CS265140B1 - Moisture Determination Method - Google Patents

Abstract

The problem of determining the moisture flow, used mainly in agro- and hydrometeorology, is solved, while the disturbing effects of instrumentation on the measurement process are significantly limited. The essence is that vertical pulsations of wind speed are measured and two independent air temperature measurements are performed at the same time, one measurement being dependent on air humidity and the other being independent of air humidity, then the measured air temperature values are correlated with vertical pulsations of wind speed.

Description

The present invention relates to a method for determining the moisture flow while reducing the interfering effects of instrumentation on the measurement process.

So far known methods of determination of moisture flow can be divided into direct methods and indirect methods. Indirect methods include profile and balance methods using different models. The direct process is based on potential evaporation from open water surfaces or evaporators. It is also known to determine the moisture flow by determining the vertical wind component and the turbulent changes in water vapor pressures.

A disadvantage of indirect methods is the considerable inaccuracy of the models resulting from the assumptions on which the models are based and thus impaired the accuracy of the moisture flow determination. A disadvantage of direct procedures is the different conditions between the measured areas and natural water bodies. The disadvantage of the method of determining the moisture flow based on the determination of the vertical wind component and the turbulent changes of water vapor is the necessity of using sensitive and expensive optical measuring instruments, which, in addition, their dimensions adversely affect the measurement.

The above-mentioned deficiencies are eliminated by the method of determining the moisture flow, which consists in measuring vertical pulsations of the wind speed and simultaneously making two mutually dependent measurements of the air temperature, one measuring the air humidity and the other measuring the air humidity. . Then the measured air temperature values are correlated with the vertical pulsations of the wind speed according to the equation

H = W ^J. t (i), where H is the heat flow, W'is the vertical pulsation of the wind speed and T'is the pulsation of the air temperature,

W ^J. T * is the mean value of the product W '. The moisture flow is then determined according to the equation

W ¹ . Th - W ¹ . Ti = 0.153

e. W

where Ta is the air temperature pulsation dependent on air humidity, Tr is the air temperature pulsation independent of humidity and is the vapor pressure pulsation.

An advantage of the method according to the invention is that the interference effects of the instrumentation are reduced to a minimum, thereby substantially increasing the accuracy of the measurement. The advantage is also the replacement of complex optical humidity measuring instruments with simpler and cheaper temperature measuring instruments, as can be seen from the following specific application.

Measurement of vertical pulsation of wind speed and measurement of air temperature dependent on air humidity based on the speed of sound propagation is performed by acoustic anemometer - thermometer, which works in real time. Air temperature independent of air humidity is measured using a resistance thermometer using a platinum wire of d - 20 mm diameter. The sensor signals amplified by the amplifiers are then applied to the correlator inputs. From the difference in correlators, the sums of moisture are obtained according to the following formulas. The dependence of the speed of sound propagation in the atmosphere on temperature and humidity is given by the equation.

Γ e 1 ^1/2 c = const. £ T (1 + 0.3192 / _p ) J (III), where c is the speed of sound, T temperature, e water vapor pressure, p air pressure. For the temperature Ta measured by an acoustic thermometer, it applies

Ta = T (1 + 0.3192 ^β / _ρ ) (IV)

The turbulent heat flow is then determined according to equation (I), determined for both the air temperature dependent on air humidity and the air temperature independent on air humidity.

According to equation (IV) it holds for the difference of both quantities

AND

W '. That - W '. T r = ^0f -3 ¹⁹² e. W'T '. (IN).

if we use the mixing ratio for water vapor and air temperature, we get from (V) equation (II). For T = 20 ° C, p = 1000 hPa, e = 15 hPa and βθ = 3,07 hPa we get

W '. Ta - W1 Tr = 0.695 e. W '(VI), which is a simplified equation (II).

The method according to the invention can be advantageously used in determining the moisture flows necessary for meteorology, in particular for agro- and hydrometeorology.

Claims (1)

Method for determining the humidity flow, characterized in that the measurement of vertical pulsations of the wind speed is carried out and at the same time two independent measurements of the air temperature are made, one measurement is dependent on the humidity and the other is independent of the humidity. of air correlate with vertical pulsations of wind speed according to the equation H = w '. Where H is the heat flow, W'is the vertical pulsation of the wind speed and T'is the pulsation of the air temperature, whereupon the moisture flow is determined according to the equation (cf. In ¹ -? - dl). W. Ta - W. Tr = 0.1531. W where Ta is the air temperature pulsation dependent on the air humidity and Tr is the air temperature pulsation independent of the air humidity.