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 49.937
Standard Deviation 1.281
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 101.584
Standard Deviation 16.244
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 170.416
Standard Deviation 52.126
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 49.937
Standard Deviation 1.281
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 101.584
Standard Deviation 16.244
Precipitation Deviate Paradise Ranger Station, Mt Rainier, WA, Snow Pack on March 15 (Inches)
Mean 170.416
Standard Deviation 52.126
Snow Deviate Year Annual PNI Annual PNI
Original with Olga
Ends 2015
5 Year
Running
Average
5 Year
Running
Average
Original with Olga
2019 51.266 1.037     81.800 1.218 158.000 0.238 2019 0.831      
2018 52.155 1.731     107.450 -0.361 167.000 0.066 2018 0.479      
2017 52.013 1.620     91.610 0.614 147.000 0.449 2017 0.895   0.901  
2016 53.580 2.843     106.320 -0.292 201.000 -0.587 2016 0.655   0.808  
2015 53.531 2.804 54.639 3.401 102.010 -0.026 58.000 2.157 2015 1.645 1.844 0.788  
2014 52.416 1.934 53.250 2.363 121.280 -1.213 150.980 0.373 2014 0.365 0.508 0.570  
2013 50.293 0.278 49.400 -0.516 90.090 0.708 162.000 0.161 2013 0.382 0.118 0.356 0.263
2012 50.216 0.218 48.870 -0.913 104.330 -0.169 204.020 -0.645 2012 -0.199 -0.575 0.120 0.002
2011 49.544 -0.306 49.010 -0.808 106.930 -0.329 202.000 -0.606 2011 -0.414 -0.581 0.113 -0.135
2010 51.140 0.939 51.660 1.174 103.350 -0.109 141.000 0.564 2010 0.465 0.543 -0.085 -0.352
2009 49.959 0.017 48.073 -1.509 90.840 0.661 154.000 0.315 2009 0.331 -0.177 0.038 -0.216
2008 48.875 -0.829 47.538 -1.909 105.140 -0.219 211.000 -0.779 2008 -0.609 -0.969 0.106 -0.184
2007 50.195 0.202 49.103 -0.738 93.490 0.498 142.000 0.545 2007 0.415 0.102 0.373 0.051
2006 51.660 1.345 50.497 0.304 117.390 -0.973 201.000 -0.587 2006 -0.072 -0.419 0.520 0.271
2005 51.952 1.573 51.882 1.340 82.050 1.203 34.000 2.617 2005 1.797 1.720 0.796 0.561
2004 52.706 2.161 52.391 1.720 85.450 0.993 168.000 0.046 2004 1.067 0.920 0.725 0.557
2003 51.919 1.547 51.000 0.680 100.700 0.054 133.000 0.718 2003 0.773 0.484 0.898 0.817
2002 50.355 0.326 50.608 0.387 87.210 0.885 224.000 -1.028 2002 0.061 0.081 0.628 0.564
2001 49.948 0.009 50.451 0.270 84.530 1.050 102.000 1.313 2001 0.790 0.877 0.286 0.263
2000 50.174 0.185 50.372 0.211 77.640 1.474 187.000 -0.318 2000 0.447 0.455 0.197 0.221
1999 50.214 0.217 50.611 0.389 105.060 -0.214 271.000 -1.930 1999 -0.642 -0.585 0.082 0.094
1998 51.353 1.105 51.351 0.943 104.790 -0.197 166.000 0.085 1998 0.331 0.277 -0.084 -0.087
1997 51.096 0.905 51.145 0.789 114.060 -0.768 258.000 -1.680 1997 -0.515 -0.553 -0.065 -0.062
1996 49.349 -0.459 49.511 -0.433 113.640 -0.742 114.000 1.082 1996 -0.040 -0.031 0.268 0.268
1995 51.689 1.367 52.085 1.492 98.610 0.183 167.000 0.066 1995 0.539 0.580 0.388 0.405
1994 51.231 1.010 51.611 1.137 81.200 1.255 128.000 0.814 1994 1.026 1.069 0.743 0.766
1993 50.451 0.402 50.756 0.498 78.000 1.452 122.000 0.929 1993 0.927 0.959 0.810 0.818
1992 51.954 1.574 52.153 1.542 81.570 1.232 119.000 0.986 1992 1.264 1.254 0.596 0.597
1991 50.774 0.653 50.696 0.453 98.520 0.189 168.000 0.046 1991 0.296 0.229 0.432 0.418
1990 50.648 0.555 50.857 0.573 131.740 -1.856 186.000 -0.299 1990 -0.533 -0.527 0.305 0.283
1989 50.416 0.374 50.471 0.285 95.000 0.405 179.000 -0.165 1989 0.205 0.175 0.273 0.255
1988 50.495 0.436 50.637 0.409 106.910 -0.328 130.000 0.775 1988 0.294 0.285 0.318 0.308
1987 51.436 1.170 51.693 1.198 73.890 1.705 148.000 0.430 1987 1.102 1.111 0.549 0.527
1986 50.754 0.638 50.837 0.558 103.990 -0.148 114.000 1.082 1986 0.524 0.497 0.604 0.589
1985 48.921 -0.792 48.825 -0.946 64.280 2.296 152.000 0.353 1985 0.619 0.568 0.623 0.594
1984 50.762 0.644 50.980 0.665 91.970 0.592 160.000 0.200 1984 0.479 0.486 0.334 0.305
1983 51.430 1.165 51.324 0.922 103.480 -0.117 164.000 0.123 1983 0.391 0.310 0.426 0.412
1982 49.962 0.020 50.151 0.045 104.400 -0.173 216.000 -0.875 1982 -0.343 -0.334 0.360 0.357
1981 51.408 1.148 51.818 1.292 102.990 -0.087 72.000 1.888 1981 0.983 1.031 0.421 0.423
1980 50.424 0.380 50.605 0.385 96.860 0.291 160.000 0.200 1980 0.290 0.292 0.452 0.487
1979 50.788 0.664 51.123 0.772 84.370 1.060 138.000 0.622 1979 0.782 0.818 0.601 0.642
1978 50.529 0.462 51.025 0.699 88.770 0.789 150.000 0.392 1978 0.548 0.626 0.387 0.434
1977 49.914 -0.018 50.230 0.104 99.990 0.098 112.000 1.121 1977 0.400 0.441 0.132 0.185
1976 49.446 -0.383 49.893 -0.148 91.480 0.622 196.000 -0.491 1976 -0.084 -0.005 -0.236 -0.189
1975 48.895 -0.813 49.129 -0.719 127.180 -1.576 200.000 -0.568 1975 -0.985 -0.954 -0.289 -0.253
1974 49.763 -0.136 49.937 -0.115 120.550 -1.168 268.000 -1.872 1974 -1.059 -1.051 -0.663 -0.626
1973 49.150 -0.614 49.362 -0.545 93.300 0.510 121.000 0.948 1973 0.281 0.304 -0.945 -0.912
1972 48.185 -1.367 48.429 -1.242 120.460 -1.162 268.000 -1.872 1972 -1.467 -1.426 -0.725 -0.696
1971 48.231 -1.331 48.562 -1.143 121.530 -1.228 271.000 -1.930 1971 -1.496 -1.434 -0.584 -0.548
1970 49.217 -0.561 49.395 -0.520 97.600 0.245 136.000 0.660 1970 0.115 0.128 -0.625 -0.588
1969 49.052 -0.690 49.315 -0.580 87.140 0.889 236.000 -1.258 1969 -0.353 -0.316 -0.354 -0.337
1968 49.405 -0.415 49.661 -0.321 112.540 -0.675 102.000 1.313 1968 0.074 0.106 -0.087 -0.067
1967 50.204 0.208 50.148 0.043 92.470 0.561 228.000 -1.105 1967 -0.112 -0.167 -0.079 -0.056
1966 49.587 -0.273 50.016 -0.056 100.940 0.040 183.000 -0.241 1966 -0.158 -0.086 -0.286 -0.257
1965 49.275 -0.517 49.534 -0.416 85.590 0.985 171.000 -0.011 1965 0.152 0.186 -0.153 -0.122
1964 48.107 -1.428 48.425 -1.245 126.160 -1.513 234.000 -1.220 1964 -1.387 -1.326 -0.074 -0.035
1963 49.972 0.028 50.293 0.151 90.740 0.668 91.000 1.524 1963 0.740 0.781 -0.108 -0.090
1962 49.467 -0.367 49.559 -0.397 87.620 0.860 152.000 0.353 1962 0.282 0.272 -0.169 -0.157
1961 50.408 0.368 50.449 0.268 111.230 -0.594 210.000 -0.759 1961 -0.328 -0.362 -0.033 -0.034
1960 49.126 -0.633 49.243 -0.634 103.170 -0.098 156.000 0.277 1960 -0.151 -0.152 -0.077 -0.082
1959 49.131 -0.629 49.239 -0.637 123.690 -1.361 177.000 -0.126 1959 -0.705 -0.708 -0.130 -0.127
1958 51.906 1.536 52.241 1.608 103.640 -0.127 163.000 0.142 1958 0.517 0.541 -0.395 -0.374
1957 49.123 -0.635 49.340 -0.561 86.160 0.950 184.000 -0.261 1957 0.018 0.043 -0.666 -0.632
1956 48.249 -1.317 48.574 -1.134 102.610 -0.063 357.000 -3.580 1956 -1.653 -1.592 -0.657 -0.614
1955 46.630 -2.580 46.888 -2.395 123.600 -1.355 201.000 -0.587 1955 -1.507 -1.446 -0.870 -0.828
1954 48.584 -1.056 48.847 -0.930 104.230 -0.163 210.000 -0.759 1954 -0.659 -0.617 -0.765 -0.710
1953 50.289 0.275 50.556 0.348 130.800 -1.799 177.000 -0.126 1953 -0.550 -0.526 -0.527 -0.472
1952 48.943 -0.776 49.396 -0.519 62.360 2.415     1952 0.546 0.632 -0.468 -0.419
1951 48.597 -1.046 48.936 -0.863 98.690 0.178 198.000 -0.529 1951 -0.466 -0.405 -0.396 -0.362
1950 47.631 -1.800 47.819 -1.699 131.410 -1.836     1950 -1.212 -1.178 -0.489 -0.457
1949 48.687 -0.975 48.640 -1.085 100.220 0.084     1949 -0.297 -0.334 -0.657 -0.642
1948 48.291 -1.284 48.459 -1.220 121.800 -1.245 198.000 -0.529 1948 -1.019 -0.998 -0.730 -0.712
1947 50.151 0.167 50.296 0.154 114.020 -0.766 185.000 -0.280 1947 -0.293 -0.297 -0.580 -0.564
1946 49.049 -0.693 49.455 -0.475 111.750 -0.626 231.000 -1.162 1946 -0.827 -0.754 -0.338 -0.313
1945 49.406 -0.414 49.655 -0.326 124.480 -1.410 148.000 0.430 1945 -0.464 -0.435 -0.073 -0.053
1944 50.108 0.134 50.295 0.153 79.640 1.351 105.000 1.255 1944 0.913 0.920 0.120 0.130
1943 49.315 -0.485 49.429 -0.495 81.060 1.263 163.000 0.142 1943 0.307 0.304 0.587 0.596
1942 50.674 0.575 50.636 0.408 98.540 0.187 105.000 1.255 1942 0.673 0.617 0.928 0.933
1941 51.972 1.588 52.488 1.793 81.860 1.214 81.000 1.715 1941 1.506 1.574 0.743 0.759
1940 51.943 1.566 52.216 1.589 83.390 1.120 116.000 1.044 1940 1.243 1.251 0.820 0.844
1939 50.772 0.652 51.201 0.830 94.780 0.419 228.000 -1.105 1939 -0.011 0.048 0.600 0.641
1938 50.398 0.360 50.714 0.466 81.010 1.267 147.000 0.449 1938 0.692 0.727 0.245 0.268
1937 49.421 -0.402 49.677 -0.309 114.780 -0.812 174.000 -0.069 1937 -0.428 -0.397 0.074 0.098
1936 49.302 -0.495 49.352 -0.552 98.860 0.168 196.000 -0.491 1936 -0.273 -0.292 0.202 0.227
1935 49.444 -0.385 49.627 -0.347 79.960 1.331 159.000 0.219 1935 0.389 0.401 -0.230 -0.211
1934 51.484 1.207 51.962 1.400 112.330 -0.662 100.000 1.351 1934 0.632 0.696 -0.365 -0.360
1933 48.305 -1.274 48.412 -1.255 138.310 -2.261 216.000 -0.875 1933 -1.470 -1.464 -0.200 -0.184
1932 48.918 -0.795 48.871 -0.912 133.130 -1.942 200.000 -0.568 1932 -1.102 -1.140 -0.104 -0.091
1931 50.495 0.436 50.825 0.549 103.180 -0.098 102.000 1.313 1931 0.550 0.588 -0.150 -0.139
1930 49.253 -0.534 49.371 -0.538 72.220 1.808 101.000 1.332 1930 0.869 0.867 0.318 0.336
1929 49.404 -0.416 49.734 -0.267 74.700 1.655 172.000 -0.030 1929 0.403 0.453 0.476 0.506
1928 51.049 0.868 51.419 0.993 87.060 0.894 126.000 0.852 1928 0.871 0.913 0.626 0.660
1927 50.125 0.147 50.375 0.213 110.670 -0.559 198.000 -0.529 1927 -0.314 -0.292 0.514 0.556
1926 52.523 2.018 53.011 2.184 89.690 0.732 110.000 1.159 1926 1.303 1.358 0.445 0.471
1925 51.459 1.188 51.855 1.320 90.600 0.676 220.000 -0.951 1925 0.304 0.348 0.201 0.212
1924 49.780 -0.123 49.783 -0.230 97.320 0.262 168.000 0.046 1924 0.062 0.026 0.201 0.210
1923 49.986 0.039 50.019 -0.053 100.210 0.085 232.000 -1.181 1923 -0.353 -0.383 -0.279 -0.277
1922 48.375 -1.218 48.515 -1.178 92.750 0.544 184.000 -0.261 1922 -0.312 -0.298 -0.426 -0.426
1921 48.919 -0.794 49.118 -0.727 128.000 -1.626 216.000 -0.875 1921 -1.098 -1.076 -0.629 -0.615
1920 49.218 -0.561 49.477 -0.459 124.200 -1.392 136.000 0.660 1920 -0.431 -0.397 -0.618 -0.597
1919 48.975 -0.750 49.203 -0.664 111.450 -0.607 248.000 -1.488 1919 -0.949 -0.920 -0.830 -0.799
1918 50.284 0.271 50.471 0.285 117.630 -0.988 180.000 -0.184 1918 -0.300 -0.296 -0.826 -0.791
1917 48.849 -0.849 49.220 -0.651 134.300 -2.014 236.000 -1.258 1917 -1.374 -1.308 -0.677 -0.630
1916 47.532 -1.877 47.749 -1.751 114.390 -0.788 200.000 -0.568 1916 -1.078 -1.036 -0.411 -0.374
1915 51.076 0.889 51.644 1.162 100.560 0.063     1915 0.317 0.408 -0.358 -0.328
1914 50.654 0.560 50.764 0.504 92.250 0.575     1914 0.378 0.359 -0.095 -0.073
1913 49.346 -0.461 49.356 -0.549 95.800 0.356     1913 -0.035 -0.064 0.085 0.114
1912 49.783 -0.120 50.019 -0.053 102.400 -0.050     1912 -0.057 -0.035 -0.096 -0.083
1911 48.476 -1.140 48.885 -0.901 91.850 0.599     1911 -0.180 -0.101 -0.286 -0.266
1910 48.872 -0.831 49.027 -0.795 116.750 -0.934     1910 -0.588 -0.576 -0.365 -0.323
1909 47.799 -1.668 47.934 -1.613 102.280 -0.043     1909 -0.570 -0.552 -0.311 -0.277
1908 49.497 -0.343 49.945 -0.109 116.860 -0.940     1908 -0.428 -0.350 -0.371 -0.346
1907 49.425 -0.400 49.481 -0.456 84.740 1.037     1907 0.212 0.194 -0.298 -0.274
1906 50.490 0.432 50.803 0.533 132.010 -1.873     1906 -0.481 -0.447 -0.135 -0.115
1905 50.026 0.070 50.209 0.089 113.640 -0.742     1905 -0.224 -0.218 -0.143 -0.131
1904 50.070 0.104 50.235 0.108 91.390 0.628     1904 0.244 0.245 -0.181 -0.153
1903 49.084 -0.666 49.336 -0.564 113.440 -0.730     1903 -0.465 -0.431 -0.116 -0.075
1902 50.010 0.057 50.434 0.257         1902 0.019 0.086 -0.173 -0.133
1901 49.353 -0.455 49.863 -0.170         1901 -0.152 -0.057 -0.362 -0.319
1900 49.516 -0.328 49.673 -0.312 121.150 -1.205     1900 -0.511 -0.506 -0.306 -0.290
1899 48.262 -1.307 48.401 -1.263 114.450 -0.792     1899 -0.700 -0.685 -0.371 -0.347
1898 49.224 -0.556 48.942 -0.859         1898 -0.185 -0.286 -0.409 -0.392
1897 48.761 -0.917 49.277 -0.608         1897 -0.306 -0.203 -0.298 -0.264
1896 48.624 -1.024 48.973 -0.836         1896 -0.341 -0.279 -0.206 -0.167
1895 50.107 0.133 50.615 0.392         1895 0.044 0.131 -0.285 -0.222
1894 48.998 -0.732 49.288 -0.600         1894 -0.244 -0.200 -0.324 -0.044
1893 47.708 -1.740 47.847 -1.678         1893 -0.580 -0.559 -0.339 0.184
1892 48.019 -1.497 52.837 2.054         1892 -0.499 0.685    
1891 48.330 -1.254 53.559 2.594         1891 -0.418 0.865