signal magnitude, ambient pressure, and temperature, and spectroscopic parameters found in the literature and/or measured in the laboratory. Preliminary water vapor mixing ratio and derived relative humidities are provided in real-time to investigators.

Instrument Type: 
Laser absorption
Measurements: 
H2O
Aircraft: 
B200 - LARC, DC-8 - AFRC, Global Hawk - AFRC, P-3 Orion - WFF, WB-57 - JSC, Sherpa - WFF, HU25 Falcon - LaRC, Twin Otter - CIRPAS - NPS
Point(s) of Contact: 
Glenn S. Diskin (PI)

BroadBand Radiometers

The Broadband Radiometers (BBR) consist of modified Kipp & Zonen CM-22 pyranometers (to measure solar irradiance) and CG-4 pyrgeometers (to measure IR irradiance) (see http://www.kippzonen.com/). The modifications to make these instruments more suitable for aircraft use include new instrument housings and amplification of the signal at the sensor. The instruments are run in current-loop mode to minimize the effects of noise in long signal cables. The housing is sealed and evacuated to prevent condensation or freezing inside the instrument. Each BBR has the following properties: Field-of-view: Hemispheric Temperature Range: -65C to +80C Estimated Accuracy: 3-5% Data Rate: 1Hz

Instrument Type: 
Radiometer
Measurements: 
Solar and IR radiative flux; Total, Direct, Diffuse Solar radiative flux
Aircraft: 
DC-8 - AFRC, ER-2 - AFRC, P-3 Orion - WFF, C-130H - WFF, WB-57 - JSC
Point(s) of Contact: 
Anthony Bucholtz (PI)

Pages

Subscribe to RSS - ARCSIX