atm 521 tropical meteorology spring 2015. atm 521 tropical meteorology spring 2015 class# 9825...
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ATM 521 Tropical Meteorology SPRING 2015 CLASS# 9825
Instructor: Chris Thorncroft Time: TUES/THURS 11:45-1:05 Room: ES B13 Grading: GradedPhone: 518 442 4555E-mail: [email protected] 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
tropicalclimate, including emphasis on the interactions between dynamics and convection. To highlight unanswered scientific questions and key research areas.
Course Assessment:1. Homework 15%2. Class exam on Wednesday Mar 10th 25%3. Class paper due Wednesday May 5th 20%3. Final exam on Friday May 8th 8.30am-10.30am 40%
Text Books:There is no recommended text book for this course.
ATM 521 Tropical Meteorology Sprimg 2015 CLASS# 9825
Relationship to other Graduate Courses dealing with the Tropics:
ATM522 Climate Variability and Predictability Interannual-to-MultidecadalATM523 Large-Scale Dynamics of the Tropics: Synoptic-to-InterannualATM521 Tropical Meteorology Mesoscale-to-Synoptic (Weather!)ATM527 Observations and Theory of Tropical Cyclones Tropical Cyclones
ATM 521 Tropical Meteorology SPRING 2015
Lecture Plan:
1. Introduction 2. Tropical Convection3. Large-scale Tropical Circulations4. Synoptic Weather Systems in the Tropics5. 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 circulationsAsymmetric circulations
2. TROPICAL CONVECTION
Conditional Instability, CAPE, tephigramsVertical 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.
TRMM based MCS climatology over Africa and tropical Atlantic for June-July-August
Rainfall Stratiform Rain Fraction
Percentage of MCSs with significant ice scattering
Average Lightning flash density
Schumacher and Houze (2006) QJRMS :Less stratiform rain over sub-Saharan Africa than Atlanticbut, 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?
MESOSCALE CONVECTIVE SYSTEMS
Cold Tongue
AEJ
SAL
ITCZ
Heat Low
Key features of the West African Monsoon Climate System during Boreal summer
3 LARGE-SCALE TROPICAL CIRCULATIONS
Observations and theory of monsoonsTheories for large-scale motionEmphasis given to West African Monsoon
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 Africa-Atlantic 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.
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.
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.
4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS
Different Approaches to Develop Understanding:
Observations
Theory
Modeling (Modeling, NWP, Climate Modeling, Cloud-Resolving)
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.
cat3
convergence
H L
convection
H L
Solution of the shallow water model
4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS
Evolution of Kelvin waveNegative phase
L H
OLR (W/m2)Shading: min convection max convection
Wind at 850 hPa (m/s)Vectors, significant at the T-test 99% level
Surface Pressure (Pa) Contours dashed: low L continue: high H
Evolution of Kelvin waveInitiation phase
L H
OLR (W/m2)Shading: min convection max convection
Wind at 850 hPa (m/s)Vectors, significant at the T-test 99% level
Surface Pressure (Pa) Contours dashed: low L continue: high H
Evolution of Kelvin waveActive phase
L
H
OLR (W/m2)Shading: min convection max convection
Wind at 850 hPa (m/s)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: min convection max convection
Wind at 850 hPa (m/s)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
5. TROPICAL CYCLONES
Observations and theory of tropical cyclones including issues that relate to genesis, structure and track.
Synoptic weather systems can influence tropical cyclogenesis – the role of Easterly waves and Kelvin waves will be discussed
AEWs
MCSs
SAL
TC
5. TROPICAL CYCLONES
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?