Pacific Northwest Index (PNI) | Columbia Basin Research

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:

PNI_y = ( TempDev_y + PrecipDev_y + SnowDev_y ) / 3

where:

: TempDev_y = - ( Mean_Temp - Temp_y ) / StDev_Temp; PrecipDev_y = ( Mean_Precip - Precip_y ) / StDev_Precip; SnowDev_y = ( Mean_Snow - Snow_y ) / StDev_Snow

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