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A Global Climatology of Temperature and Water Vapor Variance Scaling from the...

Kahn, B., and J. Teixeira (2009), A Global Climatology of Temperature and Water Vapor Variance Scaling from the Atmospheric Infrared Souñder, J. Climate, 22, 5558-5576, doi:10.1175/2009JCLI2934.1.

A global climatology of height-resolved variance scaling within the troposphere is presented using derived temperature (T ) and water vapor (q) profiles from the Atmospheric Infrared Sounder (AIRS). The powerlaw exponent of T variance scaling approaches 1.0 outside of the tropics at scales .500–800 km, but it is closer to 0.3 at scales ,500 km, similar to exponents obtained from aircraft campaigns, numerical modeling, and theoretical studies. The T exponents in the tropics at all scales become less than 0.3, with a similar pattern observed within the boundary layer in some extratropical regions. For q, the variance scaling differs substantially from T with exponents near 0.5–0.6 in parts of the tropics and subtropics with little to no scale break, showing some consistency with a very limited set of aircraft and satellite studies. Scaling differences as a function of land and ocean, altitude, and cloudy- and clear-sky scenes are quantified. Both T and q exponents indicate peak magnitudes in the midtroposphere and reductions are observed near the boundary layer and upper troposphere. Seasonal variations of T and q scaling reveal a stronger seasonal cycle over land than ocean, especially for T at large length scales. While the zonal variations of T and q exponents vary significantly for scales ,500 km, the seasonal variations are much smaller in magnitude. The exponents derived from AIRS could eventually be extrapolated to smaller scales in the absence of additional scale breaks ,150 km to provide useful information for constraining subgrid-scale cloud parameterizations.

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