WV images, Potential Vorticity and
Conceptual Models
Nuno Moreira ([email protected])
Instituto de Meteorologia, Lisboa, Portugal
2003
W V images - Characteristics
 Water Vapour absorption band : 6 - 7 m
– WV Meteosat channel
– WV 6.2 (5.35 - 7.15 m ) from MSG
– WV 7.3 (6.85 – 7.85 m ) from MSG

Water vapour absorbes Infra-Red radiation
emmited by the earth surface and lower clouds

WV image is “constructed” from the re-emission
by water vapour
W V images - Characteristics

“The instrument measures the humidity
temperature”

“Topography of water vapour emission”

Gray shades
– Light gray – humidity in the troposphere upper levels
– Dark gray - humidity in the troposphere lower levels
Regions of emission



R.H. =100% -> 250 hPa - 550 hPa
(max: 350 hPa)
R.H. = 50% -> 250 hPa - 600 hPa
(max: 400 hPa)
R.H, = 25% -> 250 hPa - 700 hPa
(max: 450 hPa)
(Bader et al, 1995)
Regions of emission

Bader et al
(1995)
Water Content in the
troposphere

48.7 % of total water content – below 850hPa

77.5% of total water content - below 700hPa

92.5% of total water content - below 550hPa
(NOAA, 1991)
W V Image
and tropospheric levels

Light areas – white / light gray
– Humidity in upper levels
– Medium and lower levels ?

Dark areas – black/ dark gray
– Low humidty in upper levels
– Higher humidity content in medium levels
– Lower levels ?
And a Water Vapour Image ...
… filter in “whiter shading”
Fenomena retrieved from
water vapour imagery
Tropopause folding
 Jet streams/streaks
 Vorticity Advection
 Rapid cyclogenesis (bombs) (?)
 Troughs and ridges in upper levels
 Cut-off lows

Related meteorological
parameters




Geopotential (eg. 300 hPa)
Wind field (eg. 300 hPa)
Potencial Vorticity
Tropopause Map
Potential Vorticity

Potential Vorticidade in isentropic levels
(constant potential temperature  )

    
VPI  g  f  k    v    
  p 

Absolute Vorticity (planetary + relative) and
static stability

Tropospheric air mass – low (I)PV
Stratospheric air mass – high (I)PV

Potential Vorticity

Dynamic Tropopause = 1.5 <-> 3.0 UVP
1UVP  106 m2s 1K Kg 1 

Advantages of Isentropic Potential Vorticity (IPV)
– Conservative property over a conservative surface
– Superposition with wind field depicts temporal
evolution of Potential Vorticity

However, PV can also be depicted in pressure levels !!
Tropopause Map




Topography of the Tropopause (isentropic
coordenates, isobaric, geopotencial)
low 
high 
-> low Tropopause
-> high Tropopause
Advantage
– Quantifies lowest tropopause level
PV ----> Tropopause Map
Conceptual Models
Jet Stream
The definiton …

Jet stream
– Upper Tropospheric wind speed > 60 kt

Jet streak (= Jet Stream maximum)
– “wind speed maximum situated along the axis of a jet
stream at the level of maximum wind”
(Palmén and Newton, 1969)
Jet Stream – vertical section

Keyser
and
Shapiro
(1986)
Jet Stream – vertical section

Holton
(1992)
Jet Stream – vertical section

Met.
Office
(1997)
Jet  Relative Vorticity
North H.:
cyclonic side
– Positive
Relative
Vorticity
South H. :
cyclonic side
– Negative
Relative
Vorticity

“Manual of Synoptic Satellite Meteorology–Conceptual
Models, v3.0”, ZAMG/KNMI/FMI/EUMETSAT
Jet  Vorticity advections
PVA- Positive
Vorticity
Advection
NVA - Negative
Vorticity
Advection

“Manual of Synoptic Satellite Meteorology–Conceptual
Models v3.0”, ZAMG/KNMI/FMI/EUMETSAT
Jet  Ageostrophic Wind  Vertical motion

1 d 
Vag  k  Vg 
f
dt

Keyser and Shapiro (1986)
Jets and Fronts

Bluestein
(1993)
Conceptual Models
Tropopause Foldings
Cut-off lows

Elizaga
et al
(1996)
Lowering Tropopause
----> Vertical Motion
Tropopause
Div Q
Elbern et al
(1998)
15Oct93

Lowering Tropopause
----> Vertical Motion
00 UTC Ertel Potential Vorticidade 250 hPa
12 UTC –
Q-G Forcing
Water Vapour
Convergence

Romero (2000)
28 Sep 94
Conceptual Models
(rapid) Cyclogenesis
Hoskins et al (1985)
Boyle and Bosart (1986)
Hirschberg and Fritsch (1991)
And ...

Malardel (2000)
.. Related NEW proposed
symbols ..

Adapted from Joly and Santurette (2000)
References










Bader, M.J., Forbes, G.S., Grant, J.R., Lilley, R.B. e Waters, A.J., 1995: Images in weather forecasting. Cambridge University Press,
Cambridge, 499 pp.
Bechtold, P., 2000: Atmospheric moist convection: effects, concepts and modelling/forecast. Módulo do Curso “Weather forecasting in
the midlatitudes” realizado na MeteoFrance de 4-15 Dezembro 2000 [ver relatório VAP01/01, Instituto de Meteorologia]
Bluestein, H.B., 1993: Synoptic-Dynamic Meteorology in Midlatitudes, Vol.II: Observations and Theory of Weather Systems. Oxford
University Press, Oxford, 594 pp.
Boyle, J.S. e Bosart, L.F., 1986: Cyclone-Anticyclone couplets over North America. Part II: Analysis of a major cyclone event over the
Eastern United States. Mon. Wea. Rev., 114, 2432-2465.
Elbern, H., Hendricks, J. e Ebel, A., 1998: A climatology of tropopause folds by global analysis. Theor. Appl. Climatology, 59, 181-200.
Elizaga, F., Martin, F., Riosalido R., Carretero, O., Elvira, B. e Garcia, A., 1996: Imágenes de vapor de agua: uso en el diagnostico de
niveles altos. IV Simposio Nacional de Predección. Memorial “Alfondo Ascaso”, Madrid, 15-19 Abril 1996, INM.
Grahame, N., 1998: Christmas Eve storm. Review of interesting synoptic cases. Fourth Meeting of the Working Group on Cooperation
between European Forecasters (WG CEF). Set. 98 Comunicação oral.
Hirschberg, P.A. e Fritsch, J.M., 1991b: Tropopause ondulations and the development of extratropical cyclones - Part II: Diagnostic
Analysis and coceptual model. Mon. Wea. Rev., 119, 518-550.
Hoskins, B.J., McIntyre, M.E. e Robertson, A.W., 1985: On the use and significance of isentropic potencial vorticity maps. Quart. J. Roy.
Meteo. Soc., 111, 877-946.
Joly, A e Santurette, P., 2000: Turning dynamical ideas into forecast practice: a proposal for a renewed graphic summary of the
synoptic scale situation. Centre National de Recherches Météorologiques, Service Central d´Exploitation Météorologique. Módulo do
Curso “Weather forecasting in the midlatitudes” realizado na MeteoFrance de 4-15 Dezembro 2000 [ver relatório VAP01/01, Instituto
de Meteorologia]
References









Keyser, D. e Shapiro, M.A., 1986: Review – A review of the structure and dynamics of upper-level frontal zones. Mon. Wea. Rev., 114,
452-499.
Malardel, S., 2000: Weather forecasting in midlatitudes regions - Large scale dynamics in the midlatitudes. Módulo do Curso “Weather
forecasting in the midlatitudes” realizado na MeteoFrance de 4-15 Dezembro 2000 [ver relatório VAP01/01, Instituto de Meteorologia]
Moreira, N., 1999: Utilização de imagens de vapor de água na avaliação de campos previstos por Modelos numéricos. Instituto de
Meteorologia.
Morgan,M.C. e Nielson-Gammon, 1998: Using tropopause maps to diagnose midlatitude weather systems. Mon. Wea. Rev., 126, 25552579.
NOAA, 1991: Water vapor imagery – Interpretation and applications to weather analysis and forecasting. NOAA Technical report
NESDIS 57, National Oceanic and Atmospheric Admnistration, Washington, 213 pp.
Prates, F., 1996: Utilização de cartas de vorticidade potencial isentrópica no diagnóstico dos processos de ciclogénese. Nota Técnica.
Instituto de Meteorologia.
Romero, R., 2000: Sensitivity of a heavy rain producing Western Mediterranean cyclone to embedded potencial vorticity anomalies.
Submetido ao Quarterly Journal of the Royal Meteorological Society.
Santurette, P., 1998: About new products and new methods for synoptic forecast in Meteo-France. Casos de estudo apresentados no
curso sobre previsão na Meteo-France, Dez. 98. Comunicação oral.
ZAMG/KNMI/FMI/EUMETSAT, 2001: Manual of Synoptic Satellite Meteorology – Conceptual Models v3.0.