General Information

Top of Page

Atmospheric Radiation Measurement (ARM) Climate Research Facility

Mobile Aerosol Observing System (MAOS)

The Mobile Aerosol Observing System (MAOS) is a platform and instrument suite for Intensive Operation Periods (IOPs) to conduct in situ measurements of aerosols and their precursors.  MAOS is part of the ARM Climate Research Facility. Physically MAOS is contained in two 20’ SeaTainers custom adapted to provide a sheltered laboratory environment for operators and instruments even under harsh conditions. The two structures are designated MAOS-A and MAOS-C for Aerosol and Chemistry respectively. Although independent, with separate data systems, inlets and power distribution, the two structures are normally a single operating unit.

The two enclosures comprising MAOS are designed for rapid deployment. All components (except for the Radar Wind Profiler) are transported internally in operating configuration. Once on site with power and internet, operations can commence with 1-2 hours of set up (erection of the sampling towers and roof railings). Internal climate control is sufficient for most conditions. 

MAOS A and C both have independent aerosol sampling inlets based on existing AOS units within the ARM Climate Research Facility. These inlets sample at ~10-m AGL. Four, 30 SLPM ports are available within the structure. Both units also have a ½” PFA inlet for trace gases. MAOS-C includes sampling and converters for labile compounds at the 10-m height.  Inlets are deiced and guyed for ~50 m/s winds. In case of severe weather forecasts, units can go into ‘Turtle Mode’ with 1-2 hour notice. In ‘Turtle Mode’, the external doors are shut and the inlet lowered.

The instrument suite includes aerosol and black carbon counters, optical and electro mobility classifiers, three measurements of aerosol absorbance, hygroscopicity measurements of aerosol growth and scattering, cloud condensation nuclei counters, two measurements of aerosol chemical composition and an extensive suite of research-grade instruments for complementary measurements of trace gas aerosol precursors.  A local meteorology sensor at the inlet, a SODAR and a Radar Wind Profiler provide context for the measurements.

MAOS Instrumentation

  • Aerosol counters
  • Aerosol size distribution
  • Aerosol absorbance
  • Hygroscopicity, growth and cloud precursors
  • Aerosol chemical composition
  • Aerosol gaseous precursors and related tracers
  • Supplemental measurements

MAOS encompasses a wide array of instruments including commercial, modified and custom made units. In order to simplify operation and data management, an individually tailored computer interface was developed for each instrument. This interface provides a uniform ‘look and feel’ for operators which simplifies training for operators and minimizes errors.  Individual instruments and associated computers can be accessed remotely by mentors reducing the on-sight personnel requirements. All external internet connections and data flow are covered through ARM Data System and Cyber Security. Guest instruments can be accommodated through a parallel system isolated from the core instruments. The customized interface for core instruments further provides a standard data output format for all raw data.  Raw data is redundantly stored on individual instrument computers, a separate local computer, the site collector computer and then off-site at the ARM Data Management Facility. Sufficient storage is available for most systems for at least one year’s operation.