Atmospheric measurements during the eclipse indicated a rapid halt to vertical motions, collapse of the convective boundary layer, and descent and decrease of water vapor concentrations aloft. A meteorological study of this same event analyzed the effect of the eclipse on boundary-layer evolution, focusing on the land–atmosphere responses to rapid changes in radiative forcing. These behaviors were attributed to light cues that evoked the familiar twilight roosting responses of diurnally active animals. Previous work investigated aerial animal abundance at continental scales during the North American solar eclipse of 2017, reporting changes in altitudinal distributions and overall animal numbers aloft associated with passage of the eclipse. Overall, decoupling the behavioral effects stemming from diurnal boundary-layer evolution, photoperiod cues, and circadian rhythm is inherently challenging.Ī total solar eclipse presents a unique case for potentially disentangling these effects by rapidly simulating twilight levels of incoming solar radiation at a novel time in the diel cycle. Further complicating these interactions, many animals also have an endogenous circadian clock that also promotes daily behavioral periodicity (e.g., ). Beyond driving atmospheric convection, sunlight also provides optical cues to organisms that can coincide with specific twilight behaviors (e.g., initiation and termination of flight, roost exodus and returns, calling by birds and insects, ascending flights by swifts ). Persistent lift provided by thermals within the convective boundary layer enables vertical ascent and long-range dispersal by organisms that would otherwise be incapable of such movements (e.g., aphids and ballooning spiders ) and extends flight range for soaring animals (e.g., butterflies and raptors ). This convective boundary layer promotes vertical fluxes of momentum, energy, and mass, enabling upward transport of surface-based water vapor, aerosols, particulates, and organisms. Both the animal behavioral response and decrease in atmospheric turbulence lagged changes in solar irradiance by approximately 30 min, suggesting that changes in flight activity were not cued by the eclipse directly, but rather by the modification of vertical air motions caused by the eclipse.ĭuring a cloud-free day over land, the atmospheric boundary layer is characterized by thermal convection resulting from surface radiative heating from the sun. Analysis of animal flight behavior confirmed that ascending and descending flight effort did change in the time period encompassing the solar eclipse, however, the response in behavior was coincident with proximate changes in boundary-layer turbulence. To analyze these interactions, we couple radar-derived animal observations with co-located lidar measurements of the convective boundary layer over north-central Oklahoma, USA during the solar eclipse of 21 August 2017. While the diel periodicity of boundary-layer dynamics and animal flight has been characterized, rare disruptions to this cycle provide a chance to investigate animal behavioral responses to boundary layer motion and photoperiod that are disjointed from their expected circadian rhythm. Lift provided by thermal updrafts is sufficiently ubiquitous that some diurnal birds and arthropods have evolved specialized flight behaviors to soar or embed in these atmospheric currents. The daytime atmospheric boundary layer is characterized by vertical convective motions that are driven by solar radiation.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |