CAMS-OPI Precipitation

CAMS_OPI anomaly precipitation

NOTICE April 10, 1998

A problem has been discovered with the OPI estimates (the satellite component of the "CAMS_OPI" raingauge/satellite merged data set) in the tropical East Pacific during strong ENSO episodes. This problem affects primarily the precipitation accumulations (not the anomalies).

We have noticed that the depiction of the ITCZ in the far eastern Pacific is shifted northward relative to mean OLR during the December 1997 through February 1998 period. NOTE THAT THE ANOAMLIES ARE IN GOOD AGREEMENT between CAMS_OPI and OLR in this region

The problem with the accumulated totals stems from the fact that the satellite algorithm ("OPI") computes anomalous precipitation (from anomalies of OLR) and adds the anomaly to climatology to form the monthly estimated precipitation accumulation. It appears the problem is associated with the large changes in precipitation distribution in the tropical far-eastern Pacific that are associated with strong ENSO events (such as 1982/83, 1997/98).

We are still investigating the problem and plan to create a modified OPI algorithm (and re-processed "CAMS_OPI" data).

Contact John Janowiak regarding problems or further info. at:

NOAA/NWS/NMC/Climate Prediction Center
Analysis Branch
5200 Auth Rd Room 605
Camp Springs, MD 20746 USA
Phone:301-763-8000 Ext. 7537