Heise, Claudia (2004) Der Einfluss durchbrochener Bewölkung auf die solare Einstrahlung : eine Studie für Kiel. (Diploma thesis), Christian-Albrechts-Universität, Kiel, Germany, 76 pp.

Text Heise, C. 2004.pdf - Published Version Restricted to Registered users only Available under License German copyright act UrhG. Download (10MB) | Contact

Abstract

In the present work the impact of broken clouds on solar irradiance at the surface is studied. This study is based on the region of Kiel, becausc of realisation of land and seameasurements. To this end data from pyranometer and ceilometer, which are available at the Institut für Meereswisscnschaften, are used. On thc basis of these data (march 1997 until october 2003) statements about variation in solar irradiance by different cloud amount over land opposite to the reference of clear sky case at the lighthouse Kiel are made. Beside the decrease in irradiance, so-called shadowing effect, an extra amount of irradiance by broken cloudiness adds to the amount of direct irradiance. The extra amount of irrandiance is given by reflection of solar radiance at cloud sides. The english technical literature refers to the enhancemcnt as "broken cloud effect" (bce). The enhancement ranges from some W/m2 until 300 W/m2. This depends on the typ of cloud and the solar zenith angle. The bc rcsults from cumuli, which accumulate by convection at the time of land-sea-breeze-circulation. The frequency of occurrence of thc bc-events are significant coupled with the sea-breeze-circulation. The effect can be observed soonest in spring and in early and late summer, if and only if the formation of sea-breeze-circulation is most likely and as a consequence thereof the fine weather cumuli are developed. In June the broken cloud effect occurs very often owing to the small solar zenith angles of 30°, which arc typical for this month. A further dependance exists in cloud amount. The increase in radiance is maximal by a cloud over of 6/8. Consequently the bce cannot be oberserved neither at cloud1ess nor at completely covered sky. A concluding aspect for this work consists in modelling the bce with the model called GRIMALDI, which is advanced at the Institut für Meereswissenschaften. In this model a homogeneous plan-parallel cumulus cloud is implemented. For different solar zenith angles and cloud covers a relation to the pre-achieved results will be carried out. There is a distinctive bce in the model, too. Differences between the modelled and the calculated radiant fluxcs can be explained by the high simplified cumulus clouds.

Actions (login required)

View Item