Satellite observations of atmospheric moisture, including precipitation, cloud properties, and water vapor, are examined over the tropical east Pacific as part of NOAA's Pan-American Climate Studies (PACS) project. Total column water vapor estimates from SSM/I are used in conjunction with clear- and all-sky brightness temperatures from SSM/T2 and AMSU to investigate changes in the large-scale distribution of water vapor at various levels. Geostationary infrared window channel and water vapor channel observations taken every 3 hours from GOES-9 are used to look at diurnal and higher frequency variability.
Interannual variability resulting from the 1997/98 El Nino shows a pattern of anomalously dry air present in the upper troposphere over both the northern and southern subtropics in the east Pacific. These features are present in conjunction with the region of intensified moisture and convection along the east Pacific intertropical convergence zone (ITCZ) normally associated with ENSO.
The production of rainfall along the east Pacific ITCZ is also investigated using data from a combination of satellite sensors. Substantial differences between satellite infrared and passive microwave rainfall estimates over the east Pacific ITCZ have not been adequately explained due to a lack of in-situ observations over this region. To address this issue, retrievals of cloud liquid water and cloud ice content from SSM/I and SSM/T2 are matched with high-resolution visible and infrared cloud imagery from geostationary
satellites to investigate the level and depth of clouds along the ITCZ. Differences are then identified in the distribution of cloud-top temperatures corresponding to precipitating systems over both the east and west Pacific for both El Nino and non El Nino conditions