humidity


The transition back to Joshua Tree from a wetter climate can be rough. For me, the worst was returning in December 2000 after a year on Maui. It was so cold and dry it felt like I was living on the moon. It took a couple weeks to acclimate.

I just spent 10 weeks traveling and camping for Not Back to School Camp, almost all in wet areas.¬†The last few weeks were in Vermont, with humidity hovering around 99%. The damp started to get to me. And the cold, and the rain. It was really nice in a lot of ways–I love the staff and campers at NBTSC like crazy, and the fall foliage was spectacular when the sun would occasionally break through the clouds–but I was definitely looking forward to my dry, sunny, warm home.

Now that I’m here, I remember that it can take a while before dry, sunny, and warm seems as pleasant as it sounds. My skin feels dry. My lips and mucous membranes feel dry. It’s hard to keep hydrated. The sunlight seems harsh and temperatures I normally call warm, like 85F, feel unpleasantly hot. I’m no longer used to sweating. I notice the dust more, too.

I know I’ll feel better in a few days, and mostly it is just a matter of waiting it out. There are some things that can help, though:

1) Drive or take overland transport of some sort. (Reanna suggests walking to really slow things down.) Flying makes the transition more abrupt and uncomfortable.

2) Use a humidifier for a while, especially at night.

3) Drink more water than is comfortable. Remember that you are exhaling water vapor each time you breathe.

4) Cover up in the sun. Lily-white skin burns quickly

5) Take it easy for a while. Rest it out.

Reanna is from the Pacific northwest and I grew up in Joshua Tree, CA, where we are currently living. We have an ongoing conversation about humidity here because having grown up in a wet climate, she is vigilant for the ways that moisture in the air decomposes things. “If we don’t keep it warm in here, won’t condensation damage the books?” No, it won’t, and probably wouldn’t even if we had a constantly boiling pot of water. The only place I’ve ever seen mildew in Joshua Tree is in one of our bathrooms which, until very recently, had no windows and no fan. This was not aggressive mildew either, just noticeable every once in a while. “If the roof of the trailer has leaks, won’t there be tons of mold in the walls?” No, not likely, because even if rain was pouring right through the trailer, it would be completely dry again within hours.

I have never tracked humidity levels before, so while I knew that Joshua Tree was dry, I didn’t know what level of humidity qualified as dry. I also didn’t fully understand the different measurements of humidity that are floating around out there. The short version of that story is that there are three units of humidity: absolute, specific, and relative humidity. Absolute humidity is grams of water per kilogram of moist air and specific humidity is kilograms of dry air. Relative humidity is more complicated. If I understand correctly (if incompletely) it is the ratio between 1) the pressure that the water vapor in a given amount of air would exert on the insides of a container, should it somehow be trapped there without its accompanying dry air, and 2) the pressure below which water would start condensing out of the air. Relative humidity is the measure of humidity that you usually see in weather reports, partly because it takes into account temperature–at lower temperatures, air holds less water.

Here are some cities with different levels of relative humidity, to give a sense of where we are in Joshua Tree. I’ll also include precipitation. (Data is from Weather Underground¬†unless otherwise noted.)

Seattle, WA, 2011: High 99%, Low 34%, Average 82%, Precipitation 12.92 inches

Honolulu, HI, 2011: High 96%, Low 18%, Average, 65.6% Precipitation 23.82 inches

Joshua Tree humidity, 2011: High = 83%, Low = 10%, Average = 30.7%, Precipitation 1.53 inches

Las Vegas, NV, 2011 (the driest city in the US): High 98%, Low 2%, Average 28.7%, Precipitation about 2.5 inches (precipitation according to climatestations.com)

Kolkata, India one of the most humid cities in the world, on July 15, 2011: High 94%, Low 64%, Average 84%, Precipitation 0.0 inches

And Kartoum, Sudan (Sahara desert), on January 4, 2011: High 43 %, Low 10%, Average 24%, Precipitation .51 inches

Nathen, Reanna, Quilt, Desert