DERIVING SIGNIFICANT-LEVEL GEOPOTENTIALS FROM RADIOSONDE REPORTS

An algorithm is developed to derive hydrostatically balanced geopotent ials at significant levels from radiosonde reports of significant-leve l temperatures and mandatory-level geopotentials and temperatures. It minimizes the square of the nonhydrostatic differences in a layer wher e at least one significant-level datum is reported and can be viewed a s being a 1D analysis step that returns an estimate of the departures from hydrostatic balance within the layer. The piecewise-polynomial in terpolation of the minimization procedure is used to produce an expand ed geopotential profile in any layer where significant-level data are reported, and the integrated minimization error can be used as a quali ty-control measure. The algorithm's performance has been evaluated usi ng the global radiosonde dataset for a given synoptic time, and it is found that it produces equivalent layer-mean temperature errors that a re generally smaller than radiosonde observational errors.