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

7.70

8.21

8.76

10

9.33

9.93

10.57

11.25

11.96

12.71

13.50

14.34

15.22

16.14

20

17.12

18.14

19,22

20.35

21.54

22.80

24.11

25.49

26.93

28.45

30

30,04

31.70

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.


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