Engineering topics

Yang, Song

Publications and source records attributed to Yang, Song.

40 records · Page 3

NASA NTRS1999

Asian Monsoons: Variability, Predictability, and Sensitivity to External Forcing

In this study, we have addressed the interannual variations of Asian monsoons including both broad-scale and regional monsoon components. Particular attention is devoted to the identities of the South China Sea monsoon and Indian monsoon. We use CPC Merged Analysis of Precipitation and NCEP reanalyses to define regional monsoon indices and to depict the various monsoons. Parallel modeling studies have also been carried out to assess the potential predictability of the broad-scale and regional monsoons. Each monsoon is characterized by its unique features. While the South Asian monsoon represents a classical monsoon in which anomalous circulation is governed by Rossby-wave dynamics, the Southeast Asian monsoon symbolizes a "hybrid" monsoon that features multi-cellular meridional circulation over eastern Asia. The broad-scale Asian monsoon links to the basin-wide atmospheric circulation over the Indian-Pacific oceans. Both Sea Surface Temperatures (SST) and land surface processes are important for determining the variations of all monsoons. For the broad-scale monsoon, SST anomalies are more important than land surface processes. However, for regional monsoons, land surface processes may become equally important. Both observation and model shows that the broad-scale monsoon is potentially more predictable than regional monsoons, and that the Southeast Asian monsoon may possess higher predictability than the South Asian monsoon.

Yang, Song↗

NASA NTRS1999

The East Asian Jet Stream and its Climate Impact

In this talk, I will present results from an analysis of the winter westerly jet stream over East Asia. The variability of the jet and its teleconnection to other climate subsystems such as the Asian winter monsoon, ENSO, and tropical convection will be focused. The role of external forcing and the predictability of the jet will be assessed using models. NCEP/NCAR reanalysis data, NASA GPCP data, and results from experiments with the NASA GOES-2 general circulation model will be studied.

Yang, Song↗

NASA NTRS1999

Monsoon and ENSO: A Review

In this presentation, I will review the relationship between ENSO and monsoon based on the results of Webster and Yang (1992). 1 will also discuss results from some following-up studies. Four aspects will be addressed: the spring predictability barrier, the selectively interactive nature of monsoon and ENSO, the Webster-Yang monsoon index, and the precursory signal of the monsoon variability. Most of the the results have been previously published in various professional journals.

Yang, Song↗

NASA NTRS1999

Wintertime East Asian Jet Stream and its Association with the Asian-Pacific-American Climate

The wintertime upper-tropospheric westerly jet stream over subtropical East Asia and western Pacific, often referred to as East Asian Jet (EAJ), is an important atmospheric circulation system in the Asian-Pacific-American (APA) region. It is characterized by variabilities on a wide range of time scales and exerts a strong impact on the weather and climate of the region. On the synoptic scale, the jet is closely linked to many phenomena such as cyclogenesis, frontogenesis, blocking, storm track activity, and the development of other atmospheric disturbances. On the seasonal time scale, the variation of the EAJ determines many characteristics of the seasonal transition of the atmospheric circulation over Asia. The variabilities of the jet on these time scales have been relatively well documented (e.g., Yeh et al. 1959, Palmen and Newton 1969; Zeng 1979). It has also been understood that the inter-annual variability of the EAJ is associated with many climate signals in the APA region. These signals include the persistent anomalies of the East Asian winter monsoon and the changes in diabatic heating and in the Hadley circulation (Bjerknes 1966; Chang and Lau 1980; Huang and Gambo 1982; Kang and Held 1986; Tao and Chen 1987; Lau et al. 1988; Yang and Webster 1990; Ding 1992; Webster and Yang 1992; Dong et al. 1999). However, many questions remain for the year-to-year variabilities of the jet and their relation to the APA climate. For example, what is the relationship between the EAJ and El Nino/Southern Oscillation (ENSO)? Will the jet and ENSO play different roles in modulating the APA climate? How is the jet linked to North Pacific sea surface temperature (SST) and the Pacific/North American (PNA) teleconnection pattern? In this study, we address several issues related to the wintertime EAJ with a focus on interannual time scales. We will examine the association between the jet core and ENSO, which has always been overshadowed by the relationship between ENSO and the upper-tropospheric winds over northern extratropics of the central Pacific. We will investigate the linkage of the jet to variabilities of the Asian winter monsoon, tropical convection, and upper tropospheric wave patterns. We will also explore the relationship between the jet core and extratropical S ST with an aim at providing helpful information for improving our understanding of the connection of the EAJ to surface boundary conditions. The analysis is expected to provide information that is helpful for improving regional climate predictions.

Yang, Song↗