How Variations in Summertime Marine Clouds Drive California Temperatures
Abstract
Six decades of summertime marine low clouds along the California coastline are investigated in regards to their association with surface air temperature and how they are related to other climate measures. Cloudiness is determined using a combination of 1-km resolution GOES albedo measurements and long-term land-based observations of cloud cover and cloud base height. Throughout California, year-to-year variability in marine stratus frequency is found to be linked inversely to daytime temperatures and directly to nighttime temperatures. In turn, low cloud occurrence is strongly correlated to low-level temperature inversion strength. Both cloud cover and inversion characteristics are quite strongly correlated with the PDO and also to coastal sea surface temperature anomalies, which along with atmospheric circulation is associated with decadal variations in cloudiness and air temperature. In this study, a cloud base height threshold of 3000 ft (~914 m) was used distinguish marine stratus from clouds occurring higher in the atmosphere. The base height of marine stratus decreases with latitude along the California coastline with lowest clouds along the northern coastline. The results indicate that long-term trends in coastal marine cloud cover depend critically on the choice of the critical height threshold.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.A42B..05I
- Keywords:
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- 3310 ATMOSPHERIC PROCESSES / Clouds and cloud feedbacks;
- 3339 ATMOSPHERIC PROCESSES / Ocean/atmosphere interactions