Description:
The precipitation anomalies shown are based on satellite precipitation estimates over ocean areas and rain guage data over land regions.  The units are milimeters (mm).  Contours are drawn at +/- 10, 25, 50,100,...,500 for the top plot and +/- 25, 50, 100,200,300,...1000 for the 3-month anomaly plot.  The period used for computing the climatology is 1979-2000 (the satellite precipitation estimates only go back to 1979). 

"CAMS" is an acronym for the "Climate Anomaly Monitoring System" in use at the Climate Prediction Center (CPC) at the US National Centers for Environmental Prediction (NCEP).  "OPI" stands for "Outgoing longwave radiation Precipitation Index" (the statellite precipitation estimates are based on emitted longwave radiation observed by polar-orbiting satellite.)