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PARAMETERS
(ProQuest: ... denotes formulae omitted.)
Despite the proliferation of increasingly long records of satellite- and GPS-based observations of atmospheric temperature, moisture, and wind, radiosonde measurements of these quantities continue to prove useful in a variety of fields. For example, radiosonde data have been used to diagnose variations in the vertical temperature structure of the atmosphere. Of increasing interest are large-scale and long-term changes in the planetary boundary layer (PBL) and tropopause region. For studies of this kind, radiosonde data represent a unique resource since they contain high vertical resolution records of above-surface conditions that are as long as 60 years.
However, raw radiosonde reports do not contain the required variables in a form in which they are commonly used in studies of atmospheric structure. For example, many applications require that the typically reported variables of dewpoint depression, wind direction, and wind speed be converted to relative or specific humidity, zonal wind, and meridional wind. In addition, geopotential height is often reported only at mandatory pressure levels, thus complicating the computation of stability parameters and vertical gradients.
With these considerations in mind, a dataset of derived parameters has been constructed that will simplify the tasks of monitoring variations in atmospheric stability and analyzing the characteristics of the PBL on a global scale. The parameters are calculated from the Integrated Global Radiosonde Archive (IGRA), a collection of quality-controlled historical and present-day soundings from around the globe.
The remainder of this paper contains a description of the methods used in computing the parameters ("Dataset Construction") as well as of the temporal and spatial coverage of the resulting dataset ("Temporal and Spatial Coverage"). A summary and some concluding remarks are offered in the final section.
DATASET CONSTRUCTION. The parameters included in the IGRA-derived dataset can be grouped into three categories: observed variables, basic derived quantities, and vertical gradients (Table 1). Observed parameters include pressure, geopotential height, and temperature. The other parameters are derived using the formulas provided in the appendix and the methodologies described in subsequent paragraphs.
Completeness requirements. As a prerequisite for inclusion in the dataset, each level, sounding, and station must meet certain completeness requirements. Since temperature and pressure are needed for the estimation of geopotential height as well as for the computation of vertical...