California heat waves: their spatial evolution, variation, and coastal modulation by low clouds
- 454 Downloads
We examine the spatial and temporal evolution of heat waves through California and consider one of the key modulating factors of summertime coastal climate—coastal low cloudiness (CLC). Heat waves are defined relative to daytime maximum temperature (Tmax) anomalies after removing local seasonality and capture unseasonably warm events during May—September. California is home to several diverse climate regions and characteristics of extreme heat events are also variable throughout these regions. Heat wave events tend to be shorter, but more anomalously intense along the coast. Heat waves typically impact both coastal and inland regions, although there is more propensity towards coastally trapped events. Most heat waves with a strong impact across regions start at the coast, proceed inland, and weaken at the coast before letting up inland. Typically, the beginning of coastal heat waves are associated with a loss of CLC, followed by a strong rebound of CLC starting close to the peak in heat wave intensity. The degree to which an inland heat wave is expressed at the coast is associated with the presence of these low clouds. Inland heat waves that have very little expression at the coast tend to have CLC present and an elevated inversion base height compared with other heat waves.
KeywordsMarine layer Heat waves Coastal climate Low clouds
We are thankful for support from NOAA Coastal and Ocean Climate Applications (COCA) program grant NA15OAR4310114. This study supports the climate science education efforts of Climate Education Partners, a project funded by a National Science Foundation Grant #DUE-1239797. The study also contributes to DOI’s Southwest Climate Science Center activities and to NOAA’s California and Nevada Applications Program. NCEP Reanalysis data are provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their website at esrl.noaa.gov/psd. Radiosonde Database at esrl.noaa.gov/ raobs/.
- Iacobellis SF, Cayan DR, Norris JR, Kanamitsu M (2010) Impact of climate change on the frequency and intensity of low-level temperature inversions in California. Final Report to the California Air Resources Board Project 06-319. http://www.arb.ca.gov/research/apr/past/06-319.pdf
- Koračin D, Leipper DF, Lewis JM (2005) Modeling sea fog on the US California coast during a hot spell event. Geofizika 22(1):59–82Google Scholar
- Leipper DF (1994) Fog on the United States West Coast: a review. Bull Am Meteorol Soc 75:229–240Google Scholar
- Lewis J, Koračin D, Rabin R, Businger J (2003). Sea fog off the California coast: Viewed in the context of transient weather systems. J Geophy Res Atmos 108(D15)Google Scholar
- Maurer EP, Wood AW, Adam JC, Lettenmaier DP, Nijssen B (2002) A long-term hydrologically-based data set of land surface fluxes and states for the conterminous United States. J Clim 15:3237–3251. doi: 10.1175/1520-0442(2002)015<3237:ALTHBD>2.0.CO;2
- National Weather Service (2012) Heat: a major killer. (http://www.nws.noaa.gov/os/heat/index.shtml
- O’Brien TA (2011) The recent past and possible future decline of California coastal fog, Doctoral thesis, p 193, Univ. of Calif., Santa Cruz, CalifGoogle Scholar
- O’Brien TA, Sloan LC, Chuang PY, Faloona IC, Johnstone JA (2012). Multidecadal simulation of coastal fog with a regional climate model. Clim Dyn 1–12Google Scholar
- Small I (2006) Forecasters handbook for extreme southwest california based on short term climatological approximations Part 1—The marine layer and its effects on precipitation and heating, NOAA Technical Memorandum NWS WR-277Google Scholar
- Williams AP, Schwartz RE, Iacobellis S, Seager R, Cook BI, Still CJ, Husak G, Michaelsen J (2015) Urbanization causes increased cloud base height and decreased fog in coastal Southern California. Geophys Res Lett. 42. doi: 10.1002/2015GL063266
- Zhong X, Sahu DK, Kleissl J (2017) WRF inversion base height ensembles for simulating marine boundary layer stratocumulus. Sol Energy 146:50–64. doi: 10.1016/j.solener.2017.02.021