Drought Conditions changing?

current map before the rains February 21, 2018

Our nation has a history of devastating droughts, most famously the Dust Bowl of the 1930s during which the iconic image (LEFT) was taken by Dorothea Lange. More recently, record-breaking precipitation deficits and scorching summer temperatures have sparked drought over different regions of the country. In the past five years, drought has affected Texas, the Great Plains, California, and the Pacific Northwest.

The goal of this story is to explain how the Texas drought evolved from 2010 to 2015 and to highlight some of the research that the NOAA Climate Program Office’s Modeling, Analysis, Predictions, and Projections (MAPP) program is supporting to better monitor, understand, and predict drought.

The year 2010 began with a relatively wet winter, spring, and summer in Texas. At the end of September only 2% of the state was classified as being in drought, according to the U.S. Drought Monitor. By October, the beginning of the West’s water year, dry conditions emerged.

Three months of dry weather provided Texas and surrounding states with one of the driest fall-early winter periods on record. Toward the end of 2010, drought increasingly covered much of the southern U.S. By the week of December 28, 2010 (LEFT) the U.S. Drought Monitor indicated short-term drought across most of Texas as well as some of the Southern Plains and Southeast U.S.

Sixty-nine percent of the state was classified as being in at least“moderate drought”, though only 10% of the state was in “extreme drought”.

The region’s wet summer and dry fall in 2010 supplied the perfect recipe for Texas wildfires. Ample precipitation during the winter, spring, and summer of the 2010 growth season allowed grass to grow in abundance. When the abundant grass dried out during the fall, it became fuel for fires during the peak of the drought the following year.

Throughout the 2011 calendar year, Texas received a statewide average of only 14.8 inches of precipitation5. Normally, the state receives about 30 inches of precipitation a year6. Texas received just less than 11 inches of precipitation on average during its water year from October 2010 through September 2011, making it the driest consecutive 12 months on record for the state6.

The average 2011 summer temperature of 86.7°F was two degrees above the former Texas record, further exacerbating the drought’s severity7,8. High temperatures can worsen a drought by increasing the evaporation stress on soil, decreasing snowpack, and consequently reducing available water resources. Research by Omid Mazdiyasni and Amir AghaKouchak (University of California, Irvine) found that the concurrence of droughts and heatwaves have significantly increased over time, especially in the south, southeast, and western U.S.14

By August 2011, the Texas AgriLife Extension Service estimated over $5 billion in agricultural losses since the beginning of the drought5. In September 2011, central Texas experienced the most devastating fire in Texas history, the Bastrop County Complex fire (click on this link to zoom in to Bastrop County on map), which destroyed over 1,600 homes and burned over 34,000 acres9 (view a Landsat image of the burn scar). According to Texas State Climatologist John Neilsen-Gammon, the amount of acreage burned by wildfire in Texas in 2011 is equal to the combined areas of Rhode Island, Connecticut, and New York City.

n the fall of 2011, nearly 1,000 out of 4,700 public water systems were under water use restrictions, which were in effect through March of 20126. Texas received above-normal rainfall from December 2011 through February 2012, giving the state a short break from the dry spell in the winter and spring of 2012 and allowing eastern Texas to improve to “normal” and “abnormally dry” conditions.

 

By April of 2012, the area of the state experiencing “severe” or worse drought conditions decreased from 80% to 50%. However, by fall of 2012, dry conditions returned and persisted, with about 70%of Texas experiencing at least “severe” drought conditions by the summer of 2013.

This is the way the drought ends, not with a drizzle, but with a flood

Spring of 2015 brought heavy rain to Texas, refilling the reservoirs and causing flooding.

Due to the warm temperatures throughout 2011 and long-term precipitation deficits, Texas did not fully recover until the spring of 2015. May 2015 was Texas’ wettest month on record, with more than twice the usual monthly precipitation total recorded10.

Although the rains caused destruction, the precipitation during the spring of 2015 provided some benefit by finally bringing the multi-year Texas drought to an end.

 

The impacts during the first year of the drought were primarily agricultural and wildfire-related. Subsequent years saw more precipitation, and the agricultural and wildfire impacts diminished substantially. However, reservoir levels remained low across most of the state until 2014–2015 when substantially above-normal precipitation was received. It is common not just in Texas for short-term drought to have primarily agricultural impacts and long-term drought to have primarily hydrologic/water supply impacts. In fact, the two types of drought categories used in the first years of the Drought Monitor were Agricultural and Hydrologic, rather than Short-term and Long-term.

Unlike El Niño events, La Niña events are associated with drought over the southern U.S. and tend to last two or more years. Researchby Pedro DiNezio (University of Hawaii), Yuko Okumura (University of Texas), and Clara Deser (NCAR) aims to address the predictability of the duration of La Niña events as well as the physics behind the increase in drought intensity during the second year of La Niña. Results from this research have the potential to help increase the reliability of drought forecasts and the ability to predict persistent conditions. More accurate predictions of drought duration 6-18 months in advance could substantially decrease societal and economic drought impacts. Additional lead time for drought prediction can enable

 

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