About the NCEP data
Author: Dr. P. A. Newman
In conjunction with the Climate Prediction Center (CPC) of the National Centers for Environmental Prediction (NCEP)—formerly known as the Climate Analysis Center of the National Meteorological Center (NMC)—NASA/GSFC Atmospheric and Chemistry branch (ACDB) maintains a collection of stratospheric climate data. These data are used to characterize and track the behavior of the stratosphere in both hemispheres.
The NCEP CPC data consist of analyses from December 1978 to the present. The analyses consist of geopotential heights and temperatures. Tropospheric data (1000–100 hpa) are produced from the NCEP Global Data Acquisition System (GDAS), while stratospheric data (70–0.4 hPa) are produced by the NCEP CPC. The GDAS data are extensively described in Trenberth and Olson [1988], while the NCEP CPC data are described in Newman et al. [1989, 1993]. The climatology has been extended from the original work of Wu et al. [1987], and is equivalent to climatologies produced by Randel [1987] and Nagatani et al. [1988]. Temperature comparisons to NASA high altitude ER-2 aircraft data indicate small biases, with root-mean-square (RMS) deviations of 1–2 K [Rood et al., 1990]. NCEP stratospheric analyses also tend to have a 1–2 K warm bias in the colder region near the pole [Rood et al., 1990].
The NCEP CCPC stratospheric analysis system generates heights and temperatures for 70–10 hPa in the Northern Hemisphere and uses a successive corrections method [Cressman, 1959; Finger et al, 1965]. The analysis for levels above 10 hPa and the Southern Hemisphere stratosphere (70–0.4 hPa) uses a similar successive corrections method [Yanai, 1964], but the successive scans are around the data rather than the gridpoints. The net result is a map that essentially uses the same analysis system for the whole stratosphere. The first guess for all maps is the map from the previous day. Satellite data are then injected into the analysis for the current map. The satellite maps are then further used as a first guess field for the northern hemisphere radiosonde analysis from 70–10 hPa, while all other fields use the satellite maps as a final field. NCEP data quality is generally quite good in the lower stratosphere [Gelman et al, 1986; Nagatani et al, 1988; Trenberth et al, 1988; Nagatani et al, 1990].
The wind fields are derived by NASA/GSFC ACDB from the NCEP CPC geopotential heights using a balanced wind approximation [Randel, 1987; Newmana et al, 1988; Newman, 1989].
References
Cressman, G. P., An operational objective analysis system, Mon. Weather Rev., 87(10), 367–374, doi:10.1175/1520-0493(1959)087<0367:AOOAS>2.0.CO;2, 1959.
Finger, F. G., H. M. Woolf, and C. E. Anderson, A Method for objective analysis of stratospheric constant-pressure charts, Mon. Weather Rev, 93(10), 619–638, doi:10.1175/1520-0493(1965)093<0619:AMFOAO>2.3.CO;2, 1965.
Gelman, M. E., A. J. Miller, K. W. Johnson, and R. M. Nagatani, Detection of long-term trends in global stratospheric temperature from NMC analyses derived from NOAA satellite data, Adv. Space Res., 6(10), 17–26, doi:10.1016/0273-1177(86)90453-9, 1986.
Nagatani, R. M., A. J. Miller, M. E. Gelman, and P. A. Newman, A comparison of Arctic lower stratospheric winter temperatures for 1988–1989 with temperatures since 1964, NOAA Tech. Rep. NWS 40, 125 pp., Natl. Weather Serv., Washington, D.C., 1988.
Nagatani, R. M., A. J. Miller, K. W. Johnson, and M. E. Gelman, An eight-year climatology of meteorological and SBUV ozone data, NOAA Tech. Rep. 17, 333 pp., Natl. Oceanic and Atmos. Admin., Silver Spring, Md., 1990.
Newman, P. A., D. J. Lamich, M. Gelman, M. R. Schoeberl, W. Baker and A. J. Krueger, Meteorological Atlas of the Southern Hemisphere Lower Stratosphere for August and September 1987, NASA Tech. Memo 4049, 131 pp., Natl. Aeronautics and Space Admin., Washington, D.C., 1988.
Newman, P. A., L. R. Lait, M. R. Schoeberl, R. M. Nagatani and A. J. Krueger, Meteorological atlas of the Northern Hemisphere lower stratosphere for January and February 1989 during the Airborne Arctic Stratospheric Expedition, NASA Tech. Memo, 4145, 185 pp., Natl. Aeronautics and Space Admin., Washington, D.C., 1989.
Randel, W. J., The evaluation of winds from geopotential height data in the stratosphere, J. Atmos Sci., 44(20), 3097–3120, doi:10.1175/1520-0469(1987)044<3097:TEOWFG>2.0.CO;2, 1987.
Rood, R. B., P. A. Newman, L. R. Lait, D. J. Lamich, and K. R. Chan, Stratospheric Temperatures during AASE: Results from STRATAN, Geophys. Res. Lett, 17(4), 337–340, doi:10.1029/GL017i004p00337, 1990.
Trenberth, K. E., and J. G. Olson, Evaluation of NMC global analyses: 1979–1987, Tech. Note NCAR/TN-299+STR, 82pp., Natl. Cent. for Atmos. Res., Boulder, Colo., 1988.
Wu, M. F., M. A. Geller, E. R. Nash, and M. E. Gelman, Global atmospheric Ccirculation statistics—Four year averages, NASA Tech. Memo 100690, 70 pp., Natl. Aeronautics and Space Admin., Washington, D.C., 1987.
Yanai, M., An experimental objective analysis in the tropics, Tech. Paper 62, 21 pp., Dept. of Atmos. Sci., Colo. State Univ., Fort Collins, Colo., 1964
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