Atlantic tropical cyclone activity 1938 2009

The data set used here for the Atlantic Ocean has the longest period of record at 72 years. Since 1938, there have been a total of 752 TCs, including 326 tropical storms, and 165, 78, 86, 70, and 27 category 1 - 5 hurricanes (Table 3a, 4). During the 2000-2009 tropical cyclone seasons, there were 72 Atlantic hurricanes (Table 3a), which means that the years since the LJ00 study were the most active during the 1938 - 2009 record. However, the Atlantic TC seasons since 1995 have been relatively active. During the six year period from 1995 - 2000, there were 49 hurricanes (81 TCs), while during the years from 2001 - 2006, there were been 47 hurricanes (94 TCs), in spite of the fact that 15 hurricanes occurred during the 2005 season. Two other six-year periods were compared to these two recent eras and both of these earlier periods occurred before the satellite era. In particular, 43 (37) hurricanes and 62 (74) TCs occurred from 1884-1889 (1932-1937). Thus, it would be reasonable to consider the activity of these pre-satellite era periods as comparable to the modern eras, since it is very likely that some TCs were missed during the pre-satellite era.

Additionally, during the 2000 - 2009, there were 35 intense hurricane (category 3 - 5), which represented 49% of all storms (Table 3a). This compares with the LJ00 study in which 42% of all storms were intense during the previous 62 years. This indicates an increase in the ratio of intense storms overall. The increased activity of the latest period, however, is similar to that of the number of intense storms for the 30-year period of 1940-69 (48% - Table 3). Thus, as shown in Tables 3a and 4 for the entire 72-year record, the inclusion of the last ten years has not made any noteworthy change in the ratio of hurricane intensities for the overall Atlantic Ocean basin activity.

Pacific Decadal Oscillation

Positive (warm) phase (PDO1) Negative (cool) phase (PDO2)

Fig. 2. The phases of the PDO as described in the text. SST anomalies are shown in color in accord with the scale shown. The arrows show anomalies in wind speed and direction. Reproduced with permission from the Joint Institute for the Study of Atmosphere and Ocean (JISAO - http://jisao.washington.edu) at the University of Washington.

Fig. 2. The phases of the PDO as described in the text. SST anomalies are shown in color in accord with the scale shown. The arrows show anomalies in wind speed and direction. Reproduced with permission from the Joint Institute for the Study of Atmosphere and Ocean (JISAO - http://jisao.washington.edu) at the University of Washington.

LJ00 reported that there were no statistically significant trends in the Atlantic Ocean basin hurricane activity. Adding the 2000-2009 hurricane and tropical storm occurrences does not result in any change in the trends for the overall occurrence of category 1 - 5 storms (Fig. 3a). Separating these by category demonstrates that the trends for category 2-5 storms were not statistically significant (not shown). The trend in tropical storms (Fig 3b) and category 1 hurricanes (not shown) show an increase stronger than that in Fig. 3a, which shows the overall trend for the total number of hurricanes (significant at the 99% confidence level). Whether this upward trend in category one storms or tropical storms is real is clouded by two issues. The trend could be the result of 1) the problem of the "fortuitous" placement starting and ending points in a long time series (the recent activity could be the peak in a long-term oscillation), or 2) that the earlier part of the 72-year period was in the pre-satellite era and storms may have been undercounted. It is likely that both of these factors are contributing to the overall increase. Nonetheless, if the 1970-2009 period only was used, there was an increase in the occurrence of Atlantic basin tropical storms and category one hurricanes and the trends were also statistically significant (not shown) at the 95% confidence level. However, an examination of Fig. 3 suggests significant interannual variability as found by LJ00 and Lupo et al. (2008).

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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