TOTAL

There are several limitations with accurately measuring the amount of liquid precipitation that occurs during an event. The liquid-equivalent and total liquid accumulation of solid winter precipitation is typically conducted through radar estimates and gauge observations; however, there are challenges with these data sets, especially with gauge observations that are used as ground truth and eventual bias corrections. Most gauge sites are prone to partial or complete blockage of the orifice, wind undercatch, and post-event thaw. Snow depth or weight could be used in obtaining liquid-equivalent values but can also be influenced by blowing snow, evaporation, and compaction. There are also limitations with acquiring accumulations of rain that are free of potential error. Wind undercatch is also an inherent issue with rainfall and becomes more amplified with smaller drop-size distributions (DSDs). Extreme rainfall rates could also result in measurement challenges (e.g., splash-out and tipping errors).

A new project between the University of Oklahoma (OU)-Cooperative Institute for Severe and High-Impact Weather Research and Operations (CIWRO) and the National Oceanic Atmospheric Administration (NOAA) National Severe Storms Laboratory (NSSL) has been developing an instrumentation platform to improve precipitation measurement accuracy across various precipitation events and types. The Telemetry of Observed Total Accumulated Liquid (TOTAL) project is designed to answer the following scientific questions over the next several years:

1. What is the true liquid value of solid winter precipitation as it reaches the surface?
2. What is the influence of wind undercatch with both liquid and solid precipitation, especially for greater wind magnitudes?
3. How can we better capture extreme rainfall rates with surface instruments?
4. How can these findings better improve remote-sensing platforms (e.g., dual-polarization radar-derived precipitation estimations)?

Studies will be conducted through a mobile instrumentation platform that allow for precipitation and atmospheric-observing equipment to be deployed in areas forecasted for precipitation. Instrumentation available for use on the platform in 2023 includes the following: heated tipping-bucket gauge, heated weighing gauge, CoCoRaHS gauge, Parsival laser optical disdrometer, 24-GHz Doppler radar precipitation sensor, hotplate precipitation gauge, mobile mesonet rack (ambient temperature, wind, pressure, etc.), infrasonic detector, electric field mill, and all-sky 360-degree camera. A series of instrumentation layouts were drafted to determine which instruments to use and their configuration on the mobile instrumentation platform based on precipitation type and research objective(s) for the event.

Initial tests of the TOTAL project mobile instrumentation platform in 2023 includes test deployments and initial data collections, including use of the ARM Southern Great Plains (SGP) atmospheric observatory and field measurement site. Data collection within the ARM facility would be conducted within proximity to other observing platforms and within adequate range of a weather radar for data comparisons. Future goals of the TOTAL project over the next several years will include the procurement and development of new, experimental instrumentation that will assist in addressing the scientific questions posed by this study. Furthermore, TOTAL field campaigns can be targeted to address specific events and precipitation types across the country to help improve the accuracy of liquid accumulation values and, in turn, improve remote-sensing platforms and reduce uncertainty in studies related to hydrologic modeling, climatology, and water resource management.

Timeline