(WEAVE) Changing Seasons? Detecting and Understanding Climate Change

9720134所有最近的研究表明，在过去的一个世纪里，美国大陆温度、降水和径流的季节模式一直在改变。在高纬度地区，一年中的最高气温和降水量可能提前了10到90天。融雪径流也可能在今年早些时候发生。在年际或年代际时间尺度上，有证据表明与厄尔尼诺事件有关的季节延迟/提前。这些趋势对预测区域农业和城市用水和能源需求的时间和规模、供水、水库调度、农业实践、生态生产力、对地表水和空气质量的环境影响的关键时期和风险以及随之而来的经济影响都有影响。对归因于特定月份或季节的变暖或降雨趋势的解释也受到了质疑。拟议研究的目标是：利用近一个世纪的仪器水文气候记录，确定北美降水、温度和径流季节性变化的空间连贯模式。将季节性变化与人为因素(如温室气体、城市化)、纬度、大陆(即距海洋的距离)和地形联系起来。探索季节性趋势和大气环流趋势(如海平面气压变化所示)之间的联系，以动态了解气候变化。探索使用大气环流模型来解释气候系统的自然变异性或温室压力的趋势。为实现这些目标，将汇编从美国大陆到北半球各区域的日/月降水量、温度、流量和海平面气压数据的综合数据库，并使用非参数统计方法对这些数据进行分析，以评估季节性及其变化、空间一致性和变化的时空结构，并制定和探讨海洋-大气环流与降水、温度和流量趋势之间的经验假设。

9720134 Lall Recent research suggests that the seasonal patterns of continental U.S. temperature, precipitation and streamflow have been changing over the last century. The peak temperature and precipitation may have shifted forward by 10 to 90 days in a calendar year in high latitudes. Snow melt runoff may also be occurring earlier in the year. At interannual or interdecadal time scales, there is evidence of delay/advance of seasons related to El Nino events. Such trends have implications for projections of the timing and magnitude of regional agrarian and urban water and energy demand, water supply, reservoir operation, agricultural practice, ecologic productivity, critical periods and risks of environmental impacts on surface waters and air quality and the consequent economic impacts. The interpretation of warming or rainfall trends attributed to particular months or seasons is also called into question. The objectives of the proposed research are to: Identify spatially coherent patterns for changes in the seasonality of precipitation, temperature and streamflow in N. America using nearly century long instrumental hydroclimate records. Relate shifts in seasonality to anthropogenic factors (e.g., greenhouse gases, urbanization), latitude, continentality (i.e., distance from ocean), and orography. Explore connections between the seasonality trends and trends in atmospheric circulation (as indicated by sea level pressure changes) for a dynamical understanding of the changing climate. Explore the use of General Circulation Models to explain the trends in terms of natural variability of the climate system or greenhouse forcing. These objectives will be addressed by assembling a comprehensive data base of daily/monthly precipitation, temperature, streamflow and sea level pressure data for regions ranging from the continental U.S. to the N. Hemisphere and the analysis of these data using nonparametric statistical methods to assess seasonality and its shifts, spatial coherenc e and space-time structure of the variations, and to develop and explore empirical hypotheses relating ocean-atmosphere circulation to the trends in precipitation, temperature and streamflow.