Presentation of some previous work with connections to BLLAST Erik - PowerPoint PPT Presentation

Presentation of some previous work with connections to BLLAST Erik Nilsson Doctoral student in Uppsala Sweden, finished 19 April 2013. working mainly with LES and field measurements of Department of influence from ocean waves on Atmospheric boundary layer Earth Science, Uppsala University I start a post-doc position in Lannemezan, France at Laboratoire d'Aérologie on October 1:st Villavägen 16 SE-752 36 Uppsala, Sweden erik.nilsson@ Outline: met.uu.se • Scalar flux loss due to sensor displacement erik.olof.nilsson @gmail.com • Initial evaluation of a GRAW radiosounding system • Multiresolution flux analysis and discussion on scale interaction

Eddy covariance method to determine scalar fluxes ′ ρ ′ = F w c c w is the vertical component of the wind ρ c is the mass density of some scalar c Erik Nilsson sensor separation Department of Earth Science, Uppsala University Laboratoire d'Aérologie Nilsson et al. 2010

In the context of BLLAST: lots of very nice measurements with different sensor configurations • Need for correction in stable stratification? Horst and Lenschow (2009) • Possibility to study reason for vertical assymetry? Why is flux loss with scalar sensor placed below the velocity sensor less?

Initial evaluation of a GRAW radiosounding system • One field week 28th June to 2nd July 2010 Erik Nilsson •16 radiosondes were launched Department of + standard soundings at Earth Science, Uppsala Gotland two times a day. University • Total of 48 theodolite trackings Laboratoire including double trackings d'Aérologie

GRAW worked well for U and WD Bias in average rising speed for the ABL Erik Nilsson of about 0.2 m/s? Uncertainty in the Department of Earth Science, comparison was Uppsala large University Laboratoire d'Aérologie Nilsson et al. 2013 written report

GRAW worked well for U and WD Bias in average rising speed for the ABL Erik Nilsson of about 0.2 m/s? Uncertainty in the Department of Earth Science, comparison was Uppsala large University Laboratoire d'Aérologie Nilsson et al. 2013 written report

GRAW worked well for U and WD Bias in average rising speed for the ABL Erik Nilsson of about 0.2 m/s? Uncertainty in the Department of Earth Science, comparison was Uppsala large University Laboratoire d'Aérologie From Firenze workshop courtesy of GRAW slightly Marie Lothon too humid? Nilsson et al. 2013 written report

Multiresolution analysis of eddy-fluxes Measurements • MR analysis involves averaging data over different averaging lengths. Erik Nilsson • Fluctuations in horizontal and vertical wind combine to Department of give vertical momentum Earth Science, ’fluxes’ Uppsala University • We assessed the amount of variability in a timeseries of Laboratoire d'Aérologie turbulent flux LES on different scales with respect to vertical wind and ’advected’ variable • Investigation of correlation between different scales is also possible (ongoing discussions with Larry Mahrt) Nilsson et al. (In revision)

Multiresolution analysis of eddy-fluxes ”Non- • Investigation of correlation between different scales is Fourier also possible (ongoing thinking” discussions with Larry Mahrt) Erik Nilsson ”Fourier • We are interested in the thinking” interaction between scales Department of Earth Science, Uppsala • For instance between University submeso or meso-scale motions (large scale) and Laboratoire turbulence (small scale) d'Aérologie • Can large-scale motions modulate turbulence on small-scales directly? without spectral cascade? • Transitioning periods an example? When we may expect several governing time-scales?

Multiresolution analysis of eddy-fluxes Possible to investigate the correlation between horizontal wind fluctuations (ordinate axis) and vertical Erik Nilsson wind variance (abscissa) on different scales Department of Earth Science, Imagine for instance that a Uppsala period of increased wind University speed taking place over a long time scale initiates Laboratoire turbulent vertical wind d'Aérologie motions on mainly smaller Some work remains scale We are looking for nice data with scale interactions to This could then also analyse. Do you have it? generate increased time- averaged fluxes on this smaller scale erik.nilsson@met.uu.se or erik.olof.nilsson@gmail.com Without going through a BLLAST Post-doc 2013-2015 spectral transfer

What was he talking Fluxes? about? Erik Nilsson Scales? Department of Earth Science, Uppsala University GRAW Laboratoire humidity and d'Aérologie Thank you! rising speed Questions? bias? erik.nilsson@ met.uu.se Fourier and Multiresolution? erik.olof.nilsson @gmail.com