Spatial and Temporal Analysis of Climatological Variations in Isentropic Surfaces

等熵分析是在20世纪30年代由大气科学家杰罗姆·纳米亚斯作为气候学研究工具引入的。在等熵分析中，依赖于与给定的潜在温度值相关联的压力水平的计算，潜在温度值是在100千帕（1000毫巴）的压力下进行压缩或绝热膨胀的空气包的温度。因此，正如韦克斯勒和纳米亚斯在20世纪30年代所写的那样，等熵面“比固定水平（等压、恒压）图更能描绘出流动模式”。与恒压图相比，这种形式的分析可以更好地将降雨模式与高空现象联系起来。”不幸的是，在第二次世界大战结束时，等熵值从常见的高空探测中消失后，对等熵分析的兴趣减弱了，美国采用了德国使用等压图的方法。该研究项目将通过开发和后续分析等熵数据的长期气候学档案，重新将这种长期被忽视的分析方法引入地理气候学。研究人员的主要目标是确定等熵数据在历史上与地表气温和降水在月度和季节性时间尺度上的关系。他们还将研究各种大尺度气候联系（遥相关）与由主成分和聚类分析确定的各种等熵模式之间的关系。研究人员将等熵模式与远相关联系起来，包括厄尔尼诺-南方涛动（ENSO）、太平洋年代际涛动（PDO）等，以及半球和全球气温。该项目的最终目标是使所提出的等熵数据库成为干旱重建、监测和预测的独特工具，使全球气候科学家能够使用。在这个项目中进行的初步分析旨在证明等熵干旱概念的价值，并为气象学和气候学课程提供一个新的有趣的教学模块。早期的气候研究人员使用等熵分析证明了一种非常有用的表示干旱的方法，这种方法与降水异常的区域模式比较有利。因此，等熵分析提供了在干旱探测和监测方面取得进展的潜力，这对从事干旱监测和缓解的科学家、水资源规划者、决策者和居民至关重要。如果预报员能够通过等熵分析更好地确定干旱地区、因果机制以及与特定天气事件的相互作用，就可以实现更好的水管理和干旱缓解。此外，这种分析形式的讨论和应用很好地融入了气候学和气象学的本科和研究生课程。由于早期等熵分析的重要工作是由气象学家和气候学家在20世纪30年代完成的，因此近70年来几乎所有的气候等熵分析都是在没有应用现代气候学进展的情况下完成的。例如，项目中涉及的研究课题之一是厄尔尼诺-南方涛动等大尺度气候联系（遥相关）对等熵面的影响。遥相关概念在20世纪后半叶发展起来，并已成为月度到季节性预报的主要工具。为了使这项工作的效益最大化，等熵数据集将通过一个可访问互联网的档案广泛提供，该档案将针对研究干旱和水文气候变化的科学家社区的特别关注。

Isentropic analysis was introduced as a climatological research tool in the 1930s by atmospheric scientist Jerome Namias. In isentropic analysis relies on the computation of the pressure level associated with a given potential temperature value, which is the temperature of an air parcel undergoing a compression or an expansion adiabatically to a pressure of 100 kPa (1000 mb). As such, as Wexler and Namias wrote in the 1930s, isentropic surfaces "give a much better picture of flow pattern than fixed-level [isobaric, constant pressure] charts ? This form of analysis allows a much better correlation of rainfall-patterns with upper-air phenomena than was possible [with constant pressure charts] ?" Unfortunately, after isentropic values were eliminated from common upper air soundings near the end of World War II, interest in isentropic analysis waned and the United States adopted the German method of using isobaric charts. This research project will reintroduce this long-neglected means of analysis to geographic climatology through development and subsequent analyses of a long-term climatological archive of isentropic data. The investigators' primary goal is to determine how well isentropic data historically associate with surface air temperature and precipitation on monthly and seasonal time scales. They also will examine how various large-scale climate linkages (teleconnections) are related to the various isentropic patterns determined from principal components and cluster analyses. The researchers will correlate isentropic patterns with teleconnections including El Nino-Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and others, as well as hemispheric and global air temperatures. The project's ultimate goal is for the proposed isentropic database to represent a unique tool for drought reconstruction, monitoring, and forecasting that will be made accessible to climate scientists globally. The initial analyses conducted during this project are intended to demonstrate the value of the isentropic-drought concept as well as to provide a new and interesting teaching module for meteorology and climatology classes.Early climate researchers using isentropic analysis demonstrated a very useful means of representing droughts that compared favorably with regional patterns of precipitation anomalies. As such, isentropic analysis offers the potential for advances in drought detection and monitoring, which can be crucial for scientists, water resource planners, policy makers, and residents engaged in drought monitoring and mitigation. If forecasters can better identify drought regions, causal mechanisms, and interactions with specific weather events through isentropic analyses, better water management and drought mitigation can be accomplished. In addition, discussion and application of this form of analysis integrates well into undergraduate and graduate classes in climatology and meteorology. Because the early important works on isentropic analysis were accomplished by meteorologists and climatologists in the 1930s, almost all climatological isentropic analysis has been done without application of the modern advances in climatology over the last seventy years. For example, one of the research topics addressed in project is the influence of large-scale climate linkages (teleconnections) like El Nino-Southern Oscillation on isentropic surfaces. The teleconnection concept evolved over the last half of the 20th century and has become the primary tool used in monthly-to-seasonal forecasting. To maximize the benefit of this work, the isentropic dataset will be made widely available through an internet-accessible archive that will target the particular attention of the community of scientists researching drought and hydroclimatic change.