Transcript ENSO_and_Weather_SYC_Feb4_2016x

EL NINO, LA NINA, ENSO
AND SEASONAL
WEATHER
PRESENTED TO: SMYRNA YACHT CLUB - FEBRUARY 4, 2016
DR. CHRIS HERBSTER
METEOROLOGY PROGRAM
EMBRY-RIDDLE AERONAUTICAL UNIVERSITY
[email protected]
http://wx.erau.edu/faculty/herbster/demo/presentations/
OVERVIEW
• A LITTLE ABOUT ME
• WHY DO WE HAVE WEATHER?
• WHAT ARE NORMAL CONDITIONS?
• WHAT ARE EL NINO AND LA NINA?
• WHAT ARE THE CURRENT CONDITIONS?
• WHAT DOES THIS MEAN FOR CENTRAL FLORIDA, AND THE REST OF
THE U.S.?
A LITTLE ABOUT ME
• GREW UP SAILING OUT OF RYE NY, ON LONG ISLAND SOUND
• STARTED IN ENGINEERING AT UNIV. OF MICH.
• B.S. ATMOSPHERIC SCIENCE FROM SUNY STONY BROOK
• M.S. AND PHD IN METEOROLOGY FROM FLORIDA STATE UNIVERSITY
• MS – MARINE BOUNDARY LAYER TURBULENT FLUX STUDY
• PHD – OBSERVATIONAL AND MODELING STUDY OF THE FL SEA BREEZE
WHY DO WE HAVE “WEATHER?”
• WHAT YOU AND I CALL “WEATHER” (THAT IS, THOSE TIMES WHEN THE
SKY IS NOT CLEAR AND/OR THE WIND IS NOT CALM) IS THE RESPONSE
THAT IS SET INTO MOTION BY AN ENERGY IMBALANCE.
• WHEN THE WEATHER IS THUNDERSTORMS, THE IMBALANCE IS DOMINATED IN
THE VERTICAL DIRECTION.
• WHEN THE WEATHER IS ASSOCIATED WITH LARGE REGIONS OF WARM AND
COLD AIR, THEN THE IMBALANCE IS LARGELY HORIZONTAL.
• THIS IS MORE COMMON IN THE WINTER SEASON, THAN IN SUMMER.
• SPRING AND FALL HAVE LESS CONTRAST THAN WINTER, AND GENERALLY
WEAKER EVENTS, BUT THESE ARE TRANSITION SEASONS WHICH MAY HAVE BIG
EVENTS TOO.
• THE JET STREAM IS CREATED/INFLUENCED BY GREATER CONTRAST DURING
THE PERIOD BEING OBSERVED.
• STRONGEST IN WINTER, LESS DEFINED IN SUMMER.
ANNUAL ENERGY BUDGET
• TROPICS EXPERIENCE A NET SURPLUS OF ENERGY (I.E. NET WARMING)
• POLES EXPERIENCE A NET DEFICIT (I.E. NET COOLING)
• ENERGY TRANSPORT FROM TROPICS TO POLES IS REQUIRED
PLANETARY HEAT TRANSPORT
• OCEAN CURRENTS – TRANSPORT HUGE QUANTITIES OF WARM
WATER POLE WARD AND COLD WATER TOWARD THE EQUATOR.
(~⅓ OF TOTAL)
• NORTH/SOUTH WINDS – ADVECTIVE TRANSPORT OF WARM AND
COLD AIR INTO NEW (CONTRASTING) REGIONS.
(~⅓ OF TOTAL)
• LATENT HEAT EXCHANGES – ENERGY LOSS FOR SURFACE DUE TO
EVAPORATION AND GAIN FOR THE ATMOSPHERE DUE TO
CONDENSATION.
(~⅓ OF TOTAL)
AVERAGE PLANETARY-SCALE
CIRCULATIONS
FLORIDA SEA BREEZE DUE TO LOCAL CONTRASTS
A local contrast in temperature
creates motions that lead to the
upward transport of energy
away from the warm surface.
HORIZONTAL CONTRAST CREATES THE JET STREAM
LARGE SCALE TEMPERATURE CONTRAST
Cold Air
Warm Air
ATMOSPHERIC CIRCULATIONS
PACIFIC OCEAN INFLUENCE
• THE PACIFIC OCEAN PLAYS AN IMPORTANT ROLE IN SHAPING THE
WEATHER THAT IS EXPERIENCED ACROSS ALL OF THE CONUS, AS
WELL AS ALASKA, AND ULTIMATELY EVERYWHERE ELSE AROUND THE
WORLD.
• THE OCEAN [SEA] SURFACE TEMPERATURE (SST) CAN VARY BY QUITE A
FEW DEGREES BETWEEN A COLD EVENT COMPARED WITH A WARM
EVENT, BUT EVEN JUST A FEW DEGREE CHANGE IN SST CAN HAVE A
VERY LARGE EFFECT ON WEATHER.
NON EL NIÑO YEARS = NORMAL = “LA NADA”
• COLDER WATER IS NORMALLY FOUND IN THE EASTERN
TROPICAL PACIFIC COMPARED WITH THE WESTERN SIDE
OF THE BASIN
• THE NORMAL EASTERLY TRADE WINDS OF THE TROPICS
DRAG THE SURFACE WATERS OF THE EASTERN PACIFIC
AWAY FROM THE COASTLINES OF THE AMERICAS.
• UPWELLING IN THE EASTERN PACIFIC BRINGS COLDER
WATER UP FROM DEEPER LEVELS TO REPLACE THE
SURFACE WATER THAT HAS BEEN DRAGGED AWAY
• THIS NORMALLY COLD WATER IS NUTRIENT RICH AND
FULL OF MARINE LIFE (ESPECIALLY ANCHOVIES)
http://www.cpc.noaa.gov/products/analysis_monitoring/ensocycle/meansst.gif
PACIFIC OCEAN
SST AND SST ANOMALIES
EL NIÑO AND LA NIÑA
EL NINO OCCURS WHEN PACIFIC OCEAN WATERS NEAR THE EQUATOR ARE WARMER THAN NORMAL (LEFT)
LA NINA OCCURS WHEN PACIFIC OCEAN WATERS NEAR THE EQUATOR ARE COLDER THAN NORMAL (RIGHT)
THESE CONTRASTS FROM NORMAL RESULT IN SHIFTS IN THE JET STREAMS AND STORM TRACKS.
El Niño - SST warmer than normal
La Niña - SST colder than normal
http://www.cpc.noaa.gov/products/precip/CWlink/
WHAT’S NORMAL?
• THE TRADE WINDS ACCUMULATE WARM SURFACE WATER AROUND INDONESIA, RAISING THE
SEA LEVEL ROUGHLY HALF A METER HIGHER IN THE WESTERN PACIFIC.
• AS UPWELLING PERSISTS, THE LEVEL OF THE THERMOCLINE RISES TO SHALLOWER DEPTHS OFF
THE SOUTH AMERICAN COAST AND IS DEPRESSED IN THE WESTERN PACIFIC.
• THE UPWELLED WATER IS RICH IN NUTRIENTS AND SUPPORTS AN ABUNDANCE OF FISH
AND MARINE LIFE.
• AS SURFACE WATER PROPAGATES WESTWARD, IT IS HEATED BY THE ATMOSPHERE AND THE
SUN, ALLOWING WARMER WATERS TO ACCUMULATE IN THE WESTERN PACIFIC.
• THE COOLER WATER IN THE EASTERN PACIFIC COOLS THE AIR ABOVE IT, AND CONSEQUENTLY
THE AIR BECOMES TOO DENSE TO RISE AND PRODUCE CLOUDS AND RAIN.
• IN THE WESTERN PACIFIC HOWEVER, THE OVERLYING AIR IS HEATED BY THE WARMER WATERS
BELOW, DESTABILIZING THE LOWER ATMOSPHERE AND INCREASING THE LIKELIHOOD OF
PRECIPITATION
• THIS IS WHY DURING MOST NON EL NIÑO YEARS, HEAVY RAINFALL IS FOUND OVER THE
WARMER WATERS OF THE WESTERN PACIFIC (NEAR INDONESIA) WHILE THE EASTERN PACIFIC IS
RELATIVELY DRY.
El Nino and the Southern Oscillation
La Niña (Index > 0.5oC for at least 5 consecutive
months)
Neutral (Index between 0.5oC and -0.5oC)
El Niño (Index < -0.5oC for at least 5 consecutive
months)
http://www.bom.gov.au/lam/Students_Teachers/elnanim/elani.shtml
How an El Nino Episode Happens
• EVERY FEW YEARS, THE PRESSURE PATTERN BREAKS DOWN  SURFACE
PRESSURE RISES OVER THE WESTERN PACIFIC AND FALLS OVER THE
EASTERN PACIFIC
• TRADE WINDS REVERSE, WARM WATER HEADS EASTWARD VIA A KELVIN WAVE
• THE ATMOSPHERIC PRESSURE REVERSAL IS CALLED THE SOUTHERN OSCILLATION
• SINCE THE ATMOSPHERIC PRESSURE REVERSAL AND OCEAN WARMING
ARE SIMULTANEOUS, IT IS CALLED EL-NINO-SOUTHERN OSCILLATION
(ENSO)
• CONDITIONS OPPOSITE OF EL NINO ARE CALLED LA NINA
• ANOMALOUSLY HIGH PRESSURE AND COLD WATER IN EASTERN PACIFIC
• ANOMALOUSLY LOW PRESSURE AND WARM WATER IN EASTERN PACIFIC
El Nino Formation
A WARM WATER KELVIN WAVE MOVING EASTWARD OVER THE TROPICAL PACIFIC DURING
THE STRONG EL-NINO OF 1997
El Nino and the Southern Oscillation
Typical winter weather patterns
under El Niño and La Niña conditions
El Nino and La Nina Formation
LA NINA FORMATION
EL NINO FORMATION
El Nino vs. La Nina
EL-NINO (RED) VS. LA NINA (BLUE)
Source: NOAA/ESRL
AN OBSERVED KELVIN WAVE HINTS AT
A SIGNIFICANT EL NINO
• OVER THE FIRST QUARTER
OF 2014 A LARGE WAVE
OF SUBSURFACE WARM
WATER TRAVELED ACROSS
THE PACIFIC OCEAN.
SUGGESTING AN EL NINO
EVENT WAS COMING
• THIS HAS BEEN OBSERVED
JUST PRIOR TO OTHER
SIGNIFICANT EVENTS IN
THE PAST.
The next several slides contain information taken
from the Climate Prediction Center’s Weekly
ENSO Briefing
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml
NIÑO REGION SST
DEPARTURES (OC) RECENT
EVOLUTION
The latest weekly SST
departures are:
Niño
Niño
Niño
Niño
4
3.4
3
1+2
1.5ºC
2.5ºC
2.3ºC
1.0ºC
Global SST Departures from Normal (oC)
During the last four weeks, tropical SSTs were above average across most of the Pacific.
Global SST Departures from Normal (oC)
During the last four weeks, tropical SSTs were above average
across the most of the Pacific and the Indian Ocean.
Atmospheric Circulation over the North Pacific
& North America During the Last 60 Days
925-hPa Temp. Anom.
During December, above-average temperatures
dominated over the East and near-to-below
average temperatures were observed over the
West.
Since January, the Pacific jet stream has
extended eastward and strengthened.
Over North America during the last half of
January, an anomalous trough over the eastern
U.S. contributed to below-average temperatures,
while temperatures remained above-average
across Alaska and most of Canada.
U.S. TEMPERATURE AND PRECIPITATION
DEPARTURES DURING THE LAST 30 DAYS
End Date: 30 January 2016
Percent of Average Precipitation
Temperature Departures
(degree C)
WHAT DOES THIS MEAN FOR CENTRAL FLORIDA?
• THE FOLLOWING SLIDES DESCRIBE A LITTLE OF WHAT WE HAVE BEEN
EXPERIENCING,
• WHAT IS TYPICAL OF EL NINO CONDITIONS IN THE PAST,
• AND WHAT IS FORECASTED OVER THE NEXT FEW MONTHS.
Found at: http://www.srh.noaa.gov/mlb/?n=cligraph_2015
U. S. SEASONAL OUTLOOKS
FEBRUARY – APRIL 2016
The seasonal outlooks combine the effects of long-term trends, soil moisture,
and, when appropriate, ENSO.
FINAL THOUGHTS
• WHEN THE PACIFIC OCEAN IS DIFFERENT FROM AVERAGE, THE WEATHER
CAN BE PREDICTABLY DIFFERENT FROM AVERAGE
• EL NINO TENDS TO INCREASE THE INFLUENCE OF WESTERLY WINDS OVER
FLORIDA AND THE TROPICS.
• THIS CAN IMPEDE HURRICANE FORMATION, OR KEEP THEM EAST OF THE U.S.
IF THEY FORM IN THE WARM SEASON.
• LA NINA TENDS TO REDUCE THE INFLUENCE OF WESTERLY WINDS OVER
FLORIDA AND THE TROPICS.
• THIS CAN MAKE HURRICANE FORMATION MORE FAVORABLE, OR ALLOW
THEM TO MOVE CLOSER TO NORTH AMERICA IF THEY FORM IN SUMMER.
• ENSO CAN INFLUENCE WEATHER PATTERNS ALL ACROSS THE PLANET, AS
A SHIFT OF FEATURES IN ONE LOCATION IS CONNECTED TO A SHIFT
OVER NEIGHBORING LOCATIONS, AND SO ON….