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


1
A Synoptic Climatological Approach to the
Identification of January Temperature Anomalies
in the United States

• Melissa Malin
• Katrina Frank
• Steven Quiring
• Richard Boutillier
• Laurence Kalkstein
• Center for Climatic Research
• Department of Geography
• University of Delaware

2
January Temperature AnomalyThe January Thaw

• 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
• extraterrestrial events sunspots meteor
  showers
• Bowen 1956 Newman 1965

3
Goal of the Project

• identify winter temperature singularities across
  the United States and the inter and intra
  regional variability of the events
• assess the potential that changes in air mass
  frequency are a causal mechanism for the events

4
Study Area
West
Mountain
East
Great Plains
Midwest
5
MethodsData

• Study Period
• December 1February 28 19482000
• Air Temperature Data
• 4 a.m. 4 p.m. Average Daily Air Temperature
• National Climatic Data Center
• Spatial Synoptic Classification Air Mass Data
• Dry 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

6
MethodsWindowing
Philadelphia Pennsylvania
Window Number

• daily average temperature data plotted for each
  station
• standardized using a fiveday moving window

7
MethodsIdentification of Singularities
Window Number

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

8
MethodsIdentification of Singularitiesexample
at Mountain Region station
Cheyenne Wyoming
Upper Bound
Thaw singularity at January 1618
Lower Bound
Winter Trendline
Freeze singularity at January 2 4
9
ResultsIdentification of SingularitiesDecember
25
10
ResultsIdentification of SingularitiesDecember
26
11
ResultsIdentification of SingularitiesDecember
27
12
ResultsIdentification of SingularitiesDecember
28
13
ResultsIdentification of SingularitiesDecember
29
14
ResultsIdentification of SingularitiesDecember
30
15
ResultsIdentification of SingularitiesDecember
31
16
ResultsIdentification of SingularitiesJanuary 1
17
ResultsIdentification of SingularitiesJanuary 2
18
ResultsIdentification of SingularitiesJanuary 3
19
ResultsIdentification of SingularitiesJanuary 4
20
ResultsIdentification of SingularitiesJanuary 5
21
ResultsIdentification of SingularitiesJanuary 6
22
ResultsIdentification of SingularitiesJanuary 7
23
ResultsIdentification of SingularitiesJanuary 8
24
ResultsIdentification of SingularitiesJanuary 9
25
ResultsIdentification of SingularitiesJanuary 10
26
ResultsIdentification of SingularitiesJanuary 11
27
ResultsIdentification of SingularitiesJanuary 12
28
ResultsIdentification of SingularitiesJanuary 13
29
ResultsIdentification of SingularitiesJanuary 14
30
ResultsIdentification of SingularitiesJanuary 15
31
ResultsIdentification of SingularitiesJanuary 16
32
ResultsIdentification of SingularitiesJanuary 17
33
ResultsIdentification of SingularitiesJanuary 18
34
ResultsIdentification of SingularitiesJanuary 19
35
ResultsIdentification of SingularitiesJanuary 20
36
ResultsIdentification of SingularitiesJanuary 21
37
ResultsIdentification of SingularitiesJanuary 22
38
ResultsIdentification of SingularitiesJanuary 23
39
ResultsIdentification of SingularitiesJanuary 24
40
ResultsIdentification of SingularitiesJanuary 25
41
ResultsIdentification of SingularitiesJanuary 26
42
ResultsIdentification of SingularitiesJanuary 27
43
ResultsIdentification of SingularitiesJanuary 28
44
ResultsIdentification of SingularitiesJanuary 29
45
MethodsAir Mass Frequency AnalysisSecondOrder
Polynomial Fit
Bismarck North Dakota Dry Polar

• fit trendline to winter air mass frequency
• found differences to winter air mass trendline

46
MethodsAir Mass Frequency AnalysisLinear Fit
Philadelphia Pennsylvania Moist Polar

• correlated air mass frequency differences with
  temperature singularities
• r 0.8 strong correlation 0.8 ? r ? 0.5
  moderate correlation r correlation

47
ResultsJanuary Thaw

• 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

48
ResultsJanuary Freeze

• West
• increased polar frequency
• decreased moderate frequency
• Plains
• decreased DP and increased DP frequency
• suggests character change

49
Conclusionsand Directions for Future Research

• 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