Project Report

This research investigates how the COSMIC data (i.e., level 2 werPrf) affects the forecasts of tropical cyclone formation, and how accurate (or vice versa) the forecasts are compared to the observations; with an emphasis on the forecast of TD8 that was heavily affected by dust outbreak. The COSMIC data is obtained by the GPS RO technique. This technique consists of a GPS transmitter and GPS receiver in low Earth orbiting satellite (LEO) which are located on opposite sides of the planetary limb. Orbital motion of one or both instruments produces the limb scanning geometry. Tropical Depression 8, as the AEW and vortex moved out over the Eastern Atlantic (12.5°N–18°W) during the early morning hours of September 12th, deep convection rapidly developed with the system. It is interesting that intense convection developed in such close proximity to the thermodynamically stable atmosphere associated with the SAL. This investigation was accomplished by a seventy-two hour simulation, were the transition from continental (e.g. MCS) to maritime system (e.g AEW) later TD8 Hurricane Helene 2006 took place. The WRF-ARW model and the WRF data assimilation system (i.e., WRF 3DVAR) were employed in this research. An evaluation was done of the impact of the different environmental conditions (e.g. sea level pressure and relative humidity), which affect TC genesis. Also, the impact of the nine RO soundings on TC genesis was evaluated. The CTRL simulation was established utilizing the FNL data. Since the CTRL experiment simulated TD8 well in terms of intensity, it is compared with the COSMIC experiment during the rest of the investigation. By analyzing the sea level pressure in the CTRL and COSMIC experiments the minimum pressure simulated using COSMIC data at the time were the AEW was classified as TD8 shows a more intense TD8. The simulated sea level pressure from the CTRL experiment shows that the intensity is more consistent with Rapid Developing Thunderstorm. Nevertheless, the simulation using the COSMIC data improved the location of TD8 in terms of lat and lon with a lat 13°N and lon 21.5°W versus observations of lat 11.9°N and lon 22.0°W at Sep 12 1200UTC. The relative humidity show that the COSMIC experiment had more dry air compared the same areas with the CTRL experiment. The opposite is true for the moisture areas. The COSMIC experiment shows more moisture areas compared with the CTRL experiment. In order to understand the cause or the causes of why the COSMIC experiment intensified faster than the CTRL, more extensive simulations were conducted. In order to accomplish this task a series of experiments were designed to evaluate how many COSMIC soundings should be assimilated in order to have a more accurate simulation. The experiments were as follows: Experiment #1 D01 was divided in to a Cartesian plane; Experiment #2 an evaluation for each of the nine RO soundings; Experiment #3 different combination of the two better RO sounding (e.g. RO sounding 4 and 8) with the RO sounding located in the area of drier air (e.g. RO sounding 2). All of these experiments were designed with the same setup as the CTRL. From all the experiments performed with the different RO soundings combination, the RO sounding that has the greatest significant impact on the TD8 simulation was RO sounding 8. From this result we can conclude that the following parameters need to be fulfilled in order to improve the simulation: Time: the RO sounding time needs to be close enough to the time the experiment is going to start. Elevation: How deep does the RO sounding reaches into the lower troposphere (2km above surface)? Levels: How many levels does the RO sounding have? E.g. vertical level. It was unimaginable how much I learned from this program. Before this program and been in Taiwan I did not have the idea of how much you can do with COSMIC data. It has been of so such more help to work with several students currently working with COSMIC data to simulate tropical cyclones. We exchange our different points of views and gave advise to one another in term of how address different type of problems that people have experience before and learned how to solve them. This type of interaction is really important to enhance your knowledge and challenge you to move to another level scientifically. After talking several times with my host, Profesor.Huang we agree on that there is a lot of more experiment and analysis that I can perform with my case study (TD8). Since he knows my plans of pursuing my PhD degree starting next Spring, he suggest me to keep this case study for my future research. Thanks do the program now I am going to start my PhD with some thing that for some student take a lot to figure out, the topic of their thesis.

National Science Foundation (NSF)
Office of International and Integrative Activities (IIA)
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Carter Kimsey
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Rosado Keren I
United States
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