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Trinidad Head, California, United States [THD]


  • Country: United States Country Flag
  • Latitude: 41.0541° North
  • Longitude: 124.151° West
  • Elevation: 107.00 masl
  • Time Zone: Local Standard Time + 8.0 hour(s) = UTC


Cooperating Agencies

Trinidad Head Observatory (THD) is located on a point jutting into the ocean along the remote northern coast of California approximately 40 km (25 miles) north of Eureka, California, the main regional population center. The coastal climate is dominated by maritime influences, with moderate year-round temperatures and moderate-to-high humidity. To the immediate west of Trinidad Head is the unobstructed Pacific Ocean. To the east, the coastal range is dominated by redwood forests. The town of Trinidad represents the primary community in the immediate vicinity and supports approximately 400 year-round residents. The Telonicher Marine Laboratory (TML), a satellite facility of Humboldt State University (HSU), is also located in Trinidad.

NOAA established an atmospheric baseline observatory at Trinidad Head in 2002. Because of its relatively remote coastal location and prevailing maritime airflow, NOAA felt the site would provide scientists with an opportunity to observe and monitor both regional and global atmospheric conditions reasonably free from local influences.

An instrument trailer was installed in April 2002 allowing measurements of aerosols, surface ozone, radiation, and flask sampling for halocarbons and carbon cycle gases. Bi-weekly airborne vertical profile measurements provide a continuous baseline of pollution and climate forcing agents in air entering the U.S. Co-located with the Trinidad Head Observatory, the Scripps Institution of Oceanography operates two in situ instruments, one as part of the Advanced Global Atmospheric Gases Experiment (AGAGE), the other for measuring changes in atmospheric oxygen concentrations.

The NOAA Trinidad Head Atmospheric Baseline Observatory was downgraded from its status as a full "Observatory" to a "Sampling Site" on June 5, 2017. Most long-term projects and infrastructure were removed from the site. Three research projects remain at THD in partnership with other entities: surface ozone monitoring instrumentation (partnership with SIO), ozonesonde launching capabilities (partnership with HSU), and halocarbons flask sampling capabilities (partnership with AGAGE). The downgrade follows a Global Monitoring Laboratory-wide evaluation of scientific goals and global observing network capabilities that resulted in realignment to best meet NOAA's mission and the nation's scientific needs.

All Trinidad Head data are available on the Global Monitoring Division's website:

GML Projects at Trinidad Head, California

Carbon Cycle Surface Flasks

Parameter Formula First Sample Date Status
Carbon Dioxide CO2 2002-04-19 Terminated - 2017-06-01
Methane CH4 2002-04-19 Terminated - 2017-06-01
Carbon Monoxide CO 2002-04-19 Terminated - 2017-06-01
Molecular Hydrogen H2 2002-04-19 Terminated - 2017-06-01
Nitrous Oxide N2O 2002-04-19 Terminated - 2017-06-01
Sulfur Hexafluoride SF6 2002-04-19 Terminated - 2017-06-01
Carbon-13/Carbon-12 in Carbon Dioxide d13C (CO2) 2002-04-19 Terminated - 2017-06-01
Oxygen-18/Oxygen-16 in Carbon Dioxide d18O (CO2) 2002-04-19 Terminated - 2017-06-01
Methyl Chloride CH3Cl 2004-10-07 Terminated - 2017-06-01
Benzene C6H6 2004-10-07 Terminated - 2017-06-01
Methylbenzene C7H8 2004-10-07 Terminated - 2017-06-01
Ethane C2H6 2004-10-07 Terminated - 2017-06-01
Ethylene C2H4 2004-10-07 Terminated - 2017-06-01
Propane C3H8 2004-10-07 Terminated - 2017-06-01
Propylene C3H6 2004-10-07 Terminated - 2017-06-01
Isobutane i-C4H10 2004-10-07 Terminated - 2017-06-01
n-Butane n-C4H10 2004-10-07 Terminated - 2017-06-01
isopentane i-C5H12 2004-10-07 Terminated - 2017-06-01
n-Pentane n-C5H12 2004-10-07 Terminated - 2017-06-01
n-Hexane n-C6H14 2004-10-07 Terminated - 2017-06-01
isoprene C5H8 2004-10-07 Terminated - 2017-06-01
Acetylene C2H2 2004-10-07 Terminated - 2017-06-01

Carbon Cycle Airborne Flasks

Parameter Formula First Sample Date Status
Carbon Dioxide CO2 2003-09-02 Ongoing
Methane CH4 2003-09-02 Ongoing
Carbon Monoxide CO 2003-09-02 Ongoing
Molecular Hydrogen H2 2003-09-02 Ongoing
Nitrous Oxide N2O 2003-09-02 Ongoing
Sulfur Hexafluoride SF6 2003-09-02 Ongoing
Sulfur Hexafluoride SF6 2014-09-27 Ongoing
Carbon-13/Carbon-12 in Carbon Dioxide d13C (CO2) 2003-10-08 Ongoing
Oxygen-18/Oxygen-16 in Carbon Dioxide d18O (CO2) 2003-10-08 Ongoing
HFC-134a CH2FCF3 2004-11-12 Ongoing
HCFC-22 CHF2Cl 2004-11-12 Ongoing
CFC-12 CCl2F2 2004-11-12 Ongoing
Methyl Chloride CH3Cl 2004-11-12 Ongoing
CFC-114 CFC-114 2004-11-12 Ongoing
HCFC-142b CH3CF2Cl 2004-11-12 Ongoing
Halon-1211 CBrClF2 2004-11-12 Ongoing
Methyl Bromide CH3Br 2004-11-12 Ongoing
CFC-11 CCl3F (ion 101) 2004-11-12 Terminated - 2015-11-12
CFC-11 CCl3F (ion 103) 2010-05-23 Ongoing
HCFC-141b CH3CCl2F 2004-11-12 Ongoing
Methyl Iodide CH3I 2004-11-12 Ongoing
CFC-113 CCl2FCClF2 2004-11-12 Ongoing
Dichloromethane CH2Cl2 2004-11-12 Ongoing
Chloroform CHCl3 2004-11-12 Ongoing
Methyl Chloroform (97) CH3CCl3 2004-11-12 Ongoing
Methyl Chloroform (99) CH3CCl3 2010-05-23 Terminated - 2012-10-04
Carbon Tetrachloride CCl4 2004-11-12 Ongoing
Methelyne Bromide CH2Br2 2004-11-12 Ongoing
Perchloroethylene (PCE) C2Cl4 2004-11-12 Ongoing
Bromoform CHBr3 2004-11-12 Ongoing
Benzene C6H6 2004-11-12 Ongoing
Carbonyl Sulfide COS 2004-11-12 Ongoing
HCFC-21 CHCl2F 2015-10-15 Ongoing
HFC-152a CH3CHF2 2004-11-12 Ongoing
HCFC-124 CHClFCF3 2004-11-12 Ongoing
Methylbenzene C7H8 2007-07-25 Ongoing
Carbon Disulfide CS2 2004-11-12 Ongoing
Ethane C2H6 2014-09-27 Ongoing
Ethylene C2H4 2014-09-27 Ongoing
Propane C3H8 2007-06-09 Ongoing
Propylene C3H6 2014-09-27 Ongoing
Isobutane i-C4H10 2014-09-27 Ongoing
n-Butane n-C4H10 2007-06-09 Ongoing
isopentane i-C5H12 2007-06-09 Ongoing
n-Pentane n-C5H12 2007-06-09 Ongoing
n-Hexane n-C6H14 2014-09-27 Ongoing
Ambient Pressure press 2004-01-22 Terminated - 2013-04-18
Relative Humidity rh 2003-09-02 Ongoing
Halon-1301 CF3Br 2007-06-09 Ongoing
Halon-2402 CBrF2CBrF2 2007-06-09 Ongoing
HFC-143a CH3CF3 2007-06-09 Ongoing
HFC-227ea CF3CHFCF3 2007-06-09 Ongoing
HFC-365mfc CH3CF2CH2CF3 2007-06-09 Ongoing
CFC-115 CClF2CF3 2007-06-09 Ongoing
HFC-125 CHF2CF3 2007-06-09 Ongoing
CFC-13 CClF3 2007-06-09 Ongoing
Ethyl Chloride CH3CH2Cl 2007-06-09 Terminated - 2014-05-11
HFC-23 CHF3 2007-06-09 Ongoing
PFC-218 C3F8 2008-03-22 Ongoing
Acetylene C2H2 2008-03-22 Ongoing
HFC-32 CH2F2 2009-04-04 Ongoing
HFC-134 CHF2CHF2 2009-04-04 Ongoing
Halon-1011 CH2BrCl 2014-09-27 Ongoing
PFC-14 CF4 2014-09-27 Ongoing
PFC-116 CF3CF3 2014-09-27 Ongoing
Trifluoroamine NF3 2015-10-15 Ongoing
Sulfuryl Fluoride SO2F2 2014-09-27 Ongoing
HFC-236fa CF3CH2CF3 2014-09-27 Ongoing
HCFC-133a CH2ClCF3 2015-10-15 Ongoing
CFC-112 CCl3CClF2 2014-09-27 Ongoing
Trichloroethylene (TCE) C2HCl3 2014-09-27 Ongoing
HFO-1234yf CH2=CFCF3 2016-09-17 Ongoing
HFO-1234zeE CHF=CHCF3 2016-09-17 Ongoing
ethylene dichloride (1,2 DCE) CH2ClCH2Cl 2018-01-13 Ongoing
HCFC-123 CHCl2CF3 2018-01-13 Ongoing
Morpholine C5F11NO 2017-12-08 Ongoing
Perfluorotriethylamine (PFTEA) (C2F5)3N 2017-12-08 Ongoing
Perfluorotripropylamine (PFTPA) (C3F7)3N 2017-12-08 Ongoing
HFC-245fa 2022-08-06 Ongoing

HATS Flask Sampling

Parameter Formula First Sample Date Status
HFC-134a CH2FCF3 2002-02-26 Ongoing
HCFC-22 CHF2Cl 2002-03-06 Ongoing
CFC-12 CCl2F2 2010-01-14 Ongoing
Methyl Chloride CH3Cl 2002-03-06 Ongoing
HCFC-142b CH3CF2Cl 2002-02-26 Ongoing
Halon-1211 CBrClF2 2002-02-26 Ongoing
Methyl Bromide CH3Br 2002-03-06 Ongoing
HCFC-141b CH3CCl2F 2002-02-26 Ongoing
CFC-113 CCl2FCClF2 2002-02-26 Ongoing
Dichloromethane CH2Cl2 2002-03-06 Ongoing
Perchloroethylene (PCE) C2Cl4 2002-03-06 Ongoing
Carbonyl Sulfide COS 2002-04-03 Ongoing
HFC-152a CH3CHF2 2002-02-26 Ongoing
Halon-2402 CBrF2CBrF2 2004-02-26 Ongoing
HFC-227ea CF3CHFCF3 2011-06-19 Ongoing
HFC-365mfc CH3CF2CH2CF3 2009-08-10 Ongoing
Methyl Chloroform CH3CCl3 2002-02-26 Ongoing
CFC-11 CCl3F 2010-01-14 Ongoing

Aerosol Surface In-Situ

Parameter Formula First Sample Date Status
Light Scattering Coefficient σsp 2002-01-01 Terminated - 2017-01-01
Light Absorption Coefficient σap 2002-01-01 Terminated - 2017-01-01
Particle Number Concentration Nt 2002-01-01 Terminated - 2017-01-01
Aerosol Chemical Composition 2002-01-01 Terminated - 2006-01-01
Aerosol Hygroscopic Growth f(RH) 2002-01-01 Terminated - 2006-01-01

Radiation In-Situ Observatory

Parameter Formula First Sample Date Status
Direct Normal 2002-04-10 Terminated - 2017-04-30
Downwelling Shortwave 2002-04-10 Terminated - 2017-04-30
Diffuse 2002-04-10 Terminated - 2017-04-30
Downwelling Longwave 2003-05-20 Terminated - 2017-04-30

Surface Ozone

Parameter Formula First Sample Date Status
Ozone O3 2002-04-18 Ongoing



Parameter Formula First Sample Date Status
Wind Speed ws 2002-04-10 Ongoing
Wind Direction wd 2002-04-10 Ongoing
Temperature temp 2007-09-19 Ongoing
Ambient Pressure press 2007-09-19 Ongoing
Relative Humidity rh 2013-06-26 Ongoing

Ozone Airborne

Trace gases from GGGRN Airborne Flasks