SeaWiFS observations of the Arabian Sea southwest monsoon bloom for the year 2000

Banzon, Viva F.; Evans, R. E.; Gordon, Howard R.; Chomko, R.

doi:10.1016/j.dsr2.2003.10.004

Cited by 47 publications

(30 citation statements)

References 38 publications

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“…Recently, the evolution of the SWM bloom has been described more clearly through the application of a spectral matching algorithm (SMA) that profoundly improves ocean color retrievals during high dust periods (Banzon, Evans, Gordon, & Chomko, 2004). Through the application of this method, an increase in data return of -75% over the northern Arabian Sea was achieved (Banzon, Evans, Gordon, & Chomko, 2002).…”

Section: Satellite-based Observations Of Surface Phytoplankton Distrimentioning

confidence: 99%

Monsoon-driven biogeochemical processes in the Arabian Sea

Wiggert

Hood

Banse

et al. 2005

Progress in Oceanography

224

171

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Although it is nominally a tropical locale, the semiannual wind reversals associated with the Monsoon system of the Arabian Sea result annually in two distinct periods of elevated biological activity. While in both cases monsoonal forcing drives surface layer nutrient enrichment that supports increased rates of primary productivity, fundamentally different entrainment mechanisms are operating in summer (Southwest) and winter (Northeast) Monsoons. Moreover, the intervening intermonsoon periods, during which the region relaxes toward oligotrophic conditions more typical of tropical environments, provide a stark contrast to the dynamic biogeochemical activity of the monsoons. The resulting spatial and temporal variability is great and provides a significant challenge for ship-based surveys attempting to characterize the physical and biogeochemical environments of the region. This was especially true for expeditions in the pre-satellite era. Here, we present an overview of the dynamical response to seasonal monsoonal forcing and the characteristics of the physical environment that fundamentally drive regional biogeochemical variability. We then review past observations of the biological distributions that provided our initial insights into the pelagic system of the Arabian Sea. These evolved through the 1980s as additional methodologies, in particular the first synoptic ocean color distributions gathered by the Coastal Zone Color Scanner, became available. Through analyses of these observations and the first large-scale physical-biogeochemical modeling attempts, a pre-JGOFS understanding of the Arabian Sea emerged. During the 1 990s, the in situ and remotely sensed observational databases were significantly extended by regional JGOFS activities and the onset of Sea-viewing Wide Field-of-View Sensor ocean color measurements. Analyses of these new data and coupled physical-biogeochemical models have already advanced our understanding and have led to either an amplification or revision of the pre-JGOFS paradigms. Our understanding of this complex and variable ocean region is still evolving. Nonetheless, we have a much better understanding of time-space variability of biogeochemical properties in the Arabian Sea and much deeper insights about the physical and biological factors that drive them, as well as a number of challenging new directions to pursue. The publl reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, Sjlfhering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of htfcrmsti n, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware tbsn notiithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a...

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Section: Satellite-based Observations Of Surface Phytoplankton Distrimentioning

confidence: 99%

Monsoon-driven biogeochemical processes in the Arabian Sea

Wiggert

Hood

Banse

et al. 2005

Progress in Oceanography

224

171

View full text Add to dashboard Cite

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“…However, the SeaWiFS-observed chlorophyll-a values were higher than the model predictions during the periods of high productivity in the Arabian Sea. In this context, we have not investigated the role of atmospheric dust which varies due to high monsoon winds (Banzon et al, 2004). The Somali Basin showed stronger annual peaks and a relatively lower semiannual peak than other locations.…”

Section: Discussionmentioning

confidence: 99%

Inter-annual Variability of Chlorophyll-a in the Arabian Sea and its Gulfs

Sarma

Azri²,

Smith³

2012

ijms

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The analysis of chlorophyll-a for a 7 year period from the ocean color images of SeaWiFS in the Arabian Sea and its marginal seas showed considerable inter-annual and geographical variability. The variability in chlorophyll-a was essentially centered on the Southwest and the Northeast monsoon seasons. The mean seasonal chlorophyll-a of the Northeast Monsoon in the western Arabian Sea showed an increasing trend from 1998 to 2004. The period of elevated chlorophyll-a levels in the Gulf of Mannar is apparently extended due to advection of chlorophyll-a rich water from the Bay of Bengal along the east coast of India. The mean distribution of chlorophyll-a from the SeaWiFS images shows a coastally trapped chlorophyll-a rich front from the east coast of India that enriches the Gulf of Mannar and continues northward along the west coast of India. As this front moves northward along the coast, the southern coastal waters turn oligotrophic. The chlorophyll-a concentration in the region is also influenced by the large-scale climatic events such as El Nino/La Nina during 1998-1999.The chlorophyll-a data from selected locations were subjected to spectral analysis to extract periodic signals. The annual signal was found to be dominant in the areas affected by only one of the two monsoons such as the Gulf of Mannar. The semiannual signal was predominant in areas affected by both the monsoons such as western and northern Arabian Sea. We built an empirical model incorporating the annual and semiannual modes of chlorophyll-a from the ocean color data. The ratio of the standard deviations of SeaWiFS-observed to the modeled chlorophyll-a, taken as a measure of model suitability, varied between 0.71 and 0.86. Thus the chlorophyll-a variability in this region can reasonably be predicted using the empirical model developed in this study.

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“…The region off Somalia shows high positive correlation between Chl-a and NASA-AOT and it is located along the path of winds carrying dust aerosols emanating from South Asia, South-West Asia, North Africa (Sahara) and the eastern Horn of Africa (Pease et al, 1998;Ginoux et al, 2001;Goudie and Middleton, 2001;Prospero et al, 2002;Léon and Legrand, 2003). Although there are several studies (Banzon et al, 2004;Kayetha et al, 2007;Patra et al, 2007;Singh et al, 2008;Nezlin et al, 2010;Banerjee and Prasanna Kumar, 2014) that have examined the relationship between Chl-a and AOT in various parts of the Arabian Sea, the region off Somalia has not yet been explored in detail, and it is the region selected for our investigation.…”

Section: Relationship Between Chl-a and Aot In The Arabian Seamentioning

confidence: 99%

Comparison of Seasonal Cycles of Phytoplankton Chlorophyll, Aerosols, Winds and Sea-Surface Temperature off Somalia

et al. 2017

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In climate research, an important task is to characterize the relationships between Essential Climate Variables (ECVs). Here, satellite-derived data sets have been used to examine the seasonal cycle of phytoplankton (chlorophyll concentration) in the waters off Somalia, and its relationship to aerosols, winds and Sea Surface Temperature (SST). Chlorophyll-a (Chl-a) concentration, Aerosol Optical Thickness (AOT), Ångström Exponent (AE), Dust Optical Thickness (DOT), SST and sea-surface wind data for a 16-year period were assembled from various sources. The data were used to explore whether there is evidence to show that dust aerosols enhance Chl-a concentration in the study area. The Cross Correlation Function (CCF) showed highest positive correlation (r 2 = 0.3) in the western Arabian Sea when AOT led Chl-a by 1-2 time steps (here, 1 time step is 8 days). A 2 × 2 • box off Somalia was selected for further investigations. The correlations of alongshore wind speed, Ekman Mass Transport (EMT) and SST with Chl-a were higher than that of AOT, for a lag of 8 days. When all four variables were considered together in a multiple linear regression, the increase in r 2 associated with the AOT is only about 0.02, a consequence of covariance among AOT, SST, EMT and alongshore wind speed. The AOT data show presence of dust aerosols most frequently during the summer monsoon season (June-September). When the analyses were repeated for the dust aerosol events, the correlations were generally lower, but still significant. Again, the inclusion of DOT in the multiple linear regression increased the correlation coefficient by only 2%, indicating minor enhancement in Chl-a concentration. Interestingly, during summer monsoon season, there is a higher probability of finding more instances of positive changes in Chl-a after one time step, regardless of whether there is dust aerosol or not. On the other hand, during the winter monsoon season (November-December) and rest of the year, the probability of Chl-a enhancement is higher when dust aerosol is present than when it is absent. The phase relationship in the 8-day climatologies of Chl-a and AOT (derived from NASA's SeaWiFS and MODIS-A ocean colour processing chain) showed that AOT Shafeeque et al.Seasonal Cycle of Phytoplankton Chlorophyll off Somalia led Chl-a for most of the summer monsoon season, except when Chl-a was very high, during which time, Chl-a led AOT. The phase shift in the Chl-a and AOT climatological relationship at the Chl-a peak was not observed when AOT from Aerosol Climate Change Initiative (Aerosol-CCI) was used.

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SeaWiFS observations of the Arabian Sea southwest monsoon bloom for the year 2000

Cited by 47 publications

References 38 publications

Monsoon-driven biogeochemical processes in the Arabian Sea

Monsoon-driven biogeochemical processes in the Arabian Sea

Inter-annual Variability of Chlorophyll-a in the Arabian Sea and its Gulfs

Comparison of Seasonal Cycles of Phytoplankton Chlorophyll, Aerosols, Winds and Sea-Surface Temperature off Somalia

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