Transcript Kyle Petrosky Physics major

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)
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)
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°C there 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.
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.
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.
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
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
1) Identify hot spots in the SST record
2) 2) Composite geophysical conditions associated with the evolution of these hot spots
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 . . .
HOT SPOTS AND TEMPERATURES IN
PACIFIC AND INDIAN OCEAN
Most directly above Australia or below India
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
Thermal contour
maps showing a
hot spot a month
before, during, and
a month following
its formation in the
Western Pacific
Ocean
Same except
graphing surface
Wind speed
instead of SST
Same with Surface
shortwave
radiation
Same except
outgoing longwave
radiation
Different area, Same idea with relative humidity.
RESULTS SUMMARY
1) La Nina tends to inhibit hot spot formation, especially in
the pacific warm pool
2) El Nino conditions favor hot spot formation, especially in
the pacific warm pool
3) 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
4) Failed to address Ocean mechanisms
SST/DEEP
CONVECTION
1) 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
2) Directly above the hot spot formation deep convection
appears to be out of phase
3) Telecommunication problem
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.
QUESTIONS?