Articles tagged as: John Nielsen-Gammon
Q: There seems to be a lot of sandstorms lately. What causes sandstorms?
A. Sandstorms are caused by strong winds that occur in desert or semi-arid regions, and they carry thick clouds of dust and sand, often reducing visibility to near zero in many cases, says John Nielsen-Gammon of Texas A&M University. In many parts of the world, such as the deserts of the Southwest U.S. or in Africa or the Middle East, sandstorms can create havoc with man and machine. “A sandstorm can last for several hours to a full day,” says Nielsen-Gammon. “Most of the time, sandstorms affect only the air from about 1-3 miles high, so airplanes flying above that range are okay. But on the ground, sand moving at about 50 miles an hour can be a real nightmare. It can clog up just about anything that is mechanical, from a soldier’s rifle to a car or an army tank. Once the sandstorm has passed, a thorough cleaning of just about anything is required.”
Q: What types of sandstorms can occur?
A: There are two types of sandstorms, says Nielsen-Gammon. “The first kind is the result of a severe thunderstorm that creates strong winds. This kind is called a ‘haboob,’ which is an Arabic word for blowing dust. The second type is the one most Americans are familiar with. It’s caused by a curving of the jet stream which brings strong winds to the surface. Sandstorms tend to be worse during the daytime because the ground is heated up by the sun and the dust can be carried greater distances. That’s why breathing can become a real problem, and some type of mask is often required. Probably the worst sandstorms occur in China and Mongolia. The sand blows so hard that there is a ‘yellow rain’ effect. So much sand is in the air that it changes the color of raindrops, and there appears to be a yellow rain falling from the sky.”
Weather Whys is a service of Texas A&M University’s Department of Atmospheric Sciences.
Q: It’s in the news that an El Niño may form this summer. What is the difference between an El Niño and La Niña?
A: The main difference between the two involves water temperature, explains John Nielsen-Gammon, a weather expert at Texas A&M University. El Niño and La Niña – Spanish for “the child” – both occur in the central Pacific Ocean. “During an El Niño event, which can last almost a year, the waters in that region are warmer than usual,” he says. “The opposite occurs during a La Niña – the waters tend to be cooler than usual. But the important thing is that both events can affect weather patterns in the United States and around the world.”
Q: How do they change our weather?
A: In years when a La Niña occurs, there are often warmer and drier conditions in many areas, including Texas, Nielsen-Gammon says. “In general terms, a La Niña period means drier weather patterns for Texas. There have been numerous studies on how El Niño and La Niña affect weather patterns, and specifically, hurricanes and their intensity. Some research indicates that the sorts of hurricanes that affect Texas are more common during La Niña periods than during a neutral or El Niño year. We do know that an El Niño can last up to 18 months and it can influence weather everywhere, so when one forms, there is naturally a lot of interest in what will happen.”
Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.
The worst drought ever to hit California could rival the historic 2011 drought that devastated Texas, says a Texas A&M University professor.
John Nielsen-Gammon, professor of atmospheric sciences who also serves as Texas’ State Climatologist, says the current drought in California is so far comparable in many ways to the 2011 Texas drought, the worst one-year drought in the state’s history that caused more than $10 billion in damages and led to numerous wildfires and lake closings.
“This is the third year of California’s drought and it is on pace to be as dry as Texas was in 2011,” Nielsen-Gammon, a California native who grew up in the San Francisco area, explains.
“However, because our severe drought year came at the beginning of the drought, reservoirs across much of the state were full. In California, reservoir levels were low to begin with.
“In addition, they are dealing with environmental flows through the Sacramento Delta that weren’t explicitly laid out until a few years ago.”
Weather patterns for both states appear similar, he adds.
“The same ridge that has kept California dry has also been keeping Texas dry,” he notes. “As the pattern changes, California is finally getting some rain and snow and the chances for precipitation in Texas are increasing as well.”
California’s drought is especially worrisome because the state produces about one-half of the country’s fruits, vegetables and nuts. It is the No.1 agricultural state in the U.S.
The 2011 drought devastated Texas farmers and ranchers, and lake levels were down as much as 50 feet in some lakes while several West Texas lakes completely dried up.
Numerous Texas cities set heat records in 2011, such as Wichita Falls, which recorded 100 days of 100-degree heat, the most ever for that city. Dallas also set a record with 70 days of 100-degree heat.
Texas’ drought is now in its fourth year, Nielsen-Gammon says, and about 52 percent of Texas is still in some form of drought status, ranging from moderate to exceptionally dry.
“January was unusually dry with an average of only about one-half an inch of precipitation statewide,” he adds.
“Reservoir levels have actually declined at a time when they should be rising. So the drought is still here. In fact, the prevalence of drought in Texas has not dropped below 40 percent since 2010 when this drought first started.”
The Texas Panhandle area has been especially hard hit.
“The past three calendar years have been among the driest three on record for the Panhandle,” he notes. “Dalhart shattered its record with just 20.54 inches total in 2011-2013.
“This current drought started with more intensity than the drought of 1950-56, the driest on record. We again have a generally warm Atlantic Ocean, and that tends to mean dry conditions. An El Nino (warmer water in the tropical Pacific Ocean) might develop later this year, but it’s still a little too early to say.”
Q: Is there a relationship between global warming and hurricanes?
A: That’s a question that a lot of people are asking, says John Nielsen-Gammon, professor of atmospheric sciences at Texas A&M University who also serves as State Climatologist. “There were more hurricanes and tropical storms in 2005 than any year in at least 70 years,” he explains. “A lot of fingers are being pointed at global warming for the rise in severe storms. There are a lot of studies being done in this area, and global warming appears to be at least a strong contributing factor. We know that some areas of the oceans are warmer than in years past, and this can contribute to more intense storms.”
Q: What specific areas of water are warmer?
A: The Atlantic Ocean, Nielsen-Gammon says, is scientifically proven to be warmer than normal. “Large areas of the Atlantic are at least one degree warmer than in years past, and this goes back to 1995,” he points out. “So we have had a decade of warmer water there, and that’s where hurricanes form. The long-range outlook tells us that this warming trend could continue another 5 to 20 years. Since warmer water means stronger storms and hurricanes, it could mean stronger storms in the future. Back in 2005, there were three hurricanes that reached category 5 status — the strongest level — but it remains to be seen if that will happen in the years to come.”
Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University
Despite recent rains, the historic Texas drought is still alive and well and about 93 percent of the state remains in drought conditions ranging from dry to exceptionally dry, says a Texas A&M University expert.
John Nielsen-Gammon, professor of atmospheric sciences who also serves as State Climatologist, says that although some much-needed rainfall covered most of the state last week, most of Texas is still unusually dry and water levels are below normal.
“Part of southeast Texas and far west Texas are in pretty good shape and have had normal or above normal rain this year,” he notes. “But those are the exceptions. The hardest hit areas are those around McAllen, west of San Antonio, the Vernon-Wichita Falls area, south of Lubbock, near Midland and Dalhart and around Bryan-College Station. Most of these areas are anywhere from 10-15 inches below normal in rainfall.”
He notes that long-range forecasts tend to be neutral since there is no La Niña or El Niño in the Pacific Ocean this year that normally affects weather patterns and rainfall.
“For its combination of intensity and longevity, I consider the current drought to be the second worst drought in Texas history,” Nielsen-Gammon says.
“The worst drought ever – the drought of record – remains the drought of 1950-57. This drought still has a few years to go to catch up.
“The other rivals in the climate record, which goes back to 1895, were the droughts of 1917-18 and 1961-66. The 1917-18 drought was intense but shorter, and the 1961-66 drought was long but milder.
“The long-term Pacific and Atlantic Ocean temperature patterns still favor drought in Texas, and probably will continue to do so for another 5-15 years. Whether this drought will last that long or whether Texas will have an occasional wet year within that stretch is impossible to say.”
He notes that many reservoirs range from low to extremely low, while many Texas lakes have still not recovered from the 2011 conditions, the worst one-year drought in the state’s history.
“Until the rain event on Sept. 19-20, Texas reservoirs were one or two days away from setting an all-time record for the gap between the amount of water stored and the storage capacity,” he notes. “Our reservoirs were essentially storing 18 million acre-feet of water and 13 million acre-feet of air.”
One acre-foot is the amount of water needed to cover one acre of land to a depth of one foot. The present record was set in 2011, “but without more rain, the record might still fall in another or month so.”
The forecast of near-normal rainfall this winter is good news for water supplies, but Nielsen-Gammon notes that the benefits will be uneven.
“Normal rainfall can fill up East Texas reservoirs, but normal rain in Central and West Texas is too little to make up the gap,” he says.