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 (P_w-P) and (t-t_w).

In meteorology, applied a simple expression

P_w-P = AH (t-t_w).

Where tw0C denotes the wet bulb temperature, P (mm) - pressure of water vapor in air, P_w- vapor pressure, saturating the air at the temperature tw, H (mm) - barometric pressure, and A - constant.Thus,the relative humidityis 100 P/P_s, where P_s - 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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Relative humidity (table of values)