Vol. 120, No. 4 * Pages 353–430 * October - December 2016

Some time variation properties of the planetary imbalance are shown by using satellite measured radiation budget data. The covered period is 1962–2014. The data have been collected from publications and data bases. The solar incom part of the budget has been homogenized using new total solar irradiance (TSI) values. The positive imbalance increases as well as the time delay between the incoming and outgoing radiation.

In Poland, no clear tendencies have been detected in multi-year trends in precipitation sums. However, the number of days with precipitation has increased significantly. Therefore, we analyzed changes in the structure of days with precipitation, i.e., trends in the percentage of days with different ranges of daily precipitation sums. The precipitation data were from 1971–2010, from four stations in Southern Poland representing agricultural areas (Stare Olesno, Glubczyce, Lapanow, and Tuchow). Statistically significant upward trends (1–9 days per 10 years) and low variability were found for the number of days with daily precipitation sums up to 5 mm, mainly in the cold half of the year, and downward trends were found for days with 20–30 mm of precipitation (1 day per 10 years), with high variability. Comparison with the results of previous studies shows that the increase in the number of days with precipitation is not linked to a significant increase in precipitation sums.

Nowadays, early warning and alarm for high impact weather situations becomes more and more important. Besides deterministic model forecasts, using ensemble forecasts gets increasing attention, but in case of the convective events, probabilistic forecasts have not been widely used. Due to the fact that convective events are very changeable in space and time, probabilistic approach can have a lot of advantages. Current horizontal resolution of the global ensemble models is around 30 km, so we cannot aim to focus on small scale convective events, but focusing on frontal zones and extended squall lines can be possible. We attempt pioneering steps to develop new methods and tools to support early warning based on ensemble (ENS) forecasts of the European Centre for Medium-Range Weather Forecast (ECMWF). We focus on the forecast probabilities of three main components generating convection.

The main objective of this article is to identify the pressure conditions conducive to the occurrence of heat waves in southeastern Europe. Before this objective could be achieved, the spatial and temporal variability of the occurrence of heat waves in the region were determined. This article defines a hot day as a day of maximum temperature (Tmax) above the 95th annual percentile, and a heat wave is considered to be a sequence of at least 5 such days. The study is based on the data of 21 stations from the period 1973–2010. In the discussed period, at all stations, a statistically significant increase in Tmax and the number of hot days were observed. The total number of heat waves fluctuated from 25 in Burgas to 48 in Drobeta-Turnu Severin, Skopje, and Split, while the sum durations of heat waves ranged between 173 days in Botosani and 414 in Split. Heat waves in southeastern Europe occurred most often when a ridge of high pressure lay over Europe. This system caused the inflow of continental air masses from the northeast or east. An alternative source of air masses causing heat waves was advection from the south.

In this paper, the effect of two types of water based cooling methods of amorphous silicon (a-Si) modules and a panel was studied in the summer period. One new (unused) and some 11-year-old a-Si modules and a panel with two different cooling techniques (sprinkling and flowing water cooling) were examined. Our reference for the evaluation was an unused a-Si module without any cooling. The results were analyzed from both statistical and technical aspects.