Non-Gaussian Temperature Distribution Tails in Observations and Models: Implications for Future Extreme Temperature Exceedances

观测和模型中的非高斯温度分布尾部：对未来极端温度超标的影响

• 批准号: 1621554
• 负责人: Paul Loikith
• 金额: $ 41.57万
• 依托单位: Portland State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-15 至 2022-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1621554&HistoricalAwards=false
• 关键词: Non; Gaussian; Temperature; Distribution; Tails

It is reasonable to expect more heat waves in a warmer climate, but it is not clear how many more heat waves should occur for a given mean warming. Days with heat waves at a specific location can be counted by determining the temperature for which 95 percent of recorded temperatures are below it, referred to as the 95th percentile temperature. Heat wave days can then be defined as exceedances of the 95th percentile temperature, and they occur by definition on the warmest five percent of days. We can then ask how many additional days are warmer than that today's 95th percentile temperature when climate warms, with the expectation that the answer will be more than five percent of days. Previous work by the PIs suggests that the increase in heat wave days for a given mean warming can be highly variable from region to region, for example their results suggest a greater increase in heat waves in western states and the northern midwest than in the southeast US. This project seeks to determine how applicable these result are for anticipating increases in heat wave frequency, and to understand the fundamental processes which produce regional differences in the increases.Estimates of change in extreme temperature occurrence often assume a "normal", or Gaussian, temperature distribution, in which the average temperature is the same as the 50th percentile (or median) temperature, which is centered between the 95th and the 5th percentile temperatures. If instead the median temperature is shifted toward the 95th percentile, so that cold exceedances are more extreme than warm exceedances, the distribution has a "short tail" on the warm side. The PIs show that if warming amounts to an overall shift in the distribution, meaning that if the 5th, 50th, 95th and other percentile temperatures all increase by the same amount, there will be a greater increase in heat wave occurrence for a short tailed distribution than for a normal distribution. Thus it is possible to gain insight into warming-induced increases in heat wave days by understanding the processes that give rise to short temperature tails in present-day climate. The PIs hypothesize, on the basis of the large-scale spatial patterns of regions of short and long tails in present-day climate, that the spatial variations in exceedance change are primarily the result of meteorology and atmospheric circulation rather than local factors such as the dryness of the soil. This hypothesis is tested using observations and climate model simulations, and differences between present-day and projected future climate in model simulations is used to assess the extent to which analysis of present-day tails can account for warming-induced exceedance change.The behavior of temperature extremes is of practical as well as scientific interest given the hazards to human and natural systems posed by extreme heat. Better guidance on changes in heat wave occurrence would be valuable for decision makers in areas including agriculture, forestry, health services, and urban infrastructure. The work has educational broader impacts through its connection with a Research Experiences for Undergrauduates (REU) site at Oregon State University, and it also provides support and training for a graduate student.

在温暖的气候中期望会有更多的热浪是合理的，但是尚不清楚给定的平均变暖应该发生多少热浪。 可以通过确定95％记录的温度低于其低于其的温度（称为第95个百分位温度）的温度来计数特定位置的热浪天数。 然后可以将热浪天数定义为超过第95个百分位温度的超过，并且按定义在最温暖的天数中发生。 然后，我们可以问一下，当气候变暖时，比今天的第95个百分位温度要温暖几天，并期望答案将超过几天以上。 PIS的先前工作表明，给定平均温暖的热浪天数在各个区域之间可能是高度可变的，例如，它们的结果表明，西方州和中西部北部的热浪增加了比美国东南部的增长。 。该项目旨在确定这些结果在预期热浪频率增加的情况下的适用程度，并了解在增加增加区域差异的基本过程。分布，平均温度与第95个百分位数和第5个百分位温度之间的50％（或中位数）温度相同。 相反，如果中位温度转移到第95个百分位数，以使其超过超过超过暖度，则分布在温暖的一侧具有“短尾巴”。 PIS表明，如果变暖量达到分布的总体变化，这意味着，如果第五，第50，95和其他百分位温度都增加了相同的量，那么短尾巴分布的热浪出现将有更大的增加而不是正态分布。 因此，通过了解在当今气候下导致短温度尾巴的过程，可以深入了解热浪天数的变暖引起的增加。 在当今气候下，PI在短尾巴区域的大规模空间模式下假设，超出性变化的空间变化主要是气象和大气循环的结果，而不是局部因素，而不是诸如诸如局部因素的结果土壤干燥。 使用观测和气候模型模拟对此假设进行了检验，并且使用模型模拟中当今和预期的未来气候之间的差异用于评估当今尾巴的分析可以解释变暖引起的超级变化。鉴于极端热量对人类和自然系统的危害，极端温度既实用又具有科学意义。 对热浪发生变化的更好指导对于包括农业，林业，卫生服务和城市基础设施等领域的决策者来说是有价值的。 这项工作通过与俄勒冈州立大学的本质上的研究经验（REU）网站的联系来产生更广泛的影响，并且还为研究生提供了支持和培训。