Konstantin Baibakov

Challenges in operating an Arctic telescope

We describe our seven year experience and the specific technical and environmental challenges we had to overcome while operating a telescope in the High Arctic, at the Eureka Weather Station, during the polar winter. The facility and the solutions implemented for remote control and maintenance are presented. We also summarize the observational challenges encountered in making precise and reliable star-photometric observations at sea-level.

Comparisons of a Chemical Transport Model with a Four-Year (April to September) Analysis of Fine- and Coarse-Mode Aerosol Optical Depth Retrievals Over the Canadian Arctic

ABSTRACT We compared April to September retrievals of total, fine-mode (sub-micron), and coarse-mode (super-micron) aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) with simulations from a global three-dimensional chemical transport model, the Goddard Earth Observing System (GEOS-Chem), across five Arctic stations and a four-year sampling period. It was determined that the AOD histograms of both the retrievals and the simulations were better represented by a lognormal distribution and that the successful simulation of this empirical feature as well as its consequences (including a better model versus retrieval coefficient of determination in log-log AOD space) represented a general indicator of model evaluation success. Seasonal (monthly averaged) AOD retrievals were sensitive to the way in which the averaging was performed; this was ascribed to the presence of highly variable fine-mode smoke in the western Arctic. The retrieved and modelled station-by-station fine-mode AOD averages showed a peak in April/May that decreased over the summer, while the model underestimated the fine-mode AOD by an average of about 0.004 (∼6%). Both the retrievals and simulations showed seasonal coarse-mode AOD variations with a peak in April/May that was attributed to Asian and/or Saharan dust. The models success in capturing such weak seasonal events helps to confirm the relevance of the separation of the fine and coarse modes and the general validity of model estimates in the Arctic.

Performance of a compact elastic 355 nm airborne lidar in tropical and mid-latitude clouds

In 2014 a new AECL (Airborne Elastic Cloud Lidar) lidar system was installed on-board the NRC Convair-580. AECL is a single wavelength elastic lidar which operates at 355nm and can supply vertical profiles of clouds and aerosols at high vertical and temporal resolution (1.5m and 0.05s). AECL is also equipped with a polarization channel and can provide information on particle phase (i.e. liquid or glaciated). The NRC AECL lidar was flown briefly on March 28, 2014 near Ottawa, Canada. In May of 2015 it was also deployed during the multi-week international HAIC (High Altitude Ice Crystals) – HIWC (High Ice Water Content) campaign near Cayenne, French Guinea. During the midlatitude flight near Ottawa, a convective cloud with cloud top extending to 4000 m was sampled by AECL. The on board in-situ cloud microphysics probes showed that the aircraft climbed through rain below 2 km reaching a mixedphase cloud above the melting layer and finally going through a supercooled layer. The lidar depolarization data from the AECL clearly identified the shallow supercooled layer near the cloud top and ice crystals with high depolarization ratio between the melting layer and the supercooled layer. In the regions of HIWC near Cayenne, the AECL laser beam was generally completely extinguished within the first 200 m. The lidar extinction coefficient, estimated using the Klett inversion technique and taken at 50 m above the aircraft showed a very good qualitative agreement with the measured in-situ extinction at flight level. The lidar extinction values had to be scaled by a factor of 5.88 to match the in-situ data. The discrepancies between the lidar estimated extinction and the direct measurements were explained, in part, by insufficient overlap correction and/or the error in the initial parameters used for the Klett inversion. In general, AECL showed promising initial results and in conjunction with other instrumentation, supplied valuable insight into the cloud optical and microphysical properties.