Abstract
This study examines the stability criterion of a saturated air parcel in an unsaturated environment using the parcel method for parcels of the same virtual temperature as their environment. By considering the lapse rate of virtual temperature in a moist adiabatic process, we get the results that the lapse rate of temperature for the criterion is larger than the usual moist adiabatic temperature lapse rate by about 20% of the difference between dry and moist adiabatic lapse rates.
In general, the dominant circulation patterns of the EA wintertime variability from each MME member model compare well with their observational counterparts. However, the temporal variations of these modes are difficult to reproduce in the model simulations. The variation of the leading mode is found to be better predicted by most models, which leads to better predictions of the winter climate over continental northeast Asia, compared to the second mode. The MME performance is further assessed in the context of circulation changes during ENSO. It is found that most models have difficulty in capturing both the timing and strength of the observed second EA climate mode variations. Analysis based on observations shows that there is Rossby wave activity from Eurasia in early boreal winter during ENSO years. The Eurasian wave train, however, is either too weak or absent in the model simulations. Overall, these results highlight the difficulties in forecasting EA winter climate in the current framework of seasonal climate prediction.
