Atmospheric integrated water vapour measured by IR and MW techniques at the Peterhof site (Saint Petersburg, Russia)

作者：Virolainen Yana^*; Timofeyev Yury; Berezin Ivan; Poberovsky Anatoly; Polyakov Alexander; Zaitsev Nikita; Imhasin Hamud

来源：International Journal of Remote Sensing, 2016, 37(16): 3771-3785.

DOI：10.1080/01431161.2016.1204025

Regular comparison of different systems for monitoring atmospheric integrated water vapour (IWV) is part of their testing and validation protocol. We compared coincident measurements of IWV over Saint Petersburg (Russia) from ground-based Fourier-transform spectrometer Bruker IFS 125 HR (FTIR) and microwave radiometer RPG-HATPRO (MW) at the Peterhof site between March 2013 and June 2015. This study is a contribution towards global efforts to make such inter-comparisons at various ground-based sites. Since FTIR measures solar radiance, the vast majority of coincident pairs correspond to the spring and summer seasons. The numbers of measurements in the dry season (from October to April) and in the wet season (from May to September) are almost identical, comprising 616 and 638 pairs, respectively. MW and FTIR data sets demonstrate a high level of agreement: the mean relative difference between MW and FTIR data is less than 3% (0.3mm), with standard deviation from the means of about 4% (0.4mm). Notwithstanding the short distance between both instruments (150m), they can monitor different air masses: MW is a zenith-viewing instrument whereas FTIR follows the sun. We analysed the FTIR observation fields under different solar zenith and azimuth angles, taking into account the location of the Peterhof site between the Gulf of Finland and rural suburbs of Saint Petersburg. Although in general MW measurements slightly overestimated IWV in comparison with the FTIR data, we detected several episodes when FTIR gave higher values than MW. These episodes relate to the FTIR observations directed at the coastal region with more humid air than that above the measurement site. We may conclude at this stage of our investigations that the spatial inhomogeneity of humidity fields in the atmosphere causes the most significant differences between the two data sets. Detailed analysis of variation in spatial IWV, e.g. using a MW radiometer in angular scanning mode, is an issue for future research.

• 出版日期2016-8-20