Land use change suppresses precipitation

Aerosols of natural and anthropogenic origin have important climate effects through interaction with clouds, which are among the main uncertainties in climate models due to the large variability of aerosol sizes, types and 3D-distributions [1]. Experimental investigations are typically restricted to high concentrations in industrial and urban aerosol plumes although in more remote areas already slight changes in the aerosol concentrations can have a large impact. This study reports on investigations of aerosols over a remote natural laboratory, along the ~1500 km long Vermin Proof Fence, also called “State Barrier Fence”, in Western Australia. This Fence, built in the first decade of the 20th century, separates an area of >100.000 square km of homogeneous terrain, converted to arable land (west), from the natural vegetation of inner Australia, conserved as a nature preserve (east). The Fence protects the agriculture from an invasion of animals but also protects the nature preserve from farming pressure and serves as a clear cut between the two types of landscape. Recent satellite images indicate that the Fence also works as a separation line between different meteorological regions. Clouds, for example, develop more often over regions with natural vegetation [2]. Early surveys of aerosols over Australia [3] found generally clean conditions with less than 1000 ultrafine (~ 20 nm) particles / cm3 throughout most of Australia. Local enhancements were occasionally observed in coastal areas, but, for the analysis of particle distributions they were considered to be unimportant. However, higher numbers of ultrafine particles were now also found downwind of tropical eucalyptus forests on the Australian east coast

MAX-DOAS measurements of formaldehyde in the Po-Valley

International audienceno abstract availabl

Corrigendum to "Measuring the 3-D wind vector with a weight-shift microlight aircraft" published in Atmos. Meas. Tech., 4, 1421–1444, 2011

This study investigates whether the 3-D wind vector can be measured reliably from a highly transportable and low-cost weight-shift microlight aircraft. We draw up a transferable procedure to accommodate flow distortion originating from the aircraft body and -wing. This procedure consists of the analysis of aircraft dynamics and seven successive calibration steps. For our aircraft the horizontal wind components receive their greatest single amendment (14 %, relative to the initial uncertainty) from the correction of flow distortion magnitude in the dynamic pressure computation. Conversely the vertical wind component is most of all improved (31 %) by subsequent steps considering the 3-D flow distortion distribution in the flow angle computations. Therein the influences of the aircraft's trim (53 %), as well as changes in the aircraft lift (16 %) are considered by using the measured lift coefficient as explanatory variable. Three independent lines of analysis are used to evaluate the quality of the wind measurement: (a) A wind tunnel study in combination with the propagation of sensor uncertainties defines the systems input uncertainty to ≈0.6 m s<sup>−1</sup> at the extremes of a 95 % confidence interval. (b) During severe vertical flight manoeuvres the deviation range of the vertical wind component does not exceed 0.3 m s<sup>−1</sup>. (c) The comparison with ground based wind measurements yields an overall operational uncertainty (root mean square error) of ≈0.4 m s<sup>−1</sup> for the horizontal and ≈0.3 m s<sup>−1</sup> for the vertical wind components. No conclusive dependence of the uncertainty on the wind magnitude (<8 m s<sup>−1</sup>) or true airspeed (ranging from 23–30 m s<sup>−1</sup>) is found. Hence our analysis provides the necessary basis to study the wind measurement precision and spectral quality, which is prerequisite for reliable Eddy-Covariance flux measurements