STUDY OF THE EFFECTIVE TEMPERATURE OF A SOLARIUM AT THE LAKE SHIRA RESORT

A. A. VOROB'EV and D. N. POPOV

Introduction

A major shortcoming of ordinary therapeutic practice is the fact that the duration of patients’ sun baths is determined only by intervals of time, without any accounting for the quantity of radiant energy falling on the surface of the skin. Meanwhile, the amount of radiant energy perceived by the skin surface can be extremely different over the same intervals of time during the taking of sun baths. In addition to the factors analyzed by us in the article “Study of Solar Radiation at the Shira Resort,” which determine the amount of radiant energy falling on the earth’s surface, the process of perception of solar radiation by the skin is connected with the processes of cooling of the body by wind and by evaporation of moisture from the surface of the body. The energy perceived by the skin surface over a certain interval of time is, in essence, the difference between the amount of energy delivered by solar radiation and the amount of energy expended on the process of evaporation and carried away by air currents.

At a relative humidity of 100% and complete absence of wind, the energy losses from the incident radiation would be determined only by the processes of reflection of radiant energy by the skin and by radiation. These factors are more or less constant and cannot be the cause influencing changes in the physical conditions under which sun baths are taken.

Cooling of the skin, caused by wind and evaporation, leads to the fact that temperature sensations are perceived by the nervous tissue of the skin as somewhat less than those usually felt in the absence of wind and evaporation of moisture. The thermal effect under various combinations of air temperature, humidity, and motion of the atmosphere is customarily expressed (conventionally) in degrees of temperature and, thus, in a single figure to give a definite characterization of the influence of complex combinations of temperature, humidity, and wind speed on the heat loss of the human organism. This temperature is called the effective temperature. Recently, Soviet climatologists have included in the complex of effective temperature (in climatology) a fourth factor—the magnitude of the radiation intensity.

For the transition from the temperature shown in the shade to the effective temperature, it is necessary to introduce corrections that lower the thermometer readings by amounts the greater, the greater the wind speed and the lower the relative humidity. To determine the effective temperature, the aerosolarian of the Yalta Tuberculosis Institute compiled Tables 1 and 2, according to which the effective temperature is determined by subtracting from the air temperature in the shade two corrections—for humidity and for wind speed¹.

The tables are valid within the range from 15 to 30°C.

Table 1

Correction for relative humidity (to be subtracted)

Table 2

Correction for wind speed in meters per second
(to be subtracted)

The effective-temperature interval from 16 to 24° is pleasantly perceived by the human skin and, for taking sun baths, is a comfortable interval. An effective temperature below 16° produces unpleasant, painful sensations of cold, while prolonged perception by bare skin of an effective temperature above 24° is difficult to tolerate, producing a sensation of burning.

Observations of the Effective Temperature of the Solarium

Observations were conducted¹ of the daily course of change in the effective temperature of the solarium of the Shira resort during the period of operation of the actinometric station, i.e., from June 24 to July 14, 1941.

Some results of the observations are shown in the form of graphs in Figs. 1 to 8. In all these figures the interval of comfortable temperature is marked by two horizontal dashed lines. Vertical dashed lines delimit the time intervals during which the effective temperature proves to be comfortable and uncomfortable for taking sun baths.

Fig. 1 shows the diurnal course of the change in effective temperature on June 24. In the first half of the day, sharp gusts of wind were observed, causing brief but considerable drops in effective temperature. The second half of the day, windless, gives a smooth course of the curve. Intervals of time with a comfortable temperature occurred from 6:45 to 12:30 and from 16:30 to 20:00.

Fig. 1

Fig. 2 characterizes the diurnal course of the change in effective temperature on an almost windless day, June 28, with cloudiness in the first half of the day and a sunny sky in the second. A comfortable effective temperature was observed in the intervals of time from early morning until 13:00 and from 16:30 until late evening.

Fig. 2

Fig. 3 presents an interesting case of the course of the change in effective temperature on July 10. After a cold, windy night, a clear, completely calm sunny day set in. Nevertheless, for taking sun baths

Fig. 3

Fig. 4

Fig. 5

it proved to be of little convenience. Before 9 o’clock the effective temperature was below the comfort level, while already after 10:30 a.m. it was above the comfort level and remained so until 7 p.m.

Fig. 6

Fig. 4 (June 30—a day with slight cloudiness and a light wind) gives us a case when, in fact, we had a comfortable temperature throughout the entire day.

Among the features of the microclimate of the Shira resort one should include the fact that on overcast, strongly windy days—for example, July 3—the effective

Fig. 7

temperature may show even for July extraordinarily large decreases, down to 8° (Fig. 5). Fig. 6 illustrates an example when, throughout the entire day of July 6, the effective temperature was below the comfort level. With sharp gusts of wind the decrease reached 6 and even 5°. At such a temperature one has to wear a coat.

On the next day, after cloudy and especially rainy days, a comfortable temperature occurs only by 9–10 o’clock, despite sunny weather. Figs. 7 and 8 show precisely such cases.

Fig. 8

Conclusions

1. A general survey of the totality of the daily course of changes in effective temperature leads to the conclusion that the time with a comfortable temperature is distributed irregularly over the course of the day. It depends not only on the state of the weather on the given day, but also on the day preceding it.

2. The unstable weather regime dictates the necessity of having at the solarium a permanent actinometric station, which would make it possible to dose sun baths on the basis of the amount of incident energy, with monitoring of the effective temperature.

In conclusion, we consider it a pleasant duty to express our profound gratitude to the scientific director of the Shira resort, Prof. K. N. Zavadovsky, for a number of valuable instructions, and to Docent D. D. Saratovkin for assistance in processing the results obtained.

1. The observations were made by D. N. Popov. ↩↩