Wednesday 13 December 2017
Solar radiation, sunshine duration and cloud cover of Hungary

The energy of the Sun that reaches the surface of the Earth is the basic of the climate. The spatial distribution of the irradiation is defined by the latitude and the cloud cover. In Hungary, there is only small latitude distance, therefore, cloud cover plays a key role.

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Figure 1.
The average annual global radiation (MJ/m2) in Hungary (20002009)

By global radiation we mean the sum of the direct radiation of the Sun and the diffuse radiation coming from the sky. In Hungary, the southeastern parts have the highest irradiation values (Fig. 1), the region of Szeged reaches 48004900 MJ/m2, also, the global radiation exceeds 4500 MJ/m2 in large areas. The lowest irradiation values are around the northern mountains, here less than 4300 MJ/m2 values could occur.

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Figure 2.a. The average monthly values of global radiation
of Hungary, based on the 19982009 period

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Figure 2.b. The average monthly values of cloud cover
of Hungary, based on the 19712000 period

The most radiation is received in July - though the daylight does not last as long as in June and the Sun is lower at noon, the amount of cloud cover is less in July than in the beginning of the summer (Fig. 2). The cloudiest weather and the short days make December with the lowest irradiation.

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Figure 3.
The average annual sunshine duration (hours) in Hungary based on the 19712000 period

By sunshine duration we mean the amount of time when the surface receives direct radiation. The factors influencing sunshine duration are the astronomically possible sunshine duration, orography and cloud cover - the latter one has a stronger effect than the irradiation itself.

In Hungary, the most sunshine with more than 2000 hours a year is common in the southern and southeastern parts, while the least sunny regions are in the northern and northeastern parts, and around the western borders, with less than 1800 hours (Fig. 3).

In winter, the highest mountains receive one and a half times as much sunshine as the plains, since in winter the inversion is a common phenomena (when the mountains rise above the fog covering the lower regions). However, in summer they have 10 percent less sunshine as the lower regions, because of the more cloudy and wet weather. December is with the least sunshine, while the maximum duration is in July (Fig. 4).

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Figure 4.
The average monthly values of sunshine duration in Hungary
based on the 19712000 period