Spatial and Temporal Changes in Climatological Degree-Days in California

Abstract

Analysis of 35 years observed trends in summertime daily maximum and minimum temperatures in two non attainment California air basins showed coastal cooling and inland warming. To study the impact of these results on the energy consumption we analyzed the cooling/heating degree days (CDD/HDD) of California long term observed temperatures. In this research historical surface 2-m air temperature data analyses consist of long-term data records, from 273 locations in California, and the primary sources of such data include the cooperative network, first order National Weather Service stations, and military weather stations. Data were used from 273 cooperative stations with more than 100 stations in the northern Central Valley (CV) of California, each with 40 to 60 years of monthly average, minimum, and maximum temperature data records. About 100 of the stations are in the San Francisco Bay (SFB) and 30 of the stations are on the South Coast Air Basin (SoCAB) of California. Analysis of the CDD/HDD has been undertaken for California in general and in the SFB and SoCAB in particular, under regional climate change conditions. Regional climate fluctuations have larger effects on surface temperatures, which in turn affect the CDD and HDD. A closer look to the CDD reflects an asymmetric increase between the coast and inland regions of California during the last 35 years. In general coastal areas experienced historical decrease of CDD while inland regions experienced increase in CDD. This is attributed to the sea breeze flows, which suggest an increase of the cold marine air intrusion due to the increase of the regional sea breeze potential, which naturally ventilates the coastal areas.