Diurnal cycle of short-term fluctuations of integrated water vapour above Switzerland

Hocke, Klemens; Bernet, Leonie Anna Luisa; Hagen, Jonas; Murk, Axel; Renker, Matthias; Mätzler, Christian (2019). Diurnal cycle of short-term fluctuations of integrated water vapour above Switzerland. Atmospheric chemistry and physics Discussions, pp. 1-15. European Geosciences Union 10.5194/acp-2019-129

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The TROpospheric WAter RAdiometer (TROWARA) continuously measures integrated water vapour (IWV) with a time resolution of 6 seconds at Bern in Switzerland. During summer, we often see that IWV has temporal fluctuations during daytime while the night-time data are without fluctuations. The data analysis is focused on the year 2010 where TROWARA has a good data quality without data gaps. We derive the spectrum of the IWV fluctuations in the period range from about 1 to 100 min. The FFT spectrum with a window size of 3 months leads to a serious underestimation of the spectral amplitudes of the fluctuations. Thus, we apply a band pass filtering method to derive the amplitudes as a function of period Tp. The amplitudes are proportional to Tp0.5. Another method is the computation of the moving standard deviation with time window lengths from about 1 to 100 min. Here, we get similar results as for the band pass filtering method. At all periods, the IWV fluctuations are strongest during summer while they are smallest during winter. We derive the diurnal variation of the short-term IWV fluctuations by applying a moving standard deviation with a window length of 10 min. The daily cycle is strongest during the summer season with standard deviations up to 0.22 mm at about 14:00 CET. The diurnal cycle disappears during winter time. Using the meteorological weather station at Bern, we derive the diurnal cycle of the short-term fluctuations of the specific kinetic energy ek. Since these data have a temporal resolution of 10 min, we apply a 20 min-moving standard deviation. The derived short-term ek fluctuations can be regarded as a proxy of turbulent kinetic energy (TKE). During summer time, the 20 min-moving standard deviation of ek increases during daytime and has a similar diurnal cycle like the short-term IWV fluctuations. Thus, we conclude that the diurnal cycle of the short-term IWV fluctuations is caused by turbulence associated with large convective heating during daytime in summer.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Applied Physics
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)

UniBE Contributor:

Hocke, Klemens; Bernet, Leonie Anna Luisa; Hagen, Jonas; Murk, Axel and Mätzler, Christian

Subjects:

600 Technology > 620 Engineering

ISSN:

1680-7375

Publisher:

European Geosciences Union

Language:

English

Submitter:

Franziska Stämpfli

Date Deposited:

16 Jul 2019 15:25

Last Modified:

24 Oct 2019 15:51

Publisher DOI:

10.5194/acp-2019-129

BORIS DOI:

10.7892/boris.130617

URI:

https://boris.unibe.ch/id/eprint/130617

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