![]() Therefore, we conclude that the updraft stronger than the insects’ downward velocities raised the insects so high. Insects fly in air with temperatures above 5☌ ( Achtemeier 1991 Drake and Reynolds 2012, 234–235). The temperature at a height of 4.3 km is about −2☌, that is, below freezing (sounding 0000 UTC 18 April 2013 at Lamont, Oklahoma data from OUN are not available from this height). The top of the layer of atmospheric biota, obtained in areas away from the thunderstorm, is at a height of 0.9 km, which is much lower than the top of the biota column in the WER. At the next available elevation of 4°, this feature disappears in the fields of dual-polarization variables, leading us to conclude that the inflow area stretches from the ground up to at least 4.3 km above ground. We submit that the inflow region stretches up to this elevation. Some streaks of large DDVs near the radar are caused by second trip echoes.Īt an elevation of 3°, the WER in the Z field is absent but an area of negative Z DR, enhanced DDV, and low CC values is still present. The WER and areas close to the radar exhibit large DDV values characteristic of echoes from insects and birds ( Melnikov et al. In the weather echo, the absolute DDV values are lower than 1 m s −1 ( Figs. 1), indicating nonmeteorological scatterers such as insects, birds, or light debris. One can see negative Z DR, high DDV, and low CC values in the WER ( Fig. S1) is an indirect indication of the inflow. Some decrease in the Doppler velocities in the WER ( Fig. The identification of inflow in the Doppler velocity field is ambiguous because the radar beam is almost orthogonal to the inflow direction, which can be deduced to be southeasterly by looking at the WER’s configuration. The WER is seen at higher elevations up to 2° ( Fig. 1 Z field, about 100 km west and 70 km south from the radar). A well-pronounced WER is seen in Z fields at the southern edge of the thunderstorm at an antenna elevation of 0.5° ( Fig. This thunderstorm produced hail with diameters up to 2 cm. (2014) showed that in radar echoes from insects and birds, DDV values are frequently larger than those in weather echoes and can exceed 5 m s −1.įigure 1 shows data collected with the dual-polarization WSR-88D KOUN, located in Norman, Oklahoma. In weather echoes, the absolute values of DDV are typically less than 1 m s −1 ( Metcalf 1986 Wilson et al. We consider herein also a new dual-polarization parameter, the difference of Doppler velocities (DDV) obtained as the difference of the velocities measured at horizontal and vertical polarizations, that is, DDV = V h − V υ. Reflectivity and the Doppler velocity ( V h) are measured at horizontal polarization. Six radar variables are measured with polarimetric Doppler weather radars these are equivalent reflectivity factor ( Z), Doppler velocity ( V), spectrum width ( W), differential reflectivity ( Z DR), differential phase (Φ DP), and correlation coefficient (CC or ρ hv). Utilizing the dual-polarization parameters to indicate inflow areas ![]() In this paper, we explore the use of dual-polarization parameters to identify the origin of scatterers in WERs and show that inflow areas can stretch to heights where WERs are not exhibited.Ģ. ![]() Dual-polarization radar capabilities allow for identification of echoes from atmospheric biota, such as birds and insects (e.g., Zrnić and Ryzhkov 1999). Nonpolarimetric Doppler radars have been used in these studies. Direct observations of insects trapped in an inflow were made by Murphey et al. (2004) hypothesized that insects, swept by a strong inflow, may penetrate deep into convective clouds. (1994) came to the conclusion that radar detects such areas because of enhanced concentration of insects, tree leaves, and lofted grass. Studying convergence areas that led to formation of convective clouds, Wilson et al. ![]() A Doppler radial velocity field is frequently difficult to interpret because the true inflow velocity can be estimated only when the direction of a radar beam coincides with the direction of inflow, which is a rare occasion. The classic approach of identifying inflow areas in radar images is looking for a weak echo region (WER) in a reflectivity field (e.g., Browning 1982, 1983 Schiesser and Waldvogel 1999). ![]() Information about inflow and updraft locations is important in operational use of weather radar when signatures are used in warning decisions ( Burgess and Lemon 1990). The location of inflow is informative in obtaining a dynamical structure of a thunderstorm. ![]()
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