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Forecasting length-of-day using numerical weather prediction models

Published online by Cambridge University Press:  03 August 2017

R. D. Rosen
Affiliation:
Atmospheric and Environmental Research, Inc., 840 Memorial Drive, Cambridge, MA 02139-3794
D. A. Salstein
Affiliation:
Atmospheric and Environmental Research, Inc., 840 Memorial Drive, Cambridge, MA 02139-3794
T. Nehrkorn
Affiliation:
Atmospheric and Environmental Research, Inc., 840 Memorial Drive, Cambridge, MA 02139-3794
J. O. Dickey
Affiliation:
Jet Propulsion Laboratory, C.I.T., Pasadena, CA 91109
T. M. Eubanks
Affiliation:
Jet Propulsion Laboratory, C.I.T., Pasadena, CA 91109
J. A. Steppe
Affiliation:
Jet Propulsion Laboratory, C.I.T., Pasadena, CA 91109
M.R.P. McCalla
Affiliation:
Climate Analysis Center/NMC, Washington, DC 20233
A. J. Miller
Affiliation:
Climate Analysis Center/NMC, Washington, DC 20233

Abstract

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A new approach to forecasting changes in length-of-day (δl.o.d) with lead times from one to ten days is examined. The approach is based on the high correlation that has been shown to exist between high frequency changes in l.o.d. and those in the atmosphere's angular momentum (M). Because forecasts of tropospheric values of M can be calculated from the zonal wind fields produced by operational numerical weather prediction models, it seems worth investigating whether these forecasts are sufficiently skillful to use to infer the evolution of δl.o.d. Here, we examine the quality of M forecasts made by the Medium Range Forecast (MRF) model of the U.S. National Meteorological Center (NMC). By comparing these forecasts against those based on a simple model of persistence, we find that skillful forecasts of M are being achieved on average by the MRF, although there has been much month-to-month variability in forecast quality. Overall, our results indicate that for prediction lead times of 1–10 days, dynamically-based forecasts of δl.o.d. represent a viable alternative to the empirical approaches currently in use.

Type
III. Determination of Earth Rotation Parameters
Copyright
Copyright © Reidel 1988