Friday, 6 April 2012

Being back and staying connected

It’s now already six weeks ago that I left Antarctica and that I am back in Belgium. Normal working life takes over rapidly. It has been time for debriefing meetings, for securing the data and to proceed to first preliminary data analysis, but also to think already what tasks have to be done during next season and what this means with respect to sending staff and cargo.

From the Belatmos instruments, three of them are still operational – the aethalometer, the TEOM-FDMS, and the laser aerosol spectrometer. The aethalometer and TEOM-FDMS are storing the data on their internal data storages and will be read out next season. Concerning the aerosol spectrometer – it is connected via an Ethernet cable to the internet. Therefore, I can regularly check the size distribution data and also download the current data. This also means that at this moment, the power supply of Princess Elisabeth station is still working. Let’s keep fingers crossed.

Above, I put some preliminary plots with examples of aerosol data. The top image shows the total scattering coefficient measured by the nephelometer at 635 nm for roughly two days (of 5min average data). These coefficients are given in units of Mm-1 (or 1*10-6 m). The scattering coefficient correlates well with the overall amount of ambient particles – the more particles there are, the higher the scattering coefficient. However, at the same time, aerosols do scatter and absorb, and the more scattering compared to absorbing they are, the higher the scattering coefficient will be. Values like shown in the graph represent low overall aerosol concentrations.

In the middle graph, the total number concentration detected by the condensation particle counter (CPC) is shown for two hours (1min averages) from the same period. The overall particle concentration was around 600 to 700 particles per cm-3. The few much higher peaks indicate very probably the measurement of the exhaust of skidoos or prinoths passing by nearby. However, this has to be analysed and confirmed in more detail. As mentioned in a former post, the usual concentration in sub-urban regions would be 10 to 100 times higher.

The bottom image gives the number size distribution over the two hours of the total number concentration of the middle graph. Although the laser aerosol spectrometer can only measure from a particle size of 90 nm onwards, the dominant size around 100 nm was within the measurement range. It also can be seen that there are hardly any particles larger than 1 micrometer. In a further analysis, I will combine the two measurements of total number concentration and of size distribution to define the concentration within the range 3 to 90 nm – as the CPC is measuring all particles from 3 nm onwards.