קולוקוויום בחוג לגאופיזיקה: Understanding the higher order temperature variability changes
Talia Tamarin, University of Reading
Extreme warm and cold temperature anomalies are captured in the tails of the Probability Density Function (PDF). The mean of the PDF naturally determines the climatology, while the variance of the PDF measures the strength of fluctuations around the mean. Atmospheric variability is often mistakenly identified with the variance, while the higher order moments describing the PDF are ignored. This can be especially misleading for weather and climate extremes, which are associated with the tails of the PDFs, and thus depend strongly on the higher order moments. For example, temperature skewness relates to the asymmetry between the magnitude of warm and cold temperature anomalies, and kurtosis is indicative of the “extremity” of the tails. Here we show that a unique relationship exists between temperature kurtosis and skewness in the midlatitudes, with kurtosis being proportional to skewness squared. Extending previous studies that found a similar relationship for sea level pressure and vorticity in oceanic jets, we present a simple model that relates kurtosis to skewness squared. In this simplest representation of temperature variability, the total PDF is represented by the sum of three Gaussians, representing the mean, the warm and the cold temperature anomalies. The former represents small deviations from the averaged climatology, while the last two represent the larger amplitude temperature anomalies associated with synoptic-scale systems. This simple model captures well the PDF structure in different regions, as well as their projected changes, giving a simple interpretation of the higher order temperature variability changes. Building a fundamental understanding of the mechanisms shaping temperature skewness and kurtosis is crucial for understanding extreme temperature events, such as heat waves or cold spells, and for gaining insight into future changes in atmospheric temperature variability and extremes.
מארגני האירוע: ד"ר רועי ברקן וד"ר אסף ענבל