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Diurnal timing of warmer air under climate change affects magnitude, timing and duration of stream temperature change

Authors

  • Mousa Diabat,

    Corresponding author
    1. College of Earth, Oceanic, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA
    2. Water Resources Graduate Program, Oregon State University, Corvallis, Oregon, USA
    • Correspondence to: Mousa Diabat, College of Earth, Oceanic, and Atmospheric Sciences, and Water Resources Graduate Program, 104 CEOAS Admin Bldg., Oregon State University, Corvallis, OR 97331-5503, USA.

      E-mail: diabatm@science.oregonstate.edu

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  • Roy Haggerty,

    1. College of Earth, Oceanic, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA
    2. Institute for Water and Watersheds, Oregon State University, Corvallis, Oregon, USA
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  • Steven M. Wondzell

    1. USDA Forest Service, Pacific Northwest Research Station, Corvallis, Oregon, USA
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Abstract

Stream temperature will be subject to changes because of atmospheric warming in the future. We investigated the effects of the diurnal timing of air temperature changes – daytime warming versus nighttime warming – on stream temperature. Using the physically based model, Heat Source, we performed a sensitivity analysis of summer stream temperatures to three diurnal air temperature distributions of +4 °C mean air temperature: i) uniform increase over the whole day, ii) warmer daytime and iii) warmer nighttime. The stream temperature model was applied to a 37-km section of the Middle Fork John Day River in northeastern Oregon, USA. The three diurnal air temperature distributions generated 7-day average daily maximum stream temperatures increases of approximately +1.8 °C ± 0.1 °C at the downstream end of the study section. The three air temperature distributions, with the same daily mean, generated different ranges of stream temperatures, different 7-day average daily maximum temperatures, different durations of stream temperature changes and different average daily temperatures in most parts of the reach. The stream temperature changes were out of phase with air temperature changes, and therefore in many places, the greatest daytime increase in stream temperature was caused by nighttime warming of air temperatures. Stream temperature changes tended to be more extreme and of longer duration when driven by air temperatures concentrated in either daytime or nighttime instead of uniformly distributed across the diurnal cycle. Copyright © 2012 John Wiley & Sons, Ltd.

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