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THE A T M O S P H E R I C R E S E R V O I R Examining the Atmosphere and Atmospheric Resource Management The Heat Index By Mark D. The Schneider physiological basis for Temperatures the creation and humidity of the HI is combined to that moist make weather air doesn’t conditions allow our oppressive across bodies to cool North Dakota this themselves as summer. There quickly as with were days when dry air. This the heat felt is explained overbearing and by slower air conditioning evaporation became more of (and thus a necessity than cooling) of a luxury. At first sweat and observation, the perspiration temperatures in moist air themselves versus drier Our bodies feel the greatest weren’t that unusual, with 85 to air. If we’re unable to cool off, effects of heat when high humidity is 95 degree readings for daily highs. conditions such as heat cramps and combined with warm temperatures. However, the dew points, which are even heat stroke can occur. These We measure this using what’s called an indication of the moisture in the health conditions are very serious the Heat Index (HI). The National atmosphere, were the highest seen in and the NWS issues Excessive Weather Service (NWS) defines the many years. Heat Outlooks, Watches, Warnings, HI as: “an accurate measure of how and Advisories when conditions are hot it really feels when the Relative Dew points during an average favorable for dangerous heat. Humidity (RH) is added to the actual North Dakota summer typically reach air temperature.” The HI graphic 65 to 70 degrees. This summer, The HI on many July afternoons shows the “feels like” temperatures at however, we experienced dew points soared beyond the century mark various temperatures and humidities. most commonly seen along the U.S. and in some cases, dangerously As you can see, dangerous HI can Gulf Coast. Several locations in the approached 120 degrees. So if you occur at temperatures as low as the state recorded dewpoint temperatures think that the 90-degree heat this mid-80s if the humidity is high. in the low 80s in the middle of July, summer felt warmer than normal, almost unheard of in this part of you weren’t just imagining it. There are other formulas to the country. Reasons for this above compute HI as well. Environment normal moisture include evaporation Canada computes HI using dew Atmospheric Resource Board from saturated soils and vegetation North Dakota State Water Commission point temperatures instead of RH across the state and weather patterns, 900 East Boulevard, Bismarck, ND 58505 as its measurement of moisture. (701) 328-2788 • http://swc.nd.gov which frequently brought moist Both indices are very good at southerly flow from the central plains. ND Weather Modification Association approximating how the outside air PO Box 2599, Bismarck, ND 58502 actually feels to us. (701) 223-4232 North Dakota Water ■ September 2011 19.

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The Relative Contributions of Temperature and Moisture to Heat Stress
1 The Relative Contributions of Temperature and Moisture to Heat Stress 2 Changes Under Warming ∗ 3 Nicholas J. Lutsko 4 Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA, USA ∗ 5 Corresponding author address: Nicholas Lutsko, [email protected] 6 E-mail: [email protected] Generated using v4.3.2 of the AMS LATEX template 1 ABSTRACT 7 Increases in the severity of heat stress extremes are potentially one of the 8 most impactful consequences of climate change, affecting human comfort, 9 productivity, health and mortality in many places on Earth. Heat stress results 10 from a combination of elevated temperature and humidity, but the relative con- 11 tributions each of these makes to heat stress changes have yet to be quantified. 12 Here, conditions on the baseline specific humidity are derived for when spe- 13 cific humidity changes will dominate heat stress changes (as measured using 14 the equivalent potential temperature, qE), and for when temperature changes 15 will dominate. Separate conditions are derived over ocean and over land, in 16 addition to a condition for when relative humidity changes dominate over the 17 temperature response at fixed relative humidity. These conditions are used to 18 interpret the qE responses in transient warming simulations with an ensemble 19 of models participating in the Sixth Climate Model Intercomparison Project. 20 The regional pattern of qE changes is shown to be largely determined by the 21 pattern of specific humidity changes, with the pattern of temperature changes 22 playing a secondary role. This holds whether considering changes in mean 23 summertime qE or in extreme (98th percentile) qE events.
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Wet Bulb Globe Temperature Faqs
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Heat Index Climatology for the North-Central United States
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The Heat Index "Equation" (Or, More Than You Ever Wanted to Know About Heat Index)
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Vocabulary Using Science Words Humidity (Hyoo MI Di Tee) 1
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