1. ATM 521 Tropical Meteorology SPRING 2015

2. ATM 521 Tropical Meteorology SPRING 2015 CLASS# 9825 Instructor:Chris ThorncroftTime: TUES/THURS 11:45-1:05 Room:ES B13Grading: Graded Phone:518 442 4555 E-mail:cthorncroft@albany.educthorncroft@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. Homework15% 2. Class exam on Wednesday Mar 10 th 25% 3. Class paper due Wednesday May 5 th 20% 3. Final exam on Friday May 8 th 8.30am-10.30am40% Text Books: There is no recommended text book for this course.

3. ATM 521 Tropical Meteorology Sprimg 2015 CLASS# 9825 Relationship to other Graduate Courses dealing with the Tropics: ATM522 Climate Variability and PredictabilityInterannual-to-Multidecadal ATM523 Large-Scale Dynamics of the Tropics:Synoptic-to-Interannual ATM521 Tropical MeteorologyMesoscale-to-Synoptic (Weather!) ATM527 Observations and Theory of Tropical CyclonesTropical Cyclones

4. 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

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

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

7. 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.

8. 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 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? MESOSCALE CONVECTIVE SYSTEMS

9. 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

10. 4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS Emphasis given to: Easterly Waves Convectively Coupled Kelvin Waves

11. 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.

12. 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

13. 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.

29. 4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS Different Approaches to Develop Understanding: Observations Theory Modeling (Modeling, NWP, Climate Modeling, Cloud-Resolving)

30. 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 HL Solution of the shallow water model 4. SYNOPTIC WEATHER SYSTEMS IN THE TROPICS

31. 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

32. 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

33. 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

34. 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

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

36. FIELD CAMPAIGN IN WEST AFRICA: AMMA

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

38. 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

39. 5. TROPICAL CYCLONES: FIELD CAMPAIGNS See: http://www.espo.nasa.gov/hs3/

40. 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?