Sponsors : National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC)

1. The Effects of Stratospheric Aerosols on Tropical Cyclone Activity in the North Atlantic Basin Abstract Results This study examines how fluctuations in stratospheric ozone levels have affected the energy of tropical cyclones in the North Atlantic basin between 1979 and 2010. We postulate that there is a correlation between stratospheric ozone concentration and tropical cyclone energy. As a result of ozone depletion from anthropogenic activities (namely chlorofluorocarbons (CFC) emissions), UV light retained near the ozone layer has decreased, leading to lower stratospheric cooling. An increase in the temperature differential between the warm sea surface and the cooler atmosphere results. This differential creates unstable air masses, hindering tropical cyclone development (Emanuel, 1986). Previous research (Rowland, 1990) has shown that a strong negative correlation exists between CFCs and ozone levels. The team’s research has shown a strong positive correlation between stratospheric ozone concentrations in the Atlantic Basin to stratospheric temperatures in the Northern Hemisphere from 1979-2010 (0.5977). Finally, a strong correlation value exists between stratospheric temperatures and tropical cyclone energy in the North Atlantic Basin from 1979-2010 (-0.47384). Ozone layer depletion should be considered when forecasting tropical cyclone development. Introduction Figure 4: Stratospheric ozone shown along with CFC-11 and CFC-12 levels over the time period of 1979 to 2010. Strong negative correlations exist between stratospheric ozone and CFC-11 and stratospheric ozone and CFC-12. CFC-11 and CFC-12 levels start to gradually decrease around 1995. Figure 3: Stratospheric ozone, measured in Dobson Units (DU), over the time period of 1979 to 2010. Overall a downward trend in the levels of ozone can be observed. The sharp drop in ozone levels in 1991 is thought to be a result of the volcanic eruption of Mount Pinatubo in the Philippines. • Tropical Cyclones: Large scale, non-frontal, low pressure systems that form and develop over tropical and subtropical waters. Tropical cyclones possess organized convection and definite cyclonic surface wind patterns. Organized convection, a supply of warm water, minimal vertical wind shear, and definite cyclonic surface wind patterns are necessary for their development. • Ozone and Stratospheric Warming: Ozone is an allotrope of oxygen that exists in the lower troposphere as a pulmonary irritant and in the stratosphere as a shield to ultra violet radiation (UVB and UVC) from the sun. When stratospheric ozone absorbs UV radiation, ozone is converted into molecular oxygen (O2) and oxygen radicals (O). This is an exothermic process that results in stratospheric warming. • Ozone depletion by CFCs and Stratospheric Cooling: • Stratospheric aerosols from human derived • pollutants such as chlorofluorocarbons (CFCs) • have depleted stratospheric ozone levels, • thereby decreasing the occurrence of this • exothermic process. This has led to a • stratospheric cooling. Figure 5: Erythemal ultraviolet levels and stratospheric ozone measured over the time period of 1979 to 2005. The lapses in the graph indicate periods in which the satellites used were unable to obtain data. Figure 6: Stratospheric ozone and stratospheric temperature anomalies for the time period of 1979 to 2010. There exists a strong positive correlation between the two. Figure 1: Mechanism for ozone depletion by CFCs. http://www.learner.org/courses/envsci/visual/visual.php?shortname=ozone_depletion Materials and Methods • Tropical cyclone energies were calculated by squaring the totals of the wind speed readings obtained from the Unisys Weather database and adding them for each year by using the kinetic energy equation E=mv² (mass was not accounted for). Tropical cyclone energy was calculated for the North Atlantic Ocean (1979-2010). Monthly stratospheric ozone data was obtained from the NASA GSFC TOMS/SBUV Merged Data Set for the region 0-90°N, 0-85°W and averaged for each year. Daily erythemal (surface) UV data was obtained from the TOMS dataset and averaged for each year. Monthly CFC-11 and CFC-12 data for the Northern Hemisphere was obtained from the NOAA HATS dataset and averaged for each year. Stratospheric temperature data was obtained from the RSS dataset for the 0º-82.5º N region. Figure 7: Stratospheric temperature and North Atlantic tropical cyclone energy for the time period of 1979 to 2010. There exists a strong negative correlation between the two. Figure 8: Numerical Correlations. Figure 2: Drawing of Nimbus-7, the first TOMS instrument launched in 1978. Conclusion and Future Work Sponsors: National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) Goddard Institute for Space Studies (GISS) New York City Research Initiative (NYCRI) CUNY Queensborough Community College Contributors: Adnan Aziz (UG) Michael Hirschberger (HSS) Alana Menendez (HSS) Mr. Daniel Mezzafonte (HST) Dr. Paul Marchese (PI) The data shows distinct correlations that support our hypothesis. Decreased ozoneconcentration correlates to decreased stratospheric temperature because of lessened ozone-UV interactions. This results in a greater temperature differential between the cool lower stratosphere and the warm sea surface. This differential creates unstable air masses which contributes to an increase in tropical cyclone energy. To better understand and support the correlation between stratospheric ozone depletion and tropical cyclone development we plan (1) to expand our study to include worldwide tropical cyclone energy, (2) to investigate the relationship between volcanic activity and tropical cyclone energy, (3) to explore the possibility of a lag period between stratospheric temperature and tropical cyclone energy, and (4) to investigate the relationship between Dimethyl Sulfide (DMS) and the development of Cloud Condensation Nuclei (CCN). http://earthobservatory.nasa.gov/Features/RemoteSensingAtmosphere/Images/nimbus7.jpg References / Emanuel, K.A.,1986. An air-sea interaction theory for tropical cyclones. Part I. J. Atmos. Sci., 43, 585-604. Rowland, F. S., 1990. Stratospheric Ozone Depletion by Chlorofluorocarbons. Ambio, 19, 281-292. http://weather.unisys.com/hurricane http://www.aoml.noaa.gov/hrd/tcfaq/A1.html http://www.aoml.noaa.gov/hrd/tcfaq/A15.html http://earthobservatory.nasa.gov/Features/RemoteSensingAtmosphere/Images/nimbus7.jpg http://www.learner.org/courses/envsci/visual/visual.php?shortname=ozone_depletion http://acdb-ext.gsfc.nasa.gov/Data_services/merged http://www.esrl.noaa.gov/gmd/hats/combined/CFC11.html http://www.esrl.noaa.gov/gmd/hats/combined/CFC12.html http://www.ncdc.noaa.gov/temp-and-precip/msu/ /