Time Variations of Precipitation in Reanalyses

Content of this page:

• Climatology of Monthly Zonal Mean -versus- GPCP
• Time Series of Global Average -versus- GPCP
• Correlation of Monthly Mean -versus- CMAP

Precipitation Variations:

Climatology of Monthly Zonal Mean -versus- GPCP

The placeholder image overlaps 12 curves showing the GPCP climatology of the Zonal Mean Precipitation for each month of the year. The zonal mean profile is a plot of the meridional mean precipitation rate (mm/day) versus latitude. Each curve is an average over the 26 years from 1979 through 2004. Click on the browser refresh button to view this again.

The 12 buttons on the right side lead to climatology comparisons of the Monthly Zonal Mean Precipitation averaged over the 22 years from 1979 through 2000. The five data sets compared are GEOS4-CERES (purple), NCEP-R2 (JRA-25orange), and GPCP (magenta).

(Point the cursor to any month to switch the view to its zonal mean plot.) plot of zonal global precipitation

JAN

FEB

MAR

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

Precipitation Variations:

Time Series of Global Average -versus- GPCP

The Global Precipitation Climatology Project (GPCP) is a data set produced by the international GEWEX program which contains monthly averaged precipitation rates (mm/day) for the time period Jan 1979 through the present. The GPCP data set combines satellite and gauge measurements of precipitation. The GPCP Version 2 documentation explains that the data are merged at the NASA GSFC Laboratory of Atmospheres and includes rain gauges, GPI, OPI, SSM/I scattering, SSM/I emission, and TOVS.

These images are time series of the monthly mean precipitation from 1979 to 2001. The top series covers the entire globe, whereas the second row compares means over land (left) versus ocean (right). The compared data sets are GEOS4-CERES (purple), NCEP-R2 (cyan), ERA-40 (green), JRA-25 (orange), and GPCP (blue). The time series also include a MEAN (magenta) of the four analysis systems.

Precipitation Variations:

Correlation of Monthly Mean -versus- CMAP

The CPC Merged Analysis of Precipitation (CMAP) is a data set produced by NOAA which contains monthly averaged precipitation rates (mm/day) for the time period Jan 1979 to Aug 2005. The standard data set incorporates 5 satellite measurements of precipitation: GPI, OPI, SSM/I scattering, SSM/I emission, and MSU. Note that the primary differences between CMAP and GPCP are that GPCP includes rain gauge measurements and treats TOVS data differently. The enhanced CMAP data set also includes NCEP reanalysis data.

These images are time series of the correlation between monthly means of precipitation against CMAP from 1979 to 2001. The top series covers the entire globe, whereas the second row compares means over land (left) versus ocean (right). The compared data sets are GEOS4-CERES (magenta), NCEP-R2 (cyan), ERA-40 (green), and JRA-25 (orange). Also plotted is the correlation between GPCP (purple) and CMAP, which not surprisingly is very high.