An Informed Guide to Climate Data Sets

Lucas and Waliser Satellite ECT-Corrected OLR Datasets
Variable(s) Outgoing Longwave Radiation
Land or Ocean Land and Ocean
Current Period of Record 6/1974-12/1999
Resolution Daily, Pentad, and Monthly, Global, 2.5o x 2.5o
Description: OLR dataset where the bias from varying satellite equatorial crossing times (ECT's) has been estimated and then removed.
Reference: Lucas, L. E., Waliser, D. E., Xie, P., Janowiak, J. E., Liebmann, B. 2001: Estimating the Satellite Equatorial Crossing Time Biases in the Daily, Global Outgoing Longwave Radiation Dataset. Journal of Climate: 14, pp. 2583-2605.
Data Set Location: NCAR's Data Suppport Section (DSS) (binary)
NCAR's Climate Analysis Section (CAS) (netCDF)

Technical Overview Expert User Guidance Relevant Articles Coverage Maps


Technical Overview

Taken from NCAR/DSS
This dataset contains daily,pentad and monthly OLR data in which the bias from varying satellite equatorial crossing times (ECT's) has been estimated and then removed. This was done by starting with the twice daily 2.5 degree NCEP/NOAA OLR archive for 1974 thru 1999. The ECT biases caused by afternoon satellite orbital drift AND the abrupt transition from a morning satellite to an afternoon satellite were estimated separately and then these estimates were removed. Please see the reference below under relevant articles for more details.

Taken from abstract of Lucas et. al. (Cited below in Relevant Articles)
Due to its long record length (approximately 25 years), the outgoing longwave radiation (OLR) dataset has been used in a multitude of climatological studies including studies on tropical circulation and convection, the El Niņo-Southern Oscillation (ENSO) phenomenon, and the earth's radiation budget. Although many of the climatological studies using OLR have proven invaluable, proper interpretation of the low-frequency components of the data could be limited by the presence of biases introduced by changes in the satellite equatorial crossing time (ECT). Since long-term global changes could be masked or contaminated by this instrumental bias, it is necessary to take steps to ensure that the daily, global OLR dataset is free from such biases and is as accurate as possible.

The goal of this study is to derive a method for estimating the ECT biases in the daily, global OLR dataset. Our analysis utilizes a Procrustes targeted empirical orthogonal function rotation (REOF) on an interpolated OLR dataset to try to isolate and remove the two major ECT biases-afternoon satellite orbital drift and the abrupt transitions from a morning satellite to an afternoon satellite-from the dataset. Two targeted REOF analyses are performed to separate and distinguish between these two artificial satellite bias modes. A "common ECT" of approximately 0245 LST is established for the dataset by removing an estimate of these two ECT biases.


Expert User Guidance

We are currently soliciting expert advice concerning this data set.


Relevant Arcticles

Lucas, L. E., Waliser, D. E., Xie, P., Janowiak, J. E., Liebmann, B. 2001: Estimating the Satellite Equatorial Crossing Time Biases in the Daily, Global Outgoing Longwave Radiation Dataset. Journal of Climate: 14, pp. 2583-2605.


Coverage Maps

Click on the links below to view data coverage maps for a particular time period. Percentage of non-missing data per time period is plotted. Data is missing from April-December 1978.

(1975-1999)

Updated: 10/28/03
Maintained by asphilli@ucar.edu