Undergraduate Research and Creativity

URECA

2007-2008

Enhancement of Winter Mid-latitude Precipitation over North America
by Upper Level Waves Propagating from the Pacific Ocean

Yang Li, Ward Melville High School
&
Edmund Chang, School of Marine and Atmospheric Sciences

Numerous studies have analyzed the induction of mid-latitude cyclogenesis by preceding upper-level wave packets (Rossby waves). This project is the first to take a systematic look at the enhancement of the associated precipitation over North America by waves propagating from the West Pacific. Data collection began with a survey of upper level wave data from the meteorological winter months over eleven consecutive seasons (1996-2007). A classification system was created to select waves as 11-day cases. 172 wave (V) cases and 172 parallel precipitation cases (PCP) were compiled, and three statistical composites of these cases—a simple PCP mean composite, the total V composite, and the propagating V composite—were created. Another variable, PCP prime, was used to isolate the propagating (enhanced) PCP. Generally, across most relevant geographic areas, the composite wave centers were precursors to above average precipitation (PCP prime). The primary composite wave formed off the East Asian coast 6-7 days ahead of precipitation near the North American East Coast. The enhanced PCP on days +1 and +3 was particularly heavy. Overall, the wave-precipitation correlation was qualitatively strong, significant for most but not all locations. During the project, geographical areas of undefined data were resolved by removing associated cases from the composites.