The results of observations of the umbral flashes in two sunspots are reported. The sunspots differ in their morphological properties (evolution rates and activity levels) and in observation conditions (heliocentric distances). The oscillation parameters of the two sunspots do not coincide. The most significant differences are pronounced in the phase relations and amplitudes of observed oscillations.

Emission core widths of K Ca H line in the umbra and penumbra of 9 sunspots and in their vicinity are measured. All sunspots are located near the solar disc center. Data on variation of widths Wt~ along the 'mean' sunspot radius are obtained. Values W~ in the umbra and penumbra centers are equal or somewhat less than on stars of the same luminosity.

The shapes of the Ca ii H and K lines in sunspot umbral spectra vary from single asymmetric peaks near the centre of the disk to almost symmetric double peaks at the limb. In addition, there are other differences in the behaviour of both H and K lines in sunspots compared to the quiet Sun. The whole complex of the phenomena observed can not be explained by large scale chromosphere motions. Instead, a satisfactory model reproducing in detail peculiarities of the umbral emission reversals contains a cloud of emitting and absorbing gas located above the chromosphere, which flows into the sunspot. The radiation field parameters in such a cloud are consistent with the concept of weak quiescent prominences above the umbra.

An inversion of line profiles H and K Ca ~I in the umbra of two sunspots is performed. By means of a numerical experiment, a tentative study of possible application of the method of intercomparison of lines in the multiplet (Goldberg's method) is made in cases when the condition of source function equality in multiplet is not fulfilled.It is found that the source functions of H and K lines in the sunspot umbra vary in a monotonous way. Their ratio in the layers for which measured values of A21) are available differs from unity. In the region of the lower chromosphere under consideration, the Doppler width is decreasing with height.

By means of an inversion of H and K Ca II line profiles the temperature and electron density in the chromosphere above the umbrae of two sunspots have been estimated. The temperature gradient 5 K km -1 exceeds the corresponding values in both quiet regions and plages. At a height of about 1500 km the umbra becomes hotter than the quiet region. At a temperature of about 10 000 K the temperature gradient increases sharply. The electron density at 1500 km is approximately the same as that in the quiet chromosphere at the same height.