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.
