by Alison Stevens (NOAA Modeling, Analysis, Predictions, and Projections Program)
Texas State Climatologist and NOAA-funded scientist, John Nielsen-Gammon, has helped the state of Texas make the best possible use of weather and climate information for 17 years. “I became a climatologist before I actually did any climatology work,” he said.
Texas State Climatologist and NOAA-funded scientist
Nielsen-Gammon, Ph.D., grew up watching the weather in California’s Bay Area. He described the weather there as a function of location rather than time. “All you have to do is go 10-15 miles in any direction and the weather is completely different,” Nielsen-Gammon said. “You have the cold ocean, the hot Central Valley, and mountains that funnel the air through gaps.” Nielsen-Gammon and his family lived in one of these gaps, which they called “hurricane hill.” He loved trying to understand the weather so much that his family bought him a rooftop weather station. With it, he took daily weather observations on his roof and then colored in weather maps.
As a schoolkid, weather seemed to be the only subject to hold Nielsen-Gammon’s interest. “I figured if it was still interesting after a year, it would probably always be interesting,” he said. “That proved to be the case.” At the Massachusetts Institute of Technology he studied meteorology, which ultimately led him to a career as a faculty member at Texas A&M University. The weather continued to be his focus until he was appointed Texas State Climatologist in 2000.
Today, Nielsen-Gammon studies both the weather and climate as a Regents Professor at Texas A&M University’s Department of Atmospheric Sciences, Texas State Climatologist, and scientist funded by the NOAA Climate Program Office’s Modeling, Analysis, Predictions, and Projections Program. As Texas State Climatologist, he spends his time researching drought monitoring in Texas, helping people understand current conditions and climate outlooks from NOAA’s Climate Prediction Center, and tracking data like precipitation and temperature.
A dry riverbed along a section of the Brazos River near the headwaters in Knox County, Texas in the summer of 2011.
(Credit: Earl Nottingham, Texas Parks and Wildlife Department)
However, it wasn’t until ten years after becoming State Climatologist that Texans avidly sought out the information Nielsen-Gammon could provide. From 2010-2015, Texas suffered a devastating drought with cumulative damages worth billions of dollars. He traveled over 10,000 miles back and forth across Texas answering questions from the press and public, and speaking with farmers, ranchers, and water managers. “That drought was probably the occasion in which people in Texas discovered that there was a State Climatologist,” Nielsen-Gammon said. “There was extreme interest in what was going on, how it compared with historical drought, and when it was going to end.” Nielsen-Gammon had the responsibility to deal with those questions.
Nielsen-Gammon noted that the multi-year drought lasted long enough to distinguish agricultural drought from hydrologic drought. Scientists define drought in several ways based on different indicators, such as soil moisture, rainfall amounts, and water levels. Agricultural drought is typically short-term and accounts for whether the moisture in the top 1-2 feet of soil will support normal crop growth. Hydrologic drought is long-term and is associated with impacts on water supply, such as water levels in reservoirs. In Texas, what started as agricultural drought eventually became hydrologic. “Most water supplies in Texas are resilient,” Nielsen-Gammon said. “But as time went on and we had one dry year after another, our reservoirs started running into difficulty.”
Texas Drought of 2011
U.S. Drought Monitor map of Texas on October 4, 2011. Almost 90% of the state was in exceptional drought, the most severe category of drought conditions.
During the peak of the drought in September 2011, almost 90% of Texas was in exceptional drought, the most severe category of drought as defined by the U.S. Drought Monitor
. Texas received some relief in 2013 and 2014, but due to the low reservoir levels, the state needed excess rainfall to recover. “We basically needed a flood to end the drought,” Nielsen-Gammon said. “That didn’t happen until May 2015, when Texas had its wettest month on record by far.” Heavy precipitation refilled the reservoirs but also caused flooding and loss of lives and property. Nielsen-Gammon recently helped describe this hydrological rollercoaster
in a new NOAA web application
that recounts the 2010-2015 Texas drought through a visual and interactive user experience.
To forecast and monitor drought like the 2010-2015 event, Nielsen-Gammon combines his own research with the NOAA Climate Prediction Center’s climate outlooks. When he first started as the Texas State Climatologist, the U.S. Department of Agriculture estimated drought severity on a county level using rain gauges to determine economic drought relief for farmers and ranchers. However, available data did not allow for distinguishing one county from another. “I got a call from a rancher in a neighboring county saying they had gotten half of their normal rainfall but their county wasn’t being shown as being in drought,” Nielsen-Gammon said. “I looked at the data and found that the only long-term station in that county was way at the other end of the county, and that end had gotten rain but not his end.” Texans needed detailed information beyond what the rain gauges could provide.
Nielsen-Gammon's Drought Monitoring Tool
Nielsen-Gammon's drought monitoring tool that combines radar with long-term rain gauge data.
Much of Nielsen-Gammon’s research addresses this lack of detailed drought information. With support from NOAA, he researches drought monitoring and prediction on a local scale using radar data to estimate drought severity. Radar estimates the rate of precipitation using signals bounced back from raindrops. However, since translating radar data to rainfall rate depends on several different variables (such as the number and size of raindrops at different altitudes), radar data isn’t always reliable.
To correct for potential errors, Nielsen-Gammon and his colleagues are developing a tool that combines radar with long-term rain gauge data. “We want this product to be something that’s useful nationally, that is reliable, and that really fills a much needed gap between satellites—which measure conditions indirectly—and rain gauges, which only measure things in individual locations,” Nielsen-Gammon said. They hope to make the tool accurate enough so that users can trust the forecast and effectively allocate resources to prepare for droughts.
NOAA web application, called a Story Map, that recounts the 2010-2015 Texas drought through a visual and interactive user experience.
Nielsen-Gammon loves being able to directly help people make successful decisions when planning for weather and climate impacts like drought, and he doesn’t seem to be losing interest any time soon. “It’s always something interesting because the weather keeps changing, and now the climate keeps changing too.”