esses and characterized the region off the west coast of North 

 America as an area of net annual oceanic heat gain. However, pre- 

 vious studies have not provided sufficient spatial resolution to 

 delineate the critical areas of surface heat flux within the California 

 Current region. 



In this report we present the long-term climatological monthly 

 mean distributions of heat exchange across the air-sea interface 

 based on a summarization of historical surface marine weather 

 observations over the California Current region. This study differs 

 from previous work for this area by calculating monthly mean val- 

 ues on a 1° latitude-longitude grid and by computing the heat 

 exchange components from individual surface marine weather 

 reports archived in the National Climatic Center's (NOAA, Envi- 

 ronmental Data and Information Service) Tape Data Family- 11 

 (TDF-1 1). Roden (1974) evaluated the surface radiative and turbu- 

 lent heat fluxes on a 1° latitude-longitude grid. However. Roden s 

 distributions were derived from monthly mean surface temperature 

 and wind analyses and satellite cloud cover data based on a 5° 

 latitude-longitude grid and interpolated to the finer mesh grid. We 

 used standard bulk aerodynamic formulae, referred to a neutrally 

 stable atmospheric boundary layer (Malkus 1962), to evaluate the 

 evaporative and conductive heat fluxes. A separate analysis was 

 performed to evaluate the dependence of these flux computations 

 on the turbulent exchange coefficients as functions of windspeed 

 and atmospheric stability. The methods are similar to procedures 

 employed by Bunker (1976) and Hastenrath and Lamb (1978) for 

 investigations of surface heat flux in the North Atlantic and in the 

 tropical Atlantic and eastern Pacific Oceans, respectively. The dis- 

 tributions of heat exchange components described in this report will 

 provide basic input data for a future simulation model of large-scale 

 variations in the California Current ecosystem. 



PROCESSING OF DATA 



Surface marine weather observations archived in the TDF- 1 1 file 

 consist of weather reports from teletype messages, ship logs, published 

 ship observations, ship weather reporting forms, and various punched 

 card decks obtained from foreign meteorological services. The sources 

 of data and periods of coverage are tabulated in the TDF-1 1 documen- 

 tation-' and in Hastenrath and Lamb (1978). Over 1 million reports are 

 within the California Current region and date from the mid- 19th 

 century through 1972. Individual reports were compiled by 1 ° squares 

 within the geographical area oudined in Figure 1 . The data grid extends 

 from lat. 2 1 °N to 50°N and parallels the coastline of British Columbia, 

 the western United States, and Baja California. The grid extends 10° 

 of longitude in the offshore direction, a distance ranging from 1.040 

 km at lat. 21 °N to 717 km at lat. 50 C N. Each 1 ° square is centered on a 

 whole degree of latitude and longitude. Approximately 25% of the 

 total available reports contain positions recorded to the nearest whole 

 degree of latitude and longitude. The grid orientation used in this study 

 reduces spatial bias which might be introduced by summarizing the 

 data according to the more conventional Marsden square numbering 

 system. 



The observations contained in the TDF- 1 1 reports vary markedly 

 in methods and precision of measurement due to the changes in 

 instrumentation and sampling techniques over the considerable 

 time period covered by the data base. An individual surface 

 weather report was used in the calculation of the heat exchange 

 processes only if it contained all the properties needed to compute 



; NationaI Climalic Center. Tape Data Family II, NOAA EDISNCC. Asheville, 

 NC 28801. 



Figure 1. — Chart of the west coast of the United States showing the grid of l c 

 squares used for summaries of the surface heat fluves. Large dots indicate 

 squares for which the annual cycles of heat evxhange processes are displayed in 

 Figure 19. 



the radiative and turbulent heat fluxes. Values for surface pressure, 

 /"(mbar), sea surface temperature, T,{°C); air temperature, T a (°C); 

 wet-bulb or dewpoint temperature, 7„ or Tj(°C); windspeed, 

 (7i (kn); and total cloud amount, C(oktas), were extracted from the 

 TDF-1 1 file and quality controlled with a single pass editor to 

 remove gross errors. Windspeed and cloud amount were converted 

 to units of meters per second and tenths before incorporating these 

 variables in the heat exchange formulae. 



A total of 560,210 reports were accepted for the heat exchange 

 calculations. These data amounted to 57% of the available reports. 

 Approximately 38% of the reports were rejected because one or 

 more of the surface meteorological observations were missing. An 

 additional 3-5% of the reports were deleted because of duplicate 

 reports and errors in position or because observed or derived varia- 

 bles could not pass specified climatic checks. An entire report was 

 removed if surface observations exceeded the following extreme 

 value limits: pressure (P) < 945 mbar or > 1 .055 mbar; windspeed 

 (t/J> lOOm/s; air temperature (r o )<-10°C or >40°C: wet-bulb 

 temperature (7"J < -5°C or >40°C; sea temperature (7"J < -2°C or 

 >35°C; and air-sea temperature difference (7" o -7" J )<-30°C or 

 >30°C. Wet-bulb and dewpoint temperatures were constrained to 

 be less than or equal to the air temperature, and a valid estimate for 

 total cloud amount (C), i.e., between 0.0 and 1.0, was required to 

 accept the report. Cloud observations originally encoded as 9 

 (oktas) in the TDF-1 1 file indicated that the sky was obscured or 

 cloud amount could not be determined. Consequently, these reports 

 were also rejected. As a result of the editing procedures, the distri- 

 butions of surface heat fluxes (Appendix I) and tables of monthly 

 mean surface atmospheric properties (Appendix III) presented in 

 this report are based on a common set of weather observations col- 

 lected during the more restricted period from 1921 to 1972. 



