Д. Т. Бакаловъ. Метерологическитѣ условия въ Ихтиманско

Д. Т. Бакаловъ. Метерологическитѣ условия въ Ихтиманско

D. T. Bacaloff. The meteorologicаl conditions of Ichtiman

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THE METEOROLOGICAL CONDITIONS OF ICHTIMAN

The meteorological Data of Ichtiman are examinated for the purposes both of Climatology and of Aeronautics.

With regard to the regime of the air-temperatures we mark a small lowering of their mean values (see Table I) in comparison with the airtemperatures reduced to the niveau of Ichtiman (see Table II). The explanation of this lowering of the mean values is to be found in the existance of very frequent ground inversion.

A case of such an inversion is examinated in full in connection with the formation of fogs (popular “sinjawitza”, I.e. the blue fog).

Another results of these inversion is the great number of freezing days which are not characteristic for this level (see Table V). The amount of the precipitations is smaller than that of the adjacent hills.

Assigning the therm “intensity” to the Ratio of amount per month, to the number of days with precipitations also taken per month; and assigning the term “density” to the Ratio of number of days with precipitations taken per month to the total number of days for the same month, we can distinguish tree types of precipitations (see Table VI):

1. summerlike with great intensity > 6.0 but smaller density;
2. winterlike - with the smallest intensity (<4.0) but moderate density (<3.0);
3. springlike - with moderate intensity but high density (>0.3)

A great number of days are found to have snow-cover (see Table VII) That snow-cover keeps more than 20 days longer than it does at Bojurishte near Sofia.

A thunderstorm formed over the Rila Mountains and having passed over the hills encircling the field of Ichtiman is studied in full (see fig.4).

The nebulosity of Ichtimna is found to be greater than that of other open fields (Sofia, Plovdiv) (see Table X).

The most frequent hights of low clouds during the cold six months of the year are found to be between 300 and 1000 m (see Table p 188).

The dominating wind directions are West and East (see Table XIII).

Because the west and east sides of the Field are surrounded by mountains and hills, the abovementioned winds can arise as local breezes.

By the help pf the formulae of Baldit for horisontal and vertical limits of the zones of wind disturbances caused by mountains, there are drown the outlines of two layers of such disturbances (see fig. 6) and the outline of whirls (see fig.7).

The general deduction from the meteorological data of the Ichtiman field is that the meteorological elements are strogly influenced by the ground.

D. T. Bacaloff

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