California rainfall is becoming greater, with heavier storms
Results show that precipitation amounts generally increased over the period of record for central and northern California, but did not change significantly in southern California. Year to year variability is large, especially to the south. The greatest percentage increases occur in the central region. All stations show a marked Pacific influence with ENSO and PDO signals showing prominently in the rainfall record, particularly in southern California. Many stations, not all, also exhibit a shift towards higher daily rainfall amounts with decreases in the proportion of light rains and increases in moderate and heavy rains. Most stations indicate some change in seasonal rainfall totals, with increases mostly in winter and decreases in fall.
The implications of our results for California water resources are unclear. Warmer state temperatures may negate any precipitation increases through greater evaporation. However, the data suggests the increased potential for flooding, particularly to the north.