U.S. heavy precipitation events are increasing, but drought is not increasing
Last week, I introduced the National Climatic Data Center's Climate Extremes Index, which uses temperature and precipitation records to see if the U.S. climate is getting more extreme. Today, I'll focus on how the drought and precipitation extremes that go into the Climate Extremes Index have changed over the past century. The three precipitation-related factors to go into the Climate Extremes Index are:
1) The sum of (a) percentage of the United States in severe drought (equivalent to the lowest tenth percentile) based on the Palmer Drought Severity Index (PDSI) and (b) percentage of the United States with severe moisture surplus (equivalent to the highest tenth percentile) based on the PDSI.
2) Twice the value of the percentage of the United States with a much greater than normal proportion of precipitation derived from extreme (equivalent to the highest tenth percentile) 1-day precipitation events.
3) The sum of (a) percentage of the United States with a much greater than normal number of days with precipitation and (b) percentage of the United States with a much greater than normal number of days without precipitation.
Items 1 and 3 have shown no change in annual average value over the past century, but there has been a marked increase in the number of heavy 1-day precipitation events in recent decades. Thus, the record values of the Climate Extremes Index in recent years is due to a combination of the increase in heavy 1-day precipitation events, plus the increase in maximum and minimum temperatures.
Figure 1. The Annual Climate Extremes Index (CEI) for heavy 1-day precipitation events shows that these events, on average, have affected 10% of the U.S. over the past century (black line). However, heavy precipitation events have increased recently, with seven of the top ten years on record having occurred since 1995. Image credit: National Climatic Data Center.
Heavy precipitation events
Global warming theory predicts that global precipitation will increase, and that heavy precipitation events--the ones most likely to cause flash flooding--will also increase. This occurs because as the climate warms, evaporation of moisture from the oceans increases, resulting in more water vapor in the air. According to the 2007 Intergovernmental Panel on Climate Change (IPCC) report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970. The Climate Extremes Index plot for extreme 1-day precipitation events (Figure 1) does indeed show a sharp increase in heavy precipitation events in recent decades, with seven of the top ten years for these events occurring since 1995. The increases in heavy precipitation events have primarily come in the Spring and Summer, when the most damaging floods typically occur. This mirrors the results of Groisman et al. (2004), who found an increase in annual average U.S. precipitation of 7% over the past century, which has led to a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events. Kunkel et al. (2003) also found an increase in heavy precipitation events over the U.S. in recent decades, but noted that heavy precipitation events were nearly as frequent at the end of the 19th century and beginning of the 20th century, though the data is not as reliable back then.
Drought and extreme wetness
Global warming theory predicts that although global precipitation should increase in a warmer climate, droughts will also increase in intensity, areal coverage, and frequency (Dai et al., 2004). This occurs because when the normal variability of weather patterns brings a period of dry weather to a region, the increased temperatures due to global warming will intensify drought conditions by causing more evaporation and drying up of vegetation. Increased drought is my number one concern regarding climate change for both the U.S. and the world in the coming century. Two of the three costliest U.S. weather disasters since 1980 have been droughts--the droughts of 1988 and 1980, which cost $71 billion and $55 billion, respectively. The heat waves associated with these droughts claimed over 17,000 lives, according to the National Climatic Data Center publication, Billion-Dollar Weather Disasters. Furthermore, the drought of the 1930s Dust Bowl, which left over 500,000 people homeless and devastated large areas of the Midwest, is regarded to be the third costliest U.S. weather disaster on record, behind Katrina and the 1988 drought. (Ricky Rood has an excellent book on the Dust Bowl that he recommends in his latest blog post).
Figure 2. The Annual Climate Extremes Index (CEI) for drought. The worst U.S. droughts on record occurred in the 1930s and 1950s. There has been no trend in the amount of the U.S. covered by drought conditions (blue bars) or by abnormally moist conditions (red bars) over the past century. About 10% of the U.S. is typically covered by abnormally dry or wet conditions (black lines). Image credit: National Climatic Data Center.
The good news is that the intensity and areal coverage of U.S. droughts has not increased in recent decades (blue bars in Figure 2). The portion of the U.S. experiencing abnormal drought and exceptionally wet conditions has remained nearly constant at 10% over the past century. A recent paper by Andreadis et al., 2006, summed up 20th century drought in the U.S. thusly: "Droughts have, for the most part, become shorter, less frequent, and cover a smaller portion of the country over the last century. The main exception is the Southwest and parts of the interior of the West, where, notwithstanding increased precipitation (and in some cases increased soil moisture and runoff), increased temperature has led to trends in drought characteristics that are mostly opposite to those for the rest of the country especially in the case of drought duration and severity, which have increased."
The rest of the globe has not been so lucky. Globally, Dai and Trenberth (2004) showed that areas experiencing the three highest categories of drought--severe, extreme, and exceptional--more than doubled (from ~12 to 30%) since the 1970s, with a large jump in the early 1980s due to an El Niño-related precipitation decrease over land, and subsequent increases primarily due to warming temperatures. According to the Global Drought Monitor, 50 million people world-wide currently live in areas experiencing the highest level of drought (exceptional).
The future of U.S. drought
As the climate continues to warm, I expect the frequency, severity, and areal coverage of droughts to increase over the U.S. We're certainly off to a dry start in 2009--the period January - February this year was the driest such period in U.S. history, according to the National Climatic Data Center.
References
Andreadis, K. M. Lettenmaier, D. P., "Trends in 20th century drought over the continental United States", Geo. Res. Letters 33, 10, L10403, DOI 10.1029/2006GL025711
Dai A., K.E. Trenberth, and T. Qian, 2004: A global data set of Palmer Drought Severity Index for 18702002: Relationship with soil moisture and effects of surface warming", J. Hydrometeorol., 5, 11171130.
Gleason, K.L., J.H. Lawrimore, D.H. Levinson, T.R. Karl, and D.J. Karoly, 2008: "A Revised U.S. Climate Extremes Index", J. Climate, 21, 2124-2137.
Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64-85.
Kunkel, K. E., D. R. Easterling, K. Redmond, and K. Hubbard, 2003, "Temporal variations of extreme precipitation events in the United States: 1895-2000", Geophys. Res. Lett., 30(17), 1900, doi:10.1029/2003GL018052.
Jeff Masters
Reader Comments
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 — Blog Index
Key word "Hardly". The ground still moves under the feet and I can't fly, so I will take my Hurricanes (since I can see them coming) and leave the shake rattle and rolling to others. :^)
Cyclone Phase Analysis (GFS)
351. RitaEvac
Yep
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
84 Hour 225 mb wind prog
http://adds.aviationweather.gov/winds/
Well done Tampa. Looks good.
After seeing the past GFS runs, my adrenaline rekindled. That feeling is quite nostalgic, it reminds me of hurricane season.
A rapidly amplifying longwave trough is expected to move in across the midwest around Monday and tuesday. The robust structure of this structure will help enhance the flow of positive vorticity advection which catalyzes cyclogenesis. The "U" structure is clearly evident on the model forecasts, and the 850mb range is showing plenty of warm air propagating northward during monday and tuesday.
Severe weather is a possible next week, however, I am still reluctant to consider this as an "outbreak", hence, I'll wait for about 48 hours to draw any real conclusions.
LI Index
Well put,
I enjoyed it...
Thanks
it was not exactly a forecast though..
He sounds like a betting man to me..
TampaSpins Forecast Link
can happen... and doesn't everyone know that after the past 5, 10, 15 years???
Surely you can tell a joke when you see one!
Please note that the orb in front of you could produce a Hurricane sooner or later somewhere.
I just cannot seem to find this anywhere /? How about a link ? ®¿ª
Keep looking. Do not sleep until you find it.
"A failure establishes only this, that our determination to succeed was not strong enough."
-- Hoshang N. Akhtar
Will do, - you always miss 100% of the shots you don't take --- EZE----.
LOL OBVIOUSLY
loving the irony in that name lol.
Ya his name represents what he his LMAO
Queensland braces for weekend cyclone
Article from: NEWS.com.au
March 20, 2009
NORTH and central Queensland will be on cyclone alert over the weekend as the weather bureau monitors a tropical low about 600km northeast of Mackay.
The forecast comes three years to the day after cyclone Larry crossed the North Queensland coast, devastating the town of Innisfail.
Bureau of Meteorology senior forecaster Ben Annells said the low pressure system was interacting with an upper level trough that was keeping it steady.
But when the trough moves away it could intensify over the weekend into a cyclone, expected to be called Jasper.
"It looks like it will stay over the Coral Sea into the weekend, but its long-term movement is uncertain,'' Mr Annells said.
"It depends on the interaction with another upper trough next week.''
Strong winds of up to 33 knots are already being felt from Cooktown to Sandy Cape, with seas to three metres in open waters and outside the reef.
"The environment at the moment is favourable for a cyclone,'' Mr Annells said.
"It's not unusual to get cyclones this time of the year and even into April.
Current Home weather station data.
Zoo is finally out of the rain :)
Just announced that Landsea et al have posted new data, through 1925.
http://www.aoml.noaa.gov/hrd/data_sub/re_anal.html
I believe that was 1900hurricane, who is a Texas resident.
the 1924 Cuba hurricane that struck as a Category 5 (and is now the first recorded Category 5 hurricane in the database).
I still wonder how many storms were underestimated back before the satellite era, particularly those out at sea, although I suspect there were some hurricanes at landfall that were underestimated, as well.
FIREBAUGH, California a ' "Now we know how the Indians felt," sighed Jim Diedrich, a farmer who said he was betrayed by the government as California's Central Valley reels from a serious drought.
No, because SSTs in that area don't reach their peak until September.
NATIONAL WEATHER SERVICE CHARLESTON SC
114 AM EDT FRI MAR 20 2009
SCZ045-050-201200-
/O.NEW.KCHS.SM.Y.0001.090320T0514Z-090320T1200Z/
BERKELEY-CHARLESTON-
INCLUDING THE CITIES OF...MONCKS CORNER...CHARLESTON
114 AM EDT FRI MAR 20 2009
...DENSE SMOKE ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING...
THE NATIONAL WEATHER SERVICE IN CHARLESTON HAS ISSUED A DENSE
SMOKE ADVISORY...WHICH IS IN EFFECT UNTIL 8 AM EDT THIS MORNING.
THE SOUTH CAROLINA STATE FORESTRY SERVICE HAS ANNOUNCED THAT
DENSE SMOKE WAS CAUSING ROAD CLOSURES IN THE FRANCIS MARION
NATIONAL FOREST AREA. THE ROAD CLOSURE CHECKPOINTS EXTEND FROM
NEAR STEED CREEK ROAD...SR 133 TO HALFWAY CREEK ROAD WEST TO
HIGHWAY 41. VISIBILITIES WERE LESS THAN A QUARTER MILE...EVEN
NEAR ZERO LOCALLY.
VISIBILITIES SHOULD IMPROVE AROUND OR BEFORE DAWN FRI AS A COLD
FRONT MOVES THROUGH AND NORTHERLY WINDS INCREASE.
A DENSE SMOKE ADVISORY MEANS FIRES WILL CREATE SMOKE THICK ENOUGH
TO GREATLY REDUCE VISIBILITIES. MOTORISTS SHOULD DRIVE WITH
CAUTION AND ALLOW FOR EXTRA TRAVEL TIME. USE LOW BEAM HEADLIGHTS
AND REDUCE DRIVING SPEEDS. LEAVE PLENTY OF DISTANCE AHEAD OF YOU
IN CASE A SUDDEN STOP IS NEEDED.
HAHA!! So true! Dr. Gray, take notes.
They've only just begun to know how our Native Americans felt.
Voluntary Versus Mandatory
Evacuations
Last Updated: January 29, 2008 ast Updated: January 29, 2008 Related resource areas: Family Caregiving
View as web page
Voluntary Versus Mandatory Evacuation
The Federal Emergency Management Agency defines evacuations as the organized, phased and supervised movement of people from dangerous or potentially dangerous areas. Some evacuations occur without the direction of government officials. This happens when residents either perceive of or are aware of an actual emergency and evacuate an area on their own. Voluntary and Mandatory/Directed Evacuations involve government direction.
The definitions for these follow:
Viewing: 351 - 401
Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 — Blog Index