Responses of Three Coral Communities to the 1997–98 El Niño–Southern Oscillation: Galápagos Islands, Ecuador

One deep (13–15 m depth) and two shallow water (1.5 and 7 m) coral communities in the Galápagos Islands, Ecuador were monitored for tissue response (bleaching, paling, morbidity) and secondary responses during and after elevated temperature stress associated with the 1997–98 El Niño–Southern Oscillation (ENSO) event. Between March and May 1998, the fungiid coral Diaseris distorta paled and bleached (up to 88.0% of all individuals bleached) at 13–15 m depth. The small branching colonial coral, Psammocora stellata, paled (79.2% of all colonies) with very little bleaching (11.1%), also at 13–15 m depth. However, by May 1998 colonies of this species in shallower water (7 m depth) suffered high mean mortality (72.4% of colony area, 85.1% decrease in numbers of live colonies). In March 1998, colonies of Pavona clavus, a massive coral species, were 100% bleached at 1.5 m depth and experienced subsequent partial mortality averaging 34.0% per colony. Both Diaseris and Psammocorain deeper water (13–15 m depth) recovered pigment by June 1999. Numbers of Diaseris individuals within permanent transect plots decreased 56.1% from March 1998 through August 2000, but this loss was most likely due to coral displacement by currents and surge rather than temperature-induced mortality. Numbers of Psammocora colonies in deep water did not change appreciably during the survey period (−16.1%). In contrast, surviving shallower water (7 m depth) Psammocora recovered pigment by June 1999, but numbers of live colonies remained low through August 2000 (−83.3% compared to March 1998). Initial recovery of pigmented tissue was evident in Pavona by June 1999, but a decline in live tissue again occurred by August 2000. Sea water temperature at the deeper site reached 28–30°C, but periods of semi-diurnal cooling may have mitigated the bleaching response. Highest temperatures occurred in shallower water (7 m), where Psammocora experienced high mortality and periodic subsurface cooling was suppressed. These data cannot be compared with those from the 1982–83 ENSO because of the lack of quantitative data from the earlier event. However, these observations provide a framework of comparison with other ENSO-affected eastern Pacific coral communities and reefs during the 1997–98 event

The construction of a vocational service rating scale

Thesis (Ed. D.)--Boston University. This item was digitized by the Internet Archive

Vertical profiles of droplet effective radius in shallow convective clouds

Conventional satellite retrievals can only provide information on cloud-top droplet effective radius (<i>r</i><sub>e</sub>). Given the fact that cloud ensembles in a satellite snapshot have different cloud-top heights, Rosenfeld and Lensky (1998) used the cloud-top height and the corresponding cloud-top <i>r</i><sub>e</sub> from the cloud ensembles in the snapshot to construct a profile of <i>r</i><sub>e</sub> representative of that in the individual clouds. This study investigates the robustness of this approach in shallow convective clouds based on results from large-eddy simulations (LES) for clean (aerosol mixing ratio <i>N</i><sub>a</sub> = 25 mg<sup>−1</sup>), intermediate (<i>N</i><sub>a</sub> = 100 mg<sup>−1</sup>), and polluted (<i>N</i><sub>a</sub> = 2000 mg<sup>−1</sup>) conditions. The cloud-top height and the cloud-top <i>r</i><sub>e</sub> from the modeled cloud ensembles are used to form a constructed <i>r</i><sub>e</sub> profile, which is then compared to the in-cloud <i>r</i><sub>e</sub> profiles. For the polluted and intermediate cases where precipitation is negligible, the constructed <i>r</i><sub>e</sub> profiles represent the in-cloud <i>r</i><sub>e</sub> profiles fairly well with a low bias (about 10 %). The method used in Rosenfeld and Lensky (1998) is therefore validated for nonprecipitating shallow cumulus clouds. For the clean, drizzling case, the in-cloud <i>r</i><sub>e</sub> can be very large and highly variable, and quantitative profiling based on cloud-top <i>r</i><sub>e</sub> is less useful. The differences in <i>r</i><sub>e</sub> profiles between clean and polluted conditions derived in this manner are however, distinct. This study also investigates the subadiabatic characteristics of the simulated cumulus clouds to reveal the effect of mixing on <i>r</i><sub>e</sub> and its evolution. Results indicate that as polluted and moderately polluted clouds develop into their decaying stage, the subadiabatic fraction <i>f</i><sub>ad</sub> becomes smaller, representing a higher degree of mixing, and <i>r</i><sub>e</sub> becomes smaller (~10 %) and more variable. However, for the clean case, smaller <i>f</i><sub>ad</sub> corresponds to larger <i>r</i><sub>e</sub> (and larger <i>r</i><sub>e</sub> variability), reflecting the additional influence of droplet collision-coalescence and sedimentation on <i>r</i><sub>e</sub>. Finally, profiles of the vertically inhomogeneous clouds as simulated by the LES and those of the vertically homogeneous clouds are used as input to a radiative transfer model to study the effect of cloud vertical inhomogeneity on shortwave radiative forcing. For clouds that have the same liquid water path, <i>r</i><sub>e</sub> of a vertically homogeneous cloud must be about 76–90 % of the cloud-top <i>r</i><sub>e</sub> of the vertically inhomogeneous cloud in order for the two clouds to have the same shortwave radiative forcing