Variability and Predictability of Near-Surface Winds

地球表面附近的空气运动最熟悉的特征是它的可变性。虽然日或季节时间尺度的变化是有规律的，但大多数近地面风变率是不规则的——从短时间尺度湍流波动到由大尺度天气和气候过程驱动的长时间尺度变化。了解近地面风的可变性很重要，因为它们是大气与陆地或海洋表面之间质量、能量和动量交换的主要控制因素；风能是一种重要的可再生能源；极端的风会对自然环境和建筑环境造成破坏。

The most familiar feature of the motion of air near the Earth's surface is its variability. While variations on daily or seasonal timescales are regular, most near-surface wind variability is irregular - from short-timescale turbulent fluctuations to longer timescale variations driven by large-scale weather and climate processes. Understanding the variability of near-surface winds is important because they are a leading-order control on exchanges of mass, energy and momentum between the atmosphere and the land or ocean surfaces; wind energy is a significant renewable energy source; and wind extremes can be damaging to the natural and built environments. Although the underlying physics is the same, wind behaves differently over land than over water. As well, different physical processes determine its variability on different timescales. A central goal of my research is to build a fundamental understanding of these controls on variability and the consequent implications for predictability. The following projects are proposed towards this end. My research group and I will: 1. use modern techniques from applied mathematics and statistics to investigate transitions between near-surface wind "regimes" which we have shown are associated with unusually strong nighttime winds. 2. determine how changes in sea surface temperature modulate the mean, variability, and extremes of near-surface wind over the ocean. 3. study new approaches to the problem of fitting wind observations to our wind models, to improve their quantitative utility. 4. examine the physical reasons for the observed difference in the statistical predictability of winds coming from different directions. 5. quantify how the predictability of wind speed changes on different timescales. 6. assess the physical controls on the fact that the "memory" of wind variability falls off at different rates for winds from different directions. This proposed research builds in new and important directions on the foundational research we have carried out in recent years. The new research will result in important advances in our fundamental physical and mathematical understanding of the variability and extremes of surface winds, with implications for their simulation in comprehensive climate models and for the assessment and prediction of the wind energy resource.