Height-resolved Scaling Properties of Tropospheric Water Vapour based on Airborne Lidar Observations

Two-dimensional vertical water vapour cross sections of the free troposphere between altitudes of 2 and 10 km, measured by nadir-viewing airborne differential-absorption lidar with high spatial resolution, were analyzed using structure functions up to the fifth order. We found scale invariance, i.e. a power-law dependency of structure function on length scale, for scales between 5 and 100 km, for the horizontal time series of water vapour mixing ratio. In contrast to one-dimensional in situ measurements, the two-dimensional water vapor lidar observations allow height-resolved analyses of power-law scaling exponents at a vertical resolution of 200 m. The data reveal significantly different scaling properties above and below an air-mass boundary. They stem from three very dissimilar aircraft campaigns: COPS/ETReC over middle and southern Europe in summer 2007, T-PARC around Japan mostly over sea in late summer 2008, and T-IPY around Spitsbergen over sea in winter 2008. After discarding flight segments with low lidar signals or large data gaps, and after averaging horizontally to a resolution of between 1 and 5 km to obtain a high signal to noise ratio, structure functions were computed for 20 flights at various heights, adding up to a length of more than 300,000 km. The power-law scaling exponents of the structure functions do not show significant latitudinal, seasonal or land/sea dependency, but they do differ between air masses influenced by moist convection and air masses aloft, not influenced. A classification of the horizontal water vapour time series into two groups according to whether the series occurred above or below the level of nearby convective cloud tops could be performed by detecting the cloud top height from the lidar backscatter signal in the corresponding flight segment. We found that the scaling exponents can be divided into two groups depending on the respective air mass: The smoothness of the time series, expressed by the first-order scaling exponent, varies from less than 0.5 in the low-level convectively influenced air masses to values greater than 0.5 and most frequently near 0.6 in the higher-level air above the convective cloud tops. The time series’ intermittency, expressed by the variation of the scaling exponent with increasing order, is larger in convectively influenced air masses. These differences in variability strongly suggest that convection provides a source of moisture variability on small scales. Our results show that the high horizontal and vertical resolution of lidar observations allows a characterisation of the scale dependency of the water vapour field at scales close to and smaller than the smallest resolved scales in modern weather and climate models. This provides both a reference for validation of high resolution models and a basis for the design of stochastic or pdf-based parameterisations of clouds and convection

The reactions of radicals produced in the decomposition of aliphatic azo compounds and di-alkyl peroxides

Evidence is given for the course of reaction outlined below when two radicals, similar or dissimilar, are produced in solution simultaneously and from the same molecule. The evidence is based on two systems: the decomposition of azo-bis-nitriles and tertiary alkyl peroxides. (1) The radicals, produced from the same molecule, may collide and react together or react simultaneously with a third species before either radical has left the site of formation. In this case the radicals are not kinetically free and the products formed are dependent upon the nature of both radicals concerned even though one of the radicals may not appear as an even product in the reaction. (2) If the radicals do not react while caged they may diffuse apart and then react with another molecule by either a kinetically third-order process or individually in bimolecular processes. (3) In the decomposition of the tertiary alkyl peroxides studied, the termolecular processes must be in competition with bimolecular processes

Legal and Ethical Precepts Governing Emerging Military Technologies: Research and Use

From the emergence and increasing use of unmanned or remotely piloted vehicles to the advent of cyber war and conflict, the development of new and exotic military technologies has provoked fierce and divisive public debate regarding the ethical challenges posed by such technologies.1 I have increasingly come to believe that the language of morality and ethics has served us poorly in this context and presently serves to further confuse us, rather than to clarify or enlighten us, on how best to cope with the continuing development and deployment of seemingly exotic new military technologies

IGUANA Architecture, Framework and Toolkit for Interactive Graphics

IGUANA is a generic interactive visualisation framework based on a C++ component model. It provides powerful user interface and visualisation primitives in a way that is not tied to any particular physics experiment or detector design. The article describes interactive visualisation tools built using IGUANA for the CMS and D0 experiments, as well as generic GEANT4 and GEANT3 applications. It covers features of the graphical user interfaces, 3D and 2D graphics, high-quality vector graphics output for print media, various textual, tabular and hierarchical data views, and integration with the application through control panels, a command line and different multi-threading models.Comment: Presented at the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 6 pages LaTeX, 4 eps figures. PSN MOLT008 More and higher res figs at http://iguana.web.cern.ch/iguana/snapshot/main/gallery.htm

When Robots Rule the Waves?

By virtue of the distinctive character of war at sea, a number of unique and complex ethical questions are likely to arise regarding the applications of autonomous unmanned underwater vehicles and unmanned surface vehicles