Monsoon Genesis

Monsoon season means storms in Arizona. Big storms. Lots of lightning. Walls of dust. Sometimes it even rains. Joseph Zehnder says that the 2006 monsoon season will be studied more extensively than any other monsoon season in Arizona, ever.

Zehnder is a meteorologist and professor of geography at Arizona State University. Beginning in July, Zehnder and a team of 20 researchers will study the formation of monsoon storms in the Santa Catalina Mountains near Tucson, Ariz. Their goal is to identify the genesis of monsoon thunderstorms.

The scientists will use an armada of instrumentation on the ground and in the air. They will use digital cameras, sounding balloons, and a specially equipped airplane to gather as much data as possible.

The plan is to use that data to build accurate representations of the very beginnings of the monsoon storms. These storms often develop into chaotic and hard to predict wind, dust, and rain storms throughout southern Arizona. To date, researchers have yet to pinpoint the crucial first stages of monsoon storm formation, Zehnder says.

“The very first stages of thunderstorm development are seen as critical to their formation, long before they become chaotic and violent storms. But very little is known about these early stages of cloud and storm development,” Zehnder explains. “It is impossible to study this early stage without knowing where the storms will develop.”

Since the clouds form very reliably over the mountain peaks, the Santa Catalina range provides the researchers a natural cloud laboratory.

“We will be able to sample the environment before the clouds form and monitor their growth and the way they modify their environment,” Zehnder says. “The sampling from prior to the cloud formation until the development of a thunderstorm hasn’t been done before.”

“The data we collect will increase our understanding of the onset and development of summer monsoon storms in Arizona,” Zehnder adds. “We expect that this information will help weather forecasters improve their short-term forecast models as well as longer range climate models.”

The Cumulus, Photogrammetric In-Situ and Doppler Observations project will consist of coordinated observations using pairs of stereo cameras, a network of surface weather stations, GPS-based vertical sounding systems. and the specially instrumented aircraft. The Summer 2006 field studies are the culmination of a three-year study. The researchers already have developed stereo analysis techniques for analyzing the cloud formation. They’ve also refined the photogrammetric techniques. Preliminary work has given the researchers an idea of how to place cameras for optimal imagery.

“We are trying to unravel and understand natural phenomena, which ultimately we want to mathematically model,” Anshuman Razdan says. Razdan is director of the Imaging and 3D Data Exploitation and Analysis Lab (I3DEA) and associate professor in the Division of Computing Studies at ASU’s Polytechnic campus. Razdan also is a researcher at ASU’s Partnership for Research in Spatial Modeling (PRISM). PRISM researchers will be doing much of the data collection and image processing for the project.

“The better understanding we can glean from the images and 3D reconstruction, the better information we can provide Joe Zehnder in his modeling effort,” Razdan adds.

Summer thunderstorms over the mountains in the desert southwest build slowly and in stages in spite of unstable conditions. The “sky islands” serve as a natural laboratory for the study of cumulus clouds. The clouds develop in a fixed location under the influence of heating and moisture transport.

“The interaction between the clouds and the environment (wind and temperature profiles) is important in reality. It is not captured well in the models,” Zehnder says.

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

A network of 10 surface weather stations will be located at the base of the Santa Catalina Mountains. Four of the stations will be equipped with additional sensors to monitor surface heat and moisture transport in addition to meteorological conditions, Zehnder says.

Surface stations located around the base of the mountains will measure the upslope transport of warm and moist air. Conditions at the top of the mountains will be monitored by a 30-meter tower located at the top of Mount Bigelow. There will be five digital cameras located at various points around the mountains as well to record storm formation and transport.

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. Everything is tracked with global positioning systems.

University of Wyoming scientists will study details on the conditions above the mountains, as well as internal structure of the clouds, with their specially equipped King Air airplane. The plane is outfitted with a 95 GHz (W-band) Wyoming Cloud Radar. The radar will reveal details of circulations within the surrounding clouds.

The team plans to create several time-lapse movies of monsoon storm formation. Computer-aided animations and scientific data transposed over the digital images will show cloud structure and dynamics. The researchers will have multiple sources of the same data. They hope to generate 3-D images and plots of the monsoon as it first fires up through completion of violent storm surges. Zehnder says that one goal is to improve short-term predictions of weather during monsoon storms. The scientists want to help weather forecasters feel less at the mercy of what can be a chaotic, hit or miss monsoon storm season.—Skip Derra