Build Your Own Weather Station

Grade Level: 6-12

Source: "Build Your Own Weather Station," DiscoverySchool.com, 2005. Adapted with permission.

Background

Atmospheric scientists study weather processes, the global dynamics of climate, solar radiation and its effects, and the role of atmospheric chemistry in ozone depletion, climate change, and pollution. They observe what's going on in our atmosphere today and compare it to records from years past. To monitor the weather, atmospheric scientists use highly specialized instruments that measure rainfall, wind speed and direction, humidity, and atmospheric pressure. You can measure these at your home or school. Begin creating a weather station by building a psychrometer, also called a hygrometer, to measure the relative humidity.

Materials

Two alcohol-filled air thermometers (they must read exactly the same temperature when placed side by side out of direct sunlight)
Clear packing tape
Cotton shoelace (the hollow type)
One- or two-liter bottle (label removed)
Water (distilled is best but tap will do)
Thread
Awl
Relative humidity chart

Procedure

Have an adult punch a hole in the side of the bottle about an inch from the bottom. Heating the awl will make a perfect hole. The same thing can be done with a hot nail held with tongs. Use great caution when doing this so you don't burn yourself or others. When you've made the hole, place the hot object in cold water.

Cut the tips off the shoestring. Cut about two inches of shoestring and slip it over the bulb of one of the thermometers. Carefully tie it in place with thread.

Cut a small piece of packing tape. Position the bulb of the shoestringed thermometer about 1/8 inch over the hole. Be sure the top of the thermometer is aligned with the top of the bottle. Tape the thermometer to the bottle. Tape the other thermometer parallel to the first one and about 1/4 inch away. Put a strip of tape around the bottle and both thermometers to make sure they don't fall off.

Push the shoelace through the hole. Put room-temperature water in the bottle until it reaches just below the hole.

Wait five to 10 minutes, and read both thermometers. There will be a difference in the two. Use the chart below to calculate the relative humidity.

Keep a record of the daily humidity for a few weeks. Next to your entries, describe the way you feel on those days.

The dry-bulb temperature can also be used to record the air temperature!

Complete your weather station by making a rain gauge, barometer, wind vane, and anemometer from the instructions at http://school.discovery.com/lessonplans/activities/weatherstation/.

Weather stations traditionally are housed in louvered sheds. Thermometers must be kept out of direct sunlight, but a barometer can be kept indoors or on a screened porch. If there are overhangs at your home or school, you could put the instruments there.

Air Temp.	Difference between wet- and dry-bulb readings in degrees F
(Dry Bulb)	1	2	3	4	5	6	7	8	9	10	15	20	25	30	35
20	85	70	55	40	26	12
25	87	74	62	49	37	25	13	1
30	89	78	67	56	46	36	26	16	6
35	91	81	72	63	54	45	36	29	19	10
40	92	83	75	68	61	52	45	37	29	22
45	93	86	78	71	64	57	51	44	38	31
50	93	87	80	74	67	61	55	49	43	38	10
55	94	88	82	46	70	65	59	54	49	43	19
60	94	89	84	78	73	68	63	58	53	48	26	5
65	95	90	85	80	75	70	66	61	56	52	31	12
70	95	90	86	81	77	72	68	64	59	55	36	19	3
75	96	91	86	82	78	74	70	66	62	58	40	24	9
80	96	91	87	83	79	75	72	68	64	61	44	29	15	3
85	96	92	88	84	80	76	73	69	66	62	46	32	20	8
90	96	92	89	85	81	78	74	71	68	65	49	36	24	13	3
95	96	93	89	85	82	79	75	72	69	66	51	38	27	17	7
100	96	93	89	86	83	80	77	73	70	68	54	41	30	21	12
105	97	93	90	87	83	80	77	74	71	69	55	43	33	23	15
110	97	93	90	87	84	81	78	75	73	70	57	46	36	26	18
115	97	94	91	88	85	82	79	76	74	71	58	47	37	28	21