Climate Data

Liquid Water Path (LWP): UWisc climatology

"This work describes a new climatology of cloud liquid water path (LWP), termed the University of Wisconsin (UWisc) climatology, derived from 18 yr of satellite-based passive microwave observations over the global oceans. The climatology is based on a modern retrieval methodology applied consistently to the Special Sensor Microwave Imager (SSM/I), the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), and the Advanced Microwave Scanning Radiometer (AMSR) for Earth Observing System (EOS) (AMSR-E) microwave sensors on eight different satellite platforms, beginning in 1988 and continuing through 2005. It goes beyond previously published climatologies by explicitly solving for the diurnal cycle of cloud liquid water by providing statistical error estimates, and includes a detailed discussion of possible systematic errors." (O'Dell et al, 2008)

Key Strengths:

  • Explicitly solves for the diurnal cycle of cloud liquid water Solutions work well with boundary layer clouds.
  • Includes Error estimates.

Key Limitations:

  • Solutions do not work as well for deep convection.
  • Method is sensitivity to cloud+rain liquid water

Expert Developer Guidance

From the README: The diurnal cycle is assumed to a be function of month and location on the global only. For example, we assume that, for a given location, the diurnal cycle is the same in every January, but the diurnal cycle for January may be different from that of February for the same location. For each 1x1 degree grid box, the diurnal cycle has been fit to the following form: LWP(t) = M + A1 cos(t-T1) + A2 cos 2(t-T2) leading to a total of five fit parameters in all. For some pixels with not very much data, the cos 2(t-T2) term was left out, so a single sinuosoid was used in the fit. For pixels and months in complete darkness, it is assumed that there is no diurnal cycle, so only the "M" parameter was determined. (O,Dell, U. Wisc)

Technical Notes

This data set is used in the diagnostics package of the Community Atmospheric Model, a component model of the CESM.

Years of Record

1998/01 to 2008/12
temporal metadataID:



Climatology | Monthly

Data Time Period Extended?

no, data set not being extended


Spatial Resolution


Ocean or Land

Ocean Only

Missing Data Flag

missing data present

Earth system components and main variables

Data Access: Please Cite data sources, following the data providers' instructions.

Key Figures

Click the thumbnails to view larger sizes



Total cloud liquid water path (July 1998) and estimated 1-sigma error. (Climate Data Guide; D. Shea)
Top: LWP at ~186E longitude. Bottom: LWP from 120E-360E at 5.5N latitude. (Climate Data Guide; D. Shea)

Cite this page

National Center for Atmospheric Research Staff (Eds). Last modified 08 Oct 2013. "The Climate Data Guide: Liquid Water Path (LWP): UWisc climatology." Retrieved from

Acknowledgement of any material taken from this page is appreciated. On behalf of experts who have contributed data, advice, and/or figures, please cite their work as well.