This is a course in the observations and underlying dynamics of large-scale tropical circulations. It forms the second part of a three course sequence on atmosphere-ocean interactions.

The course concentrates on:

• convection in the tropics and radiative convective equilibrium of the tropics
• the factors that determine regions of large scale persistent precipitation in the tropics,
• the thermal forcing of atmospheric circulations by precipitation in these regions, and
• the temporal variability of the forcing and response.

Examples of large scale convective forcing will be applied to zonally symmetric circulations (the Hadley circulation), to zonally asymmetric circulations (Walker circulation), to ENSO, and to monsoonal circulations.

TOPICS:

1. Kinematics

qe,s,h,h*, buoyancy.

Vertical Structure in disturbed and undisturbed regions.

Deep and shallow Convection.

How clouds affect the environment--cumulus parameterization.

2. Observations

SST, SLP, Precip.: Mean and annually varying.

Divergence: Mean and annually varying.

OLR: Mean and annually varying.

Surface Fluxes over the Ocean: Mean and annually varying.

Heat Transport by the Oceans and Surface Fluxes.

3. Wave Dynamics on a Equatorial b-plane

Single baroclinic mode (Matsuno).

Unbounded atmosphere (Lindzen)

Recent Results (Wu)

4. Thermal Forcing in the Tropics.

Gill Model.

Lindzen-Nigam Model.

The Reed-Recker Wave.

Adiabatic Compensation: Observations and dynamics.

5. Hadley Circulations.

Hyde's Theorem.

Role of Cumulus Friction.

Angular Momentum Conservation.

6. El Niño/Southern Oscillation.

Observations.

Current Theory.

Predictability.

7. Teleconnections to Higher Latitudes

8. Monsoonal Circulations.

Summer and Winter Monsoons.

9. Intraseasonal Variability.

30-60 day variability.

Reading List:

1. Kinematics

Sarachik, E.S., 1978: Tropical sea surface temperature: An inter-active one-dimensional atmosphere-ocean model, Dyn. Atmos.& Oceans., 2, 455-469.

Sarachik, E.S., 1985: A simple theory for the vertical structure of the tropical atmosphere, Pure and Appl. Geophys., 123, 261-271.

Yanai, M., S. Esbensen, and J-H Chu, 1973: Determination of bulk properties of tropical cloud clusters from large-scale heat and moisture budgets. J. Atmos. Sci., 30, 611-627.

2. Observations

Hastenrath, S., 1985: "Climate and Circulation of the Tropics". D.Reidel Publishing Co., 455pp.

Hastenrath, S., 1980: Heat budget of tropical ocean and atmosphere. J. Phys. Oceanogr., 10, 159-170.

Hastenrath, S., 1982: On meridional heat transports in the world ocean. J. Phys. Oceanogr., 12, 922-927.

Oberhuber, J.M., 1988: "An atlas based on the 'COADS' data set: The budgets of heat, buoyancy, and turbulent kinetic energy at the surface of the global ocean." Max-Planck-Institut für Meteor-ologie Report No. 15, Hamburg.

Oort, A.H., 1983: Global Atmospheric Circulation Statistics, 1958-1973. NOAA Professional Paper No. 14, 180 pp. + 47 microfiche.

Reynolds, R.W., 1982: A monthly averaged climatology of sea surface temperature. NOAA Technical Report NWS 31, 35pp.

Trenberth, K.E., D.P. Stepaniak, and J.M. Caron, 2000: The global monsoon as seen through the divergent atmospheric circulation. J. Climate, 13, 3969-3993.

Wright, P.B., 1988: "An atlas based on the 'COADS' data set: Fields of mean wind, cloudiness, and humidity at the surface of the global ocean." Max-Planck-Institut für Meteorologie Report No. 14, Hamburg.

3. Wave dynamics on an Equatorial Beta Plane

Lindzen, R.D., 1967: Planetary waves on beta planes. Mon. Wea. Rev., 95, 441-451.

Matsuno, T., 1966: Quasi-geostrophic motions in the equatorial area. J. Met. Soc. Japan, 44, 25-42.

4. Thermal Forcing in the Tropics.

Gill, A.E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Met. Soc., 106, 447-462.

Lindzen, R.S., and S. Nigam, 1987: On the role of sea surface temperature gradients in forcing low level winds and conver-gence in the trop-ics. J. Atmos. Sci., 44, 2440-2458.

Reed, R.J., and R.E. Recker, 1971: Structure and properties of synoptic-scale wave disturbances in the equatorial western Pacific. J. Atmos. Sci., 28, 1117-1133.

Wu, Z., E.S. Sarachik, and D.S. Battisti, 1999: Thermally forced surface winds on an equatorial beta-plane. J. Atmos. Sci., 56, 2029-2037.

5. Hadley Circulations.

Held, I.M., and A.Y. Hou, 1980: Nonlinear axially symmetric circu-lations in a nearly inviscid atmosphere. J. Atmos. Sci., 37, 515-533.

Schneider, E.K., and R.S. Lindzen, 1976. A discussion of the para-meterization of momentum exchange by cumulus convection. J. Geophys. Res., 81, 3158-3160.

Schneider, E.K., and R.S. Lindzen, 1977: Axially symmetric steady-state models of the basic state for instability and climate studies. Part I. Linearized calculations. J. Atmos. Sci., 34, 263-279.

Schneider, E.K., 1977: Axially symmetric steady-state models of the basic state for instability and climate studies. Part II. Nonlinear calculation. J. Atmos. Sci., 34, 280-296.

7. Teleconnections to Higher Latitudes

Alexander,M.A, Bladé, I., Newman,M., Lanzante, J. R, Lau, N.R-Cheung, Scott,J. D , 2002: The Atmospheric Bridge: The Influence of ENSO Teleconnections on Air–Sea Interaction over the Global Oceans. J.Climate, 15: 2205-2231

8. Monsoonal Circulations.

Fein, J.S., and P.L. Stephens, 1987: "Monsoons," Wiley-Inter-science, 632 pp.

9. Intraseasonal Variability.

Madden, R.A., and P.R. Julian, 1971: Detection of a 40-50 day oscillation in the zonal wind in the tropical Pacific. J. Atmos. Sci., 28, 702-708.

Madden, R.A., and P.R. Julian, 1972: Description of global scale circulation cells in the tropics with a 40-50 day period. J. Atmos. Sci., 29, 1109-1123.

Madden, R.A., and P.R. Julian, 1994: Observations of the 40-50-Day Tropical Oacillation—A Review. Mon. Wea. Rev., 122, 814-837.