Post on 10-Feb-2016
description
An Evaluation of January Temperature Anomalies in the
United States Utilizing a Synoptic Climatological Approach
Department of Geography, University of Delaware
Center for Climatic ResearchMelissa Malin
Dr. Katrina FrankSteven Quiring
Dr. Laurence Kalkstein
85th AMS Annual MeetingJanuary 15, 2005
has roots in New England weather folklore
“…a characteristic meteorological condition that tends to occur on or near a specific calendar date.” -American Meteorological
Society
an anomalous warm spell invading during the coldest time of year
i. identification of a January Thaw signal across the United States
ii. assess the inter- and intra- regional variability of the January Thaw
Can the Thaw be explained synoptically? …through an assessment of air mass frequency
WestMountain
Great PlainsMidwest
East
Weather DataNational Climatic Data
Center
twice daily4 a.m. & 4 p.m.
Air TemperatureDew Point Temperature
Air Mass DataSpatial Synoptic Classification
daily
Dry Moderate Dry Moderate +
Dry Polar Dry Polar -Dry Tropical Moist Polar
+Moist ModerateMoist Polar Moist TropicalTransition
1948 – 2001December 1 – February 28
• standardized using a five-day moving window• identified by date of the third day
-1-0.5
00.5
11.5
22.5
33.5
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86Window Number
Ave
rage
Tem
pera
ture
Philadelphia, Pennsylvania
average daily temperatures plotted at each station
-1.5-1
-0.50
0.51
1.52
2.53
3.5
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91
Window Number
Ave
rage
Tem
pera
ture
Philadelphia, Pennsylvania
Winter Trendline
Lower Bound
Upper Bound
the identification of singularities
• a second-order polynomial curve fit for winter trendline• upper/ lower bounds set at two standard deviations
singularity atJanuary 24 -25
the identification of singularities
an example of singularities found at a mountain region station
-4
-3
-2
-1
0
1
2
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86
Window Number
Ave
rage
Tem
pera
ture
Cheyenne, Wyoming
Upper Bound
Winter TrendlineLower Bound
(Thaw)
January 16 - 18
(Freeze)
January 2 - 4
(Thaw)
December 3
Linear MethodSecond-order
MethodMean Method
synoptic analysis
Three techniques were used to detect changes in air mass frequency during Thaw and Freeze events.
linear method
•useful for air masses that exhibit a general frequency trend across a season and for stations with winter seasons that extend beyond the period examined here
y = -0.1249x + 22.141R 2 = 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
Window Number
MP+
Fre
quen
cy
Philadelphia, Pennsylvania
second-order method
•useful for air masses that do not display such general, linear frequency tendencies and may be less (more) frequent in early and late winter though more (less) prominent throughout the middle of the season
y = -0.0183x2 + 1.7663x + 1.6291R 2 = 0.6811
0
10
20
30
40
50
60
70
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85
Window Number
DP-
Fre
quen
cy
Philadelphia, Pennsylvania
mean method
•useful here because singularity windows are scrutinized with only frequencies typical of that month and seasonal trends do not contribute to calculating the strength of that departure
Station Thaw Observed DM Frequency DM Monthly Mean Frequency
PHL 24 Jan 22.5% 21.5%
PWM 23 Jan 16.0% 14.5%
PVD 23 Jan 20.8% 19.8%
RIC 24 Jan 25.5% 26.5% SYR 24 Jan 11.6% 10.5%
finding correlations between temperature differences and frequency differences
Station Window Temp. DM DM+ DP DP- DT MM MP MP+ MT TRProvidence 52 1.16 4.15 -1.14 -17.51 2.32 -0.44 -19.49 1.02 -9.13 -2.39 11.45Portland 52 1.21 2.96 -0.41 -16.57 4.34 -0.62 3.97 6.49 -7.38 -0.04 3.46Syracuse 53 1.61 4.01 -1.05 -11.02 1.10 -0.13 12.71 -0.08 -13.12 6.25 6.09
Providence 53 1.48 5.36 -0.14 -17.51 1.11 -0.46 -21.15 0.00 -9.11 3.61 6.45Richmond 53 1.17 4.33 -3.80 -2.88 -5.52 -2.74 1.83 4.90 -7.06 3.30 8.43
Philadelphia 53 1.11 2.51 -1.24 -14.03 -2.33 6.22 5.07 4.57 -5.52 2.85 8.87Portland 53 1.49 4.04 0.61 -17.53 4.05 -0.60 5.96 4.44 -5.18 1.98 -0.60Syracuse 54 1.54 0.02 -1.03 -9.86 -3.23 -0.13 11.66 5.73 -10.71 6.27 5.04
Providence 54 1.67 2.58 -1.14 -15.50 0.89 -0.47 -24.81 1.99 -7.10 5.71 5.46Richmond 54 1.35 8.47 -0.89 -4.77 -5.61 -2.82 -0.12 1.77 -7.99 4.32 8.42
Philadelphia 54 1.14 2.57 -2.31 -12.88 -3.51 7.28 1.07 5.59 -5.40 4.86 10.86Portland 54 1.56 3.11 0.64 -12.48 0.77 -0.59 7.96 5.40 -5.98 2.01 -2.66
Providence 55 1.35 -2.21 -1.15 -12.50 5.67 0.51 -27.47 1.97 -5.08 3.86 3.47Portland 55 1.35 -3.82 0.66 -7.44 0.48 -0.57 2.95 9.36 -4.78 2.04 -0.72Syracuse 81 1.29 11.28 3.33 -8.56 -22.22 1.93 7.56 -13.39 18.33 8.74 -1.23
Correlation Coefficients -0.09 0.25 -0.12 0.22 -0.42 -0.04 -0.04 -0.23 0.37 -0.44
Eastern Region Thaws and Linear Method Output
Inter- and Intra-Regional Variability of the Thaw
15–17 January
14-16 January 14-17 January
15-17 January26-29 December22-24 January
29 December
24-25 January
23-26 January
• found rather cohesive January thaw signal in every region • appears to move somewhat systematically across the country
• found less cohesive January Freeze signal in western US
1 January
4 January3-4 January
2-7 January
28-29 January
(all stations) 5-8 January
26-28 January
Inter- and Intra-Regional Variability of the Freeze
• appears to also progress somewhat systematically eastward
January Thaw
East and West …..No Relationships
Mountain…….Significantly more frequent warm air masses (all)Significantly less frequent cold air masses (L,M)
Great Plains……….Significantly less frequent DP- (S)Significantly more frequent DP (S)
Midwest…………Significantly more frequent MT (all)Significantly less frequent DT (all)
It appears there is no single
synoptic explanation for the Thaw across
the country.
January Freeze
West ……….Significantly less frequent warm air masses (all)Significantly more frequent MP (L,S)
Mountain………Significantly more frequent DP- (L)Significantly more frequent MP (M)
Great Plains……Significantly more frequent DP- (all)Significantly less frequent DP (all)Significantly more frequent DT* (all)
It appears there is no single
synoptic explanation for
the Freeze across the country.
the Thaw and Freeze are related to variable synoptic conditions rather than a single air
mass typemost conditions observed are generally intuitive
this research provides evidence for the existence of a regionally coherent January Thaw and January Freeze
both show signs of west- east advancement across the US The Freeze often occurs just prior to the Thaw
the relationship between synoptic conditions and singularities is most apparent in the
Central USthe air mass-based methodologies used here did not detect a cause for the Thaw in the East this needs further investigation…