Fischer, Lucas (2013): Statistical characterisation of water vapour variability in the troposphere: a heightresolved analysis using airborne lidar observations and COSMODE model simulations. Dissertation, LMU München: Fakultät für Physik 

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Abstract
Tropospheric water vapour plays an important role in thermodynamic and radiative processes which have an immediate impact on the weather and climate system. However, the processes that determine the distribution of water vapour remain poorly understood. The complexity arises out of a range of source and sink processes from convective clouds on the kilometre scale to cloud systems associated with motions on scales of a thousand or more kilometres, as well as advection of water vapour as a passive tracer outside of clouds. While largescale advection of water vapour is well represented in general circulation models, the simulation of smallscale moist processes that are of central importance to the representation of clouds are heavily dependent on parameterisations. However, observations as well as processes that determine the distribution of the water vapour field are insufficiently explored, leading to constrained parameterisations and therefore contributing significantly to the uncertainty of numerical weather and climate predictions. Hence, a more accurate description of the inhomogeneous water vapour field based on highresolution observations is required. This thesis investigates a comprehensive data set of twodimensional airborne water vapour observations in the free troposphere collected by a Differential Absorption Lidar (DIAL) in order to gain a heightresolved statistical characterisation of the inhomogeneous water vapour field. Structure functions, i.e., statistical moments up to the fifth order of absolute increments over a range of scales, are investigated and powerlaw behaviour or scale dependence is identified over horizontal distances from about 5~km to 100~km. The slope of the powerlaw fit, the socalled scaling exponent, is found to take different values, depending on whether or not the observations were taken in an air mass where convective clouds were present. These results are consistent with a nonconvective regime that is dominated by largescale advective processes, leading to monofractal scaling, but strong localised input of smallscale variability by convective circulations leading to intermittent fields. Further, the observed powerlaw statistics are used to evaluate the highresolution numerical weather prediction model COSMODE of the German weather service with regard to the smallscale water vapour variability. The results of the scaling exponent analysis of cloudfree and partly cloudy scenes suggest, that the smallscale variance is modeled quite well in comparison with the lidar observations. By using the advantage of the model simulation where data is not limited to a specific flight path, the influence of sampling limitation is estimated and is found to be not significant. Further, the simulation provides humidity data in and beneath clouds which allows for an estimation of the uncertainty of data gaps in the lidar observations due to optically thick clouds. The error is identified to be in a range of only few percents. This thesis demonstrates that airborne DIAL observations are useful to build up a heightresolved statistical characterisation of tropospheric water vapour variability that allows to distinguish physical mechansims that are responsible for the water vapour distribution, to get new insights into stochastic parameterisations and further to use the structure function method as a suitable reality check of the numerical weather model COSMODE.
Dokumententyp:  Dissertation (Dissertation, LMU München) 

Keywords:  Water Vapour, Variability, Troposphere, Lidar 
Themengebiete:  500 Naturwissenschaften und Mathematik
500 Naturwissenschaften und Mathematik > 530 Physik 
Fakultäten:  Fakultät für Physik 
Sprache der Dissertation:  Englisch 
Datum der mündlichen Prüfung:  25. Oktober 2013 
1. Berichterstatter/in:  Craig, George C. 
URN des Dokumentes:  urn:nbn:de:bvb:19162089 
MD5 Prüfsumme der PDFDatei:  24bc549f31ece1a9ac6062bf91e59699 
Signatur der gedruckten Ausgabe:  0001/UMC 21612 
ID Code:  16208 
Eingestellt am:  07. Nov. 2013 13:14 
Letzte Änderungen:  24. Aug. 2015 09:47 