Condensation Particle Counters Combined with a Low-Pressure Impactor for Fast Measurement of Mode-Segregated Aerosol Number Concentration

摘要

An integrated airborne system comprising two condensation particle counters (CPCs, models 3771 and 3772, TSI Inc.) and a low-pressure impactor (LPI) has been developed (LPI-CPCs) for fast measurement of mode-segregated aerosol number concentration. The CPC 3771 is connected to the LPI to measure aerosol number concentrations below 0.17 μm in aerodynamic diameter, while the CPC 3772 directly measures the total aerosol number concentration. The former approximately corresponds to the Aitken mode fraction of the aerosol number concentration. The key concept is that the cutoff diameter of the LPI (aerodynamic diameter at which the transmission efficiency is 50) is controlled by simultaneously modifying the pressure and flow rate through the LPI. The instrument was deployed onboard the King Air B200T aircraft during the Aerosol Radiative Forcing in East Asia (A-FORCE) conducted over the western Pacific in the spring of 2009. The results from the aircraft measurements, together with those from laboratory experiments, are used to demonstrate the in-flight performance of the instrument. We propose that fast airborne measurement of mode-segregated aerosols by LPI-CPCs is useful for a better understanding of the variability of aerosol number concentration in the troposphere.