# Relative humidity (table of values)

### Relative humidity

Relative humidity is the ratio (expressed in percent) pressure of water vapor in the air, to the vapor pressure, saturating the air at the same temperature.In practice, in most cases,the relative humidityis the ratio of weight of water vapor per unit volume of air (absolute humidity) to the weight of the saturated water vapor in the same amount of air and at the same temperature.

### Balance hygrometer

The lookup table is given in grams of water contained in 1 m3of air at saturation if the total pressure is 760 mm Hg.

 Temperature, ° C 0 1 2 3 4 5 6 7 8 9 0 4.84 5.18 5.54 5.92 6.33 6.76 7.22 7.7 8.21 8.76 10 9.33 9.93 10.57 11.25 11.96 12.71 13.5 14.34 15.22 16.14 20 17.12 18.14 19,22 20.35 21.54 22.8 24.11 25.49 26.93 28.45 30 30,04 31.7 33.45 35.27 37.18 39.18 41.3 43.5 45.8 48.2

### Aspiration hygrometer (psychrometer)

Apion (1835), August (1825) and others. Deduced relationships between (Pw-P) and (t-tw).

In meteorology, applied a simple expression

Pw-P = AH (t-tw).

Where tw0C denotes the wet bulb temperature, P (mm) - pressure of water vapor in air, Pw- vapor pressure, saturating the air at the temperature tw, H (mm) - barometric pressure, and A - constant.Thus,the relative humidityis 100 P/Ps, where Ps - denotes a saturated vapor pressure at the temperature t, reckoned on dry bulb.The value of A, which depends on the air speed of about wet bulb is equal to 0.00066 Assmann aspiration psychrometer and A = 0.00080 for Stevenson device used in the Meteorological Service.

### Table relative humidity (%) as measured with a psychrometer

Cited reference tables are devices with full (free) ventilation.The complete table for the temperature range from - 30 to 55 ° C and 30 ° C to 350 F.

 Dry bulb temperature, °C The difference between the readings of the dry and wet bulb (psychrometric difference), °C 0.50 1,00 1,50 2,00 2,50 3.00 3,50 4.00 5.00 6,00 7.00 -91) 85 71 - - - - - - - - - -81) 87 73 59 46 - - - - - - - -61) 88 76 64 52 40 29 - - - - - -41) 89 78 67 57 46 36 - - - - - -21) 90 80 70 61 52 42 33 25 - - - 0 91 82 73 65 56 48 39 31 - - - 2 92 84 76 68 60 52 45 37 22 - - 4 92 85 78 70 63 56 49 42 29 - - 6 93 86 79 73 66 60 53 47 635 23 - 8 94 87 81 75 69 63 57 51 40 29 18 10 94 88 82 76 71 65 60 54 44 34 24 10 20 30 40 50 60 80 100 120 140 15 90 80 71 61 52 44 27 12 - - 20 91 83 74 66 59 51 37 24 12 - 25 92 84 77 70 63 57 44 33 22 12

1) supercooled water (not ice) on the wet thermometer.

 Dry bulb temperature, ° C The difference between the readings of the dry and wet bulb (psychrometric difference), °C 20 40 60 80 100 120 140 160 180 200 250 30 86 73 61 50 39 30 21 13 5 - - 35 87 75 64 53 44 35 27 20 13 7 - 40 87 76 66 56 47 39 32 26 20 14 1 45 88 77 67 59 51 43 36 31 25 19 7 50 89 79 70 61 53 46 40 35 29 24 12 55 90 80 72 64 56 49 42 37 32 27 16 20 40 60 80 100 150 200 250 300 350 400 60 90 81 73 65 58 42 30 19 11 4 - 70 91 83 76 69 62 47 35 25 17 11 5 80 92 85 78 71 65 51 40 30 21 15 10 90 92 86 79 73 67 54 43 33 25 19 14 100 93 86 80 74 69 56 46 37 29 22 17

### Table relative humidity - Wet iced1)

 Dry bulb temperature, ° C The difference between the readings of the dry and wet bulb (psychrometric difference), ° C -0.10 0,00 0.50 1,00 1,50 2,00 2,50 3.00 3,50 4.00 -18 64 62 47 33 - - - - - - -16 67 66 51 37 24 - - - - - -14 71 69 56 42 30 17 - - - - -12 77 75 62 49 36 24 - - - - -10 83 82 68 55 42 30 17 - - - -8 90 89 75 62 48 36 25 16 - - -6 95 94 81 68 56 45 34 25 16 - -4 98 97 85 74 63 53 42 32 24 17 -2 100 98 88 78 68 58 48 39 31 24 0 - 100 90 80 71 62 53 44 37 31

1) Relative humidityis defined as the ratio of the absolute humidity calculated per unit volume to the amount of water vapor in the air which is in equilibrium with water (but not ice) with dry bulb temperature.