CalCOFI Reports, Vol. 11, 1967 - California Cooperative Oceanic ...

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160CALIFORNIA COOPERATIVE OCEAKIC FISHERIES INVESTIGATIOKSThe papers cited have described the major featuresof the variations in temperature and salinity in theCalifornia Current region. The present study employsa totally different method of analysis which substantiatesthe previous findings. Detail is provided in someareas and for some months that has not previouslybeen available. Almost all of the statistical treatmentis new.California Cooperative Oceanic Fisheries InvestigationsAtlas No. 1 (1963) contains distributions chartsof 10-meter temperature and salinity for each Cal-COFI cruise, 1949-59. The atlas also presents chartsdrawn from 10-year monthly means of temperatureand salinity. Near the end of this paper a brief comparisonis made between the mean distribution chartsof the atlas and those derived from the present analysis.THE DATAThe CalCOFI data through 1959 are published inthe series, Oceanic Observations of the Pacific. Datafor more recent cruises are available in the data reportseries (unpublished) of the University of California Scripps Institution of Oceanography.Records for 222 stations were selected for analysisfrom the CalCOFI 10-meter data for 1950-62 accordingto criteria of occupancy and location (Figure 2).Thirty percent of the stations were occupied 14 to50 times, and the remainder 51 to 119 times. The stationswith the lesser frequency of sampling are foundat the seaward extreme of the station pattern, offCabo San Lazaro and south, and scattered among thestations north of Point Conception. These stationrecords were used to extrapolate charting of thedistributions beyond the better sampled areas. Theobservations are not evenly distributed throughout theyear but occur more frequently in April-July, andless frequently in September, November, and December.Figure 13 shows time plots of data records withall years folded into one 12-month period. (An explanationof Figure 13 is given under STATIONREGRESSION CURVES.) Only one observation permonth was used ; when duplicate observations weremade, usually the one nearest mid-month was used.In addition to the CalCOFI data, portions ofrecords from five shore stations (surface only) wereanalyzed :Temperature SalinityBlunts Reef _~ ___-_--_ __-_____ 1955-62 1957-62S.E. Farallon Island _--_ _ ____-- 1955-62 1957-62La Jolla ..................... 1950-62 1956-62 *Guadalupe Island --_-_ _ _----__ 1956-60 -Cedros Island ~ ~ ~ _ ~ ~ _ 1957-62 _ ~ _ _ ~ ~ ~ _ ~ _Observations were made daily. The records were collectedby the U.S. Coast and Geodetic Survey andScripps Institution of Oceanography (unpublished).For this analysis, monthly averages (daily observationsaveraged for each month of each year) wereentered as initial data. Thus, there is one value permonth comparable in number to the CalCOFI samplingValidity of salinity observations for 1944-55 were questioned byRoden (1961) : hence, these observations were not includedin this analysis.program, but with some high frequency variationfiltered out.CHOICE OF THE 10-METER LEVELHydrographic casts were made during about 80percent of the station occupations ; the remaining 20percent were “net-haul” stations, where work consistedof biological sampling and a 10-meter temperatureand salinity measurement. The 10-meter levelwas chosen to represent the upper mixed layer in lieuof a surface sample to avoid such transient conditionsas might be caused by rain or river runoff and bydiurnal heating and cooling. In some places a shallowsummer thermocline may develop. When this thermoclineis shoaler than 10 meters it is readily subjectto wind stirring; hence, its existence is usually brief.These arguments do not obtain in the vicinity ofCab0 San Lucas3 where oceanic fronts and othercomplex features persist (Griffiths, 1965).ANALYSISAn expression of the mean seasonal variation of acharacteristic may be obtained from a digital recordby Fourier polynomials, a method of harmonicanalysis. Because the time intervals between datameasurements are irregular, standard textbook formulasderived for processes sampled at equallyspacedintervals are unsuitable and hence an approachfrom basic concepts is necessary. A detailed descriptionof each data record by harmonic analysis is notnecessary ; the only harmonics needed are those whichcontribute significantly to the description of the seasonalvariation. This consideration leads to a differentbut totally equivalent approach which has an addedadvantage. The mean seasonal variation may be obtainedby least squares regression of the data (consideringeach station record as a time series) toannually periodic sinusoids. Van Vliet and Andersonanalysed sea surface temperature records for seasonalvariation by fitting annual and semiannual harmonicsto the observed data by regression analysis. Theiranalyses were performed on long records of dailytemperature observations at four shore stations andtwo weathership stations. Least squares regressionanalyses for curve fitting is identical to the morecommon application of estimating linear relationships.The added advantage of this method is seen inthe statistical approach; it is a natural adjunct ofregression analysis to compute measures of dispersion,correlation coefficients, and significance parameters.Though less natural, such computations can bemade with truncated Fourier polynomials.Natural events driven by insolation tend to varywith an annual cycle that may be roughly describedby a sinusoid. However, because the effect of insolationis often indirect, the rough approximation providedby the annual sinusoid can usually be refined byGeographical locations are identified in Figure 2.4 Statistical analyses of sea surface temperature time series (unpublishedmanuscript). U.S. Navy Electronics Laboratory,San Diego, Calif.
including the semiannual harmonic? The frequent3- and 4-mpnth gaps in the data records and the brevityof the records preclude any significant results fromthe third harmonic.REPORTS VOLUME XI, 1 JULY 1963 TO 30 JUNE 1966 161The general form of the regression curve is:y = AI cos0 + BlsinO + A2c0s2e + Bzsin2O + Cwhere O is the angular equivalent of the day of yearin radians. In least squares regression the sum of thesquares of the data anomalies from the regression curve,1 [y; - (Alcosei + Blsin& + Azcos20ia + B2sin20i + C)Iz,is minimized with respect to each of the five coefficientswhere,yi = data values indexed to 8;8% =27r[(month - 1) 30 + day]360The resulting set of equations is solved simultaneouslyfor the coefficients. The same coefficient formulascan be derived from the Fourier polynomialapproach. When equal intervals are assumed (integraldivision of year) the formulas simplify to thestandard textbook formulas for Fourier polynomialcoefficients.From the station regression curves were derivedthe long term mean (13-year), extreme values, andrange. Statistics describing the data and the fit ofthe regression curve were computed by standardformulas. These statistics include standard deviation,standard error of estimate, coefficient of correlation,and the P-ratio test (null hypothesis: the mean providesas adequate a fit to the data as the regressioncurve). The coefficient of correlation refers to thecorrelation of the characteristic with time of year.DISTRIBUTION OF THE 13-YEAR MEANSThe long term (13-year) mean of temperature(Figure 3) shows the influence of currents and upwelling.The mean temperature ranges from 12" C.near San Francisco to 24" C. near Cabo San Lucas.More than half the range (less than 18" C. to 24" C.)falls between Punta Eugenia and Cabo San Lucas,one-third of the total distance. The isotherms tendt0 parallel the coast along northern and centralCalifornia with the colder water inshore, whereasthe isotherms are nearly perpendicular to the shorealong the southern part of Baja California. The colderinshore water along northern and central Californiais a mixture of cold waters from the North PacificCurrent and cold waters upwelled along the coast.A second important upwelling region, indicated bya 16" C. isotherm, is near the coast immediately northof the United States-Mexican border and extendingsouthward along northem Baja California. West ofthis upwelling region is a warm tongue-like featureextending into the island area off southern California.6 Van Vliet and Anderson performed an autocorrelation analysison the long records (7-40 years) of daily temperature observationsand showed the semiannual harmonic contains a sixnificantportion of the energy of seasonal variation in four oftheir six stations.FIGURE 3. Ten-meter temperature ("C); 13-year mean, 1950-62. Interval:1" C. In this and other figures thin, shortdashed lines showhalf intervals and thick, long dashes show continuation of standardintervalisopleths into regions of infrequent sampling. Boxed valuesrefer to shore statiomr.The long term mean salinity (Figure 4) rangesfrom less than 33.0%0 near Cape Mendocino to greaterthan 34.6%0 near Cape San Lucas. More than half thisrange is along southern Baja California. The largestgradients are in the southernmost portion of the Cal-COFI area and in the upwelling region north ofPoint Conception. A low-salinity tongue, characteristicof the California Current, lies approximately240 miles from and parallel to the northern Californiacoast. The displacement of the low-salinity tonguefarther offshore from the low-temperature tongue isevidently the consequence of the mixing of upwelledwater, characteristically cold with high salinity, andCalifornia Current water. characteristically cold withlow salinity. Along southern California and northernBaja California is a body of water with a nearly uniformmean salinity, 33.55%0 I 0.05%0 and a smallstandard deviation, approximately i- 0.15%0. Thisarea shows a complex distribution of mean temperature.Reid, Schwartzlose, and Brown (1963) described ashoreward movement of water near latitude 31" N.to 32" N. Features in the 33.4%0 and 33.5%0 isohalinesprobably relate to this flow, as perhaps does the6-95757
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STATE OF CALIFORNIAMARINE RESEARCH
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STATE OF CALIFORNIADEPARTMENT OF FI
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RONALD REAGAXGovcriwr of the Slate
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PART 1REVIEW OF ACTIVITIESJuly 1,19
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REPORTS YOLUAIE SI, 1 JULY 1963 TO
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REPORTS VOLUNE XI, 1 JULY 1963 TO 3
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REPORTS YOLUME SI, 1 JULY 1963 TO 3
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REPORTS VOLUME XI, 1 JULY 1963 TO 3
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REPORTS vor,uiwIi; SI, 1 JULY 1063
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REPORTS TOT2T71\IF: SI, 1 JUJIT 196
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IiEPOHTS TOLUME XI, 1 JULY 1963 TO
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REVIEW OF THE PELAGIC WET FISHERIES
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KEI'OiiTH TOLUJIE SI, 1 JULY 1963 T
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PART IISYMPOSIUM ON ANCHOVIES, GENU
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OCEANIC ENVIRONMENTS OF THE GENUS E
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KEI'OKTS VOLIXI.: SI, 1 JULY 1963 T
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~~~REPORTS VOLUME XI, 1 JULY 1963 T
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REPORTS VOLUME SI, 1 JULY 1963 TO 3
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130'E 132' 134' 136' 138' 140' 142-
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KI3I’ORTH VOLUJIE XI, 1 JULY 1963
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REPORTS VOLUIIE SI. 1 JULY 1963 TO
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REPORTS T’OLUME XI, 1 JULY 1963 T
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INFLUENCE OF SOME ENVIRONMENTAL FAC
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REPORTS Y‘OLUJIE XI, 1 JULY 1963
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~table shows the values calculated
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ateREPORTS T-OLTJIT", SI, 1 JULl 19
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REPORTS POLGNE SI, 1 JU LY 1963 TO
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REPORTS VOLUXE XI, 1 JULY 1963 TO 3
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_________--_____REPORTS VOLUJIE SI,
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REPORTS TOLTIJIE SI, 1 JULY 1963 TO
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-20/5-0 10-f 5-w 25-0 20-= 15-: 10-
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REPORTS VOLUNE SI. 1 JULY 19G3 TO 3
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THE PREDATION OF GUANO BIRDS ON THE
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iod and after 8 AM during the rest
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Page 115 and 116: FISH E RYThe California anchovy fis
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Page 119: CO-OCCURRENCES OF SARDINE AND ANCHO
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Page 138 and 139: THE ACCUMULATION OF FISH DEBRIS IN
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Page 190: CONTENTSI. Review of Activities Pag
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