1. ATM 421 Tropical Meteorology SPRING 2011

2. ATM 421 Tropical Meteorology SPRING 2011 CLASS# 9112 Instructor:Chris ThorncroftTA: Kyle Griffin Room:ES226ES218 Phone:518 442 4555 E-mail:chris@atmos.albany.edukg849786@albany.educhris@atmos.albany.edukg849786@albany.edu Time: TUES/THURS 1:15-2:35 Office Hours: THURS 2.40-3.40; or see me or e-mail me for an appointment Aim 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. Course Assessment: 1. Homework10% 2. Class exam on Thursday March 3 rd 25% 3. Class exam on Thursday April 14 th 25% 3. Final exam on Wednesday 11 th May 1.00pm-3.00pm40% Text Books: There is no recommended text book for this course.

3. ATM 421 Tropical Meteorology SPRING 2011 Lecture Plan: 1. Introduction 2. Tropical Convection 3. Large-scale Tropical Circulations 4. Easterly Waves 5. Tropical Cyclones 6. Equatorial Waves Dry spells Flooding: Ghana 07 Flooding: New Orleans 05

4. 1. INTRODUCTION Where are the tropics and what makes them special? Zonal and time mean circulations Asymmetric circulations

5. 2. TROPICAL CONVECTION Conditional Instability, CAPE, tephigrams Vertical profiles of conserved variables

6. 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.

7. 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 monsoons Theories for large-scale motion Emphasis given to West African Monsoon

8. 4. EASTERLY WAVES 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 (see next slides).

9. 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

10. 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.

26. 5. TROPICAL CYCLONES Observations and theory of tropical cyclones including issues that relate to genesis, structure and track

27. Key weather systems in the West African and Tropical Atlantic regions An ideal region to study scale interactions including how they impact downstream tropical cyclogenesis AEWs MCSs SAL TC 5. TROPICAL CYCLONES See: http://www.espo.nasa.gov/hs3/

28. 6. Equatorial Waves – e.g. Kelvin Waves 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). We will discuss their structure and theories for their existence and growth including how they interact with MCSs. cat3 convergence H L convection HL Solution of the shallow water model

29. Evolution of Kelvin wave Negative phase LH OLR (W/m 2 ) 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

30. Evolution of Kelvin wave Initiation phase L H OLR (W/m 2 ) 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

31. Evolution of Kelvin wave Active phase L H OLR (W/m 2 ) 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

32. Evolution of Kelvin wave Dissipation phase H OLR (W/m 2 ) 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

33. MCSs embedded in Kelvin wave envelops Brightness Temperature (K) Resolution spatial : 0.5° temporal : 3 hours

34. 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.