Across the air-sea interface there is a transfer of momentum, heat and moisture. Knowledge of these is essential to the understanding of oceanic and atmospheric circulations. This study is an investigation of the vertical turbulent transfers of momentum, heat and moisture in the boundary layer of the atmosphere using an instrumented light aircraft. The data were collected at several altitudes between 18 m and 500 m in the Atlantic trade wind zone east of the island of Barbados. Since the tropical ocean is the primary source of heat input to the atmospheric heat engine, good estimates, in this region, of the transfers of heat and moisture and their vertical variations are essential to any global numerical atmospheric prediction scheme. The fluctuations of the velocity components, temperature and humidity and the transfers of momentum, heat and moisture were investigated, primarily by means of their spectra and cospectra. It was found that: ninety percent of the heat input to the atmosphere was in the form of latent heat; the sensible heat flux was positive (upward) at the small scales generated near the surface and negative at the large scales due to subsiding air; the latent heat flux was positive at all scales and similar in spectral distribution to the momentum flux; the flow appeared to be anisotropic even at scales one hundred times smaller than the distance from the boundary; the drag coefficient, from direct measurements of the momentum flux (or stress), was (1.45±0.08) x 10⁻³; shear generated turbulence was not entirely dissipated locally. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Research was conducted in Sri Lanka to evaluate the feasibility of developing cassava (Manihot esculenta Crantz) leaf meal as an animal feed. In feeding trials with broilers, improvements in performance were observed at 10% inclusion of cassava leaf meal (CLM). High levels (20 and 30%) of CLM depressed gain, feed intake and feed per gain. Weights of spleen and liver (% of body weight) linearly increased with increasing levels of CLM. Carcass pigmentation values favored the CLM-based diets. Dietary additives (methionine, sodium thiosulfate or soybean oil plus methionine) improved the growth of broilers fed 20% CLM diet without, however, having any beneficial effect when added to the basal diet. Gain of broilers tended to decrease with increasing dietary levels of cyanide. Feeding trials with growing pigs showed that CLM can be included up to 26.7% level without any effect on performance. Gain and feed per gain were improved at 13.3% CLM level, whereas marked depressions were noted at 40% CLM level. Results of the balance trials indicated that cassava leaf protein is utilized more efficiently by the pigs, although the nutrients in CLM are not as digestible as those in coconut oil meal. The overall results suggest that bulkiness, low energy content, methionine deficiency and presence of anti-nutritional factors, are the major factors limiting the high level use of CLM in non-ruminant diets. Studies on the processing of CLM revealed that simple drying is sufficient to eliminate almost 90% of the initial cyanide level in the fresh cassava leaves. A combination of chopping and 3-day wilting prior to drying proved most effective in lowering the cyanide level of CLM. Field trials conducted with a short-age cassava variety, MU 22, demonstrated that it is possible to increase cassava leaf dry matter yields by defoliating once during the growing season and to produce within 86% of the normal yield of roots. Two defoliations during the growing season depressed the root crop by more than half. / Ph. D.

No description available.

Numerical simulations using the Penn State University/NCAR MM4 model are performed to examine a stably stratified, zonal easterly flow past large scale three-dimensional mountain ranges in a rotating, initially barotropic, atmosphere. Upstream blocking by the mountain range diverts the flow primarily to the south and around the mountain. Conservation of potential vorticity results in the formation of a horizontal jet at low levels south of the mountain. This jet is barotropically unstable and leads to a continuous production of synoptic scale vorticity maxima which separate from the mountain and propagate downstream. Numerical simulations using topography representative of the Sierra Madre in Mexico imply that this mechanism may be important in providing some of the initial disturbances which grow into tropical cyclones in the eastern North Pacific Ocean. The wave train produced in the simulations corresponds to waves with 3-7 day periods which have been identified observationally in the eastern North Pacific region. The sensitivity of this effect to the stability of the basic state and the upstream wind speed is investigated. Simulations are also performed which show that the Hoggar and Atlas mountains of west-central Africa block the low-level easterlies resulting in a barotropically unstable jet and a train of vorticity maxima which separate from the mountain and propagate downstream. The spacing of these disturbances is roughly 1600 km and they propagate to the east with a period of about 2.5 days. These characteristics correspond to those of observed waves in the Africa/Atlantic region. It will also be shown that the unique topography of north-central Africa results in a mid-tropospheric easterly jet which has a maximum between 0-10°E and 15-20°N. The location and magnitude of this jet correspond to the so-called African easterly jet which is usually attributed to the strong surface temperature gradients over the continent of Africa. The numerical simulations presented in this work suggest that the mechanical effect of the topography may provide a constant source of energy for the maintenance of the African easterly jet.

This study investigates two aspects of tropical reef fish mating systems: the prevalence of paternal care in those species that exhibit some form of parental care, and the evolutionary stability of simultaneous hermaphroditism. Studies of three species of tropical reef fishes from the Gulf of California were used to investigate these two different types of mating systems. Two species of demersal egg guarders with paternal care, Malacoctenus hubbsi and Abudefduf troschelii, were studied to determine the importance of a male's mating status (the number of eggs in his territory) in regard to female choice of mates. In both species, females did not base their choice of mates on the number of eggs in the male's territory, males increased their level of parental care with increasing egg number, and egg survivorship where estimated was independent of brood size. These results corroborate, and offer the first experimental field verification of a crucial assumption of a minimal-care hypothesis proposed a decade ago by Williams (1975). Male reproductive success was studied in greater detail in one species, M. hubbsi. Territory parameters, rather than male size, were the major determinants of male reproductive success. This independence relative to male size was attributed to the unpredictability of good future territories. In Serranus fasciatus all individuals begin reproduction as simultaneous hermaphrodites, but lose female function at large sizes to become males. Males obtain disproportionate reproductive success by maintaining harems of hermaphrodites and defending them from adjacent males. These harems are similar to those found in some sequentially hermaphroditic species. Hermaphrodites obtain most of their reproductive success through female function by spawning with a male, but also engage in an alternative male strategy--streaking on pair spawns--to obtain some male reproductive success. This small amount of male reproductive success by hermaphrodites appears to stabilize simultaneous hermaphroditism with most resources allocated to female function. Facultative alternative male mating strategies in hermaphroditic individuals joins spawning reciprocation as the only known behavioral strategies that provide evolutionary stability for simultaneous hermaphroditic individuals in populations of tropical reef fishes.

Approved for public release; distribution is unlimited. / The Tropical Cyclone Vorticity Tracking Program is used to identify vortices in the western North Pacific from the Navy Operational Global Atmospheric Prediction System (NOGAPS) analyses and forecasts during May- October 2002 and 2003. Based on the NOGAPS analyses, several parameters are different between the 23vortices that developed into storms during 2002 according to the Joint Typhoon Warning Center (JTWC) and the231 vortices that did not develop. After eliminating 127 vortices that did not persist at least 24 h, this left 104 nondevelopingcases. For the developing circulations, the average 850-mb relative vorticity value at the first JTWCwarningtime was 5.0 x 10-5 s-1, with an easterly deep layer wind shear of -1.8 m s-1. The average 850-mb relativevorticity maximum for the non-developing cases was 3.3 x 10-5 s-1, with a westerly vertical shear of 4.1 m s-1. TheNOGAPS model tends to over-forecast relative vorticity prior to formation time for both developers and nondevelopers.Especially for the 72-h and 96-h forecasts, the over-forecasting tendency leads to non-developingvortices meeting the threshold vorticity value of the developing vortices. The tendency for NOGAPS to forecastthe non-developing deep layer wind shear to become increasingly easterly with time is considered to be a majorfactor in these over-forecasts of formation. Some adjustments in the cumulus parameterization heating andmoistening plus convective momentum transport may improve these forecasts of tropical cyclone formation. / Captain, United States Air Force

Since an extratropical transition (ET) of a decaying tropical cyclone (TC) often results in a fast-moving, rapidly developing extratropical cyclone and amplification of synoptic-scale systems far downstream, proper forecasting of ET events is critical to forecast accuracy over large ocean regions. Past studies have linked forecast accuracy to the phasing of a decaying TC with favorable midlatitudes conditions. Because ET events are sensitive to the analyzed initial conditions, this phasing is examined using 11 member ensemble predictions available four times daily from the National Centers for Environmental Prediction, which were combined into a single 44 member ensemble based on a common forecast verification time. Recurring ET patterns within the 44 member ensemble were objectively identified using a combination of EOF and cluster analysis. Ensemble spread first appears near the point where the TC moves into the midlatitudes and then propagates downstream. Although ensemble spread in the forecast fields was large at extended forecast intervals, the ensemble spread, and the number of ET patterns identified in successive EPS predictions, decreased as the ET process became better defined. Within 48 hours of the ET event, the ensemble prediction system properly identified the ET pattern with a minimum ensemble spread. Similar to Klein et al. (2002), the shifts in the initial position of the TC and the subsequent dynamical coupling can explain differences between weak and strong ET reintensifications.

During July 2005, Typhoon Banyan recurved and underwent tropical transition over the western North Pacific. Coincident with the extratropical transition of Banyan, a large mid-tropospheric anticyclone developed immediately east of the recurving typhoon. The anticyclone was associated with a high-amplitude Rossby wave-like pattern that developed downstream of the anticyclone and extended across the North Pacific. Development of the anticyclone is examined with respect of the interaction between the outflow from Banyan and the midlatitude jet streak. During the poleward movement of TY Banyan, an anticyclonically-curved jet streak was forced by the merger of the upper-level outflow from Banyan and a jet streak associated with an upstream trough. The anticyclonic curvature was accentuated by the presence of a mid-tropospheric cyclone east of Banyan. The anticyclonic curvature increased as Banyan moved poleward and the mid-tropospheric cyclone moved equatorward. Thermodynamic forcing of the mid-tropospheric anticyclone is examined with respect to the poleward movement of warm moist air that ascends as it is advected around the eastern side of the decaying typhoon. The combination of dynamic and thermodynamic factors is examined in a potential vorticity framework to identify the development of the anticyclone east of Banyan and the transformation of Banyan into a midlatitude cyclone.

The increase in skill of numerical model guidance and the use of consensus forecast techniques have led to significant improvements in the accuracy of tropical cyclone track forecasts at ranges beyond 72 h. Identification of instances when the forecast track from an individual numerical model may be in error could lead to additional improvement in the accuracy of tropical cyclone track forecasts. An objective methodology is tested to characterize the spread among the three primary global numerical model forecast tracks used as guidance by the Joint Typhoon Warning Center. Statistically-significant principal components derived from empirical orthogonal functions of mid-tropospheric height and vorticity forecast fields identify cases of large spread among model forecasts. Cases in which the three-model average forecast track resulted in a large error were characterized by a distribution of principal components such that one component was significantly different from the other two. Removal of the forecast track associated with the outlying principal component resulted in a reduced forecast error. Therefore, the objective methodology may be utilized to define a selective consensus by removing forecast tracks from consideration based on the projection of forecast fields onto empirical orthogonal functions and inspecting the distribution of the resulting principal components.

Significant discrepancies exist in global estimates of the atmospheric methane (CH4) budget. This is particularly true for tropical South America where bottom-up approaches, rooted in field observation, tend to under estimate atmospheric observations. As such, a better understanding of soil environments, which are capable of acting as both source and sink for atmospheric CH4, is required. Soil-atmosphere CH4 exchange is fundamentally determined by the balance between strictly anaerobic methanogenic and aerobic methanotrophic microbial processes. For this reason, CH4 emissions are typically associated with anoxic wetland soils, whilst, oxic upland soils are thought to uptake CH4 from the atmosphere. However, there is increasing evidence that upland soils may act as sources of CH4 through methanogenic activity within cryptic wetlands or anoxic microsites. This thesis aims to: document soil-atmosphere CH4 fluxes in poorly represented tropical upland and montane ecosystems, investigate controls on CH4 flux with a focus on soil oxygen (O2) concentration and investigate relationships between methanogenic and methanotrophic processes under oxic conditions. These aims are addressed in three chapters focusing on lowland terra firme, premontane and montane forests and montane humid puna grasslands and wetlands along an Amazonian to Andean transect spanning ~ 3300 m of elevation in southeastern Peru. In the lowland rainforest intensive seasonal field campaigns and laboratory incubations were conducted on higher porosity ultisol and lower porosity inceptisol soils. Mean (s.e.) net CH4 fluxes for dry and wet seasons were, respectively, -1.59 (0.06) and - 1.39 (0.07) mg CH4-C m−2 d−1 for the ultisol and -0.95 (0.06) and -0.41 (0.10) mg CH4-C m−2 d−1 for the inceptisol. Greater uptake rates in the ultisol than the inceptisol were best explained by lower water-filled pore space (WFPS). Similarly, WFPS best explained between season variation in net CH4 flux from the inceptisol, whilst, we were unable to explain the smaller variations observed for the ultisol. Methanogenic processes were active in both the ultisol and inceptisol soils despite oxic conditions. In the premontane and montane forests, long-term monthly field measurements were conducted over two and a half years in premontane, lower montane and upper montane settings. Mean (s.e.) net CH4 fluxes for aggregated dry and wet season months were, respectively, -0.20 (0.15) and -0.08 (0.13) mg CH4-C m−2 d−1 for the premontane forest, -1.12 (0.13) and -0.97 (0.11) mg CH4-C m−2 d−1 for the lower montane forest and -1.55 (0.13) and -1.04 (0.11) mg CH4-C m−2 d−1 for the upper montane forest. Increased uptake with elevation was best explained by decreases in WFPS. Significant variation in net CH4 flux between seasons, driven by variation in WFPS, was only identified for the upper montane forest.