A Synoptic Climatological Approach to the Identification of January Temperature Anomalies in the...

A Synoptic Climatological Approach to the Identification of January Temperature Anomalies in the

United States

Melissa MalinKatrina Frank

Steven QuiringRichard Boutillier

Laurence Kalkstein

Center for Climatic ResearchDepartment of Geography

University of Delaware

• an anomalous warm spell that occurs during the coldest time of year

• a singularity: “…a characteristic meteorological condition that tends to occur on or near a specific calendar date.” ~American Meteorological Society

• has roots in New England weather folklore

• discrepancies exist as to the timing of the singularity

• possible causal mechanisms include:– oceanic forcings (Hayden 1976)

– atmospheric patterns (Wahl 1953)

– extra-terrestrial events (sunspots, meteor showers) (Bowen 1956, Newman 1965)

January Temperature Anomaly

The January Thaw

identify winter temperature singularities across the United States and the inter- and intra- regional variability of the event(s)

assess the potential that changes in air mass frequency are a causal mechanism for the event(s)

Goal of the Project

WestWestMountainMountain

Great PlainsGreat PlainsMidwestMidwest

EastEast

Study Area

Study PeriodDecember 1—February 28, 1948—2000

Air Temperature Data4 a.m. + 4 p.m. Average Daily Air Temperature

~National Climatic Data Center

Spatial Synoptic Classification Air Mass DataDry Moderate (DM) / Dry Moderate + (DM+)

Dry Polar (DP) / Dry Polar - (DP-)Dry Tropical (DT)

Moist Moderate (MM)Moist Polar (MP) / Moist Polar + (MP+)

Moist Tropical (MT)Transition (TR)

MethodsData

• daily average temperature data plotted for each station

• standardized using a five-day moving window

Philadelphia, PennsylvaniaPhiladelphia, Pennsylvania

Window Number

MethodsWindowing

Window Number

• second-order polynomial curve fit for winter trendline• upper/ lower bounds set at two standard deviations

MethodsIdentification of Singularities

Philadelphia, PennsylvaniaPhiladelphia, Pennsylvania

WinterTrendline

LowerBound

UpperBound

singularity atJanuary 24 -25

Cheyenne, WyomingCheyenne, Wyoming

Freeze singularity atJanuary 2- 4

WinterTrendlin

e

LowerBound

UpperBound

Thaw singularity atJanuary 16-18

MethodsIdentification of Singularities

example at Mountain Region station

ResultsIdentification of Singularities

December 25


December 26


December 27


December 28


December 29


December 30


December 31


January 1


January 2


January 3


January 4


January 5


January 6


January 7


January 8


January 9


January 10


January 11


January 12


January 13


January 14


January 15


January 16


January 17


January 18


January 19


January 20


January 21


January 22


January 23


January 24


January 25


January 26


January 27


January 28


January 29

20

25

30

35

40

45

50

55

60

65

70

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43

Window Number

Air

Mas

s Fr

eque

ncy

.cy

DP-

Poly. (DP-)

MethodsAir Mass Frequency Analysis

Second-Order Polynomial Fit

Bismarck, North Dakota

Dry Polar -

Bismarck, North Dakota

Dry Polar -

• fit trendline to winter air mass frequency

• found differences to winter air mass trendline

y = -0.1249x + 22.141

R2 = 0.4111

5

10

15

20

25

30

1 5 9 13

17

21

25

29

33

37

41

45

49

53

57

61

65

69

73

77

81

85

Air M

ass Fr

equen

cy

MP+

Linear (MP+)

Window Number

•correlated air mass frequency differences with temperature singularities

|r| > 0.8 = strong correlation, 0.8 |r| 0.5 = moderate correlation, |r| < 0.5 = weak correlation

MethodsAir Mass Frequency Analysis

Linear Fit

Philadelphia, PennsylvaniaMoist Polar +

Philadelphia, PennsylvaniaMoist Polar +

ResultsJanuary Thaw

West RegionAir Mass Method Correlation Frequency Trend

No moderate/strong Thaw correlationMountain Region

Air Mass Method Correlation Frequency TrendDP- Second Order Moderate IncreaseMM Second Order Moderate IncreaseMP+ Second Order Moderate IncreaseTR Second Order Moderate DecreaseDM Linear Moderate Increase

DM+ Linear Moderate IncreaseDP Linear Moderate DecreaseDP- Linear Moderate DecreaseMP Linear Moderate Decrease

MP+ Linear Moderate DecreaseMT Linear Moderate DecreaseTR Linear Moderate Decrease

Great Plains RegionAir Mass Method Correlation Frequency Trend

DP Second Order Moderate IncreaseDP- Second Order Moderate DecreaseMT Second Order Moderate DecreaseMT Linear Moderate Decrease

Midwest RegionAir Mass Method Correlation Frequency Trend

DT Second Order Moderate DecreaseMM Second Order Moderate DecreaseMT Second Order Moderate Increase

DM+ Linear Moderate DecreaseDT Linear Strong DecreaseMM Linear Moderate DecreaseMT Linear Moderate Increase

East RegionAir Mass Method Correlation Frequency Trend

TR Second Order Moderate Decrease

Mountain•no clear signal•character, rather

than frequency, of air masses may be changing?

Plains•increased DP and

decreased DP- frequency

•suggests character change

Midwest•increased MT and

decreased DT suggests circulation pattern change

ResultsJanuary Freeze

West RegionAir Mass Method Correlation Frequency Trend

DM Second Order Strong DecreaseDM+ Second Order Moderate IncreaseDT Second Order Moderate IncreaseDP Second Order Strong IncreaseMT Second Order Moderate IncreaseDM Linear Strong DecreaseMP Linear Strong IncreaseTR Linear Moderate Increase

Mountain RegionAir Mass Method Correlation Frequency Trend

DP- Linear Moderate IncreaseGreat Plains Region

Air Mass Method Correlation Frequency TrendDP Second Order Moderate DecreaseDP- Second Order Moderate IncreaseDT Second Order Strong Increase

MM Second Order Moderate DecreaseMT Second Order Moderate IncreaseDP Linear Moderate DecreaseDP- Linear Moderate IncreaseDT Linear Strong Increase

MM Linear Moderate DecreaseMP Linear Moderate DecreaseMT Linear Moderate Increase

Midwest RegionAir Mass Method Correlation Frequency Trend

No moderate/strong Freeze correlationEast Region

Air Mass Method Correlation Frequency TrendNo moderate/strong Freeze correlation

West•increased polar

frequency•decreased

moderate frequency

Plains•decreased DP and

increased DP- frequency

•suggests character change

this research offers strong support for the existence of cohesive January Thaw and January

Freeze events

•show signs of systematic movement across the United States

–suggests potential of circulation as causal mechanism

air mass analysis shows . . .•Freeze associated with less frequent warm air masses, more frequent cold air masses

•Thaw not clearly associated with air mass frequency

need for an investigation of air mass character and upper level flow patterns

Conclusionsand Directions for Future Research

A Synoptic Climatological Approach to the Identification of January Temperature Anomalies in the...

Documents

Transcript of A Synoptic Climatological Approach to the Identification of January Temperature Anomalies in the...