Yihua Wu

State Climate Office of North Carolina
Room 212, Research III Building
P. O. Box 7236, North Carolina State University
1005 Capability Drive, Raleigh, NC 27695-7236, USA
Tel: (919) 515-1448
Fax: (919) 515-1441
E-Mail: wu@cumulus.meas.ncsu.edu
Homepage URL: http://www4.ncsu.edu/~ywu1/

Education and Professional Career

Ph.D. in Atmospheric Sciences, North Carolina State University,. USA (Dec. 1997)
M.S. in Horticultural Science (HS), North Carolina State University, USA (Dec. 1993)
B.S. in Agrometeorology, Nanjing Institute of Meteorology, Nanjing, China (Feb. 1982)

Researcher, State Climate Office of North Carolina, North Carolina, USA (Aug. 1998 - Present). Research includes:
1. Conducting real-time operational weather forecast using the non-hydrostatic PSU/NCAR meso scale model (MM5V2)
2. Investigating the predictability of gravity waves.
Research Associate, Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, USA (Jan. 1998 - July 1998). Research includes:
1. Applying NRL/NCSU triple nested numerical model and MM5 to North Carolina
2. Developing a trajectory model to trace the transport of Blue Mold spores in the Appalachian Mountain region.
Trainee at the UNEP/USSR/WMO Training Course on Agrometeorology at Alma-Ata, USSR, Certificate (Oct. 1996)
Graduate Research Assistant, North Carolina State University, North Carolina, USA (Jan. 1992 - Dec. 1997).
Visiting Scholar, University of Missouri-Columbia, USA (Jul. 1987 - Jul. 1988)
Trainee at Cooperative Institute for Applied Meteorology (CIAM), University of Missouri-Columbia, Missouri, USA, Certificate (1987 - 1988).
Engineer, State Meteorological Administration, China (Feb. 1982 - Dec. 1991)

Dissertation Research

Title: Investigation of Scale Interactions Associated with the Formation and the Structure of Low Level Jets
Advisor: Dr. Sethu Raman

ABSTRACT

Scale interactions associated with the formation and the structure of low level jets are investigated from observational and numerical perspectives. Radiosonde data from six stations in Kansas and Oklahoma for the period of June 16-24, 1993 were used to document the Great Plains low level jets with a detailed description of their structure and the characteristics. The formation mechanisms for the low level jets were revealed, and the interaction of the low level jet with the synoptic circulation was investigated.

Two numerical models were used and were linked with a soil-vegetation scheme and equipped with a good boundary layer parameterization in which the atmospheric boundary layer is treated as the surface layer (SL) and a transition layer, separately. The mesoscale model was used to investigate the effect of land use pattern on the formation and the development of the low level jet. The triple nested regional model was used to investigate two real cases.

Four numerical experiments were conducted to investigate the influence of the land use pattern on the formation and the development of the low level jet using the mesoscale model. The mid-west type of Low Level Jet (LLJ) was successfully generated in the model simulation. Characteristics of the LLJ generated in the numerical experiments are consistent with observations. The results suggest that land surface heterogeneities could have significant impacts on the formation and the maintenance of the LLJ. The major mechanisms for the LLJ are the horizontal temperature gradient caused by land surface heterogeneities and inertial oscillation of frictional effect. A geostrophic wind normal to the horizontal temperature gradient is also important.

The triple nested regional weather prediction model was used to test the sensitivity of the Somali jet and the southwest monsoon rainfall to the horizontal resolution of the model. Simulated results from the three different domains were considered over the same horizontal area. Both the speed and the height of the Somali jet in the three domains are found to be very different from each other. The distribution and the rate of rainfall simulated in the three domains are also found to be very different. Generally, the speed of the Somali jet is stronger, and the height of the jet is lower as model resolutions become finer. The model with a finer resolution predicted more rainfall and more detailed structures of the distribution of the wind speed and the rainfall. The simulated low pressure system moves a little faster in the finer domains.

The interaction of the Somali jet with the Western Ghat Mountains was also investigated using the triple nested regional weather prediction model. Two numerical experiments were conducted; one with the topography of western India in each domain; the other without topography of the Western Ghat in the inner most domain. The results for the inner most domain in the two experiments were analyzed and compared. The results from the simulation with topography captured several of the observed features of the Somali jet interaction with the Western Ghat Mountains, including a pressure ridge, strong vertical motions, and occurrences of highly reflective cloud and heavy rainfall rates along the west coast of India. The simulation without topography failed to reveal these features. The results suggest that the blocking effect of the Western Ghats plays an important role for the occurrence of rainfall over the west coast of India.

A numerical experiment was conducted to investigate the low level jet (LLJ) ahead of a cold front over the US. Salient features of the cold front and the LLJ were well simulated. Simulated results show that the major mechanisms for the LLJ ahead of a cold front are the thermally direct secondary circulation, the reversed temperature gradient ahead of the cold front and inertial oscillation.