These boundaries are often misanalyzed or inconsistently analyzed as cold fronts, stationary fronts, or trough axes on surface maps of the 33 cases of identified MRV drylines for which the Weather Prediction Center archived analyses were available, only 6 were correctly analyzed as drylines. MRV dryline events typically occur under synoptically active conditions with an amplified upper-air pattern, a 500-hPa shortwave trough to the west or northwest of the dryline, and a strong surface cyclone to the north. Mean and anomaly synoptic composites were created for these drylines. In total, 39 Mississippi River valley drylines (hereafter referred to as MRV drylines) were identified from the North American Regional Reanalysis (NARR) dataset through the study period. Additionally, synoptic patterns are identified that may result in drylines moving atypically far eastward into the Mississippi River valley. This study presents a 15-yr (1999-2013) climatology of these Mississippi River valley drylines and associated severe weather. Although drylines most commonly occur on the southern Great Plains, dryline passages and subsequent severe weather outbreaks have been documented in the Mississippi River valley. The dryline is an important focal point for convection initiation.
During the front–dryline merger, meso-γ-scale discrete cold pools associated with the cold front led to a diverse distribution of CI. The cold front then merged with the dryline, the baroclinity of the dryline was enhanced by the associated convergence, to a degree comparable to that caused by frontogenesis of the dryline itself, thus leading to more CI. Prior to front–dryline merger, as the cold front approached the observed boundary-layer convergence line, or the simulated meso-γ-scale secondary dryline, CI occurred ahead of the cold front with little contribution from frontogenetic baroclinity of the dryline. The formation of this dryline is analogous to that on the Great Plains of the United States, and it is conducive to CI with mesoscale updrafts generated from the baroclinic frontogenesis, and with favorable instability immediately on the moist side. This process is analyzed with S-band Doppler radar data, surface Automatic Weather Station data, and mesoscale numerical simulation results. Ultimately, movement of animal populations in the atmosphere ranges across spatial and temporal scales spanning the microscale to macroscale and is vulnerable to changes in short-term weather and long-term climate patterns.Ī case study is presented of Convection Initiation (CI) resulting from the merger of a cold front with a dryline in southwestern Beijing, China, on the afternoon of 11 June 2011. Long-distance flight of flying animals may be abruptly terminated by mid-latitude fronts, gust fronts, and precipitation. While flying, animals may engage in predatory behaviors and conversely may be preyed upon.
Flight displacement distance and direction largely depends on prevailing wind speed and wind direction at respective flight altitudes, although flying animals can add to their displacement speed and can alter their displacement direction by heading at an angle relative to the wind direction (Wolf et al., Southwestern Entomol Suppl 18:45–61, 1995), including upwind flight. Flight initiation may be influenced by air temperature, wind speed, wind direction, barometric pressure change, or other atmospheric variables and may require substantial convective lift for small invertebrates such as wingless insects and spiders. Michigan State University Press, 2001 Drake and Reynolds, Radar entomology: observing insect flight and migration. Cambridge University Press, 1995 Isard and Gage, Flow of life in the atmosphere: an airscape approach to understanding invasive organisms. Ellis Horwood, 1982 Drake and Gatehouse, Insect migration: tracking resources through space and time. The atmospheric environment can assist or restrict flight of animals (insects, birds, and bats), influencing their ability to extend their population range and find new habitats for food, mating, and shelter (Pedgley, Windborne pests and diseases: meteorology of airborne organisms.
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