CPC 5-day Merged Analysis of Precipitation (CMAP) Real-Time, version 0011

The CPC Merged Analysis of Precipitation (CMAP) is a technique which produces pentad and monthly analyses of global precipitation from observations from raingauges.

These data are comparable (but should not be confused with) similarly combined analyses by the Global Precipitation Climatology Project which are described in Huffman et al (1997).


The merging technique is thoroughly described in Xie and Arkin (1997). Briefly, the methodology is a two-step process. First, the random error is reduced by linearly combining the satellite estimates using the maximum likelihood method, in which case the linear combination coefficients are inversely proportional to the square of the local random error of the individual data sources. Over global land areas the random error is defined for each time period and grid location by comparing the data source with the raingauge analysis over the surrounding area. Over oceans, the random error is defined by comparing the data sources with the raingauge observations over the Pacific atolls. Bias is reduced when the data sources are blended in the second step using the blending technique of Reynolds (1988). Here the data output from step 1 is used to define the ""shape"" of the precipitation field and the rain gauge data are used to constrain the amplitude.

The pentad dataset consists of 73 pentads per year with the 12th pentad covering Feb 25-Mar 1 whether or not there is a leap year. The pentad starts on the date stored. The data set containing 5-day averaged precipitation rate values.

References:

Huffman, G. J. and co-authors, 1997: The Global Precipitation Climatology Project (GPCP) combined data set. Bull. Amer. Meteor. Soc., 78, 5-20.

Reynolds, R. W., 1988: A real-time global sea surface temperature analysis. J. Climate, 1, 75-86.

Spencer, R. W., 1993: Global oceanic precipitation from the MSU during 1979-91 and comparisons to other climatologies. J. Climate, 6, 1301-1326.

Xie P., and P. A. Arkin, 1996: Global precipitation: a 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteor. Soc., 78, 2539-2558.

Variables
Precipitation (mm/day)
Zonal Global by 2.5 deg
Meridional Global by 2.5 deg
Vertical surface  
Temporal Jun 5, 2000 to near present by 1 pentad
Static? no
Volume 80 MB / pentad
Server public:
Source https://www.cpc.ncep.noaa.gov/products/global_precip/html/wpage.cmap.html
Acquired Mar 18, 2019
APDRC contact
Supplements ftp://ftp.cpc.ncep.noaa.gov/precip/cmap/pentad_rt/