COMPARISON OF PREDICTED AND OBSERVED TIDES AT MONTEREY, CALIFORNIA Harold Vincent Maixner Library Naval Postgraduate School Monterey, California 93940 7 TE SCHOOL onterey, lahtornia .'.«> - j isaa Comparison of Predicted and Observed Tides at . Monterey, Calif* by Drnia Harold Vincent Maixner, Jr. Thesis Adv isor : Warren C. Thompson March 1973 T Apptiovcd ^OH. puhtic ndLaoMi; dLi>Vuhu£lon LinLuni£Q.d . Comparison of Predicted and Observed Tides at Monterey, California by Harold Vincent Maixner, Jr. Lieutenant Commander, United States Navy B.S., United States Naval Academy, 1966 Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN OCEANOGRAPHY from the NAVAL POSTGRADUATE SCHOOL March 1973 Library Naval Postgraduate ScHbof Monterey, California 93940 ABSTRACT A comparison of the predicted and observed tides at Monterey, California conducted over the period of a year revealed that the hourly water-level differences did not exceed i 0.9 feet in magnitude. 263 water-level anomalies of duration up to 362 hours were identified, of which 42 were of duration greater than twelve hours. It was determined that change in atmospheric pressure is the dominant causitive factor of hourly water-level differences and that the water-level response is approximately hydrostatic. The changes in atmospheric pressure asso- ciated with the 42 water-level anomalies examined were found to be manifestations of the eastward or westward migration of the isobaric gradient due to either intensification or movement of the quasi-permanent high and low pressure systems in the region. TABLE OF CONTENTS LIST OF TABLES 4 LIST OF FIGURES 5 I . INTRODUCTION 7 II. COLLECTION AND ANALYSIS OF TIDE DATA 8 III. DISTRIBUTION OF WATER-LEVEL DEVIATIONS H A. STATISTICAL DISTRIBUTION OF HOURLY WATER-LEVEL n DIFFERENCES B. PERIODS OF ANOMALOUS WATER LEVEL 11 1. Definition of Anomalous Water-Level Period 11 2. Occurrence of Water-Level Anomalies 12 IV. RELATIONSHIP OF WATER-LEVEL DEVIATIONS TO ATMOSPHERIC 24 PRESSURE A. INTRODUCTION 24 B. STATISTICAL RELATIONSHIP BETWEEN ATMOSPHERIC 26 PRESSURE AND WATER-LEVEL DIFFERENCE C. ATMOSPHERIC PRESSURE VARIATIONS ASSOCIATED WITH 44 WATER-LEVEL ANOMALIES D.' SYNOPTIC WEATHER EVENTS ASSOCIATED WITH ANOMALIES 46 V. SUMMARY 53 LIST OF REFERENCES 55 APPENDIX A. Tidal Constituents for Monterey, California 56 APPENDIX B. Water-Level Anomalies 58 APPENDIX C. Extreme Water-Level Anomalies 74 INITIAL DISTRIBUTION LIST 80 FORM DD 1473 82 LIST OF TABLES TABLE 1: FREQUENCY DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES 14 TABLE 2: MONTHLY DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES 16 TABLE 3: WATER-LEVEL ANOMALIES 19 TABLE 4: EXTREME WATER-LEVEL ANOMALIES 22 TABLE 5: REGRESSION ANALYSIS SUMMARY 42 LIST OF FIGURES FIGURE 1: TIDE GAGE LOCATION, MONTEREY, CALIFORNIA 10 FIGURE 2: FREQUENCY DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES 15 FIGURE 3A: SAMPLE OF THE HOURLY WATER-LEVEL DIFFERENCE DATA 17 FIGURE 3B: SAMPLE OF THE FILTERED HOURLY WATER-LEVEL DIFFERENCE DATA 18 FIGURE 4: REGRESSION ANALYSIS — FEBRUARY 1971 28 FIGURE 5: REGRESSION ANALYSIS — MARCH 1971 29 FIGURE 6: REGRESSION ANALYSIS — APRIL 1971 30 FIGURE 7: REGRESSION ANALYSIS — MAY 1971 31 FIGURE 8: REGRESSION ANALYSIS — JUNE 1971 32 FIGURE 9: REGRESSION ANALYSIS — JULY 1971 33 FIGURE 10: REGRESSION ANALYSIS — AUGUST 1971 34 FIGURE 11: REGRESSION ANALYSIS -- SEPTEMBER 1971 35 FIGURE 12: REGRESSION ANALYSIS — OCTOBER 1971 36 FIGURE 13: REGRESSION ANALYSIS ~ NOVEMBER 1971 37 FIGURE 14: REGRESSION ANALYSIS ~ DECEMBER 1971 38 FIGURE 15: REGRESSION ANALYSIS ~ JANUARY 1972 39 FIGURE 16: REGRESSION ANALYSIS -- YEAR (FEBRUARY 1971 - JANUARY 1972)40 FIGURE 17: MONTHLY ATMOSPHERIC PRESSURES AT MONTEREY, CALIFORNIA 41 FIGURE 18: WATER-LEVEL ANOMALY AND ASSOCIATED PRESSURE DISTRIBUTION 43 FIGURE 19: LONG-TERM MEAN PRESSURE PATTERN — MAY 49 FIGURE 20: SEA LEVEL PRESSURE CHART — 1600, 6 MAY 1971 50 FIGURE 21: LONG-TERM MEAN PRESSURE PATTERN — JUNE 51 FIGURE 22: SEA LEVEL PRESSURE CHART — 0400, 1 JUNE 1971 52 ACKNOWLEDGEMENTS The author desires to express his appreciation to Dr, Warren C. Thompson for his assistance and constructive criticism during the course of this study and who suggested that it be undertaken; to Mr. Robert A, Cummings, Chief of the Tides Branch, National Ocean Survey for an- alyzing the tide data used in this study. I. INTRODUCTION The astronomical tides are periodic undulations of the sea surface height which are readily predictable. Meteorological and oceanographical factors exert short-terra influences which can cause additional deviations from the mean ocean level; these additional water-level deviations are superimposed upon those caused by the tides and are not predictable with the exception of wind-induced storm tides generated over wide \ continental shelves. It was the purpose of this study to examine the nature of the non- astronomically produced water-level deviations at a selected tide station on the California coast over the period of a year and to inquire about their causes. These deviations were derived by comparing the predicted tide with the observed tide hourly. It was found that the observed water-level deviated from the predicted over varying periods of time ranging from less than six hours to as long as 15 days. These periods were considered anomalous. Initial examination of various factors that might induce anomalous water levels indicated that atmospheric pressure variations were a dominant factor. Accordingly, the effect of atmospheric pressure was examined in detail to determine the extent of its influence in producing the hourly water-level differences and the anomalous periods observed. II. COLLECTION AND ANALYSIS OF TIDE DATA The observed tide data were recorded on a standard recording tide gage maintained by the Naval Postgraduate School on Monterey Municipal Wharf No. 2, Monterey, California (Figure 1). The recording period selected for this study was an annual cycle extending from 28 January 1971 through 2 February 1972, a period of 370 days. Selection of the calendar year 1971 would have been more desirable but the tide gage required repair in January and recording during that month was incomplete. Recording was continuous throughout the entire period selected with the exception of three intervals totaling forty hours which required inter- polation. The monthly tide rolls from the tide gage were reduced to yield heurly water-level heights, and heights and times of high and low waters, following the standard procedures used by the National Ocean Survey (Coast and Geodetic Survey, 1965) . Heights were measured to the closest 0.1 foot and resolution of the time of high and low waters was to the closest six minutes. The Tides Branch, National Ocean Survey, Rockville, Maryland performed a harmonic analysis of the observed tide data, isolating 37 harmonic constituents (Appendix A). Utilizing all 37 constituents, predicted hourly heights and heights and times of high and low waters were computed for the period 1 February 1971 through 31 January 1972. Only the hourly heights were used in this study. From the predicted hourly heights, the differences between the observed and predicted hourly water levels were computed. This residual constituted the hourly water-level differences 8 that form the basic data used in this study, The variability of the values of hourly water-level difference with time indicate a precision of t 0.1 foot for the data. 1 1 1 * 122°10' 122°00' 121°50' - \V 37*00'- ~VX SANTA CRUZ ' '-T\ %P®?t93& >/^~~**\ -,, > ' "v\\ \ *•--: Ty }} a \\ 36°50- '"•• ••'"'•••. / L^:"' ::"' '<::•• •v^-/-^ MOSS ....«-•;;:•■.•:..• / J LANDING y- '5oo.....: ■" / :••" "'^ ,/y / 1 X ( \ N /"' / ( [ M c^JJ j )J •: ) /"" / ."" // / > L 1 J tide y n 36°4°- / J ■ ? .-•"""" ..- GAGE // A / / ) I I lr 4t £®£s i .NAVAL AIR = .. / v f\ 1 \\ j( ^W^^ C=3 FACILITY 7../ ...-•' I \ } % (if MONTEREY \ *-\ V\ sV ' MILES :: , * "~^\ 6 1 2 4 8 [ N; /ssSiS*A DEPTHS IN FATHOMS """ - -! i | (\ $&* j Figure 1: TIDE GAGE LOCATION, MONTEREY, CALIFORNIA 10 III. DISTRIBUTION OF WATER-LEVEL DEVIATIONS A. STATISTICAL DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES The difference between the observed and predicted tide height at a given time is referred to here as a water-level difference. A given water-level difference is termed positive (negative) when the observed water level is greater (less) than the predicted height. A sample of the hourly water-level difference data appears in Figure 3A. The differences between the observed and predicted hourly water levels were first examined independently of trends appearing in the hourly time series. The frequency distribution of the 8760 water-level differences contained in the year of tide data is shown in Table 1 and Figure 2. The distribution is very nearly normal about a zero water- level difference. The extreme water-level differences noted did not exceed _ 0.9 foot, and sixty-three percent of the hourly differences fell in the range from +0.1 to -0.1 foot. The distribution of hourly water-level differences by months is summarized in Table 2. It may be noted that the fall and winter months generally exhibit the greatest number of water-level differences. B. PERIODS OF ANOMALOUS WATER LEVEL 1. Definition of Anomalous Water-Level Period Examination of the hourly water-level data revealed that throughout the year there were periods of consecutive hourly water-level differences of like sign varying from two to 362 hours in duration. Noting that the precision of both the observed and predicted hourly water levels was 0.1 foot, the decision was made to consider only hourly 11 water-level differences equal to or greater than an absolute value of 0.2 feet as indicating a real water-level difference. Accordingly, the data were filtered so as to delete all values of -0.1, 0.0 and +0.1 feet. A sample of the hourly water-level difference data before and after filtering is presented in Figures 3A and 3B. In summary, a water-level anomaly, for the purposes of this study, is defined as follows: a. An anomaly begins when the hourly water-level differences become - 0.2 feet or greater and ends when the hourly water-level differences fall below _ 0.2 feet. It follows that a water-level anomaly consists of like signed hourly water-level differences. The existance of hourly values less than t 0.2 feet was tolerated within the interval of a water-level anomaly only when it appeared that they were indicative of the general trend of the anomaly. b. A water-level anomaly has a duration of two hours or greater. 2. Occurrence of Water-Level Anomalies All water-level anomalies occurring during the year, as defined above, were identified from the time series of hourly water-level differences, and their frequency of occurrence by duration and month are presented in Table 3. It may be noted from the table that of the 263 anomalies found, only 21 were of a duration longer than 24 hours, with a tendency for the longer anomalies to occur in the fall and winter months. There was a slight tendency for a greater number of short anomalies (11 hours or less) to occur in the spring and summer months. Those anomalies of duration 12 hours or longer were examined in detail and their properties are tabulated in Appendix B. 12 Attention was also directed to periods of extreme water-level difference, considered here to include all values of hourly water-level difference equal to or greater than +0.4 feet (667 values or eight per- cent of the total number of hourly water-level differences from Table 1) . A summary of the occurrence of those extreme periods by duration and month is given in Table 4. It may be noted that the distribution by months is irregular, with a tendency for a greater occurrence in the fall and winter months. Of the 61 extreme water-level periods identified, 47 (77%) were of a duration less than 12 hours. The properties of these extreme per- iods are tabulated in Appendix C. 13 TABLE I: FREQUENCY DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES DIFFERENCE (FEET) NO. VALUES PERCENT REMARKS +0.9 +0.8 +0.7 +0.6 +0.5 +0.4 +0.3 +0.2 6 ' 5 33 39 79 179 434 842 0.06 0.05 0.37 0.44 0.90 2.04 4.95 9.61 1617 positive values greater than 0.1 foot +0.1 0.0 -0.1 1593 2160 1799 18.11 24.65 20.39 5552 values (63.15%) -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -0.9 TOTAL 896 369 173 86 48 15 2 2 8760 10.22 4.21 1.97 0.98 0.54 0.17 0.02 0.02 99.70 1591 negative values less than -0.1 foot. 14 2500 0«V— — — f -10 -0.8 -0.6 -0.4 WATER-LEVEL DIFFERENCE (FEET) FIGURE 2: FREQUENCY DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES 15 TABLE 2: MONTHLY DISTRIBUTION OF HOURLY WATER-LEVEL DIFFERENCES NO. POSITIVE NO. VALUES OF NO. NEGATIVE [ONTH VALUES ZERO DIFFERENCE VALUES FEB 1971 280 129 263 MAR 254 113 377 APR 276 218 226 MAY 409 183 152 JUN 168 182 370 JUL 179 276 289 AUG 124 280 340 SEP 345 196 179 OCT 272 168 304 NOV 162 163 395 DEC 367 98 279 JAN 1972 374 154 216 TOTAL 3210 2160 3390 16 Figure 3A: SAMPLE OF THE HOURLY WATER-LEVEL DIFFERENCE DATA Month: June DATE HOUR 1 2 i 3 4 5_ 6 1_ 8 00 -0.3 -0.2 -0.1 -0.1 -0.1 -0.1 -0.2 0.0 ox -0.3 -0.2 -0.1 -0.1 -0.1 -0.1 -0.1 0.0 02 -0.3 -0.2 -0.1 -0.2 -0.1 0.0 -0.1 0.0 03 -0.2 -0.1 -0.1 -0.1 0.0 0.0 -0.1 -0.2 04 -0.2 -0.2 -0.1 -0.1 0.0 0.0 0.0 -0.1 05 -0.3 -0.1 -0.1 -0.1 -0.1 0.0 -0.1 0.0 06 -0.2 -0.1 -0.1 -0.1 -0.1 0.0 0.0 . 0.0 07 -0.2 -0.1 -0.1 -0.1 -0.1 0.0 -0.1 -0.1 08 -0.2 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 0.0 09 -0.2 -0.1 -0.2 -0.1 0.0 0.0 -0.1 0.0 10 -0.2 -0.1 -0.2 -0.2 -0.1 -0.1 -0.1 -0.1 11 -0.2 0.0 -0.1 -0.1 -0.1 -0.1 -0.1 -0.1 12 -0.2 -0.1 -0.2 -0.2 -0.1 -0.1 -0.1 -0.1 13 -0.2 -0.1 -0.2 -0.2 -0.1 -0.1 -0.1 0.0 14 -0.2 -0.1 -0.2 -0.2 -0.2 -0.1 -0.1 -0.1 15 -0.2 -0.1 -0.2 -0.2 -0.2 -0.1 -0.2 0.0 16 -0.2 -0.1 -0.2 -0.2 -0.3 -0.2 0.0 0.0 17 -0.2 -0.2 -0.2 -0.2 -0.3 -0.1 -0.1 0.0 18 -0.2 -0.2 -0.3 -0.2 -0.1 -0.2 -0.1 0.0 19 -0.2 -0.2 -0.2 -0.2 -0.1 -0.1 0.0 0.1 20 -0.2 -0.3 -0.2 -0.2 -0.1 -0.1 0.0 0.0 21 -0.3 -0.1 -0.2 -0.2 -0.1 -0.2 0.0 -0.1 22 -0.2 -0.2 -0.1 -0.2 -0.1 -0.1 -0.1 -0.1 23 -0.3 -0.2 -0.2 -0.1 -0.1 -0.1 -0.1 -0.1 17 Figure 3B; SAMPLE OF THE FILTERED HOURLY WATER-LEVEL DIFFERENCE DATA Month: June DATE HOUR 1 2 3 4 5_ 00 -0.3 -0.2 01 -0.3 -0.2 02 -0.3 -0.2 -0.2 03 -0.2 04 -0.2 -0.2 05 -0.3 06 -0.2 07 -0.2 08 -0.2 09 -0.2 -0.2 10 -0.2 -0.2 -0.2 11 -0.2 12 -0.2 -0.2 -0.2 13 -0.2 -0.2 -0.2 14 -0.2 -0.2 -0.2 -0.2 15 -0.2 -0.2 -0.2 -0.2 16 -0.2 -0.2 -0.2 -0.3 17 -0.2 -0.2 -0.2 -0.2 -0.3 18 -0.2 -0.2 -0.3 -0.2 19 -0.2 -0.2 -0.2 -0.2 20 -0.2 -0.3 -0.2 -0.2 21 -0.3 -0.2 -0.2 22 -0.2 -0.2 -0.2 23 -0.3 -0.2 -0.2 6- I -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 V 18 CO r-l m 53 vo in rH rH m CM CO w ►J W > w rH I PS w H s CO w rJ o •H 4-> «J o c cd c o ,0 0) o c M H O W 52 > co O P-i .J <: H O H M O P-< W CO o 53 p^ < CO r^ rH vo m cjn cti t^ r^» oo I l I vO CM 00 oo o\ cr> I I I O vD ^•invovor-r-^oocr\o> o o CM A co 19 CO m o oo r-» vo CO •d" CM CM CO CM r-i vo iH 00 Sf CM rH 00 C> CO co o CO w W g M •J ►J CM CO iH M H £> R 53 o O U § w !2 vO CO > M § W H iJ H PQ GO 5 O H PM s CT> in ON CT\ CO 0O ON Oi H I I I I I oo O o o CM co 20 o ^o cn CM o rH m U CO rH W O m o m <* m W oo w M H O c_> en W rJ w > r-l H < a w Ol vO *d" rH rH cr> cm o m cm tul CO rH CM CM rH rH 00 m pil rH cn rH in •H CM m -* cn o M H S P P m l CM rH rH 1 rH 1 CM rH cn CM 1 CO rH On CM 1 cvoi^r^MO\c\o N CM H m m H N CM H rH CM > J3 CO iH rH m rH rH CM c o CO •H w *J M CO ^J| V-i *-> w c ►J o 1 a Pi w ^ H rQ £ 0) o W CD a j_i w H V4 o o W o «4-l • • o st r^ W o rJ c 53 CD H cr M H < ►J O £> w »-> S3 vO rH rH CN rH CTi o 2; rH rH CM CM CO H U O W CO \£> rH CO W M •J 3 CD w w rJ 9 > co o P-. 53 p > M H PQ CM 00 00 CO UJ M C£ cn •O CL >H o 5| T-" u 5 C£ 53 ul O X M CO O. 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The large number of water-level anomalies occurring during the year (263) were reduced to an amenable number by focusing attention on those anomalies having a duration of twelve hours or greater. This lowered the number to be investigated to 42 (Appendix B) . In the investigation of the effect of variations of atmospheric pressure in producing anomalies, the distribution of hourly sea-level pressures at Monterey was compared with the hourly water-level differences comprising each anomaly. The hourly pressures were obtained from a standard barograph at Monterey; they agreed with the six-hourly values described in the previous section which were obtained from weather charts. An example of a water-level anomaly and the associated pressure distribution is displayed in Figure 18. The smooth curve shown in the figure represents the water-level variation derived from the pressure distribution assuming a hydrostatic response; the water-level at the beginning of the anomaly is considered to be adjusted to the initial pressure. It may be noted that the hourly water-level differences show the same trend as the hourly pressure values with almost no lag in response. The water level appeared to over respond during the rapid drop in pressure at the onset of the pressure change, but during the period of rising pressure, responded very nearly in a hydrostatic manner. The degree of response of the water level to an atmospheric pressure change can be expected to be a function of the rate of change of pressure, When the pressure change occurs slowly full hydrostatic response should be expected; however, with a rapid pressure change the amplitude of the watec-level anomaly produced should be less than that expected hydro- statically, and the time of the water-level peak (maxima or minima) should lag behind that of the pressure peak. 44 Of the 42 water-level anomalies examined, all but one were found to respond to a variation in atmospheric pressure such that an increase (decrease) in atmospheric pressure produced a negative (positive) water-level anomaly. The one exception occurred beginning on 29 Nov- ember. In response to slow changes of pressure, the water-level exhibited little or no time lag, but the lag was variable and generally amounted to one to three hours with rapid pressure changes of large magnitude. The amplitude response of the water level anomaly was nearly hydrostatic with respect to the imposed pressure. 45 D. SYNOPTIC WEATHER EVENTS ASSOCIATED WITH ANOMALIES Having noted the association of atmospheric pressure variations and water-level anomalies, the National Weather Service six-hourly surface analysis charts were examined to determine if these pressure variations could be related to synoptic weather situations. This examination was performed by comparing the isobaric patterns on each of the six-hourly charts of each month with the long-term mean monthly pressure pattern for the northern hemisphere compiled by Hesse and Stevenson (1968) . The North Pacific high-pressure cell and the predominant low pressure cell or trough extending northward over Mexico and the southwestern United States are characteristic features of the long-term surface pressure distribution throughout the year, although they vary in intensity and location with the seasons. These climatic features may be seen in Figures 19 and 21. It was found that the intensification or displacement toward Monterey of either of these features was directly related to the atmospheric pressure changes which caused the majority of the observed water-level anomalies. Examples of the two types of synoptic situations found to be respon- sible for 35 of the 42 anomalies examined are illustrated in Figures 19 through 22. Figure 19 displays the long-term mean pressure pattern for the month of May. The weather chart for 1600 PST, 6 May, 1971 shown in Figure 20 illustrates the intensification of the low-pressure trough and its advance over Northern California. Figure 21 displays the long- terra mean pressure pattern for the month of June; Figure 22 for 0400 PST, 1 June shows the intensification of the North Pacific high pressure cell and the displacement of the isobars toward the Pacific Coast. The synoptic weather situations shown in Figures 20 and 22 produced a 46 positive and a negative anomaly respectively, each of about two days duration. The synoptic weather situations that were found to be related to the atmospheric pressure changes causing 41 of the 42 anomalies examined are as follows: 1. Intensification of the North Pacific high-pressure cell and displacement of the pressure gradient toward the Pacific Coast, producing above normal pressures at Monterey (12 cases) . 2. Intensification of the predominant low-pressure trough over Mexico and the southwestern United States and its advance northward over Northern California, giving below normal pressures at Monterey (23 cases). Occasionally, low-pressure centers of small size formed within the enlarged low pressure trough. 3. Frontal passage with an associated decrease in pressure (5 cases) . 4. Passage of a high-pressure center not related to the North Pacific high-pressure cell (1 case) , In examining the successive six-hourly weather charts, these synop- tic weather situations were often closely associated with water-level anomalies of duration less than twelve hours, but these situations were not catalogued. The close relationship found here between the occurrance of these synoptic weather situations and water-level anomalies suggests that the latter can be forecasted. By way of experiment, the National Weather Service six-hourly charts were re-examined without reference to any tabulation of water-level anomalies and it was possible to correctly forecast the occurrence of 41 of the 42 water-level anomalies of 47 duration greater than twelve hours, It was possible to forecast the amplitude of the water-level anomaly quantitatively, The abilty to forecast anomalies of less than twelve hours duration was only mar- ginally demonstrated by this procedure. In view of the fact that pressure variations causing water-level anomalies were due in most cases to either an eastward or westward migration of the isobaric gradient over Monterey due to either inten- sification or movement of the quasi-permanent high and low pressure systems in the region, it may be concluded that point measurement of the surface pressure at Monterey (values of which were used in this study) is probably more useful than pressure integrated over a large area of the sea surface around Monterey. 48 FIGURE 19: LONG-TERM MEAN PRESSURE PATTERN - MAY (from Hesse and Stevenson, 1968) 49 FIGURE 20: SEA LEVEL PRESSURE CHART - 1600, 6 MAY 1971 50 FIGURE 21: LONG-TERM MEAN PRESSURE PATTERN - JUNE (from Hesse and Stevenson, 1968) 5i FIGURE 22: SEA LEVEL PRESSURE CHART - 0400, 1 JUNE 1971 52 V. SUMMARY A comparison of the predicted and observed tides at Monterey over the one-year period from 1 February 1971 through 31 January 1972 re- vealed that the hourly water-level differences did not exceed J 0,9 feet in magnitude and that they were normally distributed about zero water level. A total of 263 water-level anomalies were identified, ranging from 2 to 362 hours in duration, 42 water-level anomalies were of a duration greater than 12 hours, and these were examined in detail with regard to cause. It was determined that change in atmospheric pressure was the domi- nant cause. A regression analysis, by months, of the correlation between water-level difference and atmospheric pressure revealed that the water level responded in a near-hydrostatic manner. The response was a function of the rate of change of pressure. In those cases where the pressure changed rapidly, the water-level maxima lagged behind the pressure maxima up to three hours; however, the amplitude response of the water-level anomaly was approximately that expected from the pressure change assuming a hydrostatic relationship. The changes in atmospheric pressure which caused the 42 water-level anomalies examined were found to be associated with four kinds of syn- optic weather events: 1. Intensification of the North Pacific high-pressure cell and displacement of the pressure gradient toward the Pacific Coast, produc- ing above normal pressures at Monterey (12 cases) . 2. Intensification of the predominant low-pressure trough over Mexico and the southwestern United States and its advance northward 53 over Northern California, giving below normal pressures at Monterey (23 cases) , 3. Frontal passage with an associated decrease in pressure (5 cases) 4. Passage of a high-pressure center not related to the North Pacific high-pressure cell (1 case) . Absence of wind 'stress as a factor in producing anomalies was attri- buted to the sheltered location of the tide gage from the prevailing onshore winds. 54 LIST OF REFERENCES 1. Coast and Geodetic Survey, U, S, Department of Commerce, Manual of Tide Observations, Publication 30-1, 1965, 2. Armstrong, J. B., "The Effect of Meteorological Conditions on Sea Level," Canada Department of Transport, Meteorological Branch, CIR-3747, TEC-429, 19 p., 1958. 3. Jacobs, W. C, "Sea Level Departures on the California Coast as Related to the Dynamics of the Atmosphere Over the North Pacific Ocean," Journal of Marine Research, v. 2, No. 3, p. 181-194, 19^8. 4. O'Connor, P., Short-Term Sea Level Anomalies at Monterey, Cali- fornia, Naval Postgraduate School, Monterey. M.S. thesis, 56 p., 1964. 5. Hesse, T. S., and N. M. Stevenson, 1962-1968 Monthly Hemispheric Means, Standard Deviations, and Diurnal Variations, Fleet Numerical VJeather Central, Technical Report 43, December 1968. 55 < M O M CJ X M o PS w Pn 51 •t CM &h r-^ a en rH w CM W H K^ l » u r*; O O 525 >% & « m « 0) o Vj •-j > Pm tf M jC ^i • • X 3 to £S CO >, u CO H ,G Pi 53 rH i CT3 C W cd -v }-< c3 & eu ih QJ pq QJ -. 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Defense Documentation Center Cameron Station Alexandria, Virginia 22314 2. Library, Code 0212 Naval Postgraduate School Monterey, California 93940 3. Professor Warren C. Thompson Department of Oceanography Naval Postgraduate School Monterey, California 93940 4. LCDR Harold V. Maixner, Jr., USN c/o Col. Harold V. Maixner, USA(ret) 190 Bayshore Court Punta Gorda, Florida 33950 5. Department of Oceanography Naval Postgraduate School Monterey, California 93940 6. Oceanographer of the Navy The Madison Building 732 N. Washington Street Alexandria, Virginia 22314 7. Dr. Ned A. Osterso Code 480D Office of Naval Research Arlington, Virginia 22217 8. Evelyn L. Pruitt, Director Geography Programs, Code 414 Office of Naval Research Department of the Navy Washington, D.C. 20360 9. Commanding Officer Fleet Numerical Weather Central Monterey, California 93940 10. Mr. N. M. Stevenson Fleet Numerical Weather Central Monterey, California 93940 11. Coastal Engineering Research Center 5201 Little Falls Road, N. W. Washington, D.C. 20016 No. Copies 2 80 No. Copies 12. Mr. Charles Fisher, Chief 1 Coastal Engineering Branch U. S. Army Corps of Engineers P. 0. Box 2711 Los Angeles, California 90053 13. Commanding Officer 1 San Francisco District U. S. Army Corps of Engineers 100 McAllister Street San Francisco, California 94102 Navigation and Shoreline Planning Section Library 14. Coastal Engineering Branch 1 Planning Division U. S. Army Engineering Division, South Pacific 630 Sansome Street San Francisco, California 94111 15. Mr. Peter Badgly 1 Code 410 Office of Naval Research Naval Research Laboratory Arlington, Virginia 22217 16. Office of Naval Research 1 Code 480 Naval Research Laboratory Arlington, Virginia 22217 17. Mr. Robert A. Cummings 1 Chief, Tides Branch, Oceanographic Division National Ocean Survey National Oceanic and Atmospheric Administration Rockville, Maryland 20852 18. The Director 1 National Ocean Survey National Oceanic and Atmospheric Administration 6001 Executive Boulevard Rockville, Maryland 20852 19. Mr. Stacey D. Hicks 1 Head of Ocean Section National Oceanic and Atmospheric Administration Rockville, Maryland 20852 81 Security Classification DOCUMENT CONTROL DATA -R&D (Security clas silic *lion ol title, body ol abstract and indexing annotation nrunt be entered whan the overall r*pnrt Is classified) ~ gin a ting activity (Corporate author) 2«. report security classification i/al Postgraduate School laterey, California 93940 Unclassif ied 2b. GROUP R'ORT TITLE ]nparison of Predicted and Observed Tides at Monterey, California CSCRIPTIVE NOTES (Type ol report e.nd, inclusive dates) lster's Thesis; March 1973 < • THORisi (First name, middle Initial, last name) Irold V. Maixner, Jr. 1PORT DATE irch 1973 la. TOTAL NO. OF PAGES 81 7b. NO. OF REFS ONTRACT OR GRANT NO. ROJEC T NO. 9a. ORIGIN A TON'S REPORT NUMOER(S) 9b. OTHER REPORT NO(SI (Any other numbcra that may ba aaalfjned thlt report) ISTRIBUTION STATEMENT proved for public release; distribution unlimited UPPLEMENTARY NOTES 12. SPONSORING MILITARY ACTIVITY Naval Postgraduate School Monterey, California 93940 BSTR AC T A comparison of the predicted and observed tides at Monterey, California conducted rer the period of a year revealed that the hourly water-level differences did not :ceed _ 0.9 feet in magnitude. 263 water-level anomalies of duration up to 362 »urs were identified, of which 42 were of duration greater than twelve hours. It is determined that change in atmospheric pressure is the dominant causitive factor hourly water-level differences and that the water-level response is approximately 'drostatic. The changes in atmospheric pressure associated with the 42 water-level tomalies examined were found to be manifestations of the eastward or westward .gration of the isobaric gradient due to either intensification or movement of the lasi-permanent high and low pressure systems in the region. ),r:..i473