Equipment deployed to study the impact of burn scars, flash flooding

NSSL’s mobile radar in Colorado near the burn scar. (Photo provided.)

To find ways to better protect people from flash floods, researchers are spending this summer testing equipment and evaluating methods of observing rain and flash-flood prone areas of Colorado.

Researchers from NOAA’s National Severe Storms Laboratory and the University of Oklahoma Cooperative Institute for Mesoscale Meteorological Studies are utilizing a suite of tools, including NSSL’s mobile Doppler radar in an effort to gather new observations on rain. From June through September, researchers are gathering new observations in parts of Colorado that were affected by the 2018 Spring Creek wildfire, Colorado’s third-largest wildfire which burned 108,045 acres of land.

“Federal and state partners have teamed up to provide, for the first time, a very dense observational network on the Spring Creek burn scar in Colorado,” said Jonathan Gourley, an NSSL Researcher. “In addition to the deployment of NSSL’s mobile radar, the experimental network is comprised of rain gauges, stream radars, surface velocity measurements, and soil moisture sensors, all positioned within the burn scar.”

The scientists chose these locations because areas that are burned by wildfires are more susceptible to flash flooding and debris flows, as burned soil tends to repel, rather than absorb, water. Researchers want to demonstrate the value of observations gathered by this equipment  to develop early alerts of flash flooding and debris flows on burn scars.

From June through September, researchers are gathering new observations in parts of Colorado that were affected by the 2018 Spring Creek wildfire, Colorado’s third-largest wildfire which burned 108,045 acres of land. (Photo provided)

“Burn scars are prolific at producing flash floods,” Gourley said. “The loss of vegetation and changes to the soil structure enhances the amount and velocity of runoff for a given rainfall event. Despite their devastating impacts, we have limited knowledge about the transition of rainfall-to-runoff and the tools used to forecast flash flooding on burn scars.”

The mobile radar is deployed less than 20 miles from the burn area. Researchers are using the mobile radar to monitor the lower atmosphere and supplement current NEXRAD radar coverage. The terrain in mountainous areas, like Colorado, causes difficulties for NEXRAD radars. The radar beam cannot “see” storms as it can in flatter areas, like the plains. NSSL’s mobile radar supplements NEXRAD coverage by providing more information near the ground and providing higher-resolution data for forecasters during intense rainfall events near the burn scar.

“These observations will transform our understanding and forecasting tools, which are becoming increasingly important given the expanding areas, durations, and intensities with wildfires,” Gourley said.

So far, the observations have been promising. In July, a major storm  near La Veta brought more than 1.5 inches of rain per hour and local officials provided eight reports of flash flooding. One creek overflowed by two feet and was more than 100-yards wide. Researchers collaborated with National Weather Service forecasters to provide more products and information for increased warning time.

Researchers are also testing a product that computes rainfall accumulations at 15, 30 and 60-minute time periods and compares those accumulations to United States Geological Survey-derived debris flow thresholds for the same time period. It is one of many products developed and utilized by researchers to study flooding and debris flow in areas ravaged by wildfires. 

Known as the “Wildfire Rain” product, this algorithm utilizes short-term rainfall estimation techniques to provide forecasts of how fast rain may fall and whether it is anticipated to cause flash flooding and debris flows on the burn scars. This experimental tool is used by three local NWS Colorado forecast offices and allows a longer lead time for flash flooding events.

In addition to the Wildfire Rain product, this summer researchers deployed a network of rain gauges, soil moisture sensors and stream radars in Colorado. The stream radars use remote sensing to measure the speed, depth, and flow rates in streams. These products provide on-the-ground validation of flooding at points of interest like bridges and roadways.

Monitoring efforts will continue through 2020 as researchers continue to develop ways to monitor and warn for flash flooding and debris flow.

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NSSL uses weather radar clutter to help biologists

Dual-polarized weather radar can estimate the number of bats in a swarm similar to the way it can estimate the number of raindrops in a cloud.  This information is valuable to biologists, ecologists and entomologists as they try to understand how populations and behaviors of bats and insects are affected by changes in climate over time.

Several mobile radars, including NSSL’s dual-polarized mobile radar were used in a project to track swarms of millions of bats as they emerged from their caves each night to feast on insects. The radar images of bats appear as distinct “blooms.”

Usually data from birds, insects or bats are considered “clutter” and are filtered out.  NSSL researchers have reversed the filter to now focus on the bioscatter.  Using calculations of radar backscatter from a single bat in the laboratory, made by the University of Oklahoma, the group is developing the first means to calculate aerial densities of bats as they travel.

NSSL will use the data to enhance algorithms that remove the bioscatter clutter to see the weather more clearly.

“What we see in the dual-polarized fields provided by NSSL’s radar, and soon with WSR-88D dual-polarization, will bring a whole new era in behavioral ecology and conservation as well as radar quality control,” says NSSL’s Ken Howard.

The National Science Foundation sponsored project includes researchers from several Universities, the National Park Service and the USGS.

“The summer night sky is filled with a spectrum of biological life that is in many ways equivalent to what we observe in coral reefs,” says Howard.  The data we collected has brought a new appreciation of the rich diversity of life and that can be seen using radars, and especially dual-polarized radars.”

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Mobile radar to assist weather nowcasting for 2010 Olympic Games

NSSL's Bob Staples (left) and Doug Forsyth (right) with an Environment Canada colleague in front of the NO-XP at Birch Lake, Washington.
NSSL's Bob Staples (left) and Doug Forsyth (right) with an Environment Canada colleague in front of the NO-XP at Birch Lake, Washington.

NSSL has sent a team of researchers and the dual-polarized X-Band mobile Doppler radar to the 2010 Olympic (February 12-28, 2010) and Paralympic (March 12-21, 2010) Winter Games in Vancouver, British Columbia.  They will participate in Science and NOWcasting of Olympic Weather for Vancouver 2010 (SNOW-V10), a unique opportunity for international collaboration on the science of winter nowcasting in complex terrain.

NSSL’s NOAA-OU X-band dual-Pol Doppler radar (NO-XP) crew departed December 26 for their destination of Blaine, Washington, near the Canadian border.  The data collected by the radar will support 0-6 hour forecasts, or nowcasts, of precipitation type and amount in support of the Cypress Mountain venue where freestyle skiing, snowboard, and snowboard halfpipe competitions will take place.

You can view the NO-XP radar data here:  http://wdssii.nssl.noaa.gov/web/wdss2/products/radar/SNOW-V10.shtml

Researchers also plan to study the collected dual-polarized radar data to better understand the winter precipitation environment, including the complicated rain/snow mix scenario.  The NO-XP radar will operate from December 30-March 22, 2010, with teams rotating out every two weeks.

The X-band radar operates on a shorter, more sensitive wavelength to detect smaller particles, and the dual polarization capability provides additional details on the microphysics of storms.  This radar can be used to detect tiny water droplets as clouds form, and can see light precipitation such as snow.  NO-XP is used for very short-range weather observation, and was first deployed to Texas to scan Hurricane Ike as it made landfall in September 2008.

SNOW-V10 is a World Weather Research Project of the World Meteorological Organization.  Other organizations involved include:  Environment Canada, University of Basel, Switzerland, the Finnish Meteorological Institute, National Center for Atmospheric Research, University of Bonn, Germany.

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Mobile radar heads to California for debris flow experiment

SR-2 El ToroDecember 1, NSSL’s mobile radar team will begin to collect data with the Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) in southern California to help monitor rainstorms that may trigger dangerous debris flows.

Debris flows are rivers of rock and earth triggered by rainfall, that can destroy culverts, bridges, roadways, and structures and can cause injury or death.

Areas damaged by wildfires are particularly susceptible to flash floods and debris flows during rainstorms.  Rainfall that is normally absorbed by vegetation can run off almost instantly, causing creeks and drainage areas to flood much sooner during a storm, and with more water, than normal.

The National Oceanic and Atmospheric Administration (NOAA), NOAA National Weather Service (NWS), and the United States Geological Survey (USGS) have established a demonstration flash flood and debris-flow early warning system for recently burned areas in southern California.  The experiment focuses on helping forecasters improve flash flood and debris flow warnings by providing more detailed measurements of rainfall.

NSSL will supply real-time close-up radar data during rain events with the Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) to supplement local NWS radar in areas where the radar beam is blocked by the terrain. The SMART-R will be based at Burbank-Bob Hope Airport starting 1 December 2009-28 February 2010.

The USGS has identified the Station Fire burn area as the location for the 2009-2010 experiment.  The Station Fire burned over 160,000 acres of the Angeles National Forest, making it the largest fire in L.A. County history. “Some of the areas burned by the Station Fire show the highest likelihood for big debris flows that I’ve ever seen,” said Susan Cannon, USGS Research Geologist.

Landslides in the U.S. result in an estimated 25-50 deaths and damages between $1B and $3B annually.   This is the fifth year the SMART-R has been operated in the Debris Flow Warning System experiment.  Evaluations of the experiment indicate that small, portable radars can augment observations from the fixed—site operational radar network with highly accurate, finer-scale estimates of precipitation.

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NSSL’s mobile radar collects data on summer storms in the Colorado mountains

Mobile radars can be useful by providing additional precipitation information in areas where local radar beams are blocked by the terrain.
Mobile radars can be useful by providing additional precipitation information in areas where local radar beams are blocked by the terrain.

A team of NSSL scientists operated NOAA NSSL’s mobile X-band dual-polarized radar (NO-XP) in Colorado through September 20 to collect data and analyze storm characteristics in the Gunnison river basin.  The National Weather Service radar servicing the Gunnison area is located in Grand Junction, CO at 9991 feet, with 12,000 foot mountain peaks causing beam blockage at lower elevations to the southeast around the Gunnison area.  The high-resolution data sets will be used to explore ways to enhance capabilities at the Grand Junction National Weather Service Forecast Office.

The dual-polarization capabilities of the radar examined the microphysical characteristics of high-elevation thunderstorms.  Data will provide insight into the variations of storm characteristics for different terrain profiles.

Along with the radar, NCAR, USGS and the University of Colorado donated ten tipping bucket rain gauges to be deployed along the eastern side of the West Elk Mountains to help calibrate the radar data.  The tipping bucket gauge measurements will be complemented by existing Remote Automated Weather Station observations and 24h rain totals from the Community Collaborative Rain, Hail and Snow network (CoCoRaHS) gauges.

The project was sponsored by the Colorado Water Conservation Board.

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Mobile radar returns from California debris flow experiment

Last week’s NWS Flood Safety Awareness Week brought attention to the NOAA/NWS/USGS prototype Debris Flow Warning System experiment held for the past four years in California.  The project is focused on helping forecasters improve flash flood and debris flow warnings in areas damaged by wild fires by providing more detailed measurements of rainfall.

NSSL’s SMART-R team has deployed the radar near the target burn area each winter to supply real-time close-up radar data during rain events. The radar operated seven days and at the Santa Barbara airport to scan the Gap and Tea Fire burn areas.  The local NWS network radar beam is blocked by terrain in these areas causing a void in the data

Even though it was another low precipitation winter for coastal Southern California, the NOAA NWS in Los Angeles/Oxnard, California reported the SMART-R provided valuable information.  “In one case the SMART-R helped us question the one-hour rainfall estimate data seen on another local radar,” said Eric Boldt, Warning Coordination Meteorologist NWS Los Angeles/Oxnard.

The SMART-Radar and team returned to NSSL at the end of February.

Background:

Landslides in the U.S. result in an estimated 25-50 deaths and damages between $1B and $3B annually. Areas damaged by wildfires are particularly susceptible to flash floods and debris flow during rainstorms. Debris flows are linked with precipitation therefore are more predictable than most other types of landslides.  The weather conditions that trigger them can be the same as those monitored for flash flood warnings.

An article was published in Bulletin of the American Meteorological Society in December 2008 on the evaluation of the prototype debris-flow warning system in southern California.  The report indicated that small, portable radars can augment observations from the fixed—site operational radar network with highly accurate, finer-scale estimates of precipitation.

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