Numerical experiments on forcing dissipation and heating response of dipole (unipole) are carried out using global spectral models with quasi-geostrophic barotropic vorticity equations. For each experiment model integration is run for 90 days on the condition of three-wave quasi-resonance. The results are given as follows: Under the effects of dipole (unipole) forcing source and basic flow intensity, there exist strong interactions among the three planetary waves and quasi-biweekly and intraseasonal oscillation of the three planetary waves. In the meantime, the changes in the intensity of dipole or unipole forcing source and basic flow have different frequency modulation effects on LFO in the middle and higher latitudes. The results of the stream function field of three quasi-resonant waves evolving with time confirm that the low-frequency oscillation exists in extratropical latitude.
Taking Tropical Cyclone (TC) No.9806 (Todd) as an example, the effects of Zhoushanarchipelago terrain on landfall TC are investigated by use of numerical simulation. Results show that, undertopographic influences of Zhoushan Islands, the westward-moving landfall TC deflects. And, small orographichighs and enhanced rainfall caused by climbing airflow on the windward slope of main mountains of theseislands are a result of effects of Zhoushan Islands. These results display some particular laws of effects ofsmall-sized islands on the landfall of TC.
