Kyle Petrosky Physics major

1. Kyle Petrosky Physics major • Effect of Deep Convection on the Regulation of Tropical Sea Surface Temperature • By John M. Wallace (1992) • Formation and Limiting Mechanisms for Very High Sea surface Temperature: Linking the Dynamics and the Thermodynamics • By Duane E. Waliser (1996)

2. Importance of SST • Most of the Earth is covered in water and the heat capacity of the ocean is much greater than the heat capacity of land • In order to understand or attempt to predict climate change it is incredibly important to first attempt to understand the mechanisms which provide an upper limit to SSTs. • Also increased knowledge of the mechanisms and lifespan of hot spots on the oceans surface could help greatly in understanding and predicting hurricanes (especially true for tropical regions)

3. Background • 1979 - Peter Newell directly attempts to understand the mechanisms that provide the upper limit on sea surface temperatures factoring in constant clear skies and fixed tropical values for air temperature (27°C), relative humidity (70%), and wind speed (3m/s). • He also included equations for the net longwave, evaporative, and sensible heat loses as functions of SST. • Concluded that evaporation was the primary mechanism that limited climatological SST to about 30°C • 1987 – Graham and Barnett modify Newell’s thesis based on their analysis of the relationship between deep convection and SST. • They found that with SST above 26°Cthere was a rapid increase in the intensity and frequency of deep convection. • Tropical deep convection is accompanied by approximately 30% cloud cover. • After factoring the increased albedo into Newell's model the new energy budget balance the SST cap at 28°C which was in accordance with data.

4. Background • 1991 – Ramanathan and Collins hypothesized that solar shielding from highly reflective cirrus clouds was the primary limiting mechanism on SST. • Super greenhouse effect limits the effectiveness of evaporation as a limiting mechanism • Water vapor is imported into warmest ocean areas and evaporation rates are actually quite low in these areas • This hypothesis was highly criticized for over simplifying three dimensional circulation and dynamics.

5. Problems • Virtually all studies ignored ocean processes • Most studies on the subject had limited applicability due to the localization of the study • Studies which were not localized were not grounded in reliable data but rather in models and satellite pictures. They also fail to address circulation.

6. Waliser (1996) Purpose Determine the spatial and temporal variability of very high tropical SSTs Investigate the mechanisms leading to suppressed convective conditions, and thus the formation of very high SSTs Access the relative roles of evaporation versus cloud forcing in limiting SST Examine the coupling between local and remote forcing in both the production and subsequent cooling of high SST Examine the evolution of the near-surface ocean circulation during the formation and decay of very high SST Use as much actual data as possible

7. Data / Methods Determined to rectify previous mistakes by incorporating as much data as possible into the study. Also determined only to use satellite data when applicable. 2 part analysis procedure Identify hot spots in the SST record 2) Composite geophysical conditions associated with the evolution of these hot spots

8. I apologize but they used an obscene amount of data and figures . . .I promise this is just as exciting for me as it is for you . . .

9. Hot spots and temperatures in Pacific and Indian ocean Most directly above Australia or below India

10. Western Pacific Ocean provides more than its fair share of the global hotspots and on a more consistent basis. Also ENSO contributes toward the number of hot spots and greatly increases their duration

11. Thermal contour maps showing a hot spot a month before, during, and a month following its formation in the Western Pacific Ocean

12. Same except graphing surface Wind speed instead of SST

13. Same with Surface shortwave radiation

14. Same except outgoing longwave radiation

15. Different area, Same idea with relative humidity.

19. Results summary • La Nina tends to inhibit hot spot formation, especially in the pacific warm pool • El Nino conditions favor hot spot formation, especially in the pacific warm pool • Typical lifetime of a hot spot is about a month with multiple lasting longer than 2-3 months and very few longer than 3 months • Failed to address Ocean mechanisms

20. SST/Deep Convection • Deep convection over the Indian ocean tends to coincide with the formation of hot spots in the Western pacific coinciding with the Madden-Julian Oscillation • Directly above the hot spot formation deep convection appears to be out of phase • Telecommunication problem

21. Own thoughts • While the data presented in this study was formidable Waliser ended up localizing his study to the western pacific which directly went against his goals. • In order for the applicability of this study to increase a localized study in need focusing on the Indian ocean as well as the Western Atlantic • Telecommunication is almost insurmountable.

22. Questions?