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The daily fluctuation humidity
If the relative humidity is known, in combination with a dry bulb moisture content can be established. Meteorological data usually include a measurement of relative humidity at noon, at the moment, not far from the maximum temperature, even if the information is not more comprehensively stored. If time measurement of humidity does not coincide with the highest average daily temperature (about 15.00 h) equation (5.4) can be used to estimate the temperature at the same time as the moisture measurement. This will set the humidity of outside air. In the absence of changes of the weather, we can assume that the moisture content will remain constant during the day until the air has cooled to its dew point. Although this is not entirely true, dew point graphically in Fig. 5.2 still remains fairly constant, providing a partial verification.
In fact, it's hard to measure the dew point with a high precision, except in the laboratory, and the inconsistency of values in Fig. 5.2, can probably be attributed to bias. In hot weather, vegetation releases a large part of its moisture in the air, dehydration in the process.
This causes an increase in the moisture content of the air, although no changes in the weather happened. However, under constant moisture throughout the day, relative humidity will grow, as of the day and evening pass and the night comes, because of the fall of the dry bulb temperature. As the cooling air continues dew point is not achieved, as the air is saturated further fall in temperature will cause the dew and fog in the shape, reduce the moisture content in the atmosphere. With the dawn and the sunrise, the increase of temperature and relative humidity falls a little dew boiling, as the morning goes on. Eventually all the dew disappears, and moisture content back into his assumed constant value of the previous day.
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