Tuesday, December 22, 2015

A New Precipitation-Evapotranspiration Index to Map Global Drought

Standardized precipitation–evapotranspiration index (SPEI) is precipitation minus potential evapotranspiration (Vicente-Serrano et al 2010).  It is distinguished from other drought indices because it accounts for temperature through modelled evapotranspiration. This website maps global drought:
Drought in the US 2010-2011.

SPEI has recently been used to predict pine mortality in SW forests.  When the SPEI is below -1.68 for at least 11 months, pinyon and ponderosa pines cannot grow and mortality soon follows. (Kolb, T.E., 2015. A new drought tipping point for conifer mortality.Environmental Research Letters10(3), p.031002.)

Long-term drought graph for NM.

Friday, December 18, 2015

2015 New Mexico Weather Recap

The ABQ NWS office has an excellent recap of the state's weather over 2015.  For example, here is their summary of the summer monsoon:

The 2015 monsoon season got off to a quick start with heavy rainfall, floods, flash floods and severe weather in mid and late June, as well as the first two weeks of July.  A relatively quiet period ensued for most of the remainder of July. A resurgence of heavy rain returned from very late July through early August.  An outbreak of severe weather was the dominate weather story in mid August, and to a lesser extent on September 9th and 23rd. 
products issued during monsoon season
By the numbers:  The Albuquerque NWS office issued 53 flash flood warnings between June 15 and September 30. 

The biggest news of the year was probably the good precipitation that finally ended the drought that began in early 2011:

Drought conditions developed across New Mexico in early 2011, with few breaks in the drought through 2012, such that much of the state was gripped in the worst drought episode since the 1950s.  Near normal statewide precipitation in 2013 and 2014 did little to improve the drought.  Much of the precipitation in 2013 and 2014 fell during the monsoon season, rather than the much more needed winter mountain snowpack.
Finally, New Mexico precipitation in 2015 was above normal for much of the year, and the period January through November was the fifth wettest on record since 1895.  As shown in the graph to the right, precipitation in New Mexico was well above average in January, May, July and October, with only two months below average - August and September.  These wetter than normal conditions supported a steady reduction in the intensity and coverage of the short term drought.  Finally, in early December 2015 New Mexico was drought free!  The last time the state was without any drought status was the week of November 23, 2010!
By the numbers:  New Mexico went 263 weeks with a portion of the state in moderate or worse drought!
NM monthly precipitation for 2015
 percent of new mexico in drought since 2011
 Source: U.S. Drought Monitor