Search Results
Abstract
A methodology is developed for deriving atmospheric water vapor transports over the World Oceans from satellite-retrieved precipitation (P) and evaporation (E) datasets. The motivation for developing the method is to understand climatically varying properties of transports, that is, year-to-year changes of the seasonally averaged divergent transport distribution fields, over regions where conventional data, in particular, winds, are sparse. Ultimately, the method is intended to take advantage of the relatively complete and consistent coverage, as well as continuity in sampling, associated with E − P datasets obtained from satellite measurements. Separate P and E retrievals from Special Sensor Microwave Imager (SSM/I) measurements, along with P retrievals from Tropical Rainfall Measuring Mission (TRMM) measurements, are used to obtain the transport solutions.
In this opening study, a 7-yr climatological normal is derived for the January–February–March (JFM) period for years 1988–94, providing the basis for comparing vapor transport anomalies from the 1997/98 El Niño and 1999/2000 La Niña events. These are derived from JFM-averaged transport solutions for 1998 and 1999, respectively. These two periods correspond to times when the Multivariate ENSO Index (MEI) provided by the NOAA Climatic Data Center (CDC) was first at a relative maximum and then at a relative minimum in conjunction with back-to-back west Pacific warm and cold events. Because the El Niño–La Niña events produce such highly contrasting behavior in the transports, shifting from a largely meridionally oriented solution to a largely zonally oriented solution, focusing on this pairing, helps to explain why the methodology is reliable and effective in capturing important details embedded in full-coverage E − P fields.
The analysis includes a sensitivity study of the transport solution technique based on 20 combinations of four precipitation datasets (two satellite based and two model based) and five evaporation datasets (two satellite based, one in situ observation based, and two model based), which helps to explain the reliability of the method. The analysis also includes a comparison to water vapor transports derived with the same method, but applied to E − P datasets obtained from global analysis products prepared by the National Centers of Environmental Prediction (NCEP), again to help explain the reliability of the method. The study concludes by first showing how the anomaly JFM 1998 El Niño solution behaves in close correspondence to associated SST anomalies and is generally more realistic in comparison to the corresponding NCEP solution. Finally, its reliability is discussed in terms of the implications of the vapor transport features for the El Niño–La Niña transition, vis-à-vis north–south and east–west circulations and their accompanying impact on the atmospheric hydrological cycle.
Abstract
A methodology is developed for deriving atmospheric water vapor transports over the World Oceans from satellite-retrieved precipitation (P) and evaporation (E) datasets. The motivation for developing the method is to understand climatically varying properties of transports, that is, year-to-year changes of the seasonally averaged divergent transport distribution fields, over regions where conventional data, in particular, winds, are sparse. Ultimately, the method is intended to take advantage of the relatively complete and consistent coverage, as well as continuity in sampling, associated with E − P datasets obtained from satellite measurements. Separate P and E retrievals from Special Sensor Microwave Imager (SSM/I) measurements, along with P retrievals from Tropical Rainfall Measuring Mission (TRMM) measurements, are used to obtain the transport solutions.
In this opening study, a 7-yr climatological normal is derived for the January–February–March (JFM) period for years 1988–94, providing the basis for comparing vapor transport anomalies from the 1997/98 El Niño and 1999/2000 La Niña events. These are derived from JFM-averaged transport solutions for 1998 and 1999, respectively. These two periods correspond to times when the Multivariate ENSO Index (MEI) provided by the NOAA Climatic Data Center (CDC) was first at a relative maximum and then at a relative minimum in conjunction with back-to-back west Pacific warm and cold events. Because the El Niño–La Niña events produce such highly contrasting behavior in the transports, shifting from a largely meridionally oriented solution to a largely zonally oriented solution, focusing on this pairing, helps to explain why the methodology is reliable and effective in capturing important details embedded in full-coverage E − P fields.
The analysis includes a sensitivity study of the transport solution technique based on 20 combinations of four precipitation datasets (two satellite based and two model based) and five evaporation datasets (two satellite based, one in situ observation based, and two model based), which helps to explain the reliability of the method. The analysis also includes a comparison to water vapor transports derived with the same method, but applied to E − P datasets obtained from global analysis products prepared by the National Centers of Environmental Prediction (NCEP), again to help explain the reliability of the method. The study concludes by first showing how the anomaly JFM 1998 El Niño solution behaves in close correspondence to associated SST anomalies and is generally more realistic in comparison to the corresponding NCEP solution. Finally, its reliability is discussed in terms of the implications of the vapor transport features for the El Niño–La Niña transition, vis-à-vis north–south and east–west circulations and their accompanying impact on the atmospheric hydrological cycle.
Abstract
Historical understanding of marine biological dynamics has been limited by sparse in situ observations and the fact that dedicated ocean color satellite remote sensing only began in 1997. From these observations, it has become clear that physical oceanography controls biological variability over seasonal to interannual time scales. To quantify how multidecadal, climate-scale patterns impact biological productivity, the strong correlation with sea surface temperature and sea surface height is utilized to reconstruct a retrospective 51-yr time series of surface chlorophyll, the pigment measured by ocean color satellites. The canonical correlation analysis statistical reconstruction demonstrates greatest skill away from land and within about 10° of the equator where chlorophyll variance is greatest and predominantly associated with El Niño–Southern Oscillation dynamics. Differences in chlorophyll patterns between east or central Pacific El Niño events are observed, with larger declines east of 180° for east Pacific events and west of 180° for central Pacific events. Additionally, small but significant decadal variations in chlorophyll patterns are observed corresponding to the Pacific decadal oscillation. Decadal changes in chlorophyll west of 180° are consistent with increased stratification, whereas changes between 110°–140°W may be related to long-term shoaling of the nutrient-bearing equatorial undercurrent.
Abstract
Historical understanding of marine biological dynamics has been limited by sparse in situ observations and the fact that dedicated ocean color satellite remote sensing only began in 1997. From these observations, it has become clear that physical oceanography controls biological variability over seasonal to interannual time scales. To quantify how multidecadal, climate-scale patterns impact biological productivity, the strong correlation with sea surface temperature and sea surface height is utilized to reconstruct a retrospective 51-yr time series of surface chlorophyll, the pigment measured by ocean color satellites. The canonical correlation analysis statistical reconstruction demonstrates greatest skill away from land and within about 10° of the equator where chlorophyll variance is greatest and predominantly associated with El Niño–Southern Oscillation dynamics. Differences in chlorophyll patterns between east or central Pacific El Niño events are observed, with larger declines east of 180° for east Pacific events and west of 180° for central Pacific events. Additionally, small but significant decadal variations in chlorophyll patterns are observed corresponding to the Pacific decadal oscillation. Decadal changes in chlorophyll west of 180° are consistent with increased stratification, whereas changes between 110°–140°W may be related to long-term shoaling of the nutrient-bearing equatorial undercurrent.
