The relationship between organization of mesoscale convective systems(MCSs) ,there heating effects to the environment in the Australian region and the activity of the Madden-Julian ocsillation(MJO) and the equatorial Rossby wave(ERW) is investigated.The study mainly uses the observed Dopplar radar data , NCEP-NCAR reanalysis data and outgoing longwave radiation(OLR).
The changes into the ″active″ or ″break″ monsoon conditions of the atmospheric circulation and convection are primarily associated with eastward propagation of convective anomaly from the Indian Ocean to the western Pacific in the austral summer November through March during the dominant intraseasonal oscillation.However, the daily precipitation and clouds amount observed over the northern Australian region are not necessarily to be consistent with phase and amplitude of seasonal anomaly on the MJO mode extracted by long period bandpass-filtered OLR and wind field.It is indicated that amplitudes of short-periods-filtered convective seasonal anomaly is larger than those of MJO and peak days of those conversely exhibits enhancement of precipitation. Therefore, these precipitation variance occurred by deep convection followed with westward-moving depressions to the around of observation area, which are usually clear over the sea off northeastern coast. That is further suggested that occurrence of the convective gyre is probably due to ERW.
In most cases of continental origin MSCs(CMSCs) the isolated squall lines types composed of a leading convective line and trading stratiform region ,which occurred and developed in large low level wind shear, resulting from very strong low-level convergence accompanied with a disturbance like cyclone located over the northern ocean off continent, this is attributed to be the peak of ″break″ or transitioning ″break″ to ″active″ phase in midlevel drysituations as lately and low-level easterly . It was further characterized that convectively generated cold pool that could trigger new cells converged with moisture sea breeze, consequently enhanced rear inflow jet.
On the other hand maritime origin MCSs (MMSCs) was usually formed and developed in large wind shear between low-level and upper-level, on the contrary small in low-level, during early ″break″ phases in moderate westerly, the consequently peak of ″active″ in transitioning easterly to westerly or lately ″active″ in strong westerly.It is also indicated that MMCSs is formed on convective moisturizing condition, therefore makes it more favorable for next convection. Indeed some new convective lines evolved during short time interval, where the cool low-midlevel backyard moist outflows from self-produced stratiform region converged with developing strong rear inflow jet with a maximum of wind speed between 2 and 4 km, suggested a positive feedback between water vapor and convection.
One of the most important roles of MCSs is the heat and moisture transport.The vertical structures of convective-stratiform heating and vertical wind motions such as maximum height and magnitude were also estimated, which change according to the regimes and stages of MCSs evolution.It is found that the heating rates normalized by rainfall amount is significantly large within MMSCs stratiform rainfall region in the middle-upper troposphere. These findings suggest to the possibility of improving in parameterization of numerical models.