DOI: 10.25921/rswk-a370
title: NOAA/WDS Paleoclimatology - Wahl, et al., 2017, precipitation reconstruction for California

description: The recent dryness in California was unprecedented in the instrumental record. This article employs spatially explicit precipitation reconstructions for California in combination with instrumental data to provide perspective on this event since 1571. The period 2012–15 stands out as particularly extreme in the southern Central Valley and South Coast regions. which likely experienced unprecedented precipitation deficits over this time, apart from considerations of increasing temperatures and drought metrics that combine temperature and moisture information. Some areas lost more than two years’ average moisture delivery during these four years, and full recovery to long-term average moisture delivery could typically take up to several decades in the hardest-hit areas. These results highlight the value of the additional centuries of information provided by the paleo record, which indicates the shorter instrumental record may underestimate the statewide recovery time by over 30%. The extreme El Niño that occurred in 2015–16 ameliorated recovery in much of the northern half of the state, and since 1571 very-strong-to-extreme El Niño’s during the first year after a 2012–15-type event reduce statewide recovery times by approximately half. The southern part of California did not experience the high precipitation anticipated, and the multicentury analysis suggests the north-wet–south-dry pattern for such an El Niño was a low-likelihood anomaly. Recent wetness in California motivated evaluation of recovery times when the first two years are relatively wet, suggesting the state is benefiting from a one-infive (or lower) likelihood situation: the likelihood of full recovery within two years is ~1% in the instrumental data and even lower in the reconstruction data.
description: The reconstructions are derived from streamflow reconstructions in western 
United States, which are based on tree rings. See article for details. 
Note: The data products set was updated on September 13, 2018, to include the 
"wahl-2017-ca-all-uncert-climate-div-means-text.zip" archive, described below.

Dataset Product Contents:
    Section 1: Dataset product folder contents overview
    Section 2: Details of the content the six ZIP archive files


Section 1: Dataset product folder contents overview

    URL of folder: 
        https://www.ncei.noaa.gov/pub/data/paleo/reconstructions/wahl2017
    Item 1. readme-wahl-2017.txt - this file
    Item 2. Six ZIP archive files which contain the actual data:
        I. wahl-2017-ca-all-uncert-nc3.zip
        II. wahl-2017-ca-all-uncert-medians-nc3.zip
        III. wahl-2017-ca-all-uncert-medians-annual-maps.zip
        IV. wahl-2017-ca-climate-divs-all-uncert-nc3.zip
        V. wahl-2017-ca-climate-divs-all-uncert-medians-nc3.zip
        VI. wahl-2017-ca-all-uncert-climate-div-means-text.zip

        The first five ZIP archive files, listed above (I...IV), have the same 
        structure.
        Each contains a folder, with the same filename as the ZIP 
        file from which it was extracted (excluding the ".zip" extension), 
        which contains:
            A. One folder: data
                which contains the actual data
            B. One file: manifest-md5.txt
                which contains the md5 checksum values of the file(s) 
                in the "data" directory 
        The sixth ZIP archive file, 
        "wahl-2017-ca-all-uncert-climate-div-means-text.zip" 
        contains a folder named 
        "wahl-2017-ca-all-uncert-climate-div-means-text" 
        which contains:
            A. One folder: data
                which contains the actual data. The data 
                being seven text-based data sets (one for each climate 
                division) which have the form of flat matrices, with 407 rows 
                (years) and 1001 columns (first column has the year values, 
                columns 2-1001 have the ensemble member precipitation values). 
                The files are named 
                "wahl-2017-ca-all-uncert-text-div1-means.txt" ... 
                "wahl-2017-ca-all-uncert-text-div7-means.txt"
            B. One file: manifest-md5.txt
                which contains the md5 checksum values of the file(s)
                in the "data" directory.
        Note: this ZIP archive was added to this dataset on September 13, 2018


Section 2: Details of the content of the ZIP archive files I. through VI.

I. wahl-2017-ca-all-uncert-nc3.zip
This ZIP archive contains one folder:
    wahl-2017-ca-all-uncert-nc3, which contains:
    A. One folder: data
        which contains:
        One file: wahl-2017-ca-all-uncert-nc3.nc
            which is a NetCDF file, which contains 1000 ensemble members,
            each containing 407 years from 1571-1977 AD.
            Each year contains:
            a grid of 19 latitude X 21 longitude 0.5 x 0.5 degree grid cells
            32.5 to 42.0 decimal degrees latitude North
            -124.5 to -114.5 decimal degrees latitude East
            EACH GRID CELL VALUE REPRESENTS THE PRECIPITATION AS MILLIMETERS.
            Format: NetCDF version 3
            NetCDF Header Information:
            dimensions:
              Ensemble = 1000 ;
              Year = 407 ;
              Latitude = 19 ;
              Longitude = 21 ;
            variables:
              int Ensemble(Ensemble) ;
                      Ensemble:units = "count" ;
              int Year(Year) ;
                      Year:units = "calendar_years" ;
              double Latitude(Latitude) ;
                      Latitude:units = "degreesN" ;
              double Longitude(Longitude) ;
                      Longitude:units = "degreesE" ;
              double precipitation_amount(Longitude, Latitude, Year, Ensemble);
                      precipitation_amount:units = "Ensemble,Year,Latitude,
                      Longitude";
                      precipitation_amount:missing_value = -999. ;
    B. One file: manifest-md5.txt
        which contains the md5 checksum values and names of the
        NetCDF file in the "data" folder, described above in A.


II. wahl-2017-ca-all-uncert-medians-nc3.zip
This ZIP archive contains one folder:
    wahl-2017-ca-all-uncert-medians-nc3, which contains:
    A. One folder: data
        which contains:
        One file: wahl-2017-ca-all-uncert-medians-nc3.nc
            which is a NetCDF file, which contains the medians
            across the 1000 ensemble members, each containing 407 years
            from 1571-1977 AD.
            Each year contains:
            407 years from 1571-1977 AD.
            Each year contains:
            a grid of 19 latitude X 21 longitude 0.5 x 0.5 degree grid cells
            32.5 to 42.0 decimal degrees latitude North
            -124.5 to -114.5 decimal degrees latitude East
            EACH GRID CELL VALUE REPRESENTS THE PRECIPITATION AS MILLIMETERS.
            Format: NetCDF version 3
            NetCDF Header Information:
            dimensions:
              Year = 407 ;
              Latitude = 19 ;
              Longitude = 21 ;
            variables:
              int Year(Year) ;
                      Year:units = "calendar_years" ;
              double Latitude(Latitude) ;
                      Latitude:units = "degreesN" ;
              double Longitude(Longitude) ;
                      Longitude:units = "degreesE" ;
              double precipitation_amount(Longitude, Latitude, Year);
                      precipitation_amount:units = "Year,Latitude,Longitude";
                      precipitation_amount:missing_value = -999. ;
    B. One file: manifest-md5.txt
        which contains the md5 checksum values and names of the
        NetCDF file in the "data" folder, described above in A.


III. wahl-2017-ca-all-uncert-medians-annual-maps.zip
ZIP archive wahl-2017-ca-all-uncert-medians-annual-maps.zip contains
One folder:
wahl-2017-ca-all-uncert-medians-annual-maps, which contains:
    A. One folder: data
        Description of the information in folder "data":
        1221 Files, in three folders representing
        407 Annual Maps for years 1571-1977 AD. anomalies. EACH MAP DEPICTS 
        THE MEDIAN PRECIPITATION FOR CALIFORNIA AS STANDARDIZED ANOMALIES
        (calculated wrt the full reconstruction period).
        As detailed below, each map is stored in PDF and PNG formats in the
        "pdf" and "png" folders respectively. The data corresponding to 
        each map is stored in a tab separated file in the "tsv" folder.

        Contents of folder "data":
        One ZIP archive: wahl-2017-annual-maps-pdf-png-tsv.zip, which contains:
          One folder: wahl-2017-annual-maps-pdf-png-tsv
          which contains three folders:
            1. folder: tsv - contains the data corresponding to each map,
                in 407 tab separated value (TSV) format files
                Each TSV file contains:
                    21 columns, each spanning 0.5 degrees of longitude.
                    The center longitude coordinate for the
                    column 1, east-most, cells through the
                    column 21, west-most, cells, are listed here:
                        -124.25,-123.75,-123.25,-122.75,-122.25,
                        -121.75,-121.25,-120.75,-120.25,-119.75,
                        -119.25,-118.75,-118.25,-117.75,-117.25,
                        -116.75,-116.25,-115.75,-115.25,-114.75,
                        -114.25
                    19 rows, each spanning 0.5 degrees of latitude.
                    The center latitude coordinate for the
                    row 1, south-most cells, through the
                    row 19 north-most cells, are listed here:
                        32.5,33.25,33.75,34.25,34.75,
                        35.25,35.75,36.25,36.75,37.25,
                        37.75,38.25,38.75,39.25,39.75,
                        40.25,40.75,41.25,41.75
            2. folder: pdf - contains the 407 annual maps in PDF format
            3. folder: png - contains the 407 annual maps in PNG format
    B. One file: manifest-md5.txt
        which contains the md5 checksum value for the
        wahl-2017-annual-maps-pdf-png-tsv.zip ZIP archive
        described above in A.


IV. wahl-2017-ca-climate-divs-all-uncert-nc3.zip
This ZIP archive contains one folder:
    wahl-2017-ca-climate-divs-all-uncert-nc3, which contains:
    A. One folder: data
        which contains:
        seven files: wahl-2017-ca-div1-all-uncert-nc3.nc ...
                 wahl-2017-ca-div7-all-uncert-nc3.nc
            which are NetCDF files each representing one of the
            seven California climate divisions,
            401 ... 407 respectively.
            Each NetCDF file contains 1000 ensemble members, each containing
            407 years from 1571-1977 AD.
            Each year contains:
            a grid of 19 latitude X 21 longitude 0.5 x 0.5 degree grid cells
            32.5 to 42.0 decimal degrees latitude North
            -124.5 to -114.5 decimal degrees latitude East
            EACH GRID CELL VALUE REPRESENTS THE PRECIPITATION AS MILLIMETERS.
            Format: NetCDF version 3
            NetCDF Header Information for each file:
            dimensions:
              Ensemble = 1000 ;
              Year = 407 ;
              Latitude = 19 ;
              Longitude = 21 ;
            variables:
              int Ensemble(Ensemble) ;
                      Ensemble:units = "count" ;
              int Year(Year) ;
                      Year:units = "calendar_years" ;
              double Latitude(Latitude) ;
                      Latitude:units = "degreesN" ;
              double Longitude(Longitude) ;
                      Longitude:units = "degreesE" ;
              double precipitation_amount(Longitude, Latitude, Year, Ensemble);
                      precipitation_amount:units = "Ensemble,Year,Latitude,
                      Longitude";
                      precipitation_amount:missing_value = -999. ;
    B. One file: manifest-md5.txt
        which contains the md5 checksum values and names of the
        sevem NetCDF files in the "data" folder, described above in A.


V. wahl-2017-ca-climate-divs-all-uncert-nc3-medians.zip
This ZIP archive contains one folder:
    wahl-2017-ca-climate-divs-all-uncert-medians-nc3, which contains:
    A. One folder: data
        which contains:
        seven files: wahl-2017-ca-div1-all-uncert-medians-nc3.nc ...
                 wahl-2017-ca-div7-all-uncert-medians-nc3.nc
            which are NetCDF files, each representing one of the
            seven California climate divisions,
            401 ... 407 respectively. Each file contains the medians
            across the 1000 ensemble members, each containing 407 years
            from 1571-1977 AD.
            Each year contains:
            a grid of 19 latitude X 21 longitude 0.5 x 0.5 degree grid cells
            32.5 to 42.0 decimal degrees latitude North
            -124.5 to -114.5 decimal degrees latitude East
            EACH GRID CELL VALUE REPRESENTS THE PRECIPITATION AS MILLIMETERS.
            Format: NetCDF version 3
            NetCDF Header Information for each file:
            dimensions:
              Year = 407 ;
              Latitude = 19 ;
              Longitude = 21 ;
            variables:
              int Year(Year) ;
                      Year:units = "calendar_years" ;
              double Latitude(Latitude) ;
                      Latitude:units = "degreesN" ;
              double Longitude(Longitude) ;
                      Longitude:units = "degreesE" ;
              double precipitation_amount(Longitude, Latitude, Year);
                      precipitation_amount:units = "Year,Latitude,Longitude";
                      precipitation_amount:missing_value = -999. ;
    B. One file: manifest-md5.txt
        which contains the md5 checksum values and names of the
        NetCDF files in the "data" folder, described above in A.

VI. wahl-2017-ca-all-uncert-climate-div-means-text.zip
This ZIP archive contains one folder:
    wahl-2017-ca-all-uncert-climate-div-means-text, which contains:
    A. One folder: data
        which contains:
        seven files: wahl-2017-ca-all-uncert-text-div1-means.txt ... 
        wahl-2017-ca-all-uncert-text-div7-means.txt, which are seven 
        text-based data sets (providing the annual mean value for each 
        climate division for each of the 1000 ensemble members) which have 
        the form of flat matrices, with 407 rows (years) and 1001 columns 
        (first column has the year values, columns 2-1001 have the ensemble 
        member precipitation values).
    B. One file: manifest-md5.txt
        which contains the md5 checksum values and names of the
        .txt files in the "data" folder, described above in A.