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- Author or Editor: David A. Howarth x
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Abstract
Seasonal mean fields of precipitable water and the zonal and meridional components of the vertically integrated atmospheric water vapor transport fields are calculated from five years of Southern Hemisphere data (1 September 1973 through 31 August 1978). Data are the product of a numerical analysis procedure developed and implemented by Australian Numerical Meteorological Research Centre and are in the form of 47 × 47 matrices superimposed on a polar stereographic projection. Values of the mixing ratio and the u and v components of the wind are available at four levels between 1000 and 500 mb. Primary emphasis is directed toward examining the seasonal variations in the moisture transport fields.
Large seasonal differences in precipitable water and in the zonal and meridional fluxes are found, most notably between summer and winter. Summer season, subtropical meridional water vapor fluxes exceed those in winter by a factor of 2. A seasonal asymmetry is noted in the fields of W̄ and Q̄ λ in which the autumn magnitudes are larger than those found in spring. A seasonal asymmetry between autumn and spring is also evident in the Q̄ ϕ fields but the tendency is for spring to exhibit larger magnitudes than autumn. Strong northward flows of moisture are found west of South America and Africa. Computation of zonally averaged quantities reveals that the moisture content of the Southern Hemisphere atmosphere is greater than that calculated in other works, probably due to high values of the mixing ratios at the 1000 mb level. The zonally averaged meridional flux of moisture is most probably underestimated, possibly by a factor of 2. Spatial patterns of the fluxes, however, generally show good agreement with other works. It is therefore concluded that caution must be exercised in interpreting the results presented here and in utilizing this data set for future studies of the Southern Hemisphere circulation.
Abstract
Seasonal mean fields of precipitable water and the zonal and meridional components of the vertically integrated atmospheric water vapor transport fields are calculated from five years of Southern Hemisphere data (1 September 1973 through 31 August 1978). Data are the product of a numerical analysis procedure developed and implemented by Australian Numerical Meteorological Research Centre and are in the form of 47 × 47 matrices superimposed on a polar stereographic projection. Values of the mixing ratio and the u and v components of the wind are available at four levels between 1000 and 500 mb. Primary emphasis is directed toward examining the seasonal variations in the moisture transport fields.
Large seasonal differences in precipitable water and in the zonal and meridional fluxes are found, most notably between summer and winter. Summer season, subtropical meridional water vapor fluxes exceed those in winter by a factor of 2. A seasonal asymmetry is noted in the fields of W̄ and Q̄ λ in which the autumn magnitudes are larger than those found in spring. A seasonal asymmetry between autumn and spring is also evident in the Q̄ ϕ fields but the tendency is for spring to exhibit larger magnitudes than autumn. Strong northward flows of moisture are found west of South America and Africa. Computation of zonally averaged quantities reveals that the moisture content of the Southern Hemisphere atmosphere is greater than that calculated in other works, probably due to high values of the mixing ratios at the 1000 mb level. The zonally averaged meridional flux of moisture is most probably underestimated, possibly by a factor of 2. Spatial patterns of the fluxes, however, generally show good agreement with other works. It is therefore concluded that caution must be exercised in interpreting the results presented here and in utilizing this data set for future studies of the Southern Hemisphere circulation.
