Daily Northern Hemisphere Annular Mode (NAM) Index
or Arctic Oscillation (AO) Index
The daily NAM index (NAMI) or AO index (AOI) is defined as same as the monthly NAM (AO) index (Li and Wang, 2003) except for the daily resolution.
Correlation maps between daily SLP anomalies in the NH (1950.1.1-2006.12.31) and (a) the daily NAMI and (b) the daily AO index (ftp://ftp.cpc.ncep.noaa.gov/cwlinks/). The contour interval is 0.1. The red (blue) shaded area indicates significant at the 99.9% confidence level, and the efficient freedom of degrees is estimated at each grid (Davis 1976). The latitude lines are at 10 degree intervals starting with the equator at the edges.
- Li, J. P., and J. X. L. Wang, 2003: A modified zonal index and its physical sense. Geophys. Res. Lett., 30(12), 1632, doi:10.1029/2003GL017441. PDF
- Li, J. P., 2005: Coupled air-sea oscillations and climate variations in China, in: Climate and Environmental Evolution in China (First Volume), Edt. D. Qin, Beijing: China Meteorological Press, 324-333. PDF
- Thompson, D. W. J, and J. M. Wallace, 1998: The Arctic Oscillation signature in the wintertime geopotential height and temperature fields. Geophys. Res. Lett., 25, 1297-1300. PDF
- Li, X. F., and J. P. Li, 2009: Main submonthly timescales of Northern and Southern Hemisphere annual modes. Chinese J. Atmos. Sci., 33(2), 215-231. PDF
- Li, X. F., and J. P. Li, 2012: Meridional and vertical propagation characteristics of submonthly Northern Hemisphere Annual Mode. Acta Meteor. Sin.
- Davis, R. E., 1976: Predictability of Sea Surface Temperature and Sea Level Pressure Anomalies over the North Pacific Ocean. J. Phys. Oceanogr., 6, 249-266. PDF
NAM index (AO index)
You can download this file from here (right-click then select "Save Target As" or "Save Link As").
for year = 1948 to 2013
format (i7,365f7.2) year, 365 * daily value in the Average Year
format (i7,366f7.2) year, 366 * daily value in the Leap Year
Note: (1) Missing values represented by -99.99;
(2) The reference period is 1958-2000.
Related Link: http://cmdp.ncc.cma.gov.cn/station/cn_annular_mode.php?periodType=Daily&Elem=NAMI