HR: 0800h
AN: A51D-0725    [Abstracts]
TI: Los Angeles Heat Waves Are They Becoming More Frequent and Longer in Duration?
AU: * Tamrazian, A
EM: atamrazian@hotmail.com
AF: University of California, Berkeley, 4800 Oak Grove Drive, 300-323, Pasadena, CA 91109, United States
AU: Willis, J
EM: jwillis@pacific.jpl.nasa.gov
AF: NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, 300-323, Pasadena, CA 91109, United States
AU: Patzert, W
EM: wpatzert@pacific.jpl.nasa.gov
AF: NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, 300-323, Pasadena, CA 91109, United States
AU: LaDochy, S
EM: sladoch@calstatela.edu
AF: California State University, LA, 5151 State University Dr., Los Angeles, CA 90032, United States
AB: Los Angeles is experiencing more heat waves, an event defined by 3 consecutive days above 32.2 C (90 F) in Los Angeles, and also more extreme heat days, defined as days above 32.2 C (90 F). These numbers have increased by 1.72 C (3.09 F) per century and 22.8 per century occurrences, respectively. Both have more than tripled over the last 100 years as a consequence of the steady warming of Los Angeles. We looked at daily maximum and minimum temperatures from 1906-2006 from the Department of Water & Power (DWP) downtown station. The average annual maximum temperature in Los Angeles has warmed by 2.8 C (5.0 F) per century. Also the average annual minimum temperature is steadily warming at 2.3 C (4.2 F) per century. By season, the greatest rate of change was during the summer months for both maximum and minimum temperature, with late fall and early winter having the least rates of change. Furthermore, along with the increase in heat waves there was an increase in heat wave duration. Heat waves lasting longer than six days occurred regularly after the 1970s but were non-existent from the start of 1906 to 9/24/1956 when the first 6-day heat wave was recorded. There are two 13-day long heat waves later in the record on August 12, 1983 and August 29, 1995, while 1997 had the highest number of heat wave events (7) and 1983 and 1997 had the most extreme heat days. Both years were El Niņo years. While heat days have increased dramatically in the last century, extreme cold days, where minimum temperature is below 7.2 C (45 F), shows a slight decreasing trend. This is expected since the overall minimum temperatures are increasing. The summer of 2006 experienced an unusually high number of deaths due to extreme heat events in California. Abnormally high sea surface temperatures off the southern California coast and an influx of monsoonal moisture combined with record heat creating dangerous conditions. The trends in Los Angeles' heat waves indicate that the summer of 2006 may not be a singular event, but possibly more common in the future.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1630 Impacts of global change (1225)
DE: 1637 Regional climate change
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting