ATM 521 Tropical Meteorology SPRING 2015
ATM 521 Tropical Meteorology
SPRING 2015 CLASS# 9825
Instructor:
Room:
Phone:
E-mail:
Time: TUES/THURS 11:45-1:05
Grading: Graded
Chris Thorncroft
ES B13
518 442 4555
cthorncroft@albany.edu
Office Hours: MON 2.00-3.00 or see me or e-mail me for an appointment
Aims of Course:
To describe and understand the nature of tropical weather systems and their role in the tropical
climate, including emphasis on the interactions between dynamics and convection.
To highlight unanswered scientific questions and key research areas.
Course Assessment:
1. Homework
2. Class exam on Wednesday Mar 10th
3. Class paper due Wednesday May 5th
3. Final exam on Friday May 8th 8.30am-10.30am
Text Books:
There is no recommended text book for this course.
15%
25%
20%
40%
ATM 521 Tropical Meteorology
Sprimg 2015 CLASS# 9825
Relationship to other Graduate Courses dealing with the Tropics:
ATM522 Climate Variability and Predictability
ATM523 Large-Scale Dynamics of the Tropics:
ATM521 Tropical Meteorology
ATM527 Observations and Theory of Tropical Cyclones
Interannual-to-Multidecadal
Synoptic-to-Interannual
Mesoscale-to-Synoptic (Weather!)
Tropical Cyclones
ATM 521 Tropical Meteorology
SPRING 2015
Lecture Plan:
1. Introduction
2. Tropical Convection
3. Large-scale Tropical Circulations
4. Synoptic Weather Systems in the Tropics
5. Tropical Cyclones
Dry spells
Flooding: Ghana 07
Flooding: New Orleans 05
1. INTRODUCTION
Where are the tropics and what makes them special?
Zonal and time mean circulations
Asymmetric circulations
2. TROPICAL CONVECTION
Conditional Instability, CAPE, tephigrams
Vertical profiles of conserved variables
MESOSCALE CONVECTIVE SYSTEMS
Structure, propagation and longevity issues will be discussed as well as their
impact on larger scales.
See Houze, R. A., Jr., 2004: Mesocale convective systems Rev. Geophys., 42,
10.1029/2004RG000150, 43 pp.
MESOSCALE CONVECTIVE SYSTEMS
TRMM based MCS climatology over Africa and tropical Atlantic for June-July-August
Rainfall
Percentage of MCSs with
significant ice scattering
Stratiform Rain Fraction
Average Lightning flash density
Schumacher and Houze (2006) QJRMS :
Less stratiform rain over sub-Saharan Africa than Atlantic
but, Stratiform rain increases in monsoon season compared to pre-monsoon season due
to (i) reduced upper-level shear?, (ii) reduced impact of dry SAL?, (iii) other?
3 LARGE-SCALE TROPICAL CIRCULATIONS
Key features of the West
African Monsoon
Climate System during
Boreal summer
Heat
Low
SAL
AEJ
ITCZ
Observations and theory of monsoons
Theories for large-scale motion
Emphasis given to West African Monsoon
Cold
Tongue
4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS
Emphasis given to:
Easterly Waves
Convectively Coupled Kelvin Waves
4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS
Easterly waves are the dominant synoptic weather system in the AfricaAtlantic sector but they also exist in other basins (e.g. Pacific)
We will discuss their structure and theories for their existence and growth
including how they interact with MCSs.
We will also discuss their variability.
Diagnostics for highlighting multi-scale aspects of AEWs
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
315K Potential Vorticity (Coloured contours every 0.1PVU greater than 0.1 PVU)
with 700hPa trough lines and easterly jet axes from the GFS analysis (1 degree
resolution), overlaid on METEOSAT-7 IR imagery.
4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS
Different Approaches to Develop Understanding:
Observations
Theory
Modeling (Modeling, NWP, Climate Modeling, Cloud-Resolving)
4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS
H
H
L
L
cat3
convergence
convection
Solution of the shallow water model
Kelvin waves are the dominant synoptic weather system in the equatorial Africa
sector in Spring but they also exist in other basins (e.g. Pacific, Amazon) and
seasons.
We will discuss their structure and theories for their existence and growth including
how they interact with MCSs and EWs.
Evolution of Kelvin wave
Negative phase
L
OLR (W/m2)
Shading:
Wind at 850 hPa (m/s)
min convection
max convection
Vectors, significant at
the T-test 99% level
H
Surface Pressure (Pa)
Contours dashed: low L
continue: high H
Evolution of Kelvin wave
Initiation phase
L
OLR (W/m2)
Shading:
Wind at 850 hPa (m/s)
min convection
max convection
Vectors, significant at
the T-test 99% level
H
Surface Pressure (Pa)
Contours dashed: low L
continue: high H
Evolution of Kelvin wave
Active phase
L
H
OLR (W/m2)
Shading:
Wind at 850 hPa (m/s)
min convection
max convection
Vectors, significant at
the T-test 99% level
Surface Pressure (Pa)
Contours dashed: low L
continue: high H
Evolution of Kelvin wave
Dissipation phase
H
OLR (W/m2)
Shading:
Wind at 850 hPa (m/s)
min convection
max convection
Vectors, significant at
the T-test 99% level
Surface Pressure (Pa)
Contours dashed: low L
continue: high H
MCSs
embedded in
Kelvin wave
envelops
Brightness Temperature (K)
Resolution
spatial : 0.5°
temporal : 3 hours
FIELD CAMPAIGN IN WEST AFRICA: AMMA
5. TROPICAL CYCLONES
Observations and theory of tropical cyclones
including issues that relate to genesis, structure and
track.
5. TROPICAL CYCLONES
Synoptic weather systems can influence tropical cyclogenesis – the role of Easterly
waves and Kelvin waves will be discussed
SAL
TC
AEWs
MCSs
5. TROPICAL CYCLONES: FIELD CAMPAIGNS
See: http://www.espo.nasa.gov/hs3/
FINAL OVERVIEW COMMENTS
The course is fundamentally about the interactions between dynamics
and convection, combining observations, modeling and theory.
Ultimately a major motivation for research in this area is to improve our
ability to predict tropical convection (over a range of space and
timescales). This remains a major challenge and MUCH remains to be
learned.
While the emphasis here is given to weather systems, a worthy study in
its own right, one should always recall that climate is the sum of the
weather systems and that models used to predict climate must be able
to represent the impacts of weather.
ANY REQUESTS?