Trans-Niño Index Calculator:
Calculator Output:  Introduction   Niño Summary Statistics   Monthly Trans-Niño Index    Multi-Month Trans-Niño    Raw Data (html-formatted)   Raw Data (tab-delimited)  Standardization: Beginning Year:  1950  1951  1952  1953  1954  1955  1956  1957  1958  1959  1960  1961  1962  1963  1964  1965  1966  1967  1968  1969  1970  1971  1972  1973  1974  1975  1976  1977  1978  1979  1980  1981  1982  1983  1984  1985  1986  1987  1988  1989  1990  1991  1992  1993  1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009  Standardization: Ending Year:  1950  1951  1952  1953  1954  1955  1956  1957  1958  1959  1960  1961  1962  1963  1964  1965  1966  1967  1968  1969  1970  1971  1972  1973  1974  1975  1976  1977  1978  1979  1980  1981  1982  1983  1984  1985  1986  1987  1988  1989  1990  1991  1992  1993  1994  1995  1996  1997  1998  1999  2000  2001  2002  2003  2004  2005  2006  2007  2008  2009

Background Information:

This research investigates large-scale climate signals affecting inter-annual hydrologic variability of streams flowing into Upper Klamath Lake, Oregon, USA. Upper Klamath Lake (UKL) is an arid, mountainous basin located in the rain shadow east of the crest of the Cascade Mountains in the northwestern United States. It is an important reservoir serving the 971 km2 Klamath Irrigation Project, established in 1906 by the US Bureau of Reclamation.

Developing accurate early season streamflow prediction models for UKL is difficult because the basin has a high degree of topographic, geologic, and climatologic variability. Furthermore, peak monthly streamflow is occurring earlier, which may be associated with global climate change. In an effort to reduce early season streamflow forecast uncertainty, six large-scale climate indices - the Pacific North American Pattern, Southern Oscillation Index, Pacific Decadal Oscillation (PDO), Multivariate El Niño Southern Oscillation Index, Niño 3.4, and a revised Trans-Niño Index ( TNI) - were evaluated independently for their ability to explain inter-annual variation of the main hydrologic inputs into Upper Klamath Lake.

The TNI, which characterizes the sea surface temperature (SST) gradient between regions Niño 1+2 and Niño 4, was the only index to show significant correlations during the current warm phase of the PDO. During the warm PDO phase (1978-present), the averaged October through December TNI was strongly correlated with the subsequent April through September Williamson River discharge (r = 0.73), Sprague River discharge (r = 0.65), net inflow to UKL (r = 0.67), and moderately correlated with observed Crater Lake 1 April snow water equivalent (r = 0.51). Incorporating the TNI variable into operational statistical streamflow prediction models significantly (p-value < 0.1) reduces the uncertainty (measured by the standard error) of forecasts issued on the first of December, January, and February by 7%, 9%, and 8.3%, respectively, for the Williamson River and by 9.2%, 7.5%, and 10.4%, respectively, for the Sprague River.

These results suggest that during the current climate regime, SST gradients, as opposed to mean SST or sea-level pressure patterns, explain a significant portion of hydrologic variability observed in the streams flowing into UKL and are useful in real-time hydrologic applications.

See also:   Trenberth, K. E., and D. P. Stepaniak, 2001.  Indices of El Niño Evolution.  /J. Climate/, *14*, 1697-1701.

Calculations:

This site makes use of data made available  by the following agencies:  National Oceanic & Atmospheric Administration  National Centers for Environmental Prediction  Northwest River Forecast Center		Authored by Adam Kennedy  Site Development by Orion Imaging