stingjet extratropical cyclones in ERAInterim Oscar MartinezAlvarado OMartinezAlvaradoreadingacuk Suzanne Gray Department of Meteorology University of Reading EGU General Assembly 2010 ID: 324407
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Identification of sting-jet extratropical cyclones in ERA-Interim
Oscar Martinez-Alvarado (O.MartinezAlvarado@reading.ac.uk)Suzanne GrayDepartment of MeteorologyUniversity of Reading
EGU General Assembly 2010
04 May 2010
Vienna, AustriaSlide2
Sting Jets
Jet descending from mid-troposphere from the tip of the hooked cloud headLocated in the frontal fracture regionMesoscale (~100 km) region of strong surface winds (that can reach more than 100 km/h) occurring in rapidly deepening extratropical cyclones Transient (~ few hours), possibly composed of multiple circulations
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.uk
Shapiro-Keyser cyclogenesis
Stage III
Adapted from Clark et al. (2005)Slide3
Sting Jets
Case-studiesMechanisms hypothesized to be important:Evaporative cooling of cloudy air, and The release of conditional symmetric instability
(CSI)Global frequency and distribution are unknown
3
Great
Storm
15/16
October 1987
UK
Browning
2004;
Clark et al. 2005
Anna
25/26 February 2002
UK
Martinez-Alvarado
et al. 2010
Jeanette27 October 2002UKParton et al. 2009Oili07-11 February 2006UK, GermanyWeidle and Wernli 2008Gudrun07/08 January 2007UK, N. EuropeBaker 2009
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide4
There are just a handful of well-documented case studies on sting jets (Browning 2004, Clark et al. 2005, Parton et al. 2009, Baker 2009).
These are valuable for all the detailed insight they provide into the structure and dynamics of sting jets.However, they cannot answer the question of how frequently sting jets occur.Another unanswered question is what other regions (apart from the UK and N. Europe) are likely to experience sting jets.
The need for a
climatology of sting jets
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide5
5
Unstable slantwise convective circulations in an otherwise inertially and gravitationally stable atmosphere
Downdraught SCAPE (
DSCAPE)
is the potential energy available to parcel to descend in slanted
downdraughts
CSI and Downdraught SCAPE
q
e
*
increasing
M
g
increasing
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide6
Storm Anna:Synoptic situation
6
Synoptic situation at 0700 UTC on
26 February 2002. The bold grey
line represents the edge of the cloud
head
.
The
red
circle
marks the
position of the sting jet at each time.Sting-jet cyclones in ERA-Interim– Contact: O.MartinezAlvarado@reading.ac.ukSlide7
Storm Anna:Downdraught SCAPE
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Downdraught SCAPE (DSCAPE, in J/kg) at (A) 0100 UTC and (B) 0300 UTC on 26 February 2002. The bold dark line represents the edge of the cloud head; the grey lines are lines of constant wet-bulb potential temperature (in K). The
red
circle
marks the
position of the sting jet
at each time.
A
B
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide8
Minimum DSCAPE descending from the mid-troposphere
DSCAPE > 200 J kg-1Search restricted to upper levelspstart < 650 hPaMoisture needed to precipitate over unstable areas with large DSCAPERH > 80 %
Location within a fractured cold front
Threshold values appear to be robust for a number of cases
A climatology of sting jets
8
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide9
ERA-Interim is the new ECMWF reanalysis covering the period 1989-presentResolution: ~0.7°
This work looks at fields on pressure levelsDomain limited to 30°N - 70°N, 70°W - 30°E (North Atlantic and Europe)50 most intense cyclones during the first ten years in the reanalysis (1989-1998). Thanks to Jen Catto for kindly providing these cyclone tracks.Only winter months (DJF)
A climatology of sting jets
using ERA-Interim
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide10
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Sting Jet Cyclones in ERA-Interim:Track 39
Mid-tropospheric CSI regions near (
red circles) or far from (green circles
) cyclone.
Grey
: wet-bulb potential temperature at 600 hPa.
Blue
:
RH at 550 hPa.
RH at 550 hPa
q
w
at 600 hPa
Instability region
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide11
Sting Jet Cyclones in ERA-Interim:
Track 3911
Mid-tropospheric CSI regions near (
red circles) or far from (green circles
) cyclone.
Grey
: wet-bulb potential temperature at 600 hPa.
Blue
:
RH at 550 hPa.
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide12
From the 50 most intense cyclones: ~29 show CSI in the vicinity of the cyclone centre
~8 show the potential to develop sting jets.~16 cyclones show instability regions associated with the warm conveyor belt
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Sting Jet Cyclones in ERA-Interim:
Preliminary results
Dec 1989
Dec 1989
Dec 1991
Jan 1992
Jan 1993
Dec 1995
Feb
1996
Feb 1997
Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide13
Limitations and possible ways forward
A missing link: surface observations (how much surface damage have sting jets actually caused?)The small number of cases found in these years in ERA-Interim will allow us to look into them in detail (in mesoscale simulations)Ongoing work is to extend the period of analysis to the full ERA-Interim period, and to the rest of the extra-tropical region.
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide14
Conclusions
Mid-tropospheric regions of CSI have been shown to be very well spatially correlated with descending sting jets in mesoscale simulations of 3 sting jet storms (and are not present in a storm without a sting jet). A DSCAPE-based method to detect sting jet precursors has been developed and has started to give results.This method is being currently applied to the ECMWF reanalysis ERA-Interim.In the first 10 years of the dataset 8 out of 50 most intense cyclones show signs of mid-tropospheric CSI.
The occurrence of sting jets in these cyclones is still awaiting verification.
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide15
Other sting-jet presentations in EGU 2010
Sting jets in severe northern European wind storms: a case study of Windstorm Gudrun Laura Baker, Suzanne Gray, and Peter Clark NH1.7/AS4.10 Extreme events induced by extreme weather and climate change: Evaluation and forecasting of disaster risk and proactive planning Room 3 / Mon, 03 May, 9:00–09:15Idealised simulations of sting jet cyclones
Laura Baker, Suzanne Gray, and Peter Clark
AS1.1Dynamical Meteorology (General Session) Halls X/Y / Thu, 06 May, 08:00–19:30 XY13
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.ukSlide16
References
Baker, L., 2009: Sting jets in severe northern European wind storms. Weather, 64 (6), 143-148.Browning, K. A., 2004: The sting at the end of the tail: Damaging winds associated with extratropical cyclones. Q. J. R. Meteorol. Soc., 130, 375-399.
Clark, P. A., K. A. Browning and C. Wang, 2005: The sting jet at the end of the tail: Model diagnostics of fine-scale three-dimensional structure of the cloud head, Q. J. R.
Meteorol. Soc., 131, 2263-2292.
Martinez-Alvarado, O., F. Weidle and S. L. Gray, 2010: Robust characteristics of sting jets as simulated by two mesoscale models, Re-submitted to
Mon.
Wea
. Rev.
.
Parton, G. A., G. Vaughan, E. G. Norton, K. A. Browning and P. A. Clark, 2009: Wind profiler observations of a sting jet.
Q. J. R.
Meteorol. Soc., 135 (640), 663-680.Schultz, D. A. and P. N. Schumacher, 1999: The use and misuse of conditional symmetric instability. Mon. Wea. Rev., 127, 2709-2732.
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Sting-jet cyclones in ERA-Interim–
Contact: O.MartinezAlvarado@reading.ac.uk