Summer Lower Atmosphere Structure and Trends in Western US Coastal Environment

The eastern portion of NE Pacific Anticyclone extends over the coast of California and Oregon during the summer dominating the mean conditions in the lower atmosphere, over the ocean and land surfaces. Subsidence controls the lower atmosphere, forming an air temperature inversion and weak winds from a northerly direction. The sea level pressure field is such to cause winds west of the coastal mountains to be from a northerly direction and ocean upwelling with the strongest winds and lowest SST at the coast and along the coast of Northern California and Southern Oregon. A surface atmospheric marine boundary layer separates the ocean surface and the base of the air temperature inversion capped by the subsiding atmosphere. Inland of the coastal mountains, the subsidence sinks to interact with the land surface. This structure has changed over the period 1950-2010. The inland temperatures have increased while coastal SST had decreased. The sea level pressure gradient along the coast, which drives the winds over the coast, has weakly increased. Lower mid-level winds have increased. The sea surface temperature along the coast has decreased. The marine fog at sea level has increased. The inversion base height has decreased. Marine stratus clouds have decreased in occurrence and height. Relationships and reconciliations of all these trends will be presented amid the observation uncertainty. These changes have social consequences including navigation problems with increasing fog and increasing water demand on agricultural crops and stress on native plants above the marine layer and also east of the coastal mountains.