Ocean Reference Stations: Long-term, open ocean observations of surface meteorology and air-sea fluxes are essential benchmarks

Figure provided by Robert Weller.

Comparison of the low-passed (365-day running mean) net air-sea heat flux at three long-term surface moorings maintained by the Upper Ocean Processes Group with NOAA Support.  The Stratus Ocean Reference Station (ORS) is under the marine stratus clouds off northern Chile at ~20°S, 85°W; the WHOTS ORS is north of Oahu at the Aloha site; and the NTAS is east of Martinique in the Caribbean.  The surface meteorological data from the three ORS are withheld from assimilation into models in order to provide high quality, independent time series of surface meteorology and derived air-sea fluxes to assess the realism of models.  Here, the low-passed net air-sea heat fluxes (positive means ocean heating) from three modern atmospheric reanalyses (NCEP2 from NOAA, MERRA2 from NASA, and ERA5 from ECMWF) have been extracted at each ORS.  The black lines are the ORS time series, with red lines showing NCEP2, green lines MERRA2, and blue lines ERA5 time series.   Record means are given for each ORS, numbers coded by color.  Two findings stand out.  First, the models provide too little heat to the ocean.  Second, the biases in the model neat heat flux can vary greatly over the years.