In this study, we investigate how humidity fields at lower troposphere may affect tropical cyclone (TC) activity in the Atlantic basin by using the atmospheric humidity profiles from the Atmospheric Infrared Sounder

(AIRS) on board the EOS-Aqua satellite, long-term humidity data from the NCEP Reanalysis and TC data from the National Hurricane Center. The results show that TCs form not only over the north Atlantic near the tropics (similar to the the traditionally defined Main Development Region

or MDR), but also over the western north Atlantic region. Moreover, many more TCs are found to form over the western region than near the tropics. The humidity at the lower troposphere, such as the specific humidity at 850 hPa (Q850), and relative humidity at 700 hPa (RH700),

are found to be associated with hurricane activity, including the hurricane number or frequency, TC duration in days, intensity, and accumulated cyclone energy (ACE) over the western region. The ACE of hurricanes in the western region is associated with the humidity fields

at lower troposphere with r (Q850, ACE) as 0.4974, and r (RH700,ACE) as 0.4887 for the period from 1948 to 2006. The humidity at lower level of the atmosphere may be an important mechanism for the Atlantic hurricane activity and explain the difference between 2006 and 2005, while only emphasizing SST alone might have incorrectly predicted

another busy year for 2006.