New, Improved Algorithm for Retrieving Liquid Water Path Now Available at the ARM Data Archive

The MWRRET product uses an improved retrieval technique and a method to identify and remove biases from the data to greatly improve the retrieved LWP (blue). It also performs so-called physical retrievals at each radiosonde launch time (black dots)—physical retrievals are the best possible retrieval that can be performed.

The total amount of liquid water in clouds overhead, called the liquid water path (LWP), is a critical variable in understanding the flow of radiant energy in the cloudy atmosphere. A new algorithm recently developed provides improved estimates of LWP from the ARM 2-channel microwave radiometers. The original microwave radiometer (MWR) retrieved LWP data often had large unphysical values in clear skies (before 06 UTC and after 09 UTC in the example to the right).

Developed by ARM scientists, the algorithm called the Microwave Radiometer Retrievals of Cloud Liquid Water and Precipitable Water Vapor or MWRRET, utilizes an advanced absorption model and improved retrieval techniques to greatly improve the accuracy of the derived LWP relative to the original ARM values. A total of 18 years of data, from six ARM Climate Research Facility sites, have been processed using this new algorithm.

These data (and more) are freely available in the ARM Data Archive. The first time you visit the Archive you will need to create a new account—a relatively short form asking for contact information—you can use right away. Order MWRRET data now.