Pacific Northwest Index (PNI)

PNI 1891-2012 graph

Summary

The Pacific Northwest Index (PNI), developed by Ebbesmeyer and Strickland (1995), is a terrestrial climate index useful for studying climate effects on salmon productivity trends. It is a composite index that characterizes Pacific Northwest climate patterns in both coastal waters and freshwater habitats. In addition, it is a century-long record. A composite climate index is an effective measurement because many environmental parameters in the Northwest are statistically related to one another; consequently, they may be combined to furnish a broad-scale understanding of the state of the Pacific Northwest environment. The PNI uses three parameters: 1) air temperature at Olga in the San Juan Islands, averaged annually from daily data; 2) total precipitation at Cedar Lake in the Cascade Mountains; and 3) snowpack depth at Paradise on Mount Rainier on March 15 of each year. For each parameter, annual values were normalized by subtracting the annual value from the average of all years and dividing by the standard deviation. The sign of the normalized temperature is reversed because low temperature corresponds with high precipitation and snow. Finally, the three variables are averaged yearly giving a relative indicator of the variations in climate. Years with positive values of the PNI are warmer and drier than average and those with negative values are cooler and wetter than average.

Reference

Ebbesmeyer, C.C. and R.M. Strickland. 1995. Oyster Condition and Climate: Evidence from Willapa Bay. Publication WSG-MR 95-02, Washington Sea Grant Program, University of Washington, Seattle, WA. 11p.

Method

Annual PNI for Year Y:

PNIy = ( TempDevy + PrecipDevy + SnowDevy ) / 3

where:

TempDevy = - ( MeanTemp - Tempy ) / StDevTemp
PrecipDevy = ( MeanPrecip - Precipy ) / StDevPrecip
SnowDevy = ( MeanSnow - Snowy ) / StDevSnow

Sign of TempDev is reversed because low temperature corresponds with high precipitation and snow.

Data

Year Olga, San Juan Islands, WA, Annual Mean Air Temperature (F)
Mean 50.090
Standard Deviation 1.337
Temperature Deviate Cedar Lake, WA, Total Annual Precipitation (Inches)
Mean 101.774
Standard Deviation 17.541
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 170.505
Standard Deviation 53.039
Snow Deviate Year Annual PNI 5 Year
Running
Average
Year Olga, San Juan Islands, WA, Annual Mean Air Temperature (F)
Mean 50.090
Standard Deviation 1.337
Temperature Deviate Cedar Lake, WA, Total Annual Precipitation (Inches)
Mean 101.774
Standard Deviation 17.541
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 170.505
Standard Deviation 53.039
Snow Deviate Year Annual PNI 5 Year
Running
Average
2015 54.639 3.401 102.010 -0.013 58.000 2.121 2015 1.836  
2014 53.250 2.363 121.300 -1.113 150.980 0.368 2014 0.539  
2013 49.400 -0.516 90.090 0.666 162.000 0.160 2013 0.103 0.543
2012 48.870 -0.913 64.980 2.098 204.020 -0.632 2012 0.184 0.285
2011 49.010 -0.808 74.410 1.560 202.000 -0.594 2011 0.053 0.164
2010 51.660 1.174 103.350 -0.090 141.000 0.556 2010 0.547 -0.047
2009 48.073 -1.509 84.230 1.000 154.000 0.311 2009 -0.066 -0.067
2008 47.538 -1.909 105.140 -0.192 211.000 -0.763 2008 -0.955 -0.223
2007 49.103 -0.738 93.600 0.466 142.000 0.537 2007 0.088 -0.161
2006 50.497 0.304 135.420 -1.918 201.000 -0.575 2006 -0.730 0.032
2005 51.882 1.340 125.341 -1.344 34.000 2.574 2005 0.857 0.369
2004 52.391 1.720 85.490 0.928 168.000 0.047 2004 0.899 0.365
2003 51.000 0.680 87.621 0.807 133.000 0.707 2003 0.731 0.681
2002 50.608 0.387 87.218 0.830 224.000 -1.009 2002 0.069 0.595
2001 50.451 0.270 84.532 0.983 102.000 1.292 2001 0.848 0.302
2000 50.372 0.211 77.640 1.376 187.000 -0.311 2000 0.425 0.213
1999 50.611 0.389 105.060 -0.187 271.000 -1.895 1999 -0.564 0.095
1998 51.351 0.943 104.790 -0.172 166.000 0.085 1998 0.285 -0.078
1997 51.145 0.789 114.060 -0.700 258.000 -1.650 1997 -0.520 -0.047
1996 49.511 -0.433 113.640 -0.676 114.000 1.065 1996 -0.015 0.273
1995 52.085 1.492 98.610 0.180 167.000 0.066 1995 0.579 0.401
1994 51.611 1.137 81.200 1.173 128.000 0.801 1994 1.037 0.749
1993 50.756 0.498 78.000 1.355 122.000 0.915 1993 0.923 0.798
1992 52.153 1.542 81.590 1.151 119.000 0.971 1992 1.221 0.587
1991 50.696 0.453 98.520 0.186 168.000 0.047 1991 0.229 0.413
1990 50.857 0.573 131.740 -1.708 186.000 -0.292 1990 -0.476 0.282
1989 50.471 0.285 95.000 0.386 179.000 -0.160 1989 0.170 0.251
1988 50.637 0.409 108.490 -0.383 130.000 0.764 1988 0.263 0.306
1987 51.693 1.198 73.890 1.590 148.000 0.424 1987 1.071 0.503
1986 50.837 0.558 103.990 -0.126 114.000 1.065 1986 0.499 0.564
1985 48.825 -0.946 64.280 2.137 152.000 0.349 1985 0.513 0.573
1984 50.980 0.665 92.080 0.553 160.000 0.198 1984 0.472 0.295
1983 51.324 0.922 103.680 -0.109 164.000 0.123 1983 0.312 0.401
1982 50.151 0.045 104.400 -0.150 216.000 -0.858 1982 -0.321 0.356
1981 51.818 1.292 102.990 -0.069 72.000 1.857 1981 1.027 0.420
1980 50.605 0.385 96.860 0.280 160.000 0.198 1980 0.288 0.479
1979 51.123 0.772 84.370 0.992 138.000 0.613 1979 0.792 0.630
1978 51.025 0.699 88.770 0.741 150.000 0.387 1978 0.609 0.422
1977 50.230 0.104 99.990 0.102 112.000 1.103 1977 0.436 0.183
1976 49.893 -0.148 91.480 0.587 196.000 -0.481 1976 -0.014 -0.177
1975 49.129 -0.719 127.180 -1.448 200.000 -0.556 1975 -0.908 -0.240
1974 49.937 -0.115 120.550 -1.070 268.000 -1.838 1974 -1.008 -0.604
1973 49.362 -0.545 93.300 0.483 121.000 0.933 1973 0.291 -0.879
1972 48.429 -1.242 120.460 -1.065 268.000 -1.838 1972 -1.382 -0.673
1971 48.562 -1.143 121.530 -1.126 271.000 -1.895 1971 -1.388 -0.543
1970 49.395 -0.520 97.600 0.238 136.000 0.651 1970 0.123 -0.577
1969 49.315 -0.580 88.760 0.742 236.000 -1.235 1969 -0.358 -0.335
1968 49.661 -0.321 112.540 -0.614 102.000 1.292 1968 0.119 -0.073
1967 50.148 0.043 92.470 0.530 228.000 -1.084 1967 -0.170 -0.065
1966 50.016 -0.056 100.940 0.048 183.000 -0.236 1966 -0.081 -0.249
1965 49.534 -0.416 85.590 0.923 171.000 -0.009 1965 0.166 -0.121
1964 48.425 -1.245 126.160 -1.390 234.000 -1.197 1964 -1.278 -0.036
1963 50.293 0.151 90.740 0.629 91.000 1.499 1963 0.760 -0.088
1962 49.559 -0.397 87.620 0.807 152.000 0.349 1962 0.253 -0.150
1961 50.449 0.268 111.230 -0.539 210.000 -0.745 1961 -0.339 -0.028
1960 49.243 -0.634 103.170 -0.080 156.000 0.273 1960 -0.147 -0.071
1959 49.239 -0.637 123.690 -1.249 177.000 -0.122 1959 -0.670 -0.116
1958 52.241 1.608 103.640 -0.106 163.000 0.142 1958 0.548 -0.362
1957 49.340 -0.561 86.160 0.890 184.000 -0.254 1957 0.025 -0.613
1956 48.574 -1.134 102.610 -0.048 357.000 -3.516 1956 -1.566 -0.602
1955 46.888 -2.395 123.600 -1.244 201.000 -0.575 1955 -1.405 -0.815
1954 48.847 -0.930 104.510 -0.156 210.000 -0.745 1954 -0.610 -0.705
1953 50.556 0.348 133.000 -1.780 177.000 -0.122 1953 -0.518 -0.473
1952 49.396 -0.519 62.360 2.247     1952 0.576 -0.418
1951 48.936 -0.863 99.060 0.155 198.000 -0.518 1951 -0.409 -0.363
1950 47.819 -1.699 131.410 -1.690     1950 -1.129 -0.451
1949 48.640 -1.085 100.220 0.089     1949 -0.332 -0.621
1948 48.459 -1.220 121.800 -1.142 198.000 -0.518 1948 -0.960 -0.684
1947 50.296 0.154 114.020 -0.698 185.000 -0.273 1947 -0.273 -0.538
1946 49.455 -0.475 111.750 -0.569 231.000 -1.141 1946 -0.728 -0.295
1945 49.655 -0.326 124.480 -1.294 148.000 0.424 1945 -0.399 -0.048
1944 50.295 0.153 79.640 1.262 105.000 1.235 1944 0.883 0.128
1943 49.429 -0.495 81.060 1.181 163.000 0.142 1943 0.276 0.582
1942 50.636 0.408 98.540 0.184 105.000 1.235 1942 0.609 0.906
1941 52.488 1.793 81.860 1.135 81.000 1.688 1941 1.539 0.739
1940 52.216 1.589 83.390 1.048 116.000 1.028 1940 1.222 0.823
1939 51.201 0.830 94.780 0.399 228.000 -1.084 1939 0.048 0.627
1938 50.714 0.466 81.010 1.184 147.000 0.443 1938 0.698 0.261
1937 49.677 -0.309 114.780 -0.741 174.000 -0.066 1937 -0.372 0.091
1936 49.352 -0.552 98.860 0.166 196.000 -0.481 1936 -0.289 0.223
1935 49.627 -0.347 79.960 1.244 159.000 0.217 1935 0.371 -0.196
1934 51.962 1.400 112.330 -0.602 100.000 1.329 1934 0.709 -0.338
1933 48.412 -1.255 138.310 -2.083 216.000 -0.858 1933 -1.399 -0.163
1932 48.871 -0.912 133.130 -1.788 200.000 -0.556 1932 -1.085 -0.074
1931 50.825 0.549 103.180 -0.080 102.000 1.292 1931 0.587 -0.132
1930 49.371 -0.538 72.220 1.685 101.000 1.310 1930 0.819 0.326
1929 49.734 -0.267 74.700 1.543 172.000 -0.028 1929 0.416 0.487
1928 51.419 0.993 87.000 0.842 126.000 0.839 1928 0.892 0.636
1927 50.375 0.213 111.220 -0.538 198.000 -0.518 1927 -0.281 0.540
1926 53.011 2.184 89.850 0.680 110.000 1.141 1926 1.335 0.462
1925 51.855 1.320 90.600 0.637 220.000 -0.933 1925 0.341 0.209
1924 49.783 -0.230 97.320 0.254 168.000 0.047 1924 0.024 0.204
1923 50.019 -0.053 100.210 0.089 232.000 -1.159 1923 -0.375 -0.268
1922 48.515 -1.178 92.750 0.514 184.000 -0.254 1922 -0.306 -0.408
1921 49.118 -0.727 128.000 -1.495 216.000 -0.858 1921 -1.027 -0.593
1920 49.477 -0.459 124.000 -1.267 136.000 0.651 1920 -0.358 -0.574
1919 49.203 -0.664 111.800 -0.572 248.000 -1.461 1919 -0.899 -0.775
1918 50.471 0.285 118.280 -0.941 180.000 -0.179 1918 -0.278 -0.767
1917 49.220 -0.651 137.800 -2.054 236.000 -1.235 1917 -1.313 -0.614
1916 47.749 -1.751 113.250 -0.654 200.000 -0.556 1916 -0.987 -0.367
1915 51.644 1.162 100.650 0.064     1915 0.409 -0.326
1914 50.764 0.504 93.100 0.494     1914 0.333 -0.069
1913 49.356 -0.549 95.800 0.341     1913 -0.070 0.107
1912 50.019 -0.053 102.400 -0.036     1912 -0.030 -0.087
1911 48.885 -0.901 91.650 0.577     1911 -0.108 -0.263
1910 49.027 -0.795 117.250 -0.882     1910 -0.559 -0.327
1909 47.934 -1.613 102.280 -0.029     1909 -0.547 -0.298
1908 49.945 -0.109 120.560 -1.071     1908 -0.393 -0.355
1907 49.481 -0.456 87.530 0.812     1907 0.119 -0.283
1906 50.803 0.533 131.990 -1.723     1906 -0.397 -0.127
1905 50.209 0.089 113.640 -0.676     1905 -0.196 -0.130
1904 50.235 0.108 91.390 0.592     1904 0.233 -0.137
1903 49.336 -0.564 113.440 -0.665     1903 -0.410 -0.069
1902 50.434 0.257         1902 0.086 -0.124
1901 49.863 -0.170         1901 -0.057 -0.360
1900 49.673 -0.312 121.150 -1.105     1900 -0.472 -0.335
1899 48.401 -1.263 129.360 -1.573     1899 -0.945 -0.393
1898 48.942 -0.859         1898 -0.286 -0.437
1897 49.277 -0.608         1897 -0.203 -0.316
1896 48.973 -0.836         1896 -0.279 -0.167
1895 50.615 0.392         1895 0.131 -0.222
1894 49.288 -0.600         1894 -0.200 -0.044
1893 47.847 -1.678         1893 -0.559 0.184
1892 52.837 2.054         1892 0.685  
1891 53.559 2.594         1891 0.865