ATM 521 Tropical Meteorology FALL 2011

ATM 521 Tropical Meteorology FALL 2011 CLASS# 9070

Instructor: Chris Thorncroft Time: MON/WED 12:35-1:55 Room: ES B13 Grading: GradedPhone: 518 442 4555E-mail: chris@atmos.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

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 Oct 19th 25%3. Class paper due Wednesday Nov 16th 20%3. Final exam on Wednesday 9th Dec 10.30pm-12.30pm 40%

Text Books:There is no recommended text book for this course.

ATM 521 Tropical Meteorology FALL 2011 CLASS# 9070

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!)

See also:

ATM529 Atmosphere-Ocean Interaction Spring 2012Seminar class on Hurricanes Spring 2012 (Kristen

Corbosiero)

ATM 521 Tropical Meteorology FALL 2011

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

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.

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.

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.

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

FIELD CAMPAIGN IN WEST AFRICA: AMMA

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

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.