daniel j. leathers and gina henderson center for climatic research department of geography
DESCRIPTION
Synoptic-Scale Atmospheric Processes Associated with Snow Cover Ablation Events Across Eastern North American Stream Basins. Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography University of Delaware. Research Questions - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/1.jpg)
Synoptic-Scale Atmospheric Processes Associated with Snow Cover Ablation Events Across Eastern
North American Stream Basins
Daniel J. LeathersDaniel J. Leathers
And And
Gina HendersonGina Henderson
Center for Climatic ResearchCenter for Climatic Research
Department of GeographyDepartment of Geography
University of DelawareUniversity of Delaware
![Page 2: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/2.jpg)
Research Questions
1)How important is the ablation of snow cover to the flood hydroclimatology of selected eastern North American stream basins?
2) What are the synoptic-scale atmospheric processes associated with snow cover ablation in eastern North America?
![Page 3: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/3.jpg)
Basins of InterestSusquehanna Ohio
St. LawrenceChesapeake
![Page 4: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/4.jpg)
Data Sources
![Page 5: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/5.jpg)
Snow Depth Data
1o X 1o gridded daily snow depth data set developed by Mote et al.
Utilizes U.S. COOP and Canadian daily surface observations
Extensive quality control routines
Gridded snow cover data used to identify basin or sub-basin wide ablation episodes.
![Page 6: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/6.jpg)
The Spatial Synoptic Classification (SSC)
A statistical methodology to identify Air Mass Types for each day at a given station from hourly meteorological data (Sheridan Inter. J. Climatology, 22, 51-68).
DM – Dry moderate (“Pacific” type air mass)
DP – Dry Polar (cP)
MT – Moist Tropical (mT)
MM – Moist moderate (overrunning situation)
MP – Moist polar (mP)
TR – Transition (air mass transition, frontal passage)
SSC used to identify air mass types during major ablation episodes.
![Page 7: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/7.jpg)
Calculation of Energy fluxes during ablation events with SNTHERM Snow Pack Model….developed by Jordan (1991)
Figure from CRREL website…..
![Page 8: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/8.jpg)
Methodology
1. Examine the record of major flooding events in a basin or sub-basin to ascertain the role of snow cover ablation on the flood hydroclimatology.
2. Identify the major ablation events within a basin that were associated with flooding (using gridded snow cover data).
3. Match ablation events to air mass types using SSC.
4. Examine synoptic-scale atmospheric patterns associated with each air mass type.
5. Use SNTHERM to model atmosphere snow cover interactions under diverse air mass types.
![Page 9: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/9.jpg)
Results:
The Susquehanna River Basin…..
![Page 10: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/10.jpg)
Drains 27,500 square miles, covering half the land area of Pennsylvania and portions of New York and Maryland.
Flows 444 miles from its headwaters at Otsego Lake near Cooperstown, N.Y., to Havre de Grace, Md., where the river meets the Chesapeake Bay.
Is the largest tributary of theChesapeake Bay, providing 90percent of the fresh water flows to the upper half of the bay and 50 percent overall.
Discharge data from Harrisburg, PA
![Page 11: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/11.jpg)
Methodology
1. Examine the record of major flooding events in a basin or sub-basin to ascertain the role of snow cover ablation on the flood hydroclimatology.
2. Identify the major ablation events within a basin that were associated with flooding (using gridded snow cover data).
3. Match ablation events to air mass types using SSC.
4. Examine synoptic-scale atmospheric patterns associated with each air mass type.
5. Use SNTHERM to model atmosphere snow cover interactions under diverse air mass types.
![Page 12: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/12.jpg)
Month
J F M A M J J A S O N DNum
ber
of B
asin
Wid
e F
lood
ing
Eve
nts
0
2
4
6
8
10
31 Basin Wide Flooding Events 1949 - 2000Susquehanna River at Harrisburg
Only three "warm season" events
90% occur during snow cover season (55% during March / April Ablation period)
Agnes June 1972 Eloise Sep. 1975
Nor'easter 1955
Flooding event defined as a discharge at Harrisburg >250,000 ft3/sec
![Page 13: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/13.jpg)
Methodology
1. Examine the record of major flooding events in a basin or sub-basin to ascertain the role of snow cover ablation on the flood hydroclimatology.
2. Identify the major ablation events within a basin that were associated with flooding (using gridded snow cover data).
3. Match ablation events to air mass types using SSC.
4. Examine synoptic-scale atmospheric patterns associated with each air mass type.
5. Use SNTHERM to model atmosphere snow cover interactions under diverse air mass types.
![Page 14: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/14.jpg)
Susquehanna Basin and 12 grid boxes used to calculate ablation values.
Daily ablation calculated using:
day 1 – day 2
![Page 15: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/15.jpg)
Methodology
1. Examine the record of major flooding events in a basin or sub-basin to ascertain the role of snow cover ablation on the flood hydroclimatology.
2. Identify the major ablation events within a basin that were associated with flooding (using gridded snow cover data).
3. Match ablation events to air mass types using SSC.
4. Examine synoptic-scale atmospheric patterns associated with each air mass type.
5. Use SNTHERM to model atmosphere snow cover interactions under diverse air mass types.
![Page 16: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/16.jpg)
Identified the air mass type present (in Williamsport, PA) two days before flood stage was reached in Harrisburg. This two-day response is typical of basin-wide flooding events on the Susquehanna.
DM – Dry moderate (“Pacific” type air mass) 5 eventsMM – Moist moderate (overrunning situation) 10 eventsMT – Moist Tropical (mT) 4 eventsMP – Moist polar (mP) 1 eventTR – Transition (air mass transition, frontal passage) 8 events
![Page 17: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/17.jpg)
Methodology
1. Examine the record of major flooding events in a basin or sub-basin to ascertain the role of snow cover ablation on the flood hydroclimatology.
2. Identify the major ablation events within a basin that were associated with flooding (using gridded snow cover data).
3. Match ablation events to air mass types using SSC.
4. Examine synoptic-scale atmospheric patterns associated with each air mass type.
5. Use SNTHERM to model atmosphere snow cover interactions under diverse air mass types.
![Page 18: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/18.jpg)
DM – dry moderate (“Pacific” type air mass) 5 events
LH
SLP (mb) 500 hPa heights
Surf. T (C) R.H. (%)
![Page 19: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/19.jpg)
MM – Moist moderate (overrunning situation) 10 events
L
H
SLP (mb) 500 hPa heights
Surf. T (C) R.H. (%)
![Page 20: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/20.jpg)
MT – Moist Tropical (mT) 4 events
SLP (mb) 500 hPa heights
Surf. T (C) R.H. (%)
L
![Page 21: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/21.jpg)
TR – Transition (air mass transition, frontal passage) 8 events
SLP (mb) 500 hPa heights
Surf. T (C) R.H. (%)
L
![Page 22: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/22.jpg)
Air Mass Type
3-day Ablation (cm/day)
3- day Precipitation
(cm)
3-day Snowfall
(cm)
Mean Temp (C)
DM(5) 5.2 3.2 0.0 7.6
MM(10) 6.0 5.8 1.3 5.9
MT(4) 5.2 3.2 0.0 7.1
Trans(8) 9.3 3.9 1.5 5.6
Three-day meteorological variables associated with basin-wide flooding events
![Page 23: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/23.jpg)
Energy fluxes associated with synoptic-scale atmospheric patterns:
March 2 – 4, 1964
![Page 24: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/24.jpg)
1963-1964 Snow Cover Season
MonthNov. 1 Dec. 1 Jan. 1 Feb. 1 March 1 April 1 May 1
Sn
ow
De
pth
(cm
)
0
10
20
30
40
50
Dis
char
ge (
ft3 /
sec)
0
1e+5
2e+5
3e+5
4e+5
5e+5
Pre
cip
itatio
n (
inch
es)
0.0
0.5
1.0
1.5
2.0
2.5
snow depthdischargePrcp
will examine pre-precipitation ablation March 2-4, 1964
![Page 25: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/25.jpg)
March 2 - 4, 1964 Ablation EventEnergy Budget Components
Day
March 2 00 March 3 00 March 4 00 March 5 00
Ene
rgy
Flu
x (W
/m2 )
-100
0
100
200
300
400
Sno
w d
epth
(m
)
0.0
0.1
0.2
0.3
0.4
0.5sensible heat fluxlatent heat flux0 W/m2
snow depth net solar net longwave
H
L L
DM MT MM
![Page 26: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/26.jpg)
Initial Findings
![Page 27: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/27.jpg)
1. More than 80% of the major flooding events within the Susquehanna River Basin are associated in some way with snow cover ablation.
Month
J F M A M J J A S O N DNum
ber
of B
asin
Wid
e F
lood
ing
Eve
nts
0
2
4
6
8
10
31 Basin Wide Flooding Events 1949 - 2000Susquehanna River at Harrisburg
Only three "warm season" events
90% occur during snow cover season (55% during March / April Ablation period)
Agnes June 1972 Eloise Sep. 1975
Nor'easter 1955
![Page 28: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/28.jpg)
2. Although several different synoptic patterns can lead to ablation, a common theme is strong low pressure in the lower Great Lakes Region bringing warm and moist air across the Susquehanna Basin (also precipitation).
L
HLH
LL
DM MM
MT Tran
![Page 29: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/29.jpg)
3. Large values of sensible and latent heat flux are typically the largest components of the energy budget during the most
intense ablation events across the Susquehanna River Basin (net solar and net longwave are not as large). Latent heat flux can be particularly important in some instances.
March 2 - 4, 1964 Ablation EventEnergy Budget Components
Day
March 2 00 March 3 00 March 4 00 March 5 00
Ene
rgy
Flu
x (W
/m2
)
-100
0
100
200
300
400
Sno
w d
epth
(m
)
0.0
0.1
0.2
0.3
0.4
0.5sensible heat fluxlatent heat flux0 W/m2
snow depth net solar net longwave
![Page 30: Daniel J. Leathers And Gina Henderson Center for Climatic Research Department of Geography](https://reader036.vdocuments.us/reader036/viewer/2022081603/568147dc550346895db51145/html5/thumbnails/30.jpg)
Future Work
1. Continue similar methodology for the other three eastern North American basins.
2. Study the role of basin size in regard to the importance of snow cover ablation in the flood hydroclimatology of these basins.