March 25, 2008
Aerosols Aloft and Moderate AQI Levels in Baltimore
The boundary layer rose from 0.5 to 1.75 km during the first 2.5 hours of observations. Aloft aerosol layers above the boundary layer were observed during ELF's operation. The scatters in these layers were made up of spherical and non-spherical particles; the particles in these layers had a parallel and perpendicular polarization return, respectively (counts from parallel channel are shown in the extinction plot). Dark counts, after 20:00 UTC, are due to clouds advecting over Baltimore. Hourly PM 2.5 concentrations in the range of 11 to 19 ug/m3 [AQI Levels: 38(Good) to 58 (Moderate) were recorded at Maryland's Department of the Enviroment Oldtown site in Baltimore during ELF's operation. The Moderate AQI Levels reached in Oldtown correspond in time to the highest counts (yellow counts before 15:00 UTC and below 1 km) observed within the boundary layer in today's lidar timeseries. The nature/source of this particles will be revisited as data from passive instruments becomes available to establish if the perpendicular return is due to dust or ice particles.
Posted by Ruben Delgado at March 25, 2008 10:48 PM | TrackBackWill you perhaps put arrows on where the aerosol layers are in this picture? What are dark counts? Thanks.
Posted by: jp at March 28, 2008 8:18 AMThe colorbar indicates the amount of material involved in the light scattering as well as how effective they scatter, with blue being very clear (nothing to scatter from) and increasing towards red as the number of scatterers increase. The red (dark counts) structure after 19.5 UTC and between 4-9 km are clouds.
Posted by: Ruben Delgado at March 31, 2008 4:03 PM