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Riders on the storms: ASU-led monsoon research could advance weather forecasting


August 01, 2006

Ten weather stations strategically placed around the Santa Catalina Mountains near Tucson are continuously taking measurements of surface weather conditions. In addition, five digital cameras are unflinchingly recording clouds as they form, collapse and reform each day.

When conditions are right for spawning storms, a flight crew scrambles to its heavily equipped King Air airplane to head to where the action is, and two teams of researchers prepare sounding balloons for launching into the atmosphere.

These are the machinations of a team of researchers who are studying the monsoonal flows over southern Arizona in the greatest detail ever. The team of about 20 researchers, led by ASU meteorologists, began their full operations July 18.

The team members are armed with an armada of instruments seeking details on the genesis of monsoon thunderstorms.

Joe Zehnder, a meteorologist and a professor in ASU's School of Geographical Sciences and the Global Institute of Sustainability, is the leader of the group. Zehnder's goal is to learn as much as he possibly can about cloud formation above the Santa Catalina Mountains long before they grow large enough to spawn a thunderstorm. He says this work will lead to more precise predictions of storms and storm paths.

“We are using the Catalinas as a natural cloud laboratory,” Zehnder says. “Cloud formation over the mountain peaks is quite regular, and we are exploiting that regularity to look at very early stages of cloud development.”

The CuPIDO (Cumulus, Photogrammetric In-Situ and Doppler Observations) project will probe, test and measure a myriad of the variables – visible and invisible – that primes the engine that drives thunderstorms. It is the most exhaustive project of its type, and it focuses on the very first stages of thunderstorm development.

“We are sampling the environment before clouds form, and monitoring their growth and the way they modify their environment,” Zehnder says. “The data we collect will increase our understanding of the onset and development of summer monsoon storms in Arizona . This information will help weather forecasters improve short-term forecast models as well as longer-range climate models.”

A key component is the five digital cameras that are stationed at various points around the Catalinas. These cameras will record cloud formation and thunderstorm development through the end of this month.

“What we have is a way of looking at the clouds in great detail over long periods of time, and in a large number of cases,” Zehnder says. “We are using the airplane, weather stations and balloon data to help fill in the gaps.”

The 10 surface weather stations are located at the base of the Santa Catalina Mountains. Four of the stations are equipped with additional sensors to monitor surface heat and moisture transport, as well as meteorological conditions. Surface stations located around the base of the mountains measure the upslope transport of warm and moist air, and the University of Arizona 's 30-meter tower located at the top of Mount Bigelow monitors conditions at the top of the mountains.

Changes to moisture and temperature above the mountains will be monitored via two mobile, balloon-based sounding systems. These systems will use instrument packages that measure temperature and moisture content and are tracked via global positioning systems.

Boxing the clouds

On mornings when the conditions look right for thunderstorm development, four team members board the King Air (owned and operated by the University of Wyoming) looking for cloud development. At the appropriate area, the pilot will fly a “boxing” maneuver, squaring off an area of clouds as the team constantly monitors the conditions present in and around them. They even fly through cloud areas to obtain “in-situ” measurements.

“There is a jolt when we penetrate into the clouds,” says Larry Oolman, a senior research scientist in the department of atmospheric sciences at the University of Wyoming .

Oolman, who has been flying in and through storms for 15 years now, helps tend to the instruments on board.

Instruments aboard the airplane provide details on the conditions above the mountains, as well as internal structure of the clouds. They use a 95 GHz (W-band) Wyoming Cloud Radar, which is capable of 30-meter resolution to reveal details of circulations within the surrounding clouds. The King Air also includes laser optical probes extruding from its wingtips, as well as very short (3 mm) wavelength radar.

“The limiting factor to the instruments on board, are space, weight and power,” Oolman says. “If we could fit more on there, we would.”

The plane is packed with instruments, leaving barely enough room for a pilot, two scientists and a graduate student. Oolman says the airplane can fly in the clouds for up to four hours, capturing huge amounts of data on the conditions that spawn and nurture storm development.

As the leader of the project, Zehnder manages the various pieces of the project from a control room on the University of Arizona 's campus in Tucson . He watches what is recorded remotely from the digital cameras and sees the flow of collected data as it streams into the database. All of the members of the team are linked through Internet connections and satellite communications.

Making sense of data

Working with Zehnder is Anshuman Razdan, director of the Imaging and 3D Data Exploitation and Analysis Lab (I3DEA), which is devoted to three-dimensional data and computer imaging.

 

Razdan also is an associate professor in the Division of Computing Studies at ASU's Polytechnic campus, and it is his job to make sense of the vast amounts of data streaming in to Zehnder's computers, especially the visual data from the five digital cameras.

“We take images from multiple angles over very large distances and try to combine them into a single three-dimensional image,” Razdan says. “Clouds are dynamic, constantly changing and somewhat amorphous in terms of hard features. It is incredibly challenging, given all of the variables involved. We'll feed all of this data into an algorithm, which computes cloud depth information (vertical and horizontal is provided by the images) and results mathematically. From that, we build up a 3-D model and give it to Joe to determine when clouds well up, how much volume, etc.”

Models are the key to this research, Zehnder says.

“If you are going to do storm forecasts, you have to get the location correct and the timing correct,” he explains. “You have to get the details correct. Right now, models use assumptions about the rate clouds use energy, and we have less understanding of how the clouds initially work. We have the chance to study that initial stage of cloud development in great detail.”

Data collection for the CuPIDO project will run through the end this month, though the intensive operational period with the use of the King Air and the sounding balloons lasts through Aug. 17.

The team includes researchers from ASU, the University of Wyoming, the U.S. National Center for Atmospheric Research, the University of Arizona, the University of Miami and the University of Alabama-Huntsville. It is a $1.3 million project funded through the U.S. National Science Foundation.