1705 / 2019-08-27 16:01:23

On the budget of local available potential energy of intra-seasonal eddies

9、大气科学与全球变化 > 专题1：大气环流对气候的影响

In North Hemisphere winter, in addition to the synoptic time scale, the eddies is dominant by strong intra-seasonal variability, associated with persistent weather, especially over the East Asia and North America. We employ the concept eddy available potential energy (EAPE) which established link between background energy and baroclinic eddy energy. Compare to eddy kinetic energy (EKE), which refers to the upper level motions, the EAPE denotes the temperature variations in the low level and also links the practicality for the forcast. Compare to the synoptic variations over the ocean basins, the action centers of LF EAPE are located at high latitudes over the continents, extending downstream in upper troposphere along the jet stream. The time scale analysis shows the EAPE in the East Asia are dominant by the variance of sub-seasonal time scale. Compare to the North America, the locations of the LF active center in the Eurasia exhibits evidently year-by-year variation. The budget analysis shows the LF eddies convert the mean available potential energy into EAPE through the baroclinic instability. The interaction between synoptic and intra-seasonal eddies acts as a sink for LF EAPE and an additional source for HF EAPE, indicating the role of LF eddies in maintaining the HF EAPE. The baroclinic conversion not only plays another sink but also shows the energy conversion from LF EKE to EAPE reversely is crucial in maintain the Mediterranean climate.