Mechanisms of Meridional-Propagating High-Frequency Intraseasonal Oscillation Associated with a Persistent Rainfall over South China

AbstractThe present study divides the intraseasonal variations into high-frequency ISO (HF-ISO) with 5-20-day period and low-frequency ISO (LF-ISO) with 30-60-day period. Here, defined HF-ISO is heavily different from some previous work, because, over South China, persistent rainfall (PR) is not only related to the quasi-biweekly oscillation (10-20-day period), but also connected with the quasi-weekly oscillation (5-10-day period).Associated with a PR over South China during the first half of June, 2016 (PR1606), the propagating components of the convections are much largely attributed to the HF-ISOs. Moreover, both the southward- and northward-propagating HF-ISOs are found in this case.Over Southern China, the moisture advection dominated by anomalous flow and mean water vapor plays an important role in the southward propagation of the HF-ISO, and the cloud-radiation effect may be also, at least partially, responsible for the southward shift of the associated convective zone. Nevertheless, other two poss...