Jun 15, 2016

California Heat Waves – A New Type of Heat Wave

Alexander Gershunov and Kristen Guirguis
California-Nevada Climate Applications Program – A NOAA Risa
  • Reviews existing literature on heat trends in California
  • Finds the traditional type of heat wave, natural for California's semi-arid Mediterranean climate, has increasingly tended to be more humid and more often accentuated at night since the 1980s 
  • States humidity leads to higher night time temperatures and also makes extreme heat much more difficult for humans as it reduces our bodies’ ability to cool off by evaporating water – sweating
  • States the observed trend towards more humid, more intense and longer-lasting heat waves in California has so far culminated in the July 2006 heat wave, an event of unprecedented impact on human health in the state
  • States that heat waves impacting California are caused by a specific weather pattern characterized by high atmospheric pressure in the Great Plains and low pressure off California’s coast which together draw warm moist air from the south
  • States that coastal waters west of Baja California are an important source for this humid air; these waters have become unusually warm in recent decades as part of a global warming pattern and have been partially responsible for the fact that the rare weather patterns associated with great California heat waves have tended to bring warmer, more humid air