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 49.922
Standard Deviation 1.425
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 101.767
Standard Deviation 16.300
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 170.647
Standard Deviation 51.920
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 49.922
Standard Deviation 1.425
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 101.767
Standard Deviation 16.300
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 170.647
Standard Deviation 51.920
Snow Deviate Year Annual PNI Annual PNI
Original with Olga
Ends 2015
5 Year
Running
Average
5 Year
Running
Average
Original with Olga
2020 51.876 1.372     123.640 -1.342 194.000 -0.450 2020 -0.140      
2019 52.265 1.645     81.800 1.225 158.000 0.244 2019 1.038      
2018 52.466 1.786     107.450 -0.349 167.000 0.070 2018 0.502   0.567  
2017 51.667 1.225     91.610 0.623 147.000 0.455 2017 0.768   0.950  
2016 53.997 2.860     106.320 -0.279 201.000 -0.585 2016 0.665   0.859  
2015 54.436 3.168 54.639 3.401 102.010 -0.015 58.000 2.170 2015 1.774 1.852 0.886  
2014 53.594 2.577 53.250 2.363 121.280 -1.197 150.980 0.379 2014 0.586 0.515 0.706  
2013 51.381 1.024 49.400 -0.516 90.090 0.716 162.000 0.167 2013 0.636 0.122 0.501 0.268
2012 50.499 0.405 48.870 -0.913 104.330 -0.157 204.020 -0.643 2012 -0.132 -0.571 0.256 0.008
2011 49.698 -0.157 49.010 -0.808 106.930 -0.317 202.000 -0.604 2011 -0.359 -0.576 0.176 -0.130
2010 51.601 1.179 51.660 1.174 103.350 -0.097 141.000 0.571 2010 0.551 0.549 -0.066 -0.347
2009 49.307 -0.432 48.073 -1.509 90.840 0.670 154.000 0.321 2009 0.186 -0.173 0.041 -0.211
2008 48.871 -0.738 47.538 -1.909 105.140 -0.207 211.000 -0.777 2008 -0.574 -0.964 0.046 -0.179
2007 50.118 0.138 49.103 -0.738 93.490 0.508 142.000 0.552 2007 0.399 0.107 0.247 0.057
2006 50.694 0.542 50.497 0.304 117.390 -0.958 201.000 -0.585 2006 -0.334 -0.413 0.365 0.276
2005 51.104 0.830 51.882 1.340 82.050 1.210 34.000 2.632 2005 1.557 1.727 0.569 0.567
2004 51.731 1.270 52.391 1.720 85.450 1.001 168.000 0.051 2004 0.774 0.924 0.446 0.563
2003 50.718 0.559 51.000 0.680 100.700 0.065 133.000 0.725 2003 0.450 0.490 0.637 0.822
2002 49.183 -0.519 50.608 0.387 87.210 0.893 224.000 -1.028 2002 -0.218 0.084 0.372 0.568
2001 49.192 -0.512 50.451 0.270 84.530 1.058 102.000 1.322 2001 0.622 0.883 0.056 0.267
2000 49.249 -0.472 50.372 0.211 77.640 1.480 187.000 -0.315 2000 0.231 0.459 0.017 0.225
1999 49.515 -0.285 50.611 0.389 105.060 -0.202 271.000 -1.933 1999 -0.807 -0.582 -0.059 0.099
1998 51.162 0.870 51.351 0.943 104.790 -0.185 166.000 0.090 1998 0.258 0.282 -0.194 -0.083
1997 50.833 0.639 51.145 0.789 114.060 -0.754 258.000 -1.682 1997 -0.599 -0.549 -0.142 -0.057
1996 49.179 -0.521 49.511 -0.433 113.640 -0.728 114.000 1.091 1996 -0.053 -0.024 0.225 0.274
1995 51.644 1.209 52.085 1.492 98.610 0.194 167.000 0.070 1995 0.491 0.585 0.367 0.410
1994 51.341 0.996 51.611 1.137 81.200 1.262 128.000 0.821 1994 1.026 1.073 0.751 0.772
1993 50.646 0.508 50.756 0.498 78.000 1.458 122.000 0.937 1993 0.968 0.964 0.840 0.823
1992 52.397 1.737 52.153 1.542 81.570 1.239 119.000 0.995 1992 1.324 1.259 0.646 0.602
1991 51.240 0.925 50.696 0.453 98.520 0.199 168.000 0.051 1991 0.392 0.234 0.482 0.423
1990 50.922 0.702 50.857 0.573 131.740 -1.839 186.000 -0.296 1990 -0.478 -0.520 0.359 0.289
1989 50.429 0.356 50.471 0.285 95.000 0.415 179.000 -0.161 1989 0.203 0.180 0.295 0.260
1988 50.767 0.593 50.637 0.409 106.910 -0.315 130.000 0.783 1988 0.353 0.292 0.325 0.314
1987 51.146 0.859 51.693 1.198 73.890 1.710 148.000 0.436 1987 1.002 1.115 0.523 0.532
1986 50.880 0.672 50.837 0.558 103.990 -0.136 114.000 1.091 1986 0.542 0.504 0.554 0.595
1985 48.337 -1.112 48.825 -0.946 64.280 2.300 152.000 0.359 1985 0.516 0.571 0.540 0.599
1984 50.299 0.265 50.980 0.665 91.970 0.601 160.000 0.205 1984 0.357 0.490 0.243 0.310
1983 51.101 0.828 51.324 0.922 103.480 -0.105 164.000 0.128 1983 0.284 0.315 0.314 0.417
1982 49.320 -0.422 50.151 0.045 104.400 -0.162 216.000 -0.874 1982 -0.486 -0.330 0.268 0.362
1981 51.165 0.873 51.818 1.292 102.990 -0.075 72.000 1.900 1981 0.899 1.039 0.323 0.429
1980 50.422 0.351 50.605 0.385 96.860 0.301 160.000 0.205 1980 0.286 0.297 0.381 0.492
1979 50.200 0.195 51.123 0.772 84.370 1.067 138.000 0.629 1979 0.631 0.823 0.562 0.648
1978 50.673 0.527 51.025 0.699 88.770 0.797 150.000 0.398 1978 0.574 0.631 0.382 0.439
1977 49.960 0.027 50.230 0.104 99.990 0.109 112.000 1.130 1977 0.422 0.448 0.152 0.190
1976 49.711 -0.148 49.893 -0.148 91.480 0.631 196.000 -0.488 1976 -0.002 -0.002 -0.167 -0.184
1975 49.256 -0.467 49.129 -0.719 127.180 -1.559 200.000 -0.565 1975 -0.864 -0.948 -0.216 -0.248
1974 50.106 0.129 49.937 -0.115 120.550 -1.152 268.000 -1.875 1974 -0.966 -1.047 -0.590 -0.622
1973 49.238 -0.480 49.362 -0.545 93.300 0.519 121.000 0.956 1973 0.332 0.310 -0.879 -0.907
1972 48.027 -1.330 48.429 -1.242 120.460 -1.147 268.000 -1.875 1972 -1.451 -1.421 -0.697 -0.691
1971 48.214 -1.199 48.562 -1.143 121.530 -1.212 271.000 -1.933 1971 -1.448 -1.429 -0.581 -0.544
1970 48.803 -0.785 49.395 -0.520 97.600 0.256 136.000 0.667 1970 0.046 0.134 -0.634 -0.583
1969 48.790 -0.794 49.315 -0.580 87.140 0.897 236.000 -1.259 1969 -0.385 -0.314 -0.365 -0.332
1968 49.278 -0.452 49.661 -0.321 112.540 -0.661 102.000 1.322 1968 0.070 0.113 -0.118 -0.062
1967 50.214 0.205 50.148 0.043 92.470 0.570 228.000 -1.105 1967 -0.110 -0.164 -0.116 -0.051
1966 49.293 -0.441 50.016 -0.056 100.940 0.051 183.000 -0.238 1966 -0.209 -0.081 -0.310 -0.252
1965 48.749 -0.823 49.534 -0.416 85.590 0.992 171.000 -0.007 1965 0.054 0.190 -0.185 -0.118
1964 48.006 -1.345 48.425 -1.245 126.160 -1.496 234.000 -1.220 1964 -1.354 -1.321 -0.119 -0.030
1963 49.730 -0.135 50.293 0.151 90.740 0.677 91.000 1.534 1963 0.692 0.787 -0.166 -0.085
1962 49.118 -0.564 49.559 -0.397 87.620 0.868 152.000 0.359 1962 0.221 0.277 -0.218 -0.152
1961 49.940 0.012 50.449 0.268 111.230 -0.581 210.000 -0.758 1961 -0.442 -0.357 -0.100 -0.028
1960 48.762 -0.814 49.243 -0.634 103.170 -0.086 156.000 0.282 1960 -0.206 -0.146 -0.181 -0.076
1959 48.736 -0.832 49.239 -0.637 123.690 -1.345 177.000 -0.122 1959 -0.766 -0.701 -0.259 -0.122
1958 51.118 0.839 52.241 1.608 103.640 -0.115 163.000 0.147 1958 0.291 0.547 -0.516 -0.369
1957 48.202 -1.207 49.340 -0.561 86.160 0.958 184.000 -0.257 1957 -0.169 0.046 -0.773 -0.628
1956 47.712 -1.551 48.574 -1.134 102.610 -0.052 357.000 -3.589 1956 -1.731 -1.592 -0.765 -0.610
1955 46.288 -2.551 46.888 -2.395 123.600 -1.339 201.000 -0.585 1955 -1.492 -1.440 -0.932 -0.823
1954 48.130 -1.258 48.847 -0.930 104.230 -0.151 210.000 -0.758 1954 -0.722 -0.613 -0.825 -0.706
1953 50.287 0.256 50.556 0.348 130.800 -1.781 177.000 -0.122 1953 -0.549 -0.518 -0.621 -0.468
1952 48.056 -1.310 49.396 -0.519 62.360 2.418     1952 0.369 0.633 -0.587 -0.414
1951 47.356 -1.801 48.936 -0.863 98.690 0.189 198.000 -0.527 1951 -0.713 -0.400 -0.556 -0.358
1950 46.875 -2.138 47.819 -1.699 131.410 -1.819     1950 -1.319 -1.172 -0.658 -0.452
1949 47.364 -1.795 48.640 -1.085 100.220 0.095     1949 -0.567 -0.330 -0.821 -0.637
1948 47.883 -1.431 48.459 -1.220 121.800 -1.229 198.000 -0.527 1948 -1.062 -0.992 -0.852 -0.707
1947 49.479 -0.311 50.296 0.154 114.020 -0.752 185.000 -0.276 1947 -0.446 -0.291 -0.694 -0.558
1946 48.742 -0.828 49.455 -0.475 111.750 -0.612 231.000 -1.162 1946 -0.868 -0.750 -0.417 -0.307
1945 49.039 -0.620 49.655 -0.326 124.480 -1.393 148.000 0.436 1945 -0.526 -0.428 -0.176 -0.047
1944 49.679 -0.170 50.295 0.153 79.640 1.357 105.000 1.264 1944 0.817 0.925 0.032 0.136
1943 48.514 -0.988 49.429 -0.495 81.060 1.270 163.000 0.147 1943 0.143 0.308 0.484 0.602
1942 50.384 0.324 50.636 0.408 98.540 0.198 105.000 1.264 1942 0.596 0.623 0.805 0.939
1941 51.666 1.224 52.488 1.793 81.860 1.221 81.000 1.727 1941 1.391 1.580 0.604 0.764
1940 51.431 1.059 52.216 1.589 83.390 1.127 116.000 1.053 1940 1.080 1.256 0.670 0.849
1939 50.068 0.102 51.201 0.830 94.780 0.429 228.000 -1.105 1939 -0.191 0.051 0.448 0.646
1938 49.497 -0.298 50.714 0.466 81.010 1.273 147.000 0.455 1938 0.477 0.732 0.094 0.272
1937 48.944 -0.687 49.677 -0.309 114.780 -0.798 174.000 -0.065 1937 -0.516 -0.391 -0.081 0.102
1936 48.740 -0.829 49.352 -0.552 98.860 0.178 196.000 -0.488 1936 -0.380 -0.287 0.052 0.233
1935 48.564 -0.953 49.627 -0.347 79.960 1.338 159.000 0.224 1935 0.203 0.405 -0.332 -0.205
1934 50.937 0.712 51.962 1.400 112.330 -0.648 100.000 1.361 1934 0.475 0.704 -0.446 -0.354
1933 48.187 -1.217 48.412 -1.255 138.310 -2.242 216.000 -0.874 1933 -1.444 -1.457 -0.285 -0.177
1932 48.827 -0.769 48.871 -0.912 133.130 -1.924 200.000 -0.565 1932 -1.086 -1.134 -0.202 -0.084
1931 49.982 0.042 50.825 0.549 103.180 -0.087 102.000 1.322 1931 0.426 0.595 -0.293 -0.134
1930 48.065 -1.304 49.371 -0.538 72.220 1.813 101.000 1.341 1930 0.617 0.872 0.122 0.342
1929 47.696 -1.562 49.734 -0.267 74.700 1.661 172.000 -0.026 1929 0.024 0.456 0.241 0.511
1928 50.089 0.118 51.419 0.993 87.060 0.902 126.000 0.860 1928 0.627 0.919 0.350 0.665
1927 49.356 -0.397 50.375 0.213 110.670 -0.546 198.000 -0.527 1927 -0.490 -0.287 0.256 0.561
1926 51.368 1.015 53.011 2.184 89.690 0.741 110.000 1.168 1926 0.975 1.364 0.289 0.476
1925 50.909 0.692 51.855 1.320 90.600 0.685 220.000 -0.951 1925 0.142 0.351 0.132 0.216
1924 50.275 0.248 49.783 -0.230 97.320 0.273 168.000 0.051 1924 0.191 0.031 0.218 0.215
1923 50.801 0.617 50.019 -0.053 100.210 0.096 232.000 -1.182 1923 -0.156 -0.380 -0.131 -0.272
1922 49.232 -0.484 48.515 -1.178 92.750 0.553 184.000 -0.257 1922 -0.063 -0.294 -0.185 -0.420
1921 50.168 0.172 49.118 -0.727 128.000 -1.609 216.000 -0.874 1921 -0.770 -1.070 -0.353 -0.610
1920 50.401 0.336 49.477 -0.459 124.200 -1.376 136.000 0.667 1920 -0.124 -0.389 -0.328 -0.592
1919 50.099 0.124 49.203 -0.664 111.450 -0.594 248.000 -1.490 1919 -0.653 -0.916 -0.512 -0.793
1918 51.435 1.062 50.471 0.285 117.630 -0.973 180.000 -0.180 1918 -0.031 -0.290 -0.499 -0.785
1917 50.364 0.310 49.220 -0.651 134.300 -1.996 236.000 -1.259 1917 -0.981 -1.302 -0.347 -0.625
1916 48.806 -0.783 47.749 -1.751 114.390 -0.774 200.000 -0.565 1916 -0.708 -1.030 -0.065 -0.369
1915 52.546 1.842 51.644 1.162 100.560 0.074     1915 0.639 0.412 -0.003 -0.324
1914 52.331 1.691 50.764 0.504 92.250 0.584     1914 0.758 0.363 0.234 -0.070
1913 50.582 0.463 49.356 -0.549 95.800 0.366     1913 0.276 -0.061 0.388 0.117
1912 50.849 0.650 50.019 -0.053 102.400 -0.039     1912 0.204 -0.031 0.177 -0.080
1911 49.331 -0.414 48.885 -0.901 91.850 0.608     1911 0.065 -0.098 -0.068 -0.262
1910 49.444 -0.335 49.027 -0.795 116.750 -0.919     1910 -0.418 -0.571 -0.177 -0.319
1909 47.963 -1.375 47.934 -1.613 102.280 -0.031     1909 -0.469 -0.548 -0.158 -0.273
1908 50.104 0.127 49.945 -0.109 116.860 -0.926     1908 -0.266 -0.345 -0.242 -0.342
1907 49.713 -0.147 49.481 -0.456 84.740 1.045     1907 0.299 0.196 -0.153 -0.270
1906 51.043 0.787 50.803 0.533 132.010 -1.855     1906 -0.356 -0.441 0.031 -0.111
1905 51.065 0.802 50.209 0.089 113.640 -0.728     1905 0.025 -0.213 0.053 -0.127
1904 50.947 0.720 50.235 0.108 91.390 0.637     1904 0.452 0.248 0.042 -0.149
1903 50.270 0.245 49.336 -0.564 113.440 -0.716     1903 -0.157 -0.427 0.093 -0.073
1902 50.984 0.746 50.434 0.257         1902 0.249 0.086 -0.020 -0.130
1901 49.489 -0.304 49.863 -0.170         1901 -0.101 -0.057 -0.282 -0.316
1900 49.303 -0.434 49.673 -0.312 121.150 -1.189     1900 -0.541 -0.500 -0.333 -0.288
1899 47.362 -1.797 48.401 -1.263 114.450 -0.778     1899 -0.858 -0.680 -0.415 -0.345
1898 48.158 -1.238 48.942 -0.859         1898 -0.413 -0.286 -0.455 -0.390
1897 49.233 -0.484 49.277 -0.608         1897 -0.161 -0.203 -0.310 -0.263
1896 48.637 -0.902 48.973 -0.836         1896 -0.301 -0.279 -0.122 -0.167
1895 50.710 0.553 50.615 0.392         1895 0.184 0.131 -0.084 -0.222
1894 50.271 0.245 49.288 -0.600         1894 0.082 -0.200 -0.090 -0.044
1893 48.966 -0.671 47.847 -1.678         1893 -0.224 -0.559 -0.062 0.184
1892 49.098 -0.578 52.837 2.054         1892 -0.193 0.685    
1891 49.229 -0.486 53.559 2.594         1891 -0.162 0.865