This directory contains data files for the CPC Blended OLR (CBO) 
Version 1 products. 

1) Brief decription of the CBO Version 1 products

CBO V1 global OLR data set is constructed at NOAA Climate Prediction 
Center (CPC) by blending level 2 OLR retrievals from NASA Cloud and 
Earth Radiant Energy (CERES) broadband measurements, NOAA/NESDIS
Hyperspectral measurements, as well as High-resolution Infrared Radaition 
Sounder (HIRS) measurements.  The NASA broadband OLR, covering a period 
from March 2000 to the present with a production latency of 3-4 months, 
serves as the primary inputs to the CBO to determine the magnitude of 
OLR at the satellite measurement times.  Level 2 OLR retrievals from the
NESDIS hyperspectral OLR, passed from NESDIS Operations to NCEP Central 
Operation (NCO) as a part the NOAA Unique Combined Atmospheric Processing 
System (NUCAPS) product package, are calibrated against the NASA broadband 
OLR and utilized to fill in the real-time gap of recent months. The HIRS OLR 
data of Dr. Hai-Tien Lee (UND/ESSIC) is also calibrated against the NASA 
broadband OLR and used to back extend the CBO for period before 2000. 

The calibration of the NESDIS hyperspectral and HIRS OLR are conducted through 
Probability Density Function (PDF) matching using respective overlapping data. 
The PDF matching ensures close quantitative agreements in not only the mean but
also the frequencies of OLR with various magnitudes (including the extremes).

Diurnal correction is performed in defining the daily mean OLR from the 
Level 2 retreivals of OLR at respective satellite measurement times. The diurnal
correction is performed using hourly (3-hourly) OLR derived from the CPC full-
resolution global geostationary TBB data (NCEI GridSat geostationary TBB) for 2000
-the present (1991-1999), respectively. 
 
For more technical details, please check into 'CPC_New_OLR_20230907.pdf'. 


2)  Product Components  

The CBO V1 data files are archived at the following directory on the CPC ftp server:
   ftp.cpc.ncep.noaa.gov/precip/CBO_V1 

The CBO products are generated on 4 sets of spatial grids: 
   0.25deg lat/lon, 1deg lat/lon, 2.5deg lat/lon, and 512x256 CORe Gaussian grid.

For each spatial grid, the CBO data sets are produced for the following 4 sets of
temporal resolutions, i.e., 
    daily (00Z-00Z), pentad, weekly(ending on Sundays), and monthly. 

A 1991-2020 30-year climatology is constructed for each of the 16-combinations of 
spatial-grids and temporal resolution. 

Time series of both the total and anomaly OLR are produced for a 32+ year period 
from 1 January, 1991 to the present.


3)   Data Files and Directory Structure 

***  One Sub-Directory for one Space-Time Resolution  *** 

The CBO data files for each of the 16 combinations of space-time resolutions are 
archived in a separate sub-directory. For example, data files for OLR data of 1deg 
and daily resolution may be found in the sub-directory named '1deg-DLY'. 


***  Sub-sub-directories for climatology, yearly data, and GrADS control files  *** 

Underneath each of the above mentioned space-time resolution sub-directories, there are   
deeper-layer sub-directories for climatology, yearly data, and control control files  
(data format describers) for both the climatology and data files. 

Climatology and data files for all temporal resolutions for the spatial grid are stored 
in the same sub-directories. 

Both the total OLR and anomalies are included in the data files. 


4) Real-Time Products Handling  

The FINAL version of the CBO Version 1 product is produced at a delay of 3-4 months 
when the NASA broadband OLR level 2 data files are available. Before that, the NESDIS 
hyperspectral OLR is used to define an interim version (called internally the near 
real-time NRT production).  Once a month or so, when the NASA broadband OLR is available, 
the final version will be updated and the NRT interim data record will be over written. 

Upon requests from CPC users, we have combined the final version and the NRT interim 
version into a single time series with the same file name convention. 

For applications utilizing the OLD data across the historical / NRT data boundaries 
(e.g. plotting longitude-time sections of tropical OLR anomalies), it is suggested that 
the processing systems will refresh the OLR data back at least for 6 months so that 
the newly updated final version OLR will be utilized.

The boundaries between the historical and NRT version in the current data files are marked 
at the bottom of the respective GrADS control files.


5) Points of Contact 

Pingping Xie              Pingping.Xie@noaa.gov
Shaorong Wu               Shaorong.Wu@noaa.gov
Yanjuan Guo               Yanjuan.Guo@noaa.gov