Operations Updates
ARM Climate Research Facility Operations Update - August 15, 2006
This bimonthly report provides a brief summary of significant accomplishments and activities in the operations area of the ARM Climate Research Facility (ACRF).
Preparations Underway for 2007 ARM Mobile Facility Deployment in Germany
In the Black Forest region of Germany, the COPS field campaign will cover an area of about 700km2, as circled in red in the illustration above. The AMF will collect measurements from the floor of the Murg Valley.
In collaboration with researchers from the University of Hohenheim (Germany), the ARM Mobile Facility (AMF) will be deployed in 2007 as part of the Convective and Orographically-induced Precipitation Study (COPS), taking place in the Black Forest area of Germany. Orographic precipitation refers to rainfall resulting from atmospheric uplift (convection) in mountainous terrain. The COPS region is characterized by significant amounts of this type of precipitation, particularly in the summertime. Due to major challenges in predicting this type of precipitation, the area was chosen as a natural laboratory for a 9-month convection study within the 6-year duration of the German Quantitative Precipitation Forecasting (QPF) Program. The aim of this program is to identify the reasons for deficiencies in rainfall as predicted by the QPF. Beginning in March 2007, the AMF will collect data midway along the orographic path that, when combined with coincident radar and satellite observational data prior to significant convection and during maximum convection, will be used to improve the representation of convective clouds in models and to develop strategies for determining cloud climatologies in complex terrain.
Specific goals of the 6-year QPF program—funded by the German Research Foundation—are to:
- Identify the physical and chemical processes responsible for deficits
- Explore and apply existing and new data sets for improved representation of relevant processes
- Determine the predictability of precipitation using statistical dynamical analyses.
As part of this broader program, the COPS field campaign will obtain data for single-column modeling over low-mountain complex terrain and for improving precipitation forecasting. Extensive efforts will focus on observing the 4-dimensional state of the atmosphere, from the pre-convective environment, to the initiation of convection, to the formation of clouds, to the development and decay of precipitation. These efforts involve the operation of four heavily instrumented "supersites" situated throughout the COPS region. The AMF is one of these supersites.
Site visits and planning are well underway by AMF scientists and operations staff to prepare for the 2007 campaign, after the AMF is moved from its present deployment location in Niamey, Niger, West Africa. Site layouts have been drafted and coordination is progressing smoothly with local landowners in the Black Forest region.
Sunphotometer to Obtain Additional Aerosol Data in Niamey
Located nearby the AMF ground instruments, the sunphotometer, in the foreground, requires an unobstructed hemispheric view of the sky to obtain its measurements.
In early August, a new Cimel sunphotometer (CSPHOT) was deployed at the ARM Mobile Facility site in Niamey, Niger, as part of the ongoing RADAGAST field campaign. The CSPHOT measures the solar and sky radiance at various wavelengths in the visible and near-infrared spectrum (340, 380, 440, 500, 670, 870, 936, 1020 nm). From these measurements, a number of aerosol properties, including aerosol optical depth, can be determined. It also has application to cloud property retrievals. Adding a CSPHOT to the AMF instrument suite at Niamey was identified as a high priority for both the ARM Aerosol and Cloud Properties Working Groups, as it provides the added benefit of complementing the measurements taken by the same instrument at the other ACRF sites.
The CSPHOT has a 1.2 degree field of view and is comprised of three major components: (1) Cimel sun photometer, (2) Sutron Satlink satellite transmitter, and (3) solar panels to power the Cimel and the Satlink. The Cimel in turn is comprised of three subassemblies: (1) the sensor head, (2) the two-axis motor positioner, or "robot," and (3) the control unit. The instrument points at the sun for certain measurements, and also scans the atmosphere on a regular basis. These data are used to infer the scattering properties and particle size of aerosols.
Measurements from the CSPHOT are acquired via satellite by the NASA Aerosol Robotic Network (AERONET) Project at Goddard Space Flight Center. There, the data are processed to obtain aerosol optical thickness, precipitable water vapor amount, and other aerosol parameters. Researchers can access the processed data from the AERONET web page, which also contains additional information about the CSPHOT instrument, its measurements, and the AERONET Project. Once checked for quality, the data is also made available through the ACRF Data Archive.
