Abstract
In the present paper we provide an overview of a long term research project aimed at setting up a suitable platform for measurements in the atmospheric boundary layer on a light airplane along with some preliminary results obtained from fi eld campaigns at selected sites. Measurements of air pressure, temperature and relative humidity have been performed in various Alpine valleys up to a height of about 2500 m a.m.s.l. By means of GPS resources and specifi c post-processing procedures careful positioning of measurement points within the explored domain has been achieved. The analysis of collected data allowed detailed investigation of atmospheric vertical structures and dynamics typical of valley environment, such as morning transition from ground based inversion to fully developed well mixed convective boundary layer. Based on data collected along fl ights, 3D fi elds of the explored variables have been detected and identifi ed through application of geostatistical techniques (Kriging). The adopted procedures allowed evaluation of the intrinsic statistical structure of the spatial distribution of measured quantities and the estimate of the values of the same variable at unexplored locations by suitable weighted average of data recorded at close locations. Results thus obtained are presented and discussed.
Highlights
It is well known that in mountainous areas local valley winds arise, under fair weather conditions, as a result of different heating or cooling occurring either between different parts of the valleys or between valleys and adjacent plains.Solar heating of areas of the valley exposed to incoming radiation, varying during the day, Various physical factors, like valley shape, varied exposition to incoming solar radiation, ground nature and covering, surroundings and many others, have been identified in the literature as variously affecting the development of valley winds (Barry, 1981; Whiteman, 1990, 2000; Egger, 1990).Massimiliano de Franceschi, Gabriele Rampanelli, Domenico Sguerso, Dino Zardi and Paolo Zatelli a b c d e f g hFig. 1a-h
The attention of researchers has been recently concentrated on the understanding of some processes related to the formation or removal of thermal structures in the boundary layer (Whiteman and McKee 1982; Whiteman et al 1996; Anquetin et al, 1998; Sullivan et al, 1998), in connection with measurement campaigns performed within specific research projects, such as ALPEX, PYREX, ASCOT, MAP and many others (Whiteman, 1990). To accomplish this purpose light airplanes provide a suitable platform for the investigation of many atmospheric boundary layer structures, in particular those displaying significant horizontal inhomogeneities, such as thermally driven flows associated with cross/along-valley winds
An overview has been provided of results recently obtained by the Atmospheric Physics Group at the University of Trento with use of a small airplane. Interest in this field has increased in recent years and various research groups have pursued airborne measurements with light airplanes
Summary
It is well known that in mountainous areas local valley winds arise, under fair weather conditions, as a result of different heating (during the day) or cooling (at night) occurring either between different parts of the valleys or between valleys and adjacent plains. The attention of researchers has been recently concentrated on the understanding of some processes related to the formation or removal of thermal structures in the boundary layer (Whiteman and McKee 1982; Whiteman et al 1996; Anquetin et al, 1998; Sullivan et al, 1998), in connection with measurement campaigns performed within specific research projects, such as ALPEX, PYREX, ASCOT, MAP and many others (Whiteman, 1990) To accomplish this purpose light airplanes provide a suitable platform for the investigation of many atmospheric boundary layer structures, in particular those displaying significant horizontal inhomogeneities, such as thermally driven flows associated with cross/along-valley winds. The paper is structured as follows: in Section 2 an overview of various instruments used on the platform is presented; in Section 3 target areas where measurements have been performed are described; in Section 4 some preliminary results from the analysis of data are shown and discussed
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