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Waliser, DE, Somerville RCJ.  1994.  Preferred Latitudes of the Intertropical Convergence Zone. Journal of the Atmospheric Sciences. 51:1619-1639.   10.1175/1520-0469(1994)051<1619:plotic>2.0.co;2   AbstractWebsite

The latitude preference of the intertropical convergence zone (ITCZ) is examined on the basis of observations, theory, and a modeling analysis. Observations show that convection is enhanced at latitudes of about 4-degrees to 10-degrees relative to the equator, even in regions where the sea surface temperature (SST) is maximum on the equator. Both linear shallow-water theory and a moist primitive equation model suggest a new explanation for the off-equatorial latitude preference of the ITCZ that requires neither the existence of zonally propagating disturbances nor an off-equatorial maximum in SST. The shallow-water theory indicates that a finite-width, zonally oriented, midtropospheric heat source (i.e., an ITCZ) produces the greatest local low-level convergence when placed a finite distance away from the equator. This result suggests that an ITCZ is most likely to be supported via low-level convergence of moist energy when located at these ''preferred'' latitudes away from die equator. For a plausible range of heating widths and damping parameters, the theoretically predicted latitude is approximately equal to the observed position(s) of the ITCZ(s). Analysis with an axially symmetric, moist, primitive equation model indicates that when the latent heating field is allowed to be determined internally, a positive feedback develops between the midtropospheric latent heating and the low-level convergence, with the effect of enhancing the organization of convection at latitudes of about 4-degrees to 12-degrees. Numerical experiments show that 1) two peaks in convective precipitation develop straddling the equator when the SST maximum is located on the equator; 2) steady ITCZ-like structures form only when the SST maximum is located away from the equator; and 3) peaks in convection can develop away from the maximum in SST, with a particular preference for latitudes of about 4-degrees to 12-degrees-, even in the (''cold'') hemisphere without the SST maximum. The relationship between this mechanism and earlier theories is discussed, as are implications for the coupled ocean-atmosphere system and the roles played by midlevel latent heating and SST gradients in forcing the low-level atmospheric circulation in the tropics.

Walsh, J, Wuebbles D, Hayhoe K, Kossin JP, Kunkel K, Stephens GL, Thorne PD, Vose RS, Wehner B, Willis J, Anderson D, Kharin V, Knutson T, Landerer FW, Lenton TM, Kennedy JJ, Somerville R.  2014.  Appendix 3: Climate Science Supplement. Climate Change Impacts in the United States: The Third National Climate Assessment. ( Mellilo JM, Richmond T(TC), Yohe GW, Eds.).:735-789.: U.S. Global Change Research Program   10.7930/J0KS6PHH   Abstract

This appendix provides further information and discussion on climate science beyond that presented in Ch. 2: Our Changing Climate. Like the chapter, the appendix focuses on the observations, model simulations, and other analyses that explain what is happening to climate at the national and global scales, why these changes are occurring, and how climate is projected to change throughout this century. In the appendix, however, more information is provided on attribution, spatial and temporal detail, and physical mechanisms than could be covered within the length constraints of the main chapter.

Walsh, J, Wuebbles D, Hayhoe K, Kossin JP, Kunkel K, Stephens GL, Thorne PD, Vose RS, Wehner B, Willis J, Anderson D, Doney S, Feeley R, Hennon PA, Kharin V, Knutson T, Landerer FW, Lenton TM, Kennedy JJ, Somerville R.  2014.  Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The Third National Climate Assessment. ( Mellilo JM, Richmond T(TC), Yohe GW, Eds.).:19-67.: U.S. Global Change Research Program   10.7930/J0KW5CXT   Abstract

This chapter summarizes how climate is changing, why it is changing, and what is projected for the future. While the focus is on changes in the United States, the need to provide context sometimes requires a broader geographical perspective. Additional geographic detail is presented in the regional chapters of this report. Further details on the topics covered by this chapter are provided in the Climate Science Supplement and Frequently Asked Questions Appendices.

Walsh, J, Wuebbles D, Hayhoe K, Kossin JP, Kunkel K, Stephens GL, Thorne PD, Vose RS, Wehner B, Willis J, Anderson D, Kharin V, Knutson T, Landerer FW, Lenton TM, Kennedy JJ, Somerville R.  2014.  Appendix 4: Frequently Asked Questions (Question E). Climate Change Impacts in the United States: The Third National Climate Assessment. ( Mellilo JM, Richmond T(TC), Yohe GW, Eds.).:790-820.: U.S. Global Change Research Program   10.7930/J0G15XS3   Abstract

E. Is it getting warmer at the same rate everywhere? Will the warming continue?Temperatures are not increasing at the same rate everywhere, because temperature changes in a given location depend on many factors. However, average global temperatures are projected to continue increasing throughout the remainder of this century due to heat-trapping gas emissions from human activities.

Willis, GE, Deardorff JW, Somerville RCJ.  1972.  Roll-diameter dependence in Rayleigh convection and its effect upon the heat flux. Journal of Fluid Mechanics. 54:351-367.   10.1017/S0022112072000722   Abstract

The average roll diameter in Rayleigh convection for 2000 < R < 31000, where R is the Rayleigh number, has been measured from photographs of three convecting fluids: air, water and a silicone oil with a Prandtl number σ of 450. For air the average dimensionless roll diameter was found to depend uniquely upon R and to increase especially rapidly in the range 2000 < R < 8000. The fluids of larger σ exhibited strong hysteresis but also had average roll diameters tending to increase with R. The increase in average roll diameter with R tended to decrease with σ. Through use of two-dimensional numerical integrations for the case of air it was found that the increase in average roll diameter with R provides an explanation for the usual discrepancy in heat flux observed between experiment and two-dimensional numerical calculations which prescribe a fixed wavelength.