JISAO data
NOAA NCEP Climate Prediction Center Merged Analysis of Precipitation (CMAP)
Monthly-means for 1979 - September 2004

Introduction | Data
These datasets are prepared by Pingping Xie of NOAA NCEP.
"Please be advised that the CMAP data set may contain an artificial downward trend for period after 1996. Care must be taken when using the data set for accurate quantitative applications." Pingping Xie

There are two merged precipitation data sets:
1) Rain gauge, 5 satellite estimates( GPI, OPI, SSM/I scattering, SSM/I emission and MSU), and numerical model predictions.
2) Rain gauge, 5 satellite estimates( GPI, OPI, SSM/I scattering, SSM/I emission and MSU)
where OPI stands for OLR-based precipitation index (Janowiak and Xie, 1999).

Important information on how this data set was constructed is provided on the NCEP CPC CMAP WWW page.

A comparison of the CMAP and Global Precipitation Climatology Project (GPCP) merged precipitation datasets is given by:
Yin, X., A. Gruber, and P. Arkinc, 2004: Comparison of the GPCP and CMAP Merged Gauge-Satellite Monthly Precipitation Products for the Period 1979-2001. J. Hydromet., 5, 1207-1222.
Annual total (cm) and standard deviation (cm/mon) of monthly precipitation, 1979-95
Image indicates largest rainfall amounts over the oceans, with the deep convective regions of the western Pacific emphasized over the eastern Pacific (c.f. MSU). Wetter places are more variable.
The largest annual totals (standard deviation) are > 4m (>12.5 cm/mon). This analysis is calculated for estimate 2 above: derived from rain gauge, MSU, GPI, and 2 SSM/I products.
global domain
PostScript | JPEG
Difference in annual total precipitation in the estimates with model input and without model input. The model input has the largest effects in the high latitude oceans, for which the estimates that include the model estimates are more than 20cm wetter.
JFMAM-average 1983 and 1998 precipitation (>8 cm/mon)
Image for South America. Image for South America.
Both years are characterized by precipitation in excess of 24 cm/month in the Pacific and Atlantic Oceanic ITCZs, along the Ecuador and northern Peru coast, where the Amazon flows into the Atlantic, portions of the Amazon basin, and Paraguay-southern Brazil-northern Uruguay.
The data:

"Please be advised that the CMAP data set may contain an artificial downward trend for period after 1996. Care must be taken when using the data set for accurate quantitative applications." Pingping Xie

  • In netCDF format:
    At JISAO, these files may be found at /home/disk/muggy/data/merged_precip/cmap
    rain rate (mm/day) (with model input) (6.5 Mbytes).
    rain amount (cm/mon) (with model input) (6.5 Mbytes).
    rain rate (mm/day) (no model input) (6.5 Mbytes).
    rain amount (cm/mon) (no model input) (6.5 Mbytes).
  • The data and documentation are available in ASCII from the NCEP CPC CMAP WWW page.

    References:
    Xie, P., and P. A. Arkin, 1997: Global Precipitation: A 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78, 2539-2558.
    Janowiak, J. E. and P. Xie, 1999: CAMS-OPI: A global satellite-rain gauge merged product for real-time precipitation monitoring applications, J. Climate, 12, 3335-3342.

    Questions concerning the method used to merge the preciptation estimates should be directed to Pingping Xie ( Pingping.Xie@noaa.gov ).

    April 2005
    Todd Mitchell ( mitchell@atmos.washington.edu )
    JISAO data