Aerosol Obsveration System (AOS)in the MAGICal experiment

Gunnar SenumBNL

First MAGIC Science Workshop

Aerosol Instrumentation1. CPC (Condensation Particle Counter) Measures the Total Aerosol Particle Concentration from 10 nm and up.2. UHSAS (Ultra High Sensitivity Aerosol Spectrometer Measures the Aerosol Size Concentration Distribution from 55nm to 1000nm.3. CCN (Cloud Condensation Nuclei Counter) Measures the concentration of aerosols that can be activated as cloud nuclei at specified humidity supersaturation, 0.2 to 1 %.4. Nephelometers Measures the light scattering of aerosol particles at 450, 550 and 700 nm, humidified and or dried, and or with size cuts at 1 and 10 microns.4a. Humidigraph Dries or humidifies the aerosol sample, in between the 2 Nephs5. PSAP (Particulate Soot Absorption Photometer) Measures the light absorption of aerosols, and with the Neph data will yield

aerosol albedo. Also sized cuts at 1 and 10 microns.6. HT-DMA (Humidified Tandem-Differential Mobility Analyzer) Measures the hygroscopicity of aerosols as a function of aerosol size.7. Ozone Measures the ambient ozone concentration.8. Meteorology Ambient temperature, humidity, precipitation, windspeed and direction.

How do these aerosol measurements relate to science

Next slides will illustrate some examples

Example of the AOS Science

The discontinuity is from the aerosol particle impactor, which removes particles from greater than 1 micron (lower traces). Note how the red scattering is predominating about 0900, due to more larger particles.

Examples of AOS Science

This is an example of the “Humidigraph” which is between the two Nephs in theAOS. This alternately dries and humidifies the aerosol sample. Note between 1000 and 1400, that the aerosol particles are more hygroscopic, they grow much with theapplied humidity.

Example of AOS Science

This is the CCN data for the same data as the previous slide. Note again we have more hydrophilic aerosol particles from 1000 to 1200. The CCNs are almost all activated by 0.4% supersaturation.

Examples of AOS Science

This is an example of the UHSAS. Almost every day has evidence of ship emissionsfrom other ships in the LA-Hawaii shipping lane. Note that these sharp ship emissionspikes are anti-correlated with calculated aerosol mean radius, since diesel ship emissions are very small sizes, less that 50nm. Blindly averaging this data would leaveto an incorrect result.

Example of AOS Science

This is the same UHSAS dataset as the previous slide. I have made use of the anti-corelation and segregated out the ship emissions. Note that there are only three major ship emission peaks, but they are broader and larger, that is, more aged ship emissions. This when averaged would be realistic of a maritime aerosol background

Same day as earlier, and note the “aged” ship emissions are more hydrophilic and CCN activated

This is one of the worst examples of the UHSAS data, totally contaminated with ship emissions

Here, is the same data, but the shipemissions are segregated out

AOS Mentor: Stephen Springston:

Infrastructure, ozone, met: Stephen SpringstonCCN, UHSAS, Neph, HT-DMA: Gunnar SenumCPC : Chongai KuangPSAP: Art Sedlacek

Mentors