Atmospheric Radiation Measurement Climate Research Facility US Department of Energy

Biogenic Aerosols - Effects on Clouds and Climate: Cloud OD Sensor TWST

15 June 2014 - 31 August 2014

Lead Scientist: Herman Scott

Observatory: AMF, TMP

This deployment emphasized collaboration with other ARM sensors so as to take advantage of TWST’s combined features of fast sample rate, narrow FOV, and simultaneity in all spectral bands. These features make TWST relevant to DOE’s goals in understanding the impact of clouds and aerosols on climate change. TWST contributes significantly to the body of data used for extracting cloud microphysical properties as opposed to outputting only stand-alone COD results as in prior deployments. TWST directly collects calibrated spectral radiance at zenith for the spectral range of 350 – 1000 nm at ~2 nm spectral resolution. In stand-alone mode it retrieves Cloud Optical Depth (COD) at a sample rate of 1 Hz using the spectral radiance at 440 nm and the equivalent width of the oxygen A-band at 760 nm. When used in concert with other AMF instruments, namely the MWR, HSRL, W-Band cloud radar and Ka-Band zenith radar, it contributed to the retrieval of Liquid Water Path (LWP), vertical profiles of the effective radius of cloud droplets (re), and cloud droplet number concentration (Nd). The many instances of sensitivity to aerosols found in data collections to date give us reason to expect that TWST's high SNR and full spectral coverage support the extension of TWST capabilities to the measurement of aerosol properties.

In addition to contributing to the BAECC campaign objectives, the TWST sensor itself benefited from this deployment, making the technique more useful for subsequent campaigns. This was an opportunity to test and refine the TWST nonlinear filter algorithms designed to automatically resolve the thin cloud/thick cloud ambiguity using the equivalent width of the oxygen A-band. By examining the large body of BAECC cloud radar and lidar data we were able to immediately quantify, and improve if needed, the performance of our decision algorithms. This was a significant step toward the goal of TWST being capable of long term unattended autonomous operation in the field. Once again, TWST spectral radiance and COD results were compared to a collocated CIMEL Sunphotometer operating independently in cloud mode to confirm the accuracy and calibration stability of TWST.


Ed Niple

Related Publications


Niple ER and HE Scott. 2016. Biogenic Aerosols – Effects on Climate and Clouds: Cloud Optical Depth (COD) Sensor Three-Waveband Spectrally-Agile Technique (TWST) Field Campaign Report. DOE ARM Climate Research Facility. DOE/SC-ARM-15-064.

Niple E, H Scott, J Conant, F Iannarilli, and S Jones. 2016. Field Evaluation of Real-time Cloud OD Sensor TWST during the DOE ARM TCAP Campaign 2013 Final Campaign Report. DOE ARM Climate Research Facility. DOE/SC-ARM-14-018.

View All Related Publications

Campaign Data Sets

IOP Participant Data Source Name Final Data
Herman Scott Cloud Optical Depth from the Three Waveband Spectrally-agile Technique (TWST) sensor Order Data

TMP Data Sources

Name Full Name Browse Data
AERI Atmospheric Emitted Radiance Interferometer Browse Data
AOD Aerosol Optical Depth, derived from atmospheric extinction of solar irradiance Browse Data
AOS Aerosol Observing System Browse Data
AOSMET Meteorological Measurements associated with the Aerosol Observing System Browse Data
ASSIST Atmospheric Sounder Spectrometer for Infrared Spectral Technology Browse Data
CCN Cloud Condensation Nuclei Particle Counter Browse Data
CEIL Ceilometer Browse Data
CPC Condensation Particle Counter Browse Data
CSPHOT Cimel Sunphotometer Browse Data
ECMWFDIAG European Centre for Medium Range Weather Forecasts Diagnostic Analyses Browse Data
GNDRAD Ground Radiometers on Stand for Upwelling Radiation Browse Data
HSRL High Spectral Resolution Lidar Browse Data
HTDMA Humidified Tandem Differential Mobility Analyzer Browse Data
IRT Infrared Thermometer Browse Data
KASACR Ka-Band Scanning ARM Cloud Radar Browse Data
KAZR Ka ARM Zenith Radar Browse Data
MET Surface Meteorological Instrumentation Browse Data
MFRSR Multifilter Rotating Shadowband Radiometer Browse Data
MPL Micropulse Lidar Browse Data
MPLCMASK Cloud mask from Micropulse Lidar Browse Data
MWACR Marine W-Band (95 GHz) ARM Cloud Radar Browse Data
MWR Microwave Radiometer Browse Data
MWR3C Microwave Radiometer, 3 Channel Browse Data
NEPHELOMETER Nephelometer Browse Data
OZONE Ozone Monitor Browse Data
PBLHT Planetary Boundary Layer Height Browse Data
PSAP Particle Soot Absorption Photometer Browse Data
RAIN Rain Gauge Browse Data
RWP Radar Wind Profiler Browse Data
SACRADVVAD SACR Advance Velocity Azimuth Display Browse Data
SKYRAD Sky Radiometers on Stand for Downwelling Radiation Browse Data
SONDE Balloon-Borne Sounding System Browse Data
TSI Total Sky Imager Browse Data
VDIS Video Disdrometer Browse Data
VISST Minnis Cloud Products Using Visst Algorithm Browse Data
WACRARSCL W-band Cloud Radar Active Remote Sensing of Cloud Browse Data
XSACR X-Band Scanning ARM Cloud Radar Browse Data