Lian-Tong Zhou

The Progresses of Recent Studies on the Variabilities of the East Asian Monsoon and Their Causes

The variabilities of the East Asian summer monsoon arc an important research issue in China, Japan, and Korea. in this paper, progresses of recent studies on the intrascasonal, interannual, and interdecadal variations of the East Asian monsoon, especially the East Asian summer monsoon, and their causes are reviewed. Particularly, studies on the effects of the ENSO cycle, the western Pacific warm pool, the Tibetan Plateau and land surface processes on the variations of the East Asian summer monsoon are systematically reviewed.

Baroclinic Instability of the Silk Road Pattern Induced by Thermal Damping

AbstractIn this paper, the internal dynamics of the Silk Road pattern has been studied. Since observation indicates that the Silk Road pattern could be considered as stationary external Rossby waves, the quasigeostrophic three-layer model has been used to study the dynamics of external Rossby waves. The three-layer model well captures the essential dynamical features of stationary external Rossby waves in accordance with the observations. Theoretical analysis indicates that the quasi-stationary external modes could be destabilized by the weak thermal damping. For destabilization to occur, the vertical structures of the external modes must have a warm ridge and a cold trough from the lower to middle layers. The effect of thermal damping could be considered as modifying the eddy streamfunction in such way that the eddy streamfunction has a vertical phase tilt, so the eddy could feed on the basic zonal flow by extracting the potential energy. The implications for this baroclinic instability on the self-maint...

Regional differences in surface sensible and latent heat fluxes in China

This study documents the variability of surface sensible and latent heat fluxes in five regions of China (Northwest China, the Tibetan Plateau, Northeast China, North China, and Southeast China) using the ERA-40 reanalysis for the years 1960–2000. The surface sensible and latent heat flux variations are remarkably different in Northwest and Southeast China. The seasonal variation of the surface sensible heat fluxes is largest in Northwest China and smallest in Southeast China. In contrast, the seasonal variation in latent heat flux is largest in Southeast China and smallest in Northwest China. The interdecadal variation of surface sensible and surface latent heat fluxes strongly depends on both the region and season. The trends in surface sensible and latent heat fluxes in all four seasons are mainly caused by variations in both the land–air temperature difference and in the specific humidity. There is also a limited contribution of wind speed in some regions, depending on the season.

Regional differences in the surface energy budget over China: an evaluation of a selection of CMIP5 models

The present study provides an evaluation of the regional differences over China in surface energy budget components as simulated by a selection of models from phase five of the Coupled Model Intercomparison Project (CMIP5), covering the period 1960–2005. Similarities and differences exist among the models in terms of both spatial and magnitude patterns. For climatology, the CMIP5 models show quite different spatial distributions of shortwave radiation and sensible heat flux. In terms of seasonal variation, the surface energy budgets are remarkably different between western and eastern China. The discrepancies in the seasonal variation of sensible heat flux are mainly attributable to temperature differences and wind speed, while those of shortwave radiation are caused by the seasonal variation in total cloud cover. Cloudiness is one of the most crucial parameters in estimating the surface energy budget. In addition, the study also reveals that the magnitudes of the various components show larger (more than two-fold) differences between western and eastern parts of China, especially in net longwave and upward shortwave radiation, as well as latent and sensible heat fluxes. The results for surface soil heat flux show that there is more incoming energy during spring and summer and more outgoing energy during fall and winter in both western and eastern China. Furthermore, compared to NCEP2 data, the ERA-40 reanalysis product produces results more similar to the multi-model ensemble mean for most components.

Change in surface latent heat flux and its association with tropical cyclone genesis in the western North Pacific

The present study investigates the influence of June through November (JJASON) thermal state of the western North Pacific warm pool on surface latent heat flux and their association with tropical cyclone (TC) genesis by using 25 level water temperature data with European Centre for Medium-Range Weather Forecasts (ECWMF) operational ocean analysis (ORA-S3), the monthly mean fluxes from Objectively Analyzed Air-sea Fluxes (OAFlux) Project, and the tropical cyclone data from the International Best Track Archive for Climate Stewardship (IBTrACS). It is found that positive (negative) latent heat flux anomalies over the western North Pacific are associated with warm (cold) state of the warm pool. The analysis suggests that the change in sea-air humidity difference has a direct contribution to surface latent heat flux anomalies over the western Pacific in warm state years of the warm pool. However, the change in surface wind speed is the main cause of surface latent heat flux anomalies over central tropical Pacific. In cold state years, change in the sea-air humidity difference has a direct contribution to surface latent heat flux anomalies over the western Pacific and central and eastern tropical Pacific, and the change in surface wind speed appears not to be a cause of identified surface latent heat flux anomalies. Moreover, the results show that the sea-air humidity difference contributes to tropical cyclone genesis in warm state years, but in cold state years, tropical cyclone genesis occurs mainly in regions of sea-air humidity difference decrease and surface wind speed increase.

Evolution features of the surface latent heat flux anomalies over the tropical Pacific associated with two types of ENSO events

The present study investigates the features of the surface latent heat flux (LHF) anomalies and their related variables over the tropical Pacific during two types of El Niño-Southern Oscillation (ENSO) events and seeks a possible candidate for the main contributions to the LHF anomalies. During El Niño Modoki and canonical El Niño events, the LHFs show positive anomalies over the equatorial central Pacific and in the areas immediately south of the equatorial eastern Pacific. In addition, the largest magnitudes and widest ranges of positive LHF anomalies for both types of events occur during their mature stages rather than during their developing or decaying phases. Analyses show that the positive LHF anomalies associated with both events are largely affected by the positive sea-air humidity difference anomalies. However, the negative surface wind speed anomalies associated with the canonical El Niño events clearly contribute to the decreases in the positive LHF anomalies over the central Pacific and in the area immediately north of the equatorial eastern Pacific due to the presence of westerly and northerly anomalies, respectively. Moreover, over the equatorial central Pacific and in the area immediately south of the eastern Pacific, the LHF anomalies are mainly influenced by oceanic variables during both types of ENSO events, indicating an atmospheric response to oceanic forcing. In contrast, outside of the area spanning 10° north and south of the equator in the tropical Pacific and with the exception of the southeastern region, the LHF anomalies are greatly influenced by atmospheric variables, suggesting an oceanic response to atmospheric forcing. Distinct differences exist during the mature event phase, with oceanic forcing dominating the equatorial central Pacific during El Niño Modoki events and the area immediately south of the equatorial eastern Pacific during canonical El Niño events. In addition, both types of ENSO events suggest the increasing influence of oceanic forcing over the equatorial eastern Pacific during ENSO event evolutions.