Interactive comment on Retrieval of three-dimensional wind fields from Doppler radar data using an efficient two-step approach by C
This manuscript is concerned with the description and testing of a variational dualDoppler radar wind retrieval algorithm. The constraints imposed in the analysis procedure are: observational constraints, which incorporate data from two or more Doppler radars (and possibly other data sources, e.g., dropsonde or sounding observations), a mass conservation constraint (sometimes referred to in the literature as a mass continuity constraint), and spatial smoothness constraints. The procedure is general enough to incorporate data from two or more stationary Doppler radars or from a so-called "pseudo-dual-Doppler radar", that is, data from an airborne-radar that, when appropriately processed, are equivalent to data gathered from two stationary Doppler radars. The observational and mass conservation constraints are standard in dual-Doppler analysis procedures. The use of smoothness constraints is standard in variational (e.g., 3DVAR) analysis techniques. The new aspect of this study is a data gridding/reduction step designed to minimize loss of information and to generate estimates of the variances of the reduced velocities. Any improvements made in these directions would be of interest to radar and mesoscale meteorologists as it could potentially improve dualDoppler analyses of a variety of convective and non-convective weather phenomena. The new retrieval is tested with pseudo-dual-Doppler radar data from a tropical depression. Unfortunately, the results from these tests are inconclusive. A comparison of the retrieved horizontal wind vectors with the horizontal wind vectors from an independent data source (dropsondes) does indicate a qualitatively good agreement (Fig. 8). But there is relatively little challenge in obtaining qualitatively reasonable horizontal wind components from dual-Doppler or pseudo-dual Doppler data, especially on the coarse analysis grid indicated on that figure. A more challenging problem and one of prime interest to mesoscale meteorologists is the analysis of the vertical wind component. Apparently it was not possible to evaluate the accuracy of the retrieved vertical wind component in this test case. In the future it would probably be better to consider a more stringent test of the algorithm, perhaps
Kinematic and Thermodynamic Study of a Shallow Hailstorm Sampled by the McGill Bistatic Multiple-Doppler Radar Network
Abstract In this paper, the authors examine the kinematic and thermodynamic characteristics of a shallow hailstorm sampled by the McGill bistatic multiple-Doppler radar network on 26 May 1997. This storm consists of two main shallow convective cells (depth less than 5 km) aligned along a SW–NE convective line propagating to the southeast. The authors also analyze the interactions between the two cells during the life cycle of the convective line. In particular it is shown that dynamic interactions play a major role in the intensification of the second cell. This storm is found to evolve in a manner that shares some characteristics with both multicell and supercell storms. A rotating updraft associated with a mesocyclone develops in the mature stage of the storm, which is characteristic of a supercell. However, the lack of a “vault” structure on the precipitation field, the relatively fast evolution of the cells, and other characteristics detailed henceforth seem to indicate that this storm only shares a f...
High‐precision U‐Pb zircon age calibration of the global Carboniferous time scale and Milankovitch band cyclicity in the Donets Basin, eastern Ukraine
High‐precision ID‐TIMS U‐Pb zircon ages for 12 interstratified tuffs and tonsteins are used to radiometrically calibrate the detailed lithostratigraphic, cyclostratigraphic, and biostratigraphic framework of the Carboniferous Donets Basin of eastern Europe. Chemical abrasion of zircons, use of the internationally calibrated EARTHTIME mixed U‐Pb isotope dilution tracer, and improved mass spectrometry guided by detailed error analysis have resulted in an age resolution of <0.05%, or ∼100 ka, for these Carboniferous volcanics. This precision allows the resolution of time in the Milankovitch band and confirms the long‐standing hypothesis that individual high‐frequency Pennsylvanian cyclothems and bundles of cyclothems into fourth‐order sequences are the eustatic response to orbital eccentricity (∼100 and 400 ka) forcing. Tuning of the fourth‐order sequences in the Donets Basin to the long‐period eccentricity cycle results in a continuous age model for the Middle to Late Pennsylvanian (Moscovian‐Kasimovian‐Ghzelian) strata of the basin and their record of biological and climatic changes through the latter portion of the late Paleozoic Ice Age. Detailed fusulinid and conodont zonations allow the export of this age model to sections throughout Euramerica. Additional ages for Mississippian strata provide among the first robust radiometric calibration points within this subperiod and result in variable lowering of the base ages of its constituent stages compared to recent global time scale compilations.