Wednesday, 6 April 2016

Successful season behind and promising winter season ahead

In the meantime we are already in April. High time to post something on the blog. The BELARE 2015-2016 expedition at Utsteinen has been finished end of February when the last team left Princess Elisabeth station. The expedition season has been successful for our project. All instruments for year-round operation have been maintained and are still operational.This means that now an un-interrupted time series exists from November 2014 to present for four aerosol instruments (aethalometer, nephelometer, TEOM-FDMS, U-CPC). The laser aerosol spectrometer has been re-installed after its repair and has been operational since December 2015 – and is still running. The Brewer ozone spectrophotometer could measure the whole austral summer season until mid-February when it had to be dismounted as usual. Below there is a graph showing the time series of total atmospheric column ozone from end of November to end of December 2015. It illustrates nicely the period until mid-December when ozone hole conditons (i.e. total ozone below 220 DU) persisted over the region of Utsteinen. Normally, such conditions persist only until end of November, beginning of December. The ozone hole of 2015 was indeed one of the most stable one on record. 
time series of total ozone end of Nov-2015 to end of Dec-2015

the MAX-DOAS (left) and the sunphotometer (right) instruments on the roof of PE station

The next image shows the sunphotometer (to the right) and the new-comer instrument ‘MAX-DOAS’ (to the left). The MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy) system is part of the BIRA contribution to the AEROCLOUD project. This instrument will monitor the vertical distribution of aerosols as well as several trace gases present in the atmosphere above the station. Like the Brewer, the MAX-DOAS measures the spectrum of solar light attenuated and scattered by atmospheric particles and molecules, in the wavelenght region of 300 to 550 nm, where a number of atmospheric molecules such as ozone and other compounds (NO2, BrO, OClO, H2O, O4) can be detected. By scanning the sky from the horizon to the zenith, the instrument provides information on the vertical profile of these molecules, as well as on aerosols which affect the measured trace gas absorption. First measurements are very promising and comparisons with the Brewer instrument (total ozone) and the sunphotometer (aerosol optical depth) show good agreement. In particular interesting is , that the instrument will continue its monitoring throughout the year. Therefore (if it keeps on running), it will be possible to observe the onset of the ozone hole as soon as the light starts to illuminate the polar stratosphere in early austral spring.. In addition, the concentration of several ozone related species (NO2, BrO and OClO) will be simultaneously measured providing an ensemble of data to characterize the chemical evolution of the polar stratosphere during the spring period. 

 the new instrument 'Snowflake Video Imager' on the roof of PE station

Our partners from the KU Leuven installed in January 2016 also a new instrument on the roof of the station, the ‘SnowflakeVideo Imager’ (see third image), designed by NASA. It contains a high-speed camera with sufficient frame rate, pixels, and shutter speed to record thousands of snowflake images in an undisturbed flow. These images are used to derive information on precipitating and blowing snow particle size distribution, as well as information about particle shape. This information on snow particles is important for correct estimation of snowfall amounts based on the radar measurements. A nice test for the instruments has been an impressive storm on 29 and 30 March 2016, with wind speeds around 20 m/s, peaking up to 26 m/s and after which the automatic weather station detected a snow accumulation around 20 cm. When writing this post, just another storm is active in the area of Utsteinen. So far, the instruments cope well with these conditions and the aerosol instruments are well in their cosy shelter (fourth image) – outside storm and very low temperatures, inside around 20 °C. 

inside the aerosol instrument shelter during winter season

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