Subseasonal Variability of the Southeast Pacific Stratus Cloud Deck

Haiming Xu International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii

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Shang-Ping Xie International Pacific Research Center, and Department of Meteorology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii

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Yuqing Wang International Pacific Research Center, and Department of Meteorology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii

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Abstract

Subseasonal variability of the stratus/stratocumulus cloud deck over the subtropical southeast Pacific is studied using satellite and buoy observations as well as the NCEP–NCAR reanalysis. It is found that subseasonal variability in the stratus cloud deck is closely related to variations in surface wind velocity, water vapor, sea level pressure, and 500-hPa geopotential height. An increase in cloud liquid water (CLW) over the subtropical southeast Pacific is found to be associated with the development of an anomalous anticyclonic circulation to the south off the west coast of Chile. The enhanced southerly to southeasterly winds advect cold and dry air into the stratus region against the mean sea surface temperature (SST) gradient. This cold and dry advection, together with increased wind speed, intensifies surface latent and sensible heat fluxes and destabilizes the boundary layer. Anomalous offshore easterlies north of the anomalous anticyclone cause a low-level divergence. The associated subsidence warming, together with the cold advection in the surface layer, strengthens the temperature inversion, conducive to the development of stratus clouds. Buoy observations confirm this subseasonal cloud variability and its relationship with surface meteorological variables.

A lead/lag composite analysis indicates that circulation variables such as sea level pressure and surface wind lead cloud liquid water by 1–2 days while SST lags CLW by 1–2 days, suggesting that low-cloud variability is caused by atmospheric circulation changes rather than by the underlying ocean. The dynamic adjustment that leads to cloud fluctuations and possible orographic effects of the Andes are also discussed.

Corresponding author address: Dr. Haiming Xu, International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 2525 Correa Road, Honolulu, HI 96822. Email: hxu@hawaii.edu

Abstract

Subseasonal variability of the stratus/stratocumulus cloud deck over the subtropical southeast Pacific is studied using satellite and buoy observations as well as the NCEP–NCAR reanalysis. It is found that subseasonal variability in the stratus cloud deck is closely related to variations in surface wind velocity, water vapor, sea level pressure, and 500-hPa geopotential height. An increase in cloud liquid water (CLW) over the subtropical southeast Pacific is found to be associated with the development of an anomalous anticyclonic circulation to the south off the west coast of Chile. The enhanced southerly to southeasterly winds advect cold and dry air into the stratus region against the mean sea surface temperature (SST) gradient. This cold and dry advection, together with increased wind speed, intensifies surface latent and sensible heat fluxes and destabilizes the boundary layer. Anomalous offshore easterlies north of the anomalous anticyclone cause a low-level divergence. The associated subsidence warming, together with the cold advection in the surface layer, strengthens the temperature inversion, conducive to the development of stratus clouds. Buoy observations confirm this subseasonal cloud variability and its relationship with surface meteorological variables.

A lead/lag composite analysis indicates that circulation variables such as sea level pressure and surface wind lead cloud liquid water by 1–2 days while SST lags CLW by 1–2 days, suggesting that low-cloud variability is caused by atmospheric circulation changes rather than by the underlying ocean. The dynamic adjustment that leads to cloud fluctuations and possible orographic effects of the Andes are also discussed.

Corresponding author address: Dr. Haiming Xu, International Pacific Research Center, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 2525 Correa Road, Honolulu, HI 96822. Email: hxu@hawaii.edu

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  • Albrecht, B. A., 1981: Parameterization of trade–cumulus cloud amount. J. Atmos. Sci., 38 , 97105.

  • Albrecht, B. A., D. A. Randall, and S. Nicholls, 1988: Observations of marine stratocumulus during FIRE. Bull. Amer. Meteor. Soc., 69 , 618626.

    • Search Google Scholar
    • Export Citation
  • Ambrizzi, T., B. J. Hoskins, and H-H. Hsu, 1995: Rossby wave propagation and teleconnection patterns in the austral winter. J. Atmos. Sci., 52 , 36613672.

    • Search Google Scholar
    • Export Citation
  • Berbery, E. H., J. Nogues-Paegle, and J. D. Horel, 1992: Wavelike Southern Hemisphere extratropical teleconnections. J. Atmos. Sci., 49 , 155177.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., 1990: The diurnal variation of California coastal stratocumulus from two days of boundary layer soundings. Tellus, 42A , 302304.

    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S., E. Klinker, A. K. Betts, and J. Coakley, 1995: Comparison of ceilometer, satellite, and synoptic measurements of boundary layer cloudiness and the ECMWF diagnostic cloud parameterization scheme during ASTEX. J. Atmos. Sci., 52 , 27362751.

    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S., and Coauthors, 2004: The EPIC 2001 stratocumulus study. Bull. Amer. Meteor. Soc., 85 , 967977.

  • Del Genio, A. D., M-S. Yao, W. Kovari, and K. K. W. Lo, 1996: A prognostic cloud water parameterization for global climate models. J. Climate, 9 , 270304.

    • Search Google Scholar
    • Export Citation
  • Garreaud, R. D., and J. Rutllant, 2003: Coastal lows along the subtropical west coast of South America: Numerical simulation of a typical case. Mon. Wea. Rev., 131 , 891908.

    • Search Google Scholar
    • Export Citation
  • Garreaud, R. D., J. Rutllant, and H. Fuenzalida, 2002: Coastal lows along the subtropical west coast of South America: Mean structure and evolution. Mon. Wea. Rev., 130 , 7588.

    • Search Google Scholar
    • Export Citation
  • Ghil, M., and K. Mo, 1991: Instraseasonal oscillations in the global atmosphere. Part II: Southern Hemisphere. J. Atmos. Sci., 48 , 780790.

    • Search Google Scholar
    • Export Citation
  • Gordon, C. T., A. Rosati, and R. Gudgel, 2000: Tropical sensitivity of a coupled model to specified ISCCP low clouds. J. Climate, 13 , 22392260.

    • Search Google Scholar
    • Export Citation
  • Hashizume, H., S-P. Xie, M. Fujiwara, M. Shiotani, T. Watanabe, Y. Tanimoto, W. T. Liu, and K. Takeuchi, 2002: Direct observations of atmospheric boundary layer response to SST variations associated with tropical instability waves over the eastern equatorial Pacific. J. Climate, 15 , 33793393.

    • Search Google Scholar
    • Export Citation
  • Hosom, D. S., R. A. Weller, R. E. Payne, and K. E. Prada, 1995: The IMET (improved meteorology) ship and buoy systems. J. Atmos. Oceanic Technol., 12 , 527540.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437471.

  • Kidson, J. W., 1991: Intraseasonal variations in the Southern Hemisphere circulation. J. Climate, 4 , 939953.

  • Kiladis, G. N., and K. M. Weickmann, 1997: Horizontal structure and seasonality of large-scale circulations associated with submonthly tropical convection. Mon. Wea. Rev., 125 , 19972013.

    • Search Google Scholar
    • Export Citation
  • Klein, S. A., 1997: Synoptic variability of low-cloud properties and meteorological parameters in the subtropical trade wind boundary layer. J. Climate, 10 , 20182039.

    • Search Google Scholar
    • Export Citation
  • Klein, S. A., and D. L. Hartmann, 1993: The seasonal cycle of low stratiform clouds. J. Climate, 6 , 15871606.

  • Klein, S. A., D. L. Hartmann, and J. R. Norris, 1995: On the relationships among low cloud structure, sea surface temperature, and atmospheric circulation in the summertime northeast Pacific. J. Climate, 8 , 11401155.

    • Search Google Scholar
    • Export Citation
  • Lau, K-M., P-J. Sheu, and I-S. Kang, 1994: Multiscale low-frequency circulation modes in the global atmosphere. J. Atmos. Sci., 51 , 11691193.

    • Search Google Scholar
    • Export Citation
  • Leith, C. E., 1973: The standard error of time-average estimates of climatic means. J. Appl. Meteor., 12 , 10661069.

  • Ma, C-C., C. R. Mechoso, A. W. Robertson, and A. Arakawa, 1996: Peruvian stratus clouds and the tropical Pacific circulation: A coupled ocean–atmosphere GCM study. J. Climate, 9 , 16351645.

    • Search Google Scholar
    • Export Citation
  • Minnis, P., P. W. Heck, D. F. Young, C. W. Fairall, and J. B. Snider, 1992: Stratocumulus cloud properties derived from simultaneous satellite and island-based instrumentation during FIRE. J. Appl. Meteor., 31 , 317339.

    • Search Google Scholar
    • Export Citation
  • Nicholls, S., 1984: The dynamics of stratocumulus: Aircraft observations and comparisons with a mixed layer model. Quart. J. Roy. Meteor. Soc., 110 , 783820.

    • Search Google Scholar
    • Export Citation
  • Norris, J. R., 1998: Low cloud structure over the ocean from surface observations. Part II: Geographical and seasonal variations. J. Climate, 11 , 383403.

    • Search Google Scholar
    • Export Citation
  • Norris, J. R., and C. B. Leovy, 1994: Interannual variability in stratiform cloudiness and sea surface temperature. J. Climate, 7 , 19151925.

    • Search Google Scholar
    • Export Citation
  • Nuss, W. A., and Coauthors, 2000: Coastally trapped wind reversals: Progress toward understanding. Bull. Amer. Meteor. Soc., 81 , 719743.

    • Search Google Scholar
    • Export Citation
  • Philander, S. G. H., D. Gu, D. Halpern, G. Lambert, N-C. Lau, T. Li, and R. C. Pacanowski, 1996: Why the ITCZ is mostly north of the equator. J. Climate, 9 , 29582972.

    • Search Google Scholar
    • Export Citation
  • Randall, D. A., J. A. Coakley Jr., C. W. Fairall, R. A. Kropfli, and D. H. Lenschow, 1984: Outlook for research on subtropical marine stratiform clouds. Bull. Amer. Meteor. Soc., 65 , 12901301.

    • Search Google Scholar
    • Export Citation
  • Rozendaal, M. A., and W. B. Rossow, 2003: Characterizing some of the influences of the general circulation on subtropical marine boundary clouds. J. Atmos. Sci., 60 , 711728.

    • Search Google Scholar
    • Export Citation
  • Rozendaal, M. A., C. B. Leovy, and S. A. Klein, 1995: An observational study of diurnal variations of marine stratiform cloud. J. Climate, 8 , 17951809.

    • Search Google Scholar
    • Export Citation
  • Wang, H., and R. Fu, 2004: Influence of cross-Andes flow on the South American low-level jet. J. Climate, 17 , 12471262.

  • Wang, Y., S-P. Xie, H. Xu, and B. Wang, 2004: Regional model simulations of boundary layer clouds over the southeast Pacific off South America. Part I: Control experiment. Mon. Wea. Rev., 132 , 274296.

    • Search Google Scholar
    • Export Citation
  • Wang, Y., S-P. Xie, B. Wang, and H. Xu, 2005: Large-scale atmospheric forcing by southeast Pacific boundary layer clouds: A regional model study. J. Climate, in press.

    • Search Google Scholar
    • Export Citation
  • Weare, B., 1994: Interrelationships between cloud properties and SSTs on seasonal and interannual time scales. J. Climate, 7 , 248260.

    • Search Google Scholar
    • Export Citation
  • Weller, R. A., and S. P. Anderson, 1996: Surface meteorology and air–sea fluxes in the western equatorial Pacific warm pool during the TOGA coupled ocean–atmosphere response experiment. J. Climate, 9 , 19591992.

    • Search Google Scholar
    • Export Citation
  • Wentz, F. J., 1997: A well calibrated ocean algorithm for SSM/I. J. Geophys. Res., 102 , 87038718.

  • Wentz, F. J., C. Gentemann, D. Smith, and D. Chelton, 2000: Satellite measurements of sea surface temperature through clouds. Science, 288 , 847850.

    • Search Google Scholar
    • Export Citation
  • Wood, R., C. S. Bretherton, and D. C. Hartmann, 2002: Diurnal cycle of liquid water path over the subtropical and tropical oceans. Geophys. Res. Lett., 29 .2092, doi:10.1029/2002GL015371.

    • Search Google Scholar
    • Export Citation
  • Wylie, D., B. B. Hinton, and K. Kloesel, 1989: The relationship of marine stratus clouds to wind and temperature advection. Mon. Wea. Rev., 117 , 26202625.

    • Search Google Scholar
    • Export Citation
  • Xie, S-P., 2004a: The shape of continents, air–sea interaction, and the rising branch of the Hadley circulation. The Hadley Circulation: Past, Present and Future, H. F. Diaz and R. S. Bradley, Eds., Springer–Kluwer Academic, in press.

    • Search Google Scholar
    • Export Citation
  • Xie, S-P., 2004b: Satellite observations of cool ocean–atmosphere interaction. Bull. Amer. Meteor. Soc., 85 , 195208.

  • Xie, S-P., W. T. Liu, Q. Liu, and M. Nonaka, 2001: Far-reaching effects of the Hawaiian Islands on the Pacific ocean–atmosphere system. Science, 292 , 20572060.

    • Search Google Scholar
    • Export Citation
  • Xu, H., Y. Wang, and S-P. Xie, 2004: Effects of the Andes on eastern Pacific climate: A regional atmospheric model study. J. Climate, 17 , 589602.

    • Search Google Scholar
    • Export Citation
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