Operations Updates
ARM Climate Research Facility Operations Update - May 31, 2006
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Comprehensive Instrument Validation Campaign Concludes
As the Aqua satellite moves along, the AIRS mirror scans a "swath" across the Earth's surface and directs infrared energy into the instrument. This energy is separated into wavelengths, which are transferred from Aqua to computers on the ground for additional processing. (Source: http://airs.jpl.nasa.gov)
After almost four years, the last soundings in the final phase of the Atmospheric Infrared Sounder (AIRS) validation program were completed on May 14 at the ACRF Tropical Western Pacific locale. Since late July 2002, operators at the ACRF sites launched approximately 2600 radiosondes (or sondes) in support of validation studies for the AIRS instrument aboard the National Aeronautics and Space Administration's Aqua satellite. The AIRS instrument measures the amount of infrared energy emitted from the atmosphere. These measurements are used to calculate vertical profiles of atmospheric temperature, humidity, and concentrations of greenhouse gases. Data from AIRS can also be used to reveal land and sea surface temperatures.
Sponsored by NASA, the special series of sonde launches were conducted in phases to sample the annual climate cycle at each ACRF site. Radiosonde flights were timed so that two radiosondes were in the air (one near the tropopause and one near the surface) when the Aqua satellite flew over the sites. The sondes were launched approximately 40 minutes apart. The aim was to (a) provide in situ validation data for the development and testing of water vapor retrievals obtained from the AIRS sensor aboard Aqua, and (b) demonstrate and quantify the accuracy of AIRS water vapor retrieval algorithms. Analyses to-date indicate excellent data returns, and researchers have already begun using the data.
Global water vapor distributions are important in the study of climate, so the accuracy of the instrumentation providing these data is very important. The data set obtained from this four-year effort will be used by scientists around the world to better understand weather and climate.
New Shortwave Spectroradiometer Deployed at SGP
A ceiling port in the SGP Optical Trailer houses the optic element of the SWS, which connects to the spectrometer inside the trailer via fiber optic cable.
An integrating sphere (left) is used to calibrate the optic element (right). The spectrometer itself is in the middle of the photo.
In late April, a new Shortwave Spectroradiometer (SWS) began operating at the ACRF Southern Great Plains (SGP) site. The instrument measures the zenith solar spectral radiance (1.4° field of view) between 300-2200 nm. The SWS incorporates two Zeiss miniature monolithic spectrometers having a spectral resolution of 8 nm in the range 300-975 nm, and 12 nm in the range 975-2200 nm. These measurements of visible and near infrared radiation will be used for testing shortwave radiation transfer models, as well as input to retrievals of cloud and aerosol properties.
As previously reported, a prototype of the new instrument—a modified version of the Solar Spectral Flux Radiometer (SSFR)—operated uninterrupted throughout a 29 day test period at the SGP site between November and December 2004. Based on the successful test period, ACRF management approved the proposal to deploy a new SWS a part of the permanent instrument suite at the SGP site.
Technicians at the SGP will calibrate the instrument biweekly, using a dedicated 12-inch diameter LabSphere integrating sphere. This task involves removing the optic element from the roof port and placing it in a fixture designed to align it with the integrating sphere. To perform these routine calibrations without moving the sensitive spectrometer, SGP Site Operations staff created a "darkroom" by partitioning the east end of the SGP Optical Trailer (where the spectrometer is located) and painting it black. Development of the data collection and ingest modules is progressing
