Extraction of Geopotential Height and Temperature Structure from Profiler and Rawinsonde Winds

Abstract

Mesoscale height and temperature fields can be extracted from the observed wind field by making use of the full divergence equation. Mass changes associated with irrotational ageostrophic motions are retained for a nearly complete description of the height field. Above the boundary layer, in the absence of friction, the divergence equation includes terms composed of the components of the wind and a Laplacian of the geopotential height field. Once the mass field is determined, the thermal structure is obtained through application of the hypsometric equation.In this paper an error analysis of this divergence method is undertaken to estimate the potential magnitude of errors associated with random errors in the wind data. Previous applications of the divergence method have been refined in the following ways. (i) The domain over which the method is applied is expanded to encompass the entire STORM-FEST domain. (ii) Wind data from 23 profiler and 38 rawinsonde sites are combined in the analysis. (iii) Observed profiler and rawinsonde data are interpolated to grid points through a modified objective analysis, and (iv) the variation in elevation of the profiler sites is taken into account.The results of the application of the divergence method to the combined wind data from profiler and rawinsonde sites show good agreement between the retrieved heights and temperatures and the observed values at rawinsonde sites. Standard deviations of the difference between the retrieved and observed data lie well within the precision of the rawinsonde instruments. The difference field shows features whose magnitude is significantly larger than the errors predicted by the error analysis, and these features are systematic rather than random in nature, suggesting that the retrieved fields are able to resolve mesoscale signatures not fully captured by the rawinsonde data alone.The divergence method is also applied solely to the profiler data to demonstrate the potential of the divergence method to provide mass and thermal fields on a routine basis at synoptic times when operational rawinsonde data are not available. A comparison of the heights derived from the profiler winds with those independently measured by rawinsondes indicates that valuable information on the evolution of atmospheric height and temperature fields can be retrieved between conventional rawinsonde release times through application of the divergence method. The implications of the results for applications of the method in weather analysis and in numerical weather prediction are discussed.

Temporal Trend Analyses of Alpine Data Using North American Regional Reanalysis and In Situ Data: Temperature, Wind Speed, Precipitation, and Derived Blowing Snow

“…In regions with sparsely distributed gauges (deserts, mountains, rangelands, and remote, unpopulated areas) and a limited number of rawinsonde launch sites, misrepresentation of large or diverse areas has resulted (Hiemstra et al 2006;Businger et al 2001). Weaknesses were confirmed in Canada, where the numbers of precipitation gauges and rawinsonde launches are few (Mesinger et al 2006).…”

A Comparative Study to Quantify Sensitive Dependence in Numerical Models for a Developing Low in the Southern Plains

“…In the models and observations, the uncertainty of the initial conditions was approximately 1% (or 0.01) or less for measuring height at 500 hPa (e.g., [27]). We can define tolerance as a good forecast, which should be a value larger than the uncertainty.…”

The derivation of a numerical diagnostic model for the forcing of the geopotential

“…The quadratic and Jacobian forcing terms (the results of further manipulation of terms 2-5 in equation (1)) in the classical ∇ 2 · V equation mix up these contributions and carry no synoptic signals. For example, the sign of the quadratic term (∇ 2 · V) 2 in the classical ∇ 2 · V equation used by Businger et al(2001) does not change in the opposite cases of convergence with ∇ 2 · V < 0 and divergence with ∇ 2 · V > 0. None of the dominant Jacobian terms in the classical ∇ 2 · V equation can identify synoptic signals because their signs do not change in the opposite synoptic systems either.…”

“…For these reasons, previous studies (e.g. Fankhauser, 1974;Kuo and Anthes, 1985;Modica and Warner, 1987;Businger et al, 2001) use the classical ∇ 2 · V equation to extract information from knowledge of the wind fields in local regions but not to diagnose the global fields and their anomalies.…”