Laserfiche WebLink
<br />LOREP 1993 SUMMARY REPORT: <br /> <br />AIRBORNE MEASUREMENTS OF METEOROLOGICAL VARIABLES, ATMOSPHERIC <br />PARTICLES AND SULFUR HEXAFLUORIDE <br /> <br />Stan W. Wilkison and Dennis L. Wellman <br /> <br />ABSTRACT. Meteorological variables and sulfur hexafluoride (SF6) were measured <br />using the NOAA King Air research aircraft during February and March, 1993, over <br />the Sierra Nevada Range of northern California as part of the Lake Oroville Runoff <br />Enhancement Prototype Program (LOREP 1993). Race track pattern flights were <br />made from approximately Sierraville, CA, to Gansner, CA. Airborne sampling was <br />used to locate a plume containing sulfur hexafluoride as a tracer and propane as a <br />seeding agent. The aircraft also carried a optical imaging probe. Data from the probe <br />will be analyzed by the State of California and the U. S. Bureau of Reclamation to <br />assess the seeding efficiency of the propane. This report introduces the program in <br />general, discusses the objectives ofLOREP 1993, the instrumentation used and the <br />data obtained by the NOAA airborne operation. <br /> <br />1. INTRODUCTION <br /> <br />The Lake Oroville Runoff Enhancement Prototype Program (LOREP) is a five-year <br />experimental research program to determine whether seeding winter storm clouds with high elevation <br />release of liquid propane is a viable and economic method of increasing water supplies. For LOREP <br />1993, the State of California Department of Water Resources and the U. S. Bureau of Reclamation <br />(USBR) proposed a simultaneous release of sulfur hexafluoride (SF 6) and liquid propane into the <br />atmosphere at two sites northwest of Reno, NY, in the Sierra Nevada Mountains of California. The <br />National Oceanic and Atmospheric Administration (NOAA) King Air research aircraft was engaged <br />to aid in the collection of data to document the physical processes leading to enhanced precipitation. <br />Two primary instruments carried were a sulfur hexafluoride (SF 6) analyzer for plume detection and <br />an optical imaging probe to detect ice particles. The SF 6 analyzer was used to determine when the <br />aircraft was sampling within the plume of propane and SF 6' The probe data will be analyzed to show <br />the vertical and horizontal extent of the plume and confirm microphysical changes in the formation <br />of ice crystals due to the propane seeding. <br />The principles upon which the experimental objectives of this project are based are far more <br />comprehensive than could be included in this summary report. However, a very brief synopsis is <br />warranted. Winter storm clouds, typical of those found over the Sierra Nevada, are deficient in ice- <br />forming nuclei; or the nuclei present are unable to convert cloud condensate, produced by the <br />orographic lifting of the air over the mountain barrier, to crystals soon enough to remove all the cloud <br />water. A large portion of that supercooled cloud water then becomes part of precipitation processes <br />well downwind of the barrier. The introduction of an ice-nucleating agent, under proper conditions, <br />promotes the conversion of supercooled cloud condensate to ice before it passes the ridge. An agent <br />capable of transforming supercooled water droplets directly to ice crystals at temperatures between <br />o and -5 DC is liquid propane sprayed into the atmosphere as a fine mist. This type of release very <br />rapidly cools the air to temperatures well below ODC through the process of vaporization. The use <br />of liquid propane, when released as a fine spray for glaciogenic seeding, has been documented <br />