Abstract

The atmospheric circulation is driven by heat transport from the tropics to the polar regions, embedding energy conversions between available potential and kinetic energy through various mechanisms. The processes of energy transformations related to the dynamics of the atmosphere can be quantitatively investigated through the Lorenz energy cycle formalism. Here we examine these variations and the impacts of modes of climate variability on the Lorenz energy cycle by using reanalysis data from the Japanese Meteorological Agency (JRA-55). We show that the atmospheric circulation is overall becoming more energetic and efficient. For instance, we find a statistically significant trend in the eddy available potential energy, especially in the transient eddy available potential energy in the Southern Hemisphere. We find significant trends in the conversion rates between zonal available potential and kinetic energy, consistent with an expansion of the Hadley cell, and in the conversion rates between eddy available potential and kinetic energy, suggesting an increase in mid-latitudinal baroclinic instability. We also show that planetary-scale waves dominate the stationary eddy energy, while synoptic-scale waves dominate the transient eddy energy with a significant increasing trend. Our results suggest that interannual variability of the Lorenz energy cycle is determined by modes of climate variability. We find that significant global and hemispheric energy fluctuations are caused by the El Nino-Southern Oscillation, the Arctic Oscillation, the Southern Annular Mode, and the meridional temperature gradient over the Southern Hemisphere.

摘要

大气环流是由从热带到极地的热传输驱动的，通过各种机制将能量转换嵌入在可用势和动能之间。可以通过洛伦兹能量循环形式主义对与大气动力学有关的能量转换过程进行定量研究。在这里，我们使用来自日本气象厅（JRA-55）的再分析数据，研究了这些变化以及气候变化模式对劳伦兹能量循环的影响。我们表明，大气环流总体上变得更加活跃和高效。例如，我们发现涡旋可用势能具有统计学上的显着趋势，尤其是南半球的瞬变涡旋可用势能。我们发现，与Hadley细胞的膨胀一致的区域可用势和动能之间的转换率，以及涡流可用势和动能之间的转换率都有明显的趋势，这表明中纬度斜压不稳定性增加。我们还表明，行星尺度波主导着静止涡流能量，而天气尺度波主导着瞬时涡流能量，并具有显着增加的趋势。我们的结果表明，洛伦兹能量周期的年际变化取决于气候变化的模式。我们发现，重大的全球和半球能量波动是由厄尔尼诺-南方涛动，北极涛动，南半球环状模和南半球的子午温度梯度引起的。