DATASET TITLE: TREE-RING CHRONOLOGY INDEXES AND RECONSTRUCTIONS                 
      OF PRECIPITATION IN CENTRAL IOWA, USA                                     
                                                                                
CONTRIBUTORS: T. J. BLASING AND D. N. DUVICK, ENVIRONMENTAL                     
      SCIENCES DIVISION, OAK RIDGE NATIONAL LABORATORY, OAK                     
      RIDGE, TENNESSEE 37831.                                                   
                                                                                
SCOPE OF THE DATA: CORE SAMPLES 4 MM IN DIAMETER WERE EXTRACTED                 
      FROM THE TRUNKS OF WHITE OAK (QUERCUS ALBA) TREES AT                      
      LEDGES, PAMMEL AND DUVICK BACK WOODS IN CENTRAL IOWA.                     
      GROWTH RINGS OF EACH CORE WERE DATED BY CALENDAR YEAR                     
      FOLLOWING THE STANDARD PROCEDURE DESCRIBED IN STOKES                      
      AND SMILEY (1968).  RING WIDTHS WERE MEASURED TO THE                      
      NEAREST HUNDREDTH OF A MM.  LOW-FREQUENCY VARIATIONS                      
      DUE TO TREE AGE, CHANGE IN COMPETITIVE STATUS, AND OTHER                  
      NONCLIMATIC FACTORS WERE MINIMIZED BY FITTING A SPLINE                    
      CURVE TO THE RING-WIDTH SERIES AND DIVIDING EACH RING WIDTH               
      BY THE VALUE OF THE CURVE FOR THE CORRESPONDING YEAR                      
      (FRITTS 1971; FRITTS 1976). THE ADJUSTED RING WIDTHS ARE                  
      KNOWN AS RING-WIDTH INDICES.  THE AVERAGE RING-WIDTH INDEX                
      FOR EACH YEAR WAS COMPUTED FROM THE INDICES OF ALL CORES                  
      AT A SITE.  INITIAL YEARS OF THE CHRONOLOGIES WERE 1635                   
      AT PAMMEL, 1654 AT DUVICK BACK WOODS, AND 1663 AT LEDGES,                 
      IOWA. SAMPLE SIZES RANGED FROM 6 TO 16 CORES BY THE YEAR                  
      1680 AND INCREASED STEADILY IN EACH CHRONOLOGY AFTER 1800.                
      THE INDICES EXTEND THROUGH 1981.  THE INDICES ARE USED                    
      TO ESTIMATE OR RECONSTRUCT PAST VALUES OF NUMEROUS                        
      CLIMATIC AND HYDROLOGIC VARIABLES, INCLUDING LARGE-SCALE                  
      SEASONAL PATTERNS OF TEMPERATURE, PRECIPITATION, AND                      
      ATMOSPHERIC CIRCULATION (DUVICK AND BLASING 1981; BLASING                 
      AND DUVICK 1984).                                                         
                                                                                
DATA FORMAT: FOUR ASCII TEXT FILES ARE PROVIDED WITHIN THIS                 
SUBDIRECTORY (NDP002) INCLUDING THIS DESCRIPTIVE FILE (NDP002.TXT),         
ONE DATA FILE CONTAINING TREE-RING INDICES FROM THE THREE SITES                 
(NDP002.TRE), ONE DATA FILE CONTAINING RECONSTRUCTED PRECIPITATION              
ESTIMATES FOR CENTRAL IOWA (NDP002.PRE), AND A FORTRAN RETRIEVAL CODE           
TO READ AND PRINT ALL THESE FILES (NDP002.FOR).  THE TREE-RING                  
INDICES FILE IS FORMATTED SUCH THAT COLUMNS 1-6 CONTAIN THE SITE                
IDENTIFICATION DENOTED AS FOLLOWS:                                              
                                                                                
                IDENTIFIER           SITE                                       
                 645814          DUVICK BACK WOODS                              
                 648813          LEDGES STATE PARK                              
                 464813          PAMMEL STATE PARK                              
                                                                                
      COLUNMS 7-10 CONTAIN THE YEAR OF THE FIRST DATUM ON THE                   
      CARD.  COLUMNS 11-80 CONTAIN 10 SETS OF SEVEN COLUMNS EACH.               
      FIRST FOUR COLUMNS CONTAIN THE RING-WIDTH INDEX VALUE                     
      IN DIMENSIONLESS UNITS, TO THREE DECIMAL PLACES (E.G., AN                 
      INDEX OF 1234 IS ACTUALLY 1.234), AND THE NEXT THREE                      
      COLUMNS CONTAIN THE NUMBER OF CORE SAMPLES (SAMPLE SIZE)                  
      USED TO OBTAIN THE INDEX VALUE.  A 9990, FOLLOWED BY                      
      EITHER THREE BLANKS OR A ZERO, INDICATES NO DATA FOR THAT                 
      YEAR.  THESE VALUES OCCUR EITHER AT THE BEGINNING OR END                  
      OF A SERIES. AND THUS, HAVE VALUE IN INDICATING THE                       
      START/END OF A SERIES.  THE FIRST DATUM, OR 9990, ON                      
      A CARD CORRESPONDS TO THE BEGINNING OF A DECADE (E.G., 1650,              
      1660, ETC.).                                                              
                                                                                
     THE ANNUAL PRECIPITATION RECONSTRUCTION DATA ARE FORMATTED                 
     AS DECADAL YEAR FOLLOWED BY 10 VALUES (ONE FOR EACH YEAR IN                
     THE DECADE). THE UNITS ARE CM. AND THE DATA ARE FORMATTED                  
     ON FILE 4 AS:                                                              
                        FORMAT(I4,10(1X,F6.2))                                  
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                          REFERENCES                                            
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BLASING, T. J. AND D. N. DUVICK. 1984. "RECONSTRUCTION OF                       
      PRECIPITATION HISTORY IN NORTH AMERICAN CORN BELT USING                   
      TREE RINGS," NATURE 307(12):143-145.                                      
DUVICK, D. N. AND T. J. BLASING. 1981. "A DENDROCLIMATIC                        
      RECONSTRUCTION OF ANNUAL PRECIPITATION AMOUNTS IN IOWA                    
      SINCE 1680," WATER RESOURCES RESEARCH 17:1183-1189.                       
FRITTS, H. C. 1971. "DENDROCLIMATOLOGY AND DENDROECOLOGY,"                      
      QUATERNARY RESEARCH 1:419-449.                                            
FRITTS, H. C. 1976. TREE RINGS AND CLIMATE. ACADEMIC PRESS,                     
      NEW YORK.                                                                 
STOKES, M. A. AND SMILEY, T. L. 1968. AN INTRODUCTION TO TREE-                  
      RING DATING. UNIVERSITY OF CHICAGO PRESS, ILLINOIS.