Pacific Northwest Index (PNI)

PNI 1891-2019 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.

Development of aPNI (alternate PNI)

In April 2016, the Olga 2 SE air temperature location ceased with no replacement. This jeopardized the continuation of the PNI past 2015. We use dynamic factor analysis (DFA) modeled temperatures as a surrogate for Olga 2 SE mean annual temperatures in an alternative PNI calculation (aPNI) through the available time series and publish the results in parallel with the original PNI. We will continue to explore opportunities in modeling an annual temperature value for the Pacific Northwest that can improve upon this DFA analysis.

Van Holmes, C. & Gosselin J. (2020). Development of a Mean Annual Temperature Value for the Continued Calculation of the Pacific Northwest Climate Index . Available from: www.cbr.washington.edu/sites/default/files/papers/Olga_Surrogate_DFA_FINAL.pdf

Data

Year Dynamic Factor Analysis Annual Air Temperature (F)
Mean 49.929
Standard Deviation 1.422
Used in aPNI
Temperature Deviate Olga, San Juan Islands, WA, Annual Mean Air Temperature (F)
Mean 50.090
Standard Deviation 1.337
Ends 2015
Temperature Deviate Cedar Lake, WA, Total Annual Precipitation (Inches)
Mean 101.744
Standard Deviation 16.234
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 171.049
Standard Deviation 51.825
Snow Deviate Year Annual aPNI Annual PNI
Original with Olga
5 Year
Running
Average
5 Year
Running
Average
Original with Olga
Year Dynamic Factor Analysis Annual Air Temperature (F)
Mean 49.929
Standard Deviation 1.422
Temperature Deviate 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 101.744
Standard Deviation 16.234
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 171.049
Standard Deviation 51.825
Snow Deviate Year Annual aPNI Annual PNI
Original with Olga
Ends 2015
5 Year
Running
Average
5 Year
Running
Average
Original with Olga
2021 50.870 0.662     98.970 0.171 212.000 -0.790 2021 0.014      
2020 51.876 1.370     123.640 -1.349 194.000 -0.443 2020 -0.141      
2019 52.265 1.643     81.800 1.229 158.000 0.252 2019 1.041   0.438  
2018 52.466 1.784     107.450 -0.351 167.000 0.078 2018 0.504   0.568  
2017 51.667 1.222     91.610 0.624 147.000 0.464 2017 0.770   0.952  
2016 53.997 2.861     106.320 -0.282 201.000 -0.578 2016 0.667   0.861  
2015 54.436 3.170 54.639 3.401 102.010 -0.016 58.000 2.181 2015 1.778 1.855 0.888  
2014 53.594 2.578 53.250 2.363 121.280 -1.203 150.980 0.387 2014 0.587 0.516 0.708  
2013 51.381 1.021 49.400 -0.516 90.090 0.718 162.000 0.175 2013 0.638 0.125 0.502 0.270
2012 50.499 0.400 48.870 -0.913 104.330 -0.159 204.020 -0.636 2012 -0.132 -0.569 0.257 0.010
2011 49.698 -0.162 49.010 -0.808 106.930 -0.319 202.000 -0.597 2011 -0.360 -0.575 0.177 -0.127
2010 51.601 1.176 51.660 1.174 103.350 -0.099 141.000 0.580 2010 0.552 0.552 -0.065 -0.345
2009 49.307 -0.438 48.073 -1.509 90.840 0.672 154.000 0.329 2009 0.188 -0.169 0.041 -0.209
2008 48.871 -0.744 47.538 -1.909 105.140 -0.209 211.000 -0.771 2008 -0.575 -0.963 0.046 -0.177
2007 50.118 0.133 49.103 -0.738 93.490 0.508 142.000 0.561 2007 0.401 0.110 0.248 0.060
2006 50.694 0.538 50.497 0.304 117.390 -0.964 201.000 -0.578 2006 -0.335 -0.413 0.366 0.279
2005 51.104 0.827 51.882 1.340 82.050 1.213 34.000 2.644 2005 1.561 1.732 0.571 0.570
2004 51.731 1.268 52.391 1.720 85.450 1.004 168.000 0.059 2004 0.777 0.928 0.448 0.565
2003 50.718 0.555 51.000 0.680 100.700 0.064 133.000 0.734 2003 0.451 0.493 0.639 0.825
2002 49.183 -0.525 50.608 0.387 87.210 0.895 224.000 -1.022 2002 -0.217 0.087 0.374 0.571
2001 49.192 -0.519 50.451 0.270 84.530 1.060 102.000 1.332 2001 0.625 0.887 0.057 0.270
2000 49.249 -0.478 50.372 0.211 77.640 1.485 187.000 -0.308 2000 0.233 0.463 0.018 0.228
1999 49.515 -0.291 50.611 0.389 105.060 -0.204 271.000 -1.929 1999 -0.808 -0.581 -0.058 0.101
1998 51.162 0.867 51.351 0.943 104.790 -0.188 166.000 0.097 1998 0.259 0.284 -0.194 -0.081
1997 50.833 0.635 51.145 0.789 114.060 -0.759 258.000 -1.678 1997 -0.600 -0.549 -0.142 -0.056
1996 49.179 -0.527 49.511 -0.433 113.640 -0.733 114.000 1.101 1996 -0.053 -0.022 0.226 0.276
1995 51.644 1.206 52.085 1.492 98.610 0.193 167.000 0.078 1995 0.492 0.588 0.368 0.413
1994 51.341 0.993 51.611 1.137 81.200 1.266 128.000 0.831 1994 1.030 1.078 0.754 0.775
1993 50.646 0.504 50.756 0.498 78.000 1.463 122.000 0.946 1993 0.971 0.969 0.843 0.827
1992 52.397 1.736 52.153 1.542 81.570 1.243 119.000 1.004 1992 1.328 1.263 0.648 0.605
1991 51.240 0.922 50.696 0.453 98.520 0.199 168.000 0.059 1991 0.393 0.237 0.483 0.426
1990 50.922 0.698 50.857 0.573 131.740 -1.848 186.000 -0.288 1990 -0.479 -0.521 0.360 0.291
1989 50.429 0.352 50.471 0.285 95.000 0.415 179.000 -0.153 1989 0.205 0.182 0.296 0.262
1988 50.767 0.589 50.637 0.409 106.910 -0.318 130.000 0.792 1988 0.354 0.294 0.326 0.316
1987 51.146 0.856 51.693 1.198 73.890 1.716 148.000 0.445 1987 1.006 1.120 0.525 0.536
1986 50.880 0.669 50.837 0.558 103.990 -0.138 114.000 1.101 1986 0.544 0.507 0.556 0.598
1985 48.337 -1.120 48.825 -0.946 64.280 2.308 152.000 0.368 1985 0.518 0.576 0.542 0.603
1984 50.299 0.260 50.980 0.665 91.970 0.602 160.000 0.213 1984 0.358 0.493 0.244 0.313
1983 51.101 0.825 51.324 0.922 103.480 -0.107 164.000 0.136 1983 0.285 0.317 0.315 0.420
1982 49.320 -0.428 50.151 0.045 104.400 -0.164 216.000 -0.867 1982 -0.486 -0.329 0.269 0.365
1981 51.165 0.869 51.818 1.292 102.990 -0.077 72.000 1.911 1981 0.901 1.042 0.324 0.431
1980 50.422 0.347 50.605 0.385 96.860 0.301 160.000 0.213 1980 0.287 0.300 0.382 0.495
1979 50.200 0.191 51.123 0.772 84.370 1.070 138.000 0.638 1979 0.633 0.827 0.564 0.651
1978 50.673 0.523 51.025 0.699 88.770 0.799 150.000 0.406 1978 0.576 0.635 0.384 0.443
1977 49.960 0.022 50.230 0.104 99.990 0.108 112.000 1.139 1977 0.423 0.451 0.153 0.193
1976 49.711 -0.153 49.893 -0.148 91.480 0.632 196.000 -0.481 1976 -0.001 0.001 -0.167 -0.182
1975 49.256 -0.473 49.129 -0.719 127.180 -1.567 200.000 -0.559 1975 -0.866 -0.948 -0.216 -0.246
1974 50.106 0.124 49.937 -0.115 120.550 -1.158 268.000 -1.871 1974 -0.968 -1.048 -0.591 -0.621
1973 49.238 -0.486 49.362 -0.545 93.300 0.520 121.000 0.966 1973 0.333 0.314 -0.881 -0.907
1972 48.027 -1.338 48.429 -1.242 120.460 -1.153 268.000 -1.871 1972 -1.454 -1.422 -0.699 -0.690
1971 48.214 -1.206 48.562 -1.143 121.530 -1.219 271.000 -1.929 1971 -1.451 -1.430 -0.582 -0.542
1970 48.803 -0.792 49.395 -0.520 97.600 0.255 136.000 0.676 1970 0.047 0.137 -0.635 -0.582
1969 48.790 -0.801 49.315 -0.580 87.140 0.900 236.000 -1.253 1969 -0.385 -0.311 -0.366 -0.330
1968 49.278 -0.458 49.661 -0.321 112.540 -0.665 102.000 1.332 1968 0.070 0.115 -0.117 -0.060
1967 50.214 0.200 50.148 0.043 92.470 0.571 228.000 -1.099 1967 -0.109 -0.162 -0.116 -0.049
1966 49.293 -0.447 50.016 -0.056 100.940 0.050 183.000 -0.231 1966 -0.209 -0.079 -0.310 -0.251
1965 48.749 -0.830 49.534 -0.416 85.590 0.995 171.000 0.001 1965 0.055 0.193 -0.185 -0.115
1964 48.006 -1.353 48.425 -1.245 126.160 -1.504 234.000 -1.215 1964 -1.357 -1.321 -0.119 -0.027
1963 49.730 -0.140 50.293 0.151 90.740 0.678 91.000 1.545 1963 0.694 0.791 -0.166 -0.083
1962 49.118 -0.571 49.559 -0.397 87.620 0.870 152.000 0.368 1962 0.222 0.280 -0.218 -0.150
1961 49.940 0.007 50.449 0.268 111.230 -0.584 210.000 -0.752 1961 -0.443 -0.356 -0.100 -0.026
1960 48.762 -0.821 49.243 -0.634 103.170 -0.088 156.000 0.290 1960 -0.206 -0.144 -0.181 -0.074
1959 48.736 -0.839 49.239 -0.637 123.690 -1.352 177.000 -0.115 1959 -0.769 -0.701 -0.259 -0.120
1958 51.118 0.836 52.241 1.608 103.640 -0.117 163.000 0.155 1958 0.292 0.549 -0.517 -0.368
1957 48.202 -1.215 49.340 -0.561 86.160 0.960 184.000 -0.250 1957 -0.168 0.050 -0.775 -0.627
1956 47.712 -1.559 48.574 -1.134 102.610 -0.053 357.000 -3.588 1956 -1.734 -1.592 -0.766 -0.609
1955 46.288 -2.561 46.888 -2.395 123.600 -1.346 201.000 -0.578 1955 -1.495 -1.440 -0.934 -0.822
1954 48.130 -1.265 48.847 -0.930 104.230 -0.153 210.000 -0.752 1954 -0.723 -0.612 -0.827 -0.705
1953 50.287 0.252 50.556 0.348 130.800 -1.790 177.000 -0.115 1953 -0.551 -0.519 -0.623 -0.467
1952 48.056 -1.318 49.396 -0.519 62.360 2.426     1952 0.369 0.636 -0.589 -0.414
1951 47.356 -1.810 48.936 -0.863 98.690 0.188 198.000 -0.520 1951 -0.714 -0.398 -0.558 -0.357
1950 46.875 -2.148 47.819 -1.699 131.410 -1.827     1950 -1.325 -1.175 -0.661 -0.452
1949 47.364 -1.804 48.640 -1.085 100.220 0.094     1949 -0.570 -0.330 -0.824 -0.637
1948 47.883 -1.439 48.459 -1.220 121.800 -1.235 198.000 -0.520 1948 -1.065 -0.992 -0.855 -0.707
1947 49.479 -0.316 50.296 0.154 114.020 -0.756 185.000 -0.269 1947 -0.447 -0.291 -0.696 -0.558
1946 48.742 -0.835 49.455 -0.475 111.750 -0.616 231.000 -1.157 1946 -0.869 -0.749 -0.418 -0.306
1945 49.039 -0.626 49.655 -0.326 124.480 -1.400 148.000 0.445 1945 -0.527 -0.427 -0.176 -0.045
1944 49.679 -0.176 50.295 0.153 79.640 1.362 105.000 1.274 1944 0.820 0.930 0.033 0.138
1943 48.514 -0.995 49.429 -0.495 81.060 1.274 163.000 0.155 1943 0.145 0.312 0.486 0.605
1942 50.384 0.320 50.636 0.408 98.540 0.197 105.000 1.274 1942 0.597 0.627 0.808 0.943
1941 51.666 1.222 52.488 1.793 81.860 1.225 81.000 1.738 1941 1.395 1.585 0.606 0.768
1940 51.431 1.056 52.216 1.589 83.390 1.131 116.000 1.062 1940 1.083 1.261 0.673 0.852
1939 50.068 0.097 51.201 0.830 94.780 0.429 228.000 -1.099 1939 -0.191 0.054 0.450 0.649
1938 49.497 -0.304 50.714 0.466 81.010 1.277 147.000 0.464 1938 0.479 0.736 0.095 0.275
1937 48.944 -0.693 49.677 -0.309 114.780 -0.803 174.000 -0.057 1937 -0.518 -0.390 -0.081 0.105
1936 48.740 -0.836 49.352 -0.552 98.860 0.178 196.000 -0.481 1936 -0.380 -0.285 0.052 0.235
1935 48.564 -0.960 49.627 -0.347 79.960 1.342 159.000 0.232 1935 0.205 0.409 -0.333 -0.204
1934 50.937 0.709 51.962 1.400 112.330 -0.652 100.000 1.371 1934 0.476 0.706 -0.447 -0.353
1933 48.187 -1.225 48.412 -1.255 138.310 -2.252 216.000 -0.867 1933 -1.448 -1.458 -0.286 -0.176
1932 48.827 -0.775 48.871 -0.912 133.130 -1.933 200.000 -0.559 1932 -1.089 -1.135 -0.203 -0.082
1931 49.982 0.037 50.825 0.549 103.180 -0.088 102.000 1.332 1931 0.427 0.598 -0.293 -0.131
1930 48.065 -1.311 49.371 -0.538 72.220 1.819 101.000 1.352 1930 0.620 0.877 0.122 0.345
1929 47.696 -1.570 49.734 -0.267 74.700 1.666 172.000 -0.018 1929 0.026 0.460 0.242 0.514
1928 50.089 0.113 51.419 0.993 87.060 0.905 126.000 0.869 1928 0.629 0.922 0.352 0.669
1927 49.356 -0.403 50.375 0.213 110.670 -0.550 198.000 -0.520 1927 -0.491 -0.286 0.257 0.564
1926 51.368 1.012 53.011 2.184 89.690 0.743 110.000 1.178 1926 0.977 1.368 0.290 0.479
1925 50.909 0.689 51.855 1.320 90.600 0.686 220.000 -0.945 1925 0.144 0.354 0.133 0.218
1924 50.275 0.243 49.783 -0.230 97.320 0.273 168.000 0.059 1924 0.192 0.034 0.219 0.217
1923 50.801 0.614 50.019 -0.053 100.210 0.095 232.000 -1.176 1923 -0.156 -0.378 -0.131 -0.271
1922 49.232 -0.490 48.515 -1.178 92.750 0.554 184.000 -0.250 1922 -0.062 -0.291 -0.185 -0.419
1921 50.168 0.168 49.118 -0.727 128.000 -1.617 216.000 -0.867 1921 -0.772 -1.071 -0.354 -0.609
1920 50.401 0.332 49.477 -0.459 124.200 -1.383 136.000 0.676 1920 -0.125 -0.389 -0.329 -0.591
1919 50.099 0.120 49.203 -0.664 111.450 -0.598 248.000 -1.485 1919 -0.654 -0.915 -0.513 -0.793
1918 51.435 1.059 50.471 0.285 117.630 -0.979 180.000 -0.173 1918 -0.031 -0.289 -0.501 -0.785
1917 50.364 0.306 49.220 -0.651 134.300 -2.005 236.000 -1.253 1917 -0.984 -1.303 -0.348 -0.625
1916 48.806 -0.790 47.749 -1.751 114.390 -0.779 200.000 -0.559 1916 -0.709 -1.029 -0.066 -0.369
1915 52.546 1.841 51.644 1.162 100.560 0.073     1915 0.638 0.412 -0.004 -0.324
1914 52.331 1.690 50.764 0.504 92.250 0.585     1914 0.758 0.363 0.233 -0.069
1913 50.582 0.459 49.356 -0.549 95.800 0.366     1913 0.275 -0.061 0.387 0.117
1912 50.849 0.647 50.019 -0.053 102.400 -0.040     1912 0.202 -0.031 0.175 -0.080
1911 49.331 -0.420 48.885 -0.901 91.850 0.609     1911 0.063 -0.097 -0.071 -0.262
1910 49.444 -0.341 49.027 -0.795 116.750 -0.924     1910 -0.422 -0.573 -0.180 -0.319
1909 47.963 -1.383 47.934 -1.613 102.280 -0.033     1909 -0.472 -0.549 -0.160 -0.274
1908 50.104 0.123 49.945 -0.109 116.860 -0.931     1908 -0.269 -0.347 -0.245 -0.343
1907 49.713 -0.152 49.481 -0.456 84.740 1.047     1907 0.298 0.197 -0.156 -0.271
1906 51.043 0.784 50.803 0.533 132.010 -1.864     1906 -0.360 -0.444 0.028 -0.112
1905 51.065 0.799 50.209 0.089 113.640 -0.733     1905 0.022 -0.215 0.050 -0.128
1904 50.947 0.716 50.235 0.108 91.390 0.638     1904 0.451 0.249 0.040 -0.150
1903 50.270 0.240 49.336 -0.564 113.440 -0.720     1903 -0.160 -0.428 0.091 -0.073
1902 50.984 0.742 50.434 0.257         1902 0.247 0.086 -0.022 -0.131
1901 49.489 -0.310 49.863 -0.170         1901 -0.103 -0.057 -0.285 -0.317
1900 49.303 -0.440 49.673 -0.312 121.150 -1.195     1900 -0.545 -0.503 -0.336 -0.288
1899 47.362 -1.806 48.401 -1.263 114.450 -0.783     1899 -0.863 -0.682 -0.418 -0.346
1898 48.158 -1.246 48.942 -0.859         1898 -0.415 -0.286 -0.458 -0.390
1897 49.233 -0.490 49.277 -0.608         1897 -0.163 -0.203 -0.312 -0.264
1896 48.637 -0.909 48.973 -0.836         1896 -0.303 -0.279 -0.124 -0.167
1895 50.710 0.550 50.615 0.392         1895 0.183 0.131 -0.086 -0.222
1894 50.271 0.240 49.288 -0.600         1894 0.080 -0.200 -0.092 -0.044
1893 48.966 -0.677 47.847 -1.678         1893 -0.226 -0.559 -0.064 0.184
1892 49.098 -0.585 52.837 2.054         1892 -0.195 0.685    
1891 49.229 -0.492 53.559 2.594         1891 -0.164 0.865