Projects in Climate Dynamics

该项目主要涉及气候动力学的三个重要研究领域：a)布鲁尔-多布森环流中热带上升流强度的季节和年际变化。一个主要目标是确定年度周期主要是由于高纬度波动活动向上通量的变化，还是由于赤道对流层行星波强度的季节变化所致。可能的焦点是(I)干旱事件和/或(Ii)显著的北半球温带温度的年代际变化。c)中频(6-20天周期)变化的结构和动力学，以及它在多大程度上受线性Rossby波动力学和非线性过程(如波浪破裂)的支配。此外，该项目还将初步探索一种定量评估全球变暖对太平洋西北地区积雪影响的策略，该策略在采样波动方面比传统的积雪测量趋势分析更可靠。用四种不同的方法评估积雪的温度敏感性(即每°C温度上升时积雪损失的百分比)。这项研究将有助于促进评估全球变暖影响的更有力的战略，更有用的全球变暖影响的测量，对热带低平流层温度和痕量组分浓度长期趋势的机制的理解，对20世纪气候变化的更明确的归属，以及更可靠的长期天气预报的现象学基础。更广泛的影响包括改进天气和气候预测的可能性以及对几名研究生的培训和指导。

This project mainly covers three important research areas under the broad umbrella of climate dynamics by focusing on:a) Seasonal and year-to-year variations in the strength of the tropical upwelling in the Brewer-Dobson circulation. A major goal is to determine whether the annual cycle is forced primarily by variations in the upward flux of wave activity at high latitudes or by seasonal variations in the strength of the equatorial tropospheric planetary waves.b) 20th century climate variability. Possible foci are (i) drought episodes and/or (ii) the pronounced interdecadal variability of extratropical Northern Hemisphere temperature.c) Structure and dynamics of intermediate frequency (6-20 day period) variability and the degree to which it is dominated by linear Rossby-wave dynamics versus nonlinear processes such as wave breaking.In addition, this project will also explore preliminarily a strategy for quantitatively assessing the impact of global warming upon snowpack over the Pacific Northwest that is more robust with respect to sampling fluctuations than conventional analysis of trends in snowpack measurements. The temperature sensitivity of snowpack (i.e., the percentage loss in snowpack per °C temperature rise) is evaluated using four different approaches. This research will serve to promote more robust strategies for assessing the impacts of global warming, more useful measures of the impacts of global warming, understanding of mechanisms responsible for the secular trends in temperature and concentrations of trace constituents in the tropical lower stratosphere, a more definitive attribution of 20th century climate change, and a more sound phenomelogical basis for long range weather prediction.Broader impacts include the potential for improved weather and climate prediction and the training and mentoring of several graduate students.