Thesis (M.S. in Meteorology)--Naval Postgraduate School, June 1990. / Thesis Advisor(s): Wash, Carlyle H. Second Reader: Nuss, Wendell L. "June 1990." Description based on title screen as viewed on October 19, 2009. DTIC Indicator(s): Weather forecasting, computerized simulation, cyclogenesis, ERICA (Experiment on Rapidly Intensifying Cycloner over the Atlantic), NORAPS (Naval Operational Regional Atmospheric Prediction System), Theses. Author(s) subject terms: Rapid cyclogenesis, ERICA, NORAPS. Includes bibliographical references (p. 77-79). Also available in print.

Thesis (M. Sc.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 175-187). Also available via the World Wide Web.

Thesis (M.S. in Meteorology and Oceanography)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Elsberry, Russell L. ; Harr, Patrick A. "September 1990." Description based on title screen as viewed on December 16, 2009. DTIC Identifier(s): EOF (empirical orthogonal functions). Author(s) subject terms: Tropical cyclones, recurvature, empirical orthogonal functions. Includes bibliographical references (p. 73-74). Also available in print.

Thesis (M.S. in Meteorology and Oceanography)--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Elsberry, Russell L. ; Harr, Patrick A. "September 1990." Description based on title screen as viewed on December 16, 2009. DTIC Identifier(s): EOF (empirical orthogonal functions). Author(s) subject terms: Tropical cyclones, recurvature, empirical orthogonal functions. Includes bibliographical references (p. 73-74). Also available in print.

Thesis (M.S. in Meteorology)--Naval Postgraduate School, March 2005. / Thesis Advisor(s): Russell L. Elsberry. Includes bibliographical references (p. 89-90). Also available online.

No description available.

Tropical cyclones (TCs) are destructive, natural occurring phenomena that can cause the loss of lives, extensive structural damage, and negative economic impacts. A major hazard associated with these tropical systems is rainfall, which can result in flood conditions, contributing to the death and destruction. The role rainfall plays in the severity of the TC aftermath emphasizes the importance for models to produce reliable precipitation forecasts. Hurricane model precipitation forecasts can be improved through precipitation verification as the model weaknesses are identified. In this study, the Hurricane Analysis and Forecast System (HAFS), an experimental NOAA hurricane model, is evaluated for its skillfulness in forecasting TC precipitation. An object-based verification method is used as it is demonstrated to more accurately represent the model skill compared to traditional point-based verification methods. A 600 km search radius is implemented to capture the TC rainfall and the objects are defined by 2, 5, and 10 mm/hr rain rate thresholds. The 2 mm/hr threshold is chosen to predominantly represent stratiform precipitation, and the 5 and 10 mm/hr thresholds are used as approximate thresholds between stratiform and convective precipitation. Shape metrics such as area, closure, dispersion, and fragmentation, are calculated for the forecast and observed objects and compared using a Mann Whitney U test. The evaluation showed that model precipitation characteristics were consistent with storms that are too intense due to forecast precipitation being too central and enclosed around the TC center at the 2 mm/hr threshold, and too cohesive at the 10 mm/hr threshold. Changes in the model skill with lead time were also investigated. The model spin-up negatively impacted the model skill up to six hours at the 2 mm/hr threshold and up to three hours at the 5 mm/hr threshold, and the skill was not affected by the spin-up at the 10 mm/hr threshold. This indicates that the model took longer to realistically depict stratiform precipitation compared to convective precipitation. The model skill also worsened after 48 hours at the 2 and 10 mm/hr thresholds when the precipitation tended to be too cohesive. Future work will apply the object-based verification method to evaluate the TC precipitation forecasts of the Basin-Scale Hurricane Weather Research and Forecasting (HWRF-B) model. / Master of Science / Tropical cyclone (TC) precipitation can impose serious threats, such as flood conditions, which can result in death and severe damage. Due to these negative consequences associated with TC rainfall, it is important for affected populations to be sufficiently prepared once these TCs make landfall. Hurricane models play a large role in the preparations that are made as they predict the location and intensity of TC rainfall, which influences the peoples' choices in taking precautionary measures. Therefore, hurricane models need to be accurate, and comparing the forecast precipitation to the observed precipitation allows for areas in which the model performs poorly to be identified. Model developers can then be informed of the areas that need to be improved. In this study, the precipitation forecasts from the Hurricane Analysis and Forecast System (HAFS) model, a hurricane model that is currently under development, are evaluated. The shape and size of the forecast and observed precipitation are quantified for light, moderate, and heavy precipitation using metrics such as area, perimeter, and elongation. The values of these metrics for the forecast and observed precipitation are compared using a statistical test. The results show that the hurricane model tended to forecast storms that are too weak due to forecast precipitation being too close to the TC center, too wrapped around the TC center, and too connected. The hurricane model is also evaluated for the accuracy of its forecasts with time from model initialization. The model had a harder time representing lighter precipitation than heavier precipitation during the first 6 hours after initialization. A decrease in the accuracy of the model forecasts was also shown 48 hours after initialization due to the general degradation of model accuracy with time after initialization. Future work will evaluate the TC precipitation forecasts of another hurricane model, the Basin-Scale Hurricane Weather Research and Forecasting (HWRF-B) model.

Hurricane Matthew (2016) was a category 5 hurricane that interacted with remote terrain over northern South America in the early stages of its life cycle. Because tropical cyclone (TC) precipitation and convection are known to be crucial factors in the understanding and forecasting of TC intensity, this study investigates how this terrain impacted Hurricane Matthew's rainband structure. Remote terrain is hypothesized to play a role in the strength of TC rainband convection by modifying the thermodynamic environment such that subsiding dry air advects over an extremely moist ocean surface layer leading to increased moist static instability. To investigate this hypothesis, this study utilizes the Advanced Research Weather and Research Forecasting Model (WRF-ARW) to create a high-resolution (2-km horizontal grid spacing) control simulation (CTL) of Hurricane Matthew and a second experimental simulation with a 50% reduction of terrain height over the topography of northern South America (T50). This study focuses on a particular convective rainband positioned downstream of the terrain that displayed prolonged robust convection during the initial stages of Hurricane Matthew's life cycle. Results indicate that characteristics of this robust rainband are consistent with prior research on an inner core rainband called a principal rainband. This rainband does not display differences in intensity in the two simulations but is located closer to the TC center and more persistent in the control simulation. In the region downstream of the topography, significantly (p < 0.05) drier conditions exist in the control simulation, which is consistent with the hypothesis that downslope motion would lead to a drier air mass. TC structural changes are also apparent, with a weaker TC in the reduced topography simulation. This research emphasizes the potentially important role of terrain distant from the TC center with possible influences on TC rainband convection and warm core structure. Conclusions of this research are limited due to the small sample size of a single case study. An ensemble modeling study and additional cases are needed for a more thorough conclusion on the impact of remote terrain on TC structure. / Master of Science / Predicting the intensity of hurricanes remains a monumental challenge for hurricane forecasters. Many factors can influence the intensity of hurricanes, including the strength, frequency, and spatial distribution of hurricane rainbands (band of precipitation). The hypothesis for this study is that terrain distant from the hurricane center can alter the hurricane environment and cause more frequent and stronger rainbands to form. To assess this hypothesis, I use a weather model to simulate Hurricane Matthew (2016) while it was interacting with remote terrain over northern South America on September 30 - October 1, 2016. Then I use the same model, but with terrain height reduced by 50% over northern South America and analyze the similarities and differences in the hurricane structure and rainband patterns. The results of this study suggest that terrain did not alter the peak rain rates in the hurricane rainbands but may have caused more frequent, widespread, and prolonged precipitation. Also, differences in hurricane structure were apparent when comparing the two model simulations. The reduced terrain simulation produced a weaker hurricane, lending some evidence to support the hypothesis that terrain may have played a role in altering the hurricane structure. These results demonstrate the potential importance of distant terrain on forecasting hurricane precipitation and intensity.

Introduction Krypton-81m is a radioactive gas with a half-life of 13 s, and found to be useful in many applications in nuclear medicine, particularly for lung perfusion studies and ventilations. Due to high demands for 81mKr, we have developed an automated Krypton system to be installed in one of the Cyclotron’s beamlines at King Faisal Specialist Hospital and Research Centre (KFSH&RC) and to deliver large activity of the radioactive gas. Material and Methods The effective cross section of producing 81Rb is between 15 and 30 MeV [1]. Therefore, range and stopping power of the effective cross section were calculated with respect to gas density of 0.0185 g/cm3. This value is equivalent to gas density at 5.0 bars at room temperature. SRIM calculations resulted in a range of 589 mm. However, due to limitation in fabricating such long target chamber, the target length is chosen to be 250 mm. Attached to the end of target body is a special water circulating flange ‘back-pool’, its purpose is to absorb the rest of the energy and protons Bragg peak. The target body is made of Aluminum with the inner part being electroplated with nickel. The target body is of conical shape. The target body is electrically isolated from other parts to allow accurate beam current reading. Full access to the target loading/unloading steps is made through touch screen technology (FIG. 2) for user access. Additionally, the target control system is designed to be protected through chain of interlock steps. The production cycle of 81Rb is explained as follow. Target is evacuated to approximately 10−3 mbar before being filled with natKr at pressure of 5 bars. At the end of bombardment, recovery of natKr is done via cryogenic vessel. Finally, the radioactivity is washed with KCl and pushed to Hotcells through the nitrogen gas for chemistry processing. Irradiation time was approximately 30 min. Results and Conclusion Experimental results clearly showed a fairly good activity of 81mKr as shown in TABLE 1. In all experiments, the radionuclidic purity of 81mKr was above 99.59%. 79mKr and 79Kr were also measured with a percentage of, respectively, 0.34 and 0.07 %. Special attention has to be drawn to last experiment where the yield significantly in-creased, due to the period where the KCl left inside the target (10 min) before pushing the solution to the Hotcells

Introduction Nitrogen [13N] NH3 is a liquid radioisotope, produced by medical cyclotrons for nuclear medicine application and widely applied for evaluation of myocardial perfusion in clinical assessments [1,2]. Owing to its short half-life (10 minutes), the unloading procedure of the radio-active solution of [13N]NH3 from the target is crucial in saving the activity produced for patient. Therefore, an efficient technique in un-loading the radioactive solution from the target body was developed using COMSOL Multiphysics. The new design of the target with improved unloading technique resulted in 30% increase of the available 13N activity. In our experiments, 13N was produced by the 16O(p,α)13N reaction. The energy of proton beam was 16.5 MeV. Material and Methods A 2D model was developed using COMSOL Multiphysics to simulate the inner geometry of [13N] Ammonia target. In the 2D model, water and aluminum were used as materials for the inner body and outer boundary (walls), respectively. The physical equations used to solve the problem of allocating proper place for the loading/unloading opening is turbulent, k-ε Module being extracted from fluid flow module. FIGURE 1 shows the result of simulating water flow on the target water channels. The entrance of the pushing solution (for unloading) was designed to create a turbulent flow inside the target body and, hence, to collect most of the activity inside the target. FIGURE 2 shows the setup for 13N production. A peristaltic pump is used to push the solution after irradiation to the hotcell at 6 ml/min flowrate. The distance from the target to the hotcell is approximately 30 meters. Results and Conclusion FIGURE 3 presents activity produced in milicurie (mCi) for several patient runs. The activity obtained in some experiments reached up to 330 mCi when we irradiated the target with 25 μA for 15 min. This was satisfactory for delivery to the patient at the nuclear medicine department. Moreover, purity of [13N] purity was above 95 % what meets the standard regulation for administration to a patient.