A divergent and rotational kinetic energy budget for January and July

Abstract

Rotational and divergent kinetic energy (K) exchanges are studied using a budget which partitions the global K into four components: zonal divergent K, zonal rotational K, eddy divergent K, and eddy rotational K. Vertically integrated results are given for the energies, the exchanges between them, and the conversions from available potential energy (APE) using the National Meteorological Center global operational analyses for the five Januarys and the five Julys from 1983 to 1987. Both the January and the July results show that the flow of energy is generally from eddy APE to eddy divergent K and then to eddy rotational K. From the eddy rotational K, energy flows to zonal rotational K and then to zonal divergent K. The conversion of zonal APE to zonal divergent K is seasonally dependent. In January the conversion is indirect (APE is converted to divergent K) and in July it is in the opposite sense. The results also indicate that the amounts of divergent energy in the atmosphere are small compared to the amounts of rotational energy even though the sources and sinks of divergent energy are relatively large, supporting the idea suggested by previous studies that the divergent K plays a “catalytic” role in the conversion of APE to rotational K.