Arabian Sea Region Research Articles

Analysis of aerosol and carbon monoxide characteristics over Arabian Sea during crop residue burning period in the Indo-Gangetic Plains using multi-satellite remote sensing datasets

In this study, we have used multi-satellite data to retrieve aerosol loadings and carbon monoxide (CO) pollution over the Arabian Sea, caused due to anthropogenic activities over the Indo-Gangetic Plains (IGP) in India. Relatively high aerosol and CO loadings during 9–14 November 2007 over Arabian Sea were attributed to crop residues burning in the IGP and fireworks during Diwali festival. Aerosol index (AI) obtained from ozone monitoring instrument (OMI) and CO from measurements of pollution in the troposphere instrument (MOPITT). CO showed higher values over the Arabian Sea suggesting long-range transport of anthropogenic aerosols and trace gases from the continental to Arabian Sea region.

Variability of the Oceanic Mixed Layer, 1960–2004

Abstract A new monthly uniformly gridded analysis of mixed layer properties based on the World Ocean Atlas 2005 global ocean dataset is used to examine interannual and longer changes in mixed layer properties during the 45-yr period 1960–2004. The analysis reveals substantial variability in the winter–spring depth of the mixed layer in the subtropics and midlatitudes. In the North Pacific an empirical orthogonal function analysis shows a pattern of mixed layer depth variability peaking in the central subtropics. This pattern occurs coincident with intensification of local surface winds and may be responsible for the SST changes associated with the Pacific decadal oscillation. Years with deep winter–spring mixed layers coincide with years in which winter–spring SST is low. In the North Atlantic a pattern of winter–spring mixed layer depth variability occurs that is not so obviously connected to local changes in winds or SST, suggesting that other processes such as advection are more important. Interestingly, at decadal periods the winter–spring mixed layers of both basins show trends, deepening by 10–40 m over the 45-yr period of this analysis. The long-term mixed layer deepening is even stronger (50–100 m) in the North Atlantic subpolar gyre. At tropical latitudes the boreal winter mixed layer varies in phase with the Southern Oscillation index, deepening in the eastern Pacific and shallowing in the western Pacific and eastern Indian Oceans during El Niños. In boreal summer the mixed layer in the Arabian Sea region of the western Indian Ocean varies in response to changes in the strength of the southwest monsoon.

Length-Weight Relationships, Maturity, and Reproductive Season of the Fringelip Mullet Crenimugil crenilabis (Forsskål, 1775) from the Arabian Sea Coast of Oman

Fringelip mullet (Crenimugil crenilabis) caught at Al Duqum and Salalah in the Arabian Sea region of Omanwere sampled monthly between January 2001 and December 2002. The total length (TL) of mullet caught with gill- and seine nets ranged from 12 to 54.5 cm (32.4 cm mean ± SD; n = 2445) but <2% of specimens had a TL<24 cm, suggesting gear selectivity. Females dominated samples (1 : 0.36) and reached L at 32.8 cm TL (32.2 cm in males). Length weight relationships were non-linear and conversion factors between TL, fork length (FL) and standard length (SL) were calculated. Proportionately, most females had ripe gonads in September and October, and males in September to November. Both female and male gonadosomatic indices (GSI) peaked in September and October and were lowest between May and August. The peak in reproductive activity coincides with the fall intermonsoon, when the Arabian Sea upwellings caused by the onshore winds of the SW monsoon season (June to August/September) retreat. During this intermonsoon period the inshore water temperatures begin to rise after reaching a minimum in August/September. Some reproductive activity also occurs in other months, particularly February, when water temperatures are seasonally lower.

The response of microzooplankton (20–200 μm) to coastal upwelling and summer stratification in the southeastern Arabian Sea

During the late summer monsoon (LSM), coastal upwelling and river runoff have increased the nutrient concentration in the inshore region of the southeastern Arabian Sea. This has resulted in elevated chlorophyll- a (av. 40±18 mg m −2), phytoplankton abundance (av. 474±116×10 6 ind. m −2) and primary production (av. 917±616 mg C m −2 d −1). Diatoms were the major component of the phytoplankton community (av. 60±8% of the total abundance) during this period, followed by dinoflagellates (18±12%). However, the inshore locations of 10°N and 13°N transects behaved differently, with an exceptional abundance of phytoflagellates (>10 10 ind. m −2). The microzooplankton (MZP) community was comprised of heterotrophic dinoflagellates (av. 60%), ciliates (av. 30%) and copepod nauplii (av. 5%); these showed marked variation in abundance between stations. The highest abundance (av. 283×10 4 ind. m −2) was at the inshore location of 10°N transect, where phytoflagellates were abundant. Contrasting to the LSM, intense surface layer stratification and depletion of nitrate (with a nitracline at 60 m depth), observed in the southeastern Arabian Sea during the spring intermonsoon (SIM) period, caused low phytoplankton abundance (av. 141±86×10 6 ind. m −2), chlorophyll- a (av. 19±11 mg m −2) and primary production (av. 146±68 mg C m −2 d −1). High temperature (>29 °C) and nitrate-depleted surface waters favoured the proliferation of Trichodesmium erythraeum at most of the locations. Total abundance of MZP during the SIM was markedly low (av. 20×10 4±13×10 4 ind. m −2), as was the species richness and diversity (0.36±0.02 and 0.57±0.15, respectively) compared to the LSM (1.17±0.31 and 2.72±0.34, respectively). During the SIM, the MZP community that occurs in the southeastern Arabian Sea is important, since smaller individuals are widespread and form the majority of phytoplankton community. The present study points also to the fact that the MZP could play an important role, even in nutrient-enriched environment, if smaller phytoplankton are abundant.

Validation of ERS-1 and High-Resolution Satellite Gravity with in-situ Shipborne Gravity over the Indian Offshore Regions: Accuracies and Implications to Subsurface Modeling

Geoid and gravity anomalies derived from satellite altimetry are gradually gaining importance in marine geoscientific investigations. Keeping this in mind, we have validated ERS-1 (168 day repeat) altimeter data and very high-resolution free-air gravity data sets generated from Seasat, Geosat GM, ERS-1 and TOPEX/POSEIDON altimeters data with in-situ shipborne gravity data of both the Bay of Bengal and the Arabian Sea regions for the purpose of determining the consistencies and deviations. The RMS errors between high resolution satellite and ship gravity data vary from 2.7 to 6.0 mGal, while with ERS-1 data base the errors are as high as 16.5 mGal. We also have generated high resolution satellite gravity maps of different regions over the Indian offshore, which eventually have become much more accurate in extracting finer geological structures like 85° E Ridge, Swatch of no ground, Bombay High in comparison with ERS-1satellite-derived gravity maps. Results from the signal processing related studies over two specific profiles in the eastern and western offshore also clearly show the advantage of high resolution satellite gravity compared to the ERS-1 derived gravity with reference to ship gravity data.

Evolutionary Features of Marine Atmospheric Boundary Layer (MABL) over the Arabian Sea and the Onset of Monsoon over Kerala during ARMEX-2003

In this study an attempt has been made to examine the evolutionary features of the dynamic and thermodynamic characteristics of the marine atmosphere over the South-East Arabian Sea near 9.22°N, 74.51°E just two to three days prior to the onset of southwest monsoon over Kerala during 2003 and seek the linkages with the large-scale flow in the lower and middle troposphere at that time over the region. The marine meteorological data collected onboard ORV Sagarkanya as part of the experiment ARMEX-2003 for 4–8 June, 2003 are used. The monsoon onset over Kerala occurred on 8 June, 2003. The observed changes in the marine atmospheric boundary layer (MABL) characteristics just two days prior to the onset are discussed. It is observed that the MABL increased in height up to 4 km on 6 June from an initial height 2.8 km on 5 June. The top of the MABL dried up (Relative Humidity RH ~ 30–40%) with weak and variable winds throughout the day on 6 June while the air at 850 hPa is relatively humid (RH ~ 50–80%) but not saturated. A sequential increase in RH is associated with a change in the winds from southwesterly to westerly from 6 June onwards until the onset date. The changes in the lower and middle troposphere flow patterns over the Arabian Sea and Indian region are highlighted.

Atmospheric deposition and surface stratification as controls of contrasting chlorophyll abundance in the North Indian Ocean

Intense upwelling during summer and convection in winter are believed to drive higher biological productivity in the Arabian Sea than in the Bay of Bengal. Although the Arabian Sea receives substantial atmospheric deposition of dust aerosols, its role in biological activity is unknown. We have analyzed chlorophyll‐a (SeaWiFS), absorbing aerosol index (TOMS), surface winds (NCEP), and modeled dust deposition and SST (OI) data during two distinct seasons June–August (JJA, summer months) and October–December (OND, winter months) for the period 1997–2004. Climatologies of physicochemical properties have been developed from World Ocean Atlas 2001 (WOA01). Our results suggest that despite the strong vertical supply of nutrients in the western and central Arabian Sea regions, maximal chlorophyll‐a was limited to the former region in both JJA and OND periods, suggesting the importance of atmospherically transported substances in determining chlorophyll abundance in the North Indian Ocean. Time‐averages (1997–2004) revealed chlorophyll abundances in northwestern regions are larger than in other regions of the respective basins. The NW regions of the Arabian Sea and the Bay of Bengal have exhibited contrasting chlorophyll distribution patterns during El Niño years (1997–1998 and 2002–2003; positive SST anomalies); decreased and increased chlorophyll contents in respective regions. Following the passage of tropical cyclones, SeaWiFS records depicted large areas in the Arabian Sea to experience intensified chlorophyll production with strong wind speeds of 55–65 knots whereas its enhanced production occurred only in small patches even under the influence of Orissa Super Cyclone of October 1999 (wind speed up to 140 knots) due to strong stratification.

Effect of dust storm on ocean color and snow parameters

The present study clearly shows the influence of dust storms on chlorophyll bloom in the offshore region of the Arabian Sea, with a time lag of few days, during the pre-monsoon season. Various satellite derived parameters over the Arabian Sea, Himalayan and Tibet snow covered regions show large changes due to the influence of dust storms. The MODIS snow albedo gives unreliable values under the influence of dust storms due to increase in the aerosol loading over these regions and snow albedo product must be used in combination with snow pixel counts during the dust storm season. A detailed study is required for the quantitative evaluation of dust storms on the chlorophyll blooms in the Arabian Sea region and on the snow parameters in the Himalayan region.

Sea surface temperature pattern reconstructions in the Arabian Sea

Sea surface temperature (SST) and seawater δ18O (δ18Ow) were reconstructed in a suite of sediment cores from throughout the Arabian Sea for four distinct time intervals (0 ka, 8 ka, 15 ka, and 20 ka) with the aim of understanding the history of the Indian Monsoon and the climate of the Arabian Sea region. This was accomplished through the use of paired Mg/Ca and δ18O measurements of the planktonic foraminifer Globigerinoides ruber. By analyzing basin‐wide changes and changes in cross‐basinal gradients, we assess both monsoonal and regional‐scale climate changes. SST was colder than present for the majority of sites within all three paleotime slices. Furthermore, both the Indian Monsoon and the regional Arabian Sea mean climate have varied substantially over the past 20 kyr. The 20 ka and 15 ka time slices exhibit average negative temperature anomalies of 2.5°–3.5°C attributable, in part, to the influences of glacial atmospheric CO2 concentrations and large continental ice sheets. The elimination of the cross‐basinal SST gradient during these two time slices likely reflects a decrease in summer monsoon and an increase in winter monsoon strength. Changes in δ18Ow that are smaller than the δ18O signal due to global ice volume reflect decreased evaporation and increased winter monsoon mixing. SSTs throughout the Arabian Sea were still cooler than present by an average of 1.4°C in the 8 ka time slice. These cool SSTs, along with lower δ18Ow throughout the basin, are attributed to stronger than modern summer and winter monsoons and increased runoff and precipitation. The results of this study underscore the importance of taking a spatial approach to the reconstruction of processes such as monsoon upwelling.

Seven year satellite observations of the mean structures and variabilities in the regional aerosol distribution over the oceanic areas around the Indian subcontinent

Abstract. Aerosol distribution over the oceanic regions around the Indian subcontinent and its seasonal and interannual variabilities are studied using the aerosol optical depth (AOD) derived from NOAA-14 and NOAA-16 AVHRR data for the period of November 1995–December 2003. The air-mass types over this region during the Asian summer monsoon season (June–September) are significantly different from those during the Asian dry season (November–April). Hence, the aerosol loading and its properties over these oceanic regions are also distinctly different in these two periods. During the Asian dry season, the Arabian Sea and Bay of Bengal are dominated by the transport of aerosols from Northern Hemispheric landmasses, mainly the Indian subcontinent, Southeast Asia and Arabia. This aerosol transport is rather weak in the early part of the dry season (November–January) compared to that in the later period (February–April). Large-scale transport of mineral dust from Arabia and the production of sea-salt aerosols, due to high surface wind speeds, contribute to the high aerosol loading over the Arabian Sea region during the summer monsoon season. As a result, the monthly mean AOD over the Arabian Sea shows a clear annual cycle with the highest values occurring in July. The AOD over the Bay of Bengal and the Southern Hemisphere Indian Ocean also displays an annual cycle with maxima during March and October, respectively. The amplitude of the annual variation is the largest in coastal Arabia and the least in the Southern Hemisphere Indian Ocean. The interannual variability in AOD is the largest over the Southeast Arabian Sea (seasonal mean AOD varies from 0.19 to 0.42) and the northern Bay of Bengal (seasonal mean AOD varies from 0.24 to 0.39) during the February–April period and is the least over the Southern Hemisphere Indian Ocean. This study also investigates the altitude regions and pathways of dominant aerosol transport by combining the AOD distribution with the atmospheric circulation. Keywords. Atmospheric composition and structure (Aerosols and particles) – Meteorology and atmospheric dynamics (Climatology) – Oceanography: physical (Ocean fog and aerosols)

Aerosol optical depth, physical properties and radiative forcing over the Arabian Sea

The Arabian Sea region $(4^{o} N-20^{o} N to 50^{o} E-78^{o} E)$ has a unique weather pattern on account of the Indian monsoon and the associated winds that reverse direction seasonally. The aerosol data, collected using ship-borne and island platforms (for 8 years from 1995 to 2002) along with MODIS (onboard TERRA satellite) data (from 2000 to 2003) have been used to evolve a comprehensive characterisation of the spatial and temporal variation in the physical, chemical, and radiative properties of aerosols over the Arabian Sea. The aerosol optical depth (AOD) was found to increase with latitude between the equator and $12^{o} N$. Over the northern Arabian Sea (regions lying north of $12^{o} N$), AODs do not show significant latitudinal variations; the average aerosol optical depth for this region was 0.29\pm0.12 during winter monsoon season (WMS; November to March) and 0.47\pm0.14 during summer monsoon season (SMS; April=May to September). The corresponding Angstrom exponents were 0.7\pm0.12 and 0.3\pm0.08, respectively. The low values of the exponent during SMS indicate the dominance of large aerosols (mainly dust particles > 1 \mu m). The latitudinal gradient in AOD in the southern Arabian Sea is larger during SMS compared to WMS. The size distribution of aerosols shows two well-defined modes, one in the accumulation size regime and the other in the coarse size regime. During WMS, a third mode (nucleation) also appears in the sub micron range below ~0.1 mm. The single scattering albedo does not show significant seasonal variations (remains within ~0.93 to 0.98 through out the year). During WMS (SMS), top of the atmosphere diurnally averaged aerosol forcing remains around -6.1 (-14.3)W$m^{-2}$ over the northern Arabian Sea up to around $12^{o} N$ and decreases southwards till it attains a value of -3.8 (-3.4)W$m^{-2}$ at the equator. The surface forcing remains around -16.2 (-15.2)W$m^{-2}$ over the northern Arabian Sea up to $12^{o} N$ and decreases southwards to a value of -5.5 (-3.5)Wm$m^{-2}$ at the equator. Over the north Arabian Sea, instantaneous forcing (flux change) at the surface can be as high as -50W$m^{-2}$. The instantaneous forcing decreases with latitude in the southern Arabian Sea at a rate of ~3W$m^{-2} deg^{-1}$.

Validation of upper-air observations taken during the ARMEX-I and its impact on the global analysis-forecast system

During ARMEX-I several special observations were taken over Arabian Sea region and adjoining west coast of India, which gave an opportunity to study this region more thoroughly. To handle such voluminous data, ARMEX data center has been established at National Centre for Medium Range Weather Forecasting (NCMRWF), in collaboration with India Meteorological Department (IMD) and Indian Institute Technology (IIT), Delhi. One of the tasks of this center is to produce reanalysis for ARMEX period, utilizing these observations. It is essential to assimilate every observation from all available sources, especially over the data sparse oceanic regions for accurate determination of the three-dimensional structure of the atmospheric circulation. Before assimilating these data in global data assimilation system of NCMRWF, an attempt has been made to validate some of these data against observational facts from other sources. Upper-air observations (Digicora) from Dabolim, Goa have been compared with RS/RW observation of IMD, at Panjim, Goa. Though the trend in variations of all the meteorological parameters of these two stations is similar but there is a large difference in their absolute values. Reanalysis generated using the specially collected upper-air observations have been compared with the operational analysis of NCMRWF. The impact of these special observations on analysis and forecast system is found to be confined over the Arabian Sea region only in the lower troposphere. However, in the upper troposphere and stratosphere the impact is seen also over the equatorial Indian Ocean region.

Characteristics of Arabian Sea mini warm pool during May 2003

Oceanographic surveys were carried out onboard INS Sagardhwani as a part of ARMEX in the deep and coastal regions of the eastern Arabian Sea during May 2003 to study the mini warm pool characteristics. The observational period was characterized by typical pre-monsoon conditions, as indicated by weak winds and clear skies. TMI SST data showed very good agreement with the ground truth observations (root mean square departure of ~0.2oC). Both the satellite imagery and ground truth showed surface temperature (SST) in excess of 31° C in the eastern Arabian Sea. This mini warm pool attained its maximum dimension ~8 days prior to the onset of summer monsoon over Kerala and the dissipated stated prior to the onset date. This information can be used as an index for the prediction of summer monsoon onset. Alternate bands of cyclonic and anti-cyclonic circulation pattern were evident both in the ground truth and satellite imagery. In the regions of SST more than 31° C, surface salinity was found to be less than 34.75 PSU and its depth extent was limited to thin surface layer resulting highly stratified layer. The low saline water present in this region was due to the northward / northwestward advection of low saline waters of equatorial Indian Ocean origin and the re-circulation of Bay of Bengal water mass trapped in the central Arabian Sea during winter by the eddy type of circulation.

Atmospheric boundary layer during ARMEX-2002 at stationary positions - comparative study

A study has been carried out to explore the salient features of the Atmospheric Boundary Layer (ABL) over the eastern Arabian Sea regions during the summer monsoon season of 2002. For this purpose the aerological observations and surface meteorological observations collected onboard ORV Sagar Kanya during the Phase-I of ARMEX-2002 for the two stationary positions (30 June-10 July and 22 July – 5 August 2002) have been considered. Utilizing these observations the vertical structure of the Atmospheric Boundary Layer and the temporal variation of different surface parameters has been investigated. The results showed prominent diurnal variation in different surface meteorological parameters. The study also revealed that there is no influence of the offshore trough on the vertical structure of the Atmospheric Boundary Layer. The ABL showed multilayered structure with shallow sub cloud layer, deep cloud layer, weak stable layer and the ABL extending up to higher levels in the presence of the cyclonic circulation (2-4 August 2002). Whereas the ABL is associated with deep sub cloud layer, shallow cloud layer, strong stable layer (inversion layer) and shallow ABL depth under the influence of weak offshore trough observed along the west coast of India.

First observations of aerosol black carbon over coastal Arabian Sea during ARMEX

Extensive measurements of the mass concentrations of BC and composite aerosols were made for the first time during the inter-monsoon and summer monsoon seasons (March to June, 2003) over coastal Arabian Sea region under the Arabian Sea Monsoon Experiment (ARMEX). Results showed a gradual and continuous decrease (by a factor of 7) in the mean concentration of BC from ~700 ng m-3 in March to reach as low as ~ 104 ng m-3 in June. The diurnal variations were very weak during March, weakened progressively and almost vanished by May and June. Consistent with this, there is a rapid decrease in the share of BC to the composite aerosol system.

The Tectonic and Climatic Evolution of the Arabian Sea Region

This multi‐authored volume provides a sampling of current research into the geology of the Arabian Sea region. The editors emphasize the importance of this area as the Earth's best natural laboratory for studying relations between climate and the growth and erosion of an orogenic belt.Uplift of the Himalaya and Tibetan Plateau is now believed to have altered global climate during the Cenozoic, and also to have affected the development of the region's monsoonal climate. The geological features of the region that make it a good area to study such processes include the excellent rock outcrops in the surrounding arid Arabian and Asian landmasses, the locally high rates of sedimentation which provide high‐resolution sedimentological and geochemical information, and the monsoon itself, that imparts an annual time beat in some sedimentary successions. However, the region is very large and access is not always easy. Also, many areas are still poorly known geologically such that this volume contains some papers on basic survey geology.

Continental influence on the spatial distribution of particulate loading over the Indian Ocean during winter season

Advection of continental aerosols over to the Arabian Sea and Indian Ocean regions during winter (when the prevailing synoptic wind is north-easterly) has been studied by examining the spatial distribution of the near-surface aerosol mass concentration ( M C). In the northern part of Arabian Sea and north of the inter-tropical convergence zone (ITCZ) M C is significantly larger than that in the southern side of ITCZ. A prominent high in M C is observed near the mid-Arabian Sea region ∼12° to 15°N. Associated with local convergences introduced by mesoscale weather systems, pockets of high M C are observed at different locations over the oceanic regions. Significantly low values of M C are observed in the ITCZ. Surface streamlines and wind patterns indicate advection of continental aerosols from the adjoining landmass over to the oceanic environment. Aerosol mass concentration in the far oceanic region is also influenced by in situ production of sea-spray aerosols, which depends on wind speed. The nature of advection of continental aerosols has been studied by separating the wind-induced component of M C and chemical nature of the aerosols. The spatial variation of the wind-independent component matches well with that of the non-sea-salt aerosols estimated from chemical composition.

CLIFT, P. D., KROON, D., GAEDICKE, C. & CRAIG, J. (eds) 2002. The Tectonic and Climatic Evolution of the Arabian Sea Region. Geological Society Special Publication no. 195. vii + 525 pp. London, Bath: Geological Society of London. Price £120.00, US $200.00; members' price £60.00, US $100.00; AAPG members' price £72.00, US $120.00 (hard covers). ISBN 1 86239 111 4

The Arabian Sea region is a key area for deciphering plate tectonic reconstructions including the opening of the Red Sea/Gulf of Aden, the northward drift of India, the evolution of the Makran accretionary prism and the geometry and extent of the Indus Fan. It is also a key area for testing models of climatic–tectonic interrelationships, in particular the evolution of the Indian summer monsoon. This volume contains 26 papers documenting plate reconstructions, magnetic and gravity data, seismic surveys, magnetic isochrons, neotectonics and the Pleistocene–Holocene climatic record of the Arabian Sea. It begins with papers that include a new compilation of magnetic and gravity data used to reconstruct the Paleogene plate tectonic evolution of the Arabian Sea and East Somali basin. Multi-channel seismic surveys are used to constrain the sub-surface stratigraphy and structure. Papers document the onshore geology of the Iranian Zagros belt and Makran accretionary prism, the Kirthar fold belt along western Pakistan and the Ladakh Himalaya. Soon after the initial …

Analysis of moist convective instability over Indian monsoon region and neighbourhood

The nature of deep convection over the Indian monsoon region and neighbourhood during different seasons is investigated by analysing Dry Static Energy (DSE), Moist Static Energy (MSE), Precipitable Water Content (PWC) and Convective Available Potential Energy (CAPE) computed from 13 years (1982-1994) monthly mean data obtained from the National Centre for Environmental Prediction (NCEP) reanalysis.
 
 It is seen from this study that the mean atmosphere over the Indian monsoon region is convectively unstable at lower levels during all seasons with highest degree of instability and maximum PWC during the monsoon season compared to other seasons. The results also show that during the monsoon season from June to September the convectively most unstable region is situated over the Head Bay of Bengal (HBOB) region and decreases gradually from West Pacific (WP), Equatorial South Indian Ocean (ESIO) and to Arabian Sea (AS) regions. Similarly the CAPE value is also highest over HBOB region and it is about 362 Joules/kg (24%) more than the CAPE value over WP region. The composite MSE profiles for strong and weak monsoon years indicate higher values of MSE at all levels during the strong monsoon years compared to weak monsoon years. It is also observed that the surface MSE and PWC over Indian monsoon region during June to September show significant positive correlation with All India Summer Monsoon Rainfall (AISMR).

176 New Discoveries Regarding the Benthic Marine Algal Flora of the Sultanate of Oman

Intensive littoral and sublittoral collecting on the monsoon‐impacted rocky shores of southern Oman, made at the end of the summertime monsoon (Sept. 2000 and Sept. 2001), has produced a remarkably high number of undescribed taxa and new records for this region of the Northern Arabian Sea. Taxa to be discussed in this presentation include: a new species of Centroceras that reaches 60 cm in height, is heavily corticated, has distinctively secund branching, and occurs well into the ‘supralittoral fringe’; a new species of Jolyna, which is often branched, is not as long or thick as the more common J. laminarioides, has ascocysts but lacks hair tufts, and also occurs in the supralittoral; a Turbinaria (T. foliosa) that has the least modified blades known in the genus; a remarkably robust and erect species of Leveillea; and an undescribed Gelidium, which has previously passed under the name of ‘Suhria vittata’. A complicated picture has emerged that shows this flora to have biogeographical affinities with pantropical and subtropical regions, the tropical‐subtropical Indo‐Pacific, South Africa, temperate Europe and the Mediterrranean, Japan, as well as revealing components that are characteristic of the Arabian Sea monsoon season and apparent endemics restricted to Oman. This research (the Algal Biodiversity Project of Oman) has been funded by the British Government's Darwin's Initiative grant for the ‘Survival of Species’ and managed by HTS Development, Ltd., of the U.K.