Drop In Sea Surface Temperature Research Articles

Climate variations in eastern Hudson bay over the past 3000 years

Palynological analyses of the marine sediment core AMD0509-20 collected north of Whapmagoostui-Kuujjuarapik in Nunavik were performed to investigate past changes in climate and sea-surface conditions based on pollen and spores and dinoflagellate cysts, respectively. Our results show relatively warm sea-surface temperatures before 2600 BP, about 2 °C higher than at present in summer, in addition to higher salinity suggesting relatively low freshwater inputs, thus low precipitation over the watershed. After 2400 years BP, an abrupt drop in sea-surface temperatures was recorded, followed by a decrease in salinity particularly pronounced until ∼2000 years BP. After 1600 years BP, summer sea-surface temperatures and salinity stabilized around current values. The changes recorded in surface waters during the late Holocene can be associated with a regional shift in the hydroclimatic regime that led to a gradual decline of spruce (Picea) in pollen assemblages.

Assessing the effect of coastal upwelling on the air temperature at the south-eastern coast of the Baltic Sea

Coastal upwelling along the SE Baltic Sea coast is a common feature, especially during the warm season. It significantly lowers sea surface temperature (SST) in the coastal areas, and, therefore, may be responsible for modifying meteorological conditions in those coastal areas, where upwelling is most frequently observed. This study aims to assess the effect of coastal upwelling on the air temperature at the south-eastern coast of the Baltic Sea based on long-term period observations (2002–2021) from coastal hydrometeorological stations and satellite data. Overall, our study revealed that due to its high frequency and spatial extent, upwelling is responsible for lowering the mean summer season SST of the SE Baltic Sea coast by about 1°C. And even though upwelling is a short-term event, upwelling-induced SST drop results in cooling air temperatures in the coastal areas, i.e., the mean air temperatures during upwelling are typically 2−4°C lower than before. It was also observed that upwelling is favouring the development of advective fog. Thus, sudden changes in meteorological parameters during upwelling can have versatile effects on various socio-economic activities. The results of this study contribute to the understanding of upwelling feedback onto the lower atmosphere and, therefore, are important for advancing the accuracy of weather forecasts that are needed for coastal communities, including marine and coastal industries.

Typhoon-Induced Extreme Sea Surface Temperature Drops in the Western North Pacific and the Impact of Extra Cooling Due to Precipitation

Sea surface temperature (SST) responses have been perceived as crucial to consequential tropical cyclone (TC) intensity development. In addition to regular cooling responses, a few TCs could cause extreme SST drops (ESSTDs) (e.g., SST drops more than 6 °C) during their passage. Given the extreme temperature differences and the consequentially marked air–sea flux modulations, ESSTDs are intuitively supposed to play a serious role in modifying TC intensities. Nevertheless, the relationship between ESSTDs and consequential storm intensity changes remains unclear. In this study, satellite-observed microwave SST drops and the International Best Track Archive for Climate Stewardship TC data from 2001 to 2021 were used to elucidate the relationship between ESSTDs and the consequential TC intensity changes in the Western North Pacific typhoon season (July–October). Subsequently, the distributed characteristics of ESSTDs were systematically examined based on statistical analyses. Among them, Typhoon Kilo (2015) triggered an unexpected ESSTD behind its passage, according to existing theories. Numerical experiments based on the Regional Ocean Modeling System were carried out to explore the possible mechanisms that resulted in the ESSTD due to Kilo. The results indicate that heavy rainfall leads to additional SST cooling through the enhanced sensible heat flux leaving the surface layer in addition to the cooling from momentum-driven vertical mixing. This process enhanced the sensible heat flux leaving the sea surface since the temperature of the raindrops could be much colder than the SST in the tropical ocean, specifically under heavy rainfall and relatively less momentum entering the upper ocean during Kilo.

Paleoceanographic importance of tri- and di-unsaturated alkenones through the early phase of Cretaceous Oceanic Anoxic Event 2 from southern high latitudes of the proto-Indian Ocean

Alkenones are biomarkers derived exclusively from species of haptophyte algae. The relative abundance of di- to tri-unsaturated C37 alkenones expressed as UK'37 is widely applied as a sea surface paleotemperature proxy for Cenozoic marine sediments. However, the absence of alkatrienones prior to the Eocene has precluded application of the UK'37 proxy for assessment of Cretaceous paleoclimates. Herein, we report a C40 alkatrienone (tetraconta-9E, 16E, 23E-trien-3-one; C40:3 Et) in deep-sea sediments from southern high latitudes (International Ocean Discovery Program: IODP site U1516). This discovery extends the geologic record of alkatrienones to the late Cenomanian, ∼70 million years earlier than previous reports. The parallel occurrence of higher abundances of a C40 alkadienone (tetraconta-16E, 23E-dien-3-one; C40:2 Et) allowed calculation of the UK’40 unsaturation index, comparable to UK’37. Stratigraphic variations in the δ13C of C40:2 Et revealed an elevated (∼1.5 ‰) positive carbon isotope excursion (CIE) relative to those observed in carbonate from other OAE2 sequences likely reflecting a decrease in global pCO2. The UK’40 profile suggests a concurrent drop in sea surface temperature associated with the decline in pCO2 during the early phase of OAE2. The timing of these environmental perturbations in the southern high latitude of the proto-Indian Ocean suggests they were triggered by volcanism associated with large igneous province (LIP) formation.

Eocene paleoceanographic and paleoclimatic events recognized by assemblages of dinoflagellate cysts in the Southwest Atlantic Ocean

Variations in the relative frequencies between cosmopolitan dinoflagellate cysts and Antarctic assemblage species indicate temperature changes and variations of ocean currents during the Paleogene. This study is based on the analysis of 23 samples from two stratigraphic intervals from the Well BP-01 (Imbé Formation), drilled by in the Pelotas Basin offshore. We identified 66 dinoflagellate cyst taxa, 47 of them belong to the Order Gonyaulacales and 19 to the Order Peridiniales. The relative abundance data highlight two different dinoflagellate ecogroups represented by Apectodinium and Enneadocysta in the intervals A and B, respectively. The level with the highest percentages of Apectodinium recorded in the Calcareous Nannofossil Zone N-410 (Ypresian), suggest that the Apectodinium maximum represents the Early Eocene Maximum Thermal Event (EMT-2). Enneadocysta Acmes registered near the Bartonian/Priabonian boundary, can be correlated with a drop in sea surface temperature that occurred after the Mid-Eocene Climatic Optimum. Dinoflagellate occurrences suggest deposition in open sea conditions during the transgressive phase. The P/G ratio does not reach significant values in the analyzed intervals, indicating low dissolved nutrient concentrations.

Impact of the Deep Chlorophyll Maximum in the Equatorial Pacific as Revealed in a Coupled Ocean GCM‐Ecosystem Model

AbstractA coupled ocean general circulation model (OGCM)‐ocean ecosystem model is used to investigate the effects of the deep chlorophyll maximum (DCM) on the ocean state in the equatorial Pacific Ocean. Climatological and interannual three‐dimensional (3‐D) chlorophyll (CHL) fields are captured well in control runs using the coupled ocean physics‐ecosystem model forced by prescribed atmospheric fields. Further sensitivity experiments are performed to assess the effects of 3‐D CHL structure using the OGCM with the prescribed CHL fields taken from the control runs: CHLclim and are runs in which climatological DCM effect is included or only surface CHL effect is included; CHLinter and are runs with interannually varying DCM effects included or not. The differences in the simulated ocean conditions are analyzed to explore DCM effects on sea surface temperature (SST) and amplitude of El Niño‐Southern Oscillation (ENSO). Two competing mechanisms responsible for the DCM effects are revealed: an ocean biology‐induced direct heating (OBH) effect, and an indirect cooling effect due to dynamic processes associated with vertical mixing and shallow meridional overturning circulation. There are three major findings: (a) DCM acts to reduce mean SST by around 0.2°C in the eastern equatorial Pacific, being larger than the surface CHL effects. (b) DCM interannual variability increases the ENSO amplitude to a comparable degree as the surface CHL effects. (c) The total net impact of vertical mixing, currents, and net surface heat flux makes SST drop more under the DCM effect than the surface CHL effect in the eastern Pacific. These findings provide a new insight into the feedback mechanisms for the bioclimate interactions.

A pathway for multi-stage cyclone-induced hazard tracking—case study for Yaas

A Very Severe Cyclonic Storm ‘Yaas’ developed over the Bay of Bengal (BoB) on 23 May 2021 and crossed over the Odisha coast on 26 May with maximum sustained wind speed of 75 kts. Herein, a pathway has been developed and exemplified for ‘Yaas’ through three-stage cyclone-induced hazard tracking. Days before the cyclone formation, cyclone genesis potential parameter, sea surface temperature (SST) (> 30 °C) and tropical cyclone heat potential (anomaly of 40–80 kJ/cm2) indicated a strong possibility of cyclogenesis in the BoB. A Lagrangian advection model used for its track prediction with 24-h lead-time provided an accuracy of ~ 19 km and ~ 6 h in its landfall location and time. Further, intensity prediction was done using numerical weather prediction model. Geostationary satellites, INSAT-3D/3DR, were used to visualize cyclone structure. Passing of cyclone had its reverbarations in oceans, which are observed in SST drop of ~ 3 °C, salinity and density increase by ~ 1 psu and ~ 2 kg/m3, respectively. During the period, 23–26 May 2021, the Ekman suction velocity and chlorophyll concentration were found significantly high at ~ 5 m/day and > 0.5 mg/m3, respectively. Forecast of storm surge was found to be between 3.5 and 4 m at coastal locations. Significant wave height was found to be 5.5–9.2 m. The coastal inundation forecast for 24 May 2021 provided its quantitative maximum inland extent. Finally, loss of the crop, fishery and forest areas by strong winds and inundation/ingress of saline water associated with storm surge were examined using SAR and optical data.

Extreme cooling of 12.5 °C triggered by Typhoon Fungwong (2008)

Typhoon Fungwong, a category-2 but deadly typhoon in the 2008 Pacific typhoon season, made landfall first on Taiwan and then on Southeast China. During its approach toward Taiwan, it triggered an extreme sea surface temperature (SST) drop of 12.5 °C, which was the strongest SST drop recorded by Longdong buoy northeast of Taiwan coast from 1998 to 2017. In this study, including moored buoy temperature measurements, Argo float temperature profiles, satellite-observed SSTs, and a suite of numerical experiments performed using the Regional Ocean Modeling System were used to unveil the detailed processes of how Fungwong triggered such an extreme cooling. Subsequently, the source of the cold waters feeding the extreme cooling, possible mechanisms triggering the cooling, and consequential effects of cooling on the ambient ocean environment were systematically investigated. Results show that the extreme cooling was triggered mainly by a process of uplift of subsurface cold water tied to shore-ward Kuroshio intrusion driven by easterly/northeasterly winds and consequential entrainment mixing, while coastal upwelling driven by persistent longshore (southerly) winds plays a minor role. Nevertheless, the southerly winds still help the enhancement of entrainment mixing and thus the sea surface cooling. Finally, modeled float trajectories with temperature tracers identified where the cold water goes and indicate that the temperature drop might extend all the way toward the south end of Japan (Kyushu) along the flowing path of Kuroshio.

О МЕХАНИЗМЕ РЕЗКОГО ПОНИЖЕНИЯ ТЕМПЕРАТУРЫ ПОВЕРХНОСТИ В СЕВЕРО-ЗАПАДНОЙ ЧАСТИ ЧЕРНОГО МОРЯ И У ПОБЕРЕЖЬЯ КРЫМА

An analysis of high-resolution satellite data on sea surface temperature (SST) and surface wind for 2008-2021 confirmed that the areas of a dramatic SST drop exceeding several degrees per day regularly occur in the northwestern Black Sea and off the western coast of Crimea. These areas are located not only in coastal upwelling zones. Extensive areas of this type are found in the open water areas in the northwestern part of the sea and in the vicinity of the western large-scale cyclonic gyre. A reason for the formation of such areas during the period of the stable vertical thermal stratification in the upper layer is the strengthening of wind in the atmospheric surface layer and the intensification of cyclonic vorticity. This leads to the generation of upward motions, additional turbulent mixing in the upper sea layer, and, as a consequence, the SST drop within a few days after the passage of the cyclone over the sea. This mechanism is especially effective in the case of slowly moving cyclones in the presence of a blocking or a high-pressure ridge northeast of the Black Sea region.

Comprehensive Satellite Observations and a Numerical Study of a Wintertime Shallow Sea Smoke Event in the Yellow Sea

Abstract A winter storm triggered a significant sea smoke with the northwesterly wind to the Yellow Sea, China, on 7 January 2021. The ocean responses to this event lasted about 3 days. Satellite observations show that the sea surface temperature dropped from 5.7° to 4.7°C on the following day and then recovered to the previous level; the chlorophyll-a, a bio-growth indicator, increased from 3.6 to 3.9 mg m−3 due to cooling-induced coastal upwelling between 7 and 9 January. Two buoys measurements showed that the air temperature dropped to −13.3°C and high relative humidity with a maximum value of 89.0% above the sea surface, creating favorable conditions for sea smoke generation. A Regional Ocean Modeling System (ROMS) and Weather Research and Forecasting (WRF) Model coupled model with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) chemical module was implemented to reproduce this sea smoke phenomenon and analyze the air–sea interaction. The 20°C temperature difference between extreme cold air (−13.3°C) and the relatively warm stable sea surface (4.7°–5.7°C) enhanced the seawater evaporation. In addition, we suppose the concentration of sea salt, a kind of condensation nucleus, with a particle diameter of 0.5–1.5 μm above the sea surface increased quickly on 7 January. The boiling-water-like sea surface was imaged on a synthetic aperture image. We developed an image analysis method to describe the cell-shaped texture characteristics imaged by Synthetic Aperture Radar (SAR). We also found that the sea surface imprints of sea smoke are governed by the thermal, not the dynamical instability. Significance Statement On 7 January 2021, a significant sea smoke event happened in the Yellow Sea. The ocean response to the event lasted 3 days. First, on a synoptic scale, this study presents the comprehensive satellite observations of the sea surface temperature drop and chlorophyll-a increase associated with the sea smoke. Second, a coupled air–sea interaction model with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) chemical module was implemented to reproduce this sea smoke phenomenon and identify which condensation nucleus induced such heavy sea smoke. Third, we developed an image analysis method to analyze high-resolution synthetic aperture radar images and found that the sea surface imprints of sea smoke are governed by the thermal, not the dynamical instability.

Global cooling initiated the Middle-Late Mississippian biodiversity crisis

During the Mississippian period, metazoan reefs and other marine faunas gradually recovered from the Late Devonian mass extinctions and reached a peak in the late Visean (~334–332 Ma). Faunal diversity started to decline from the latest Visean (~332–330 Ma) through Serpukhovian (~330–323 Ma), with significant genera/species losses and ecosystem reconstruction. This Middle-Late Mississippian biodiversity crisis (M-LMBC) was thought to have been caused by global cooling associated with the late Paleozoic Ice Age (LPIA), but existing sedimentological and temperature proxy data suggest that the global cooling event—that marks the onset of the main glaciation phase of LPIA—happened either ~4 Myr before or ~ 1–5 Myr after the initial biodiversity decline at ~332 Ma. Here, we report oxygen isotope data of diagenetically screened, well-preserved brachiopod calcite (δ18Ocalcite) from late Visean-Serpukhovian (or Middle-Late Mississippian; ~334–323 Ma) strata in South China where biodiversity data are well documented. The δ18Ocalcite data reveal a ~ 2.0‰ positive shift from −4.6 ± 0.2‰ to −2.7 ± 0.5‰ with an estimated ~4.7–5.5 °C drop in sea surface temperature (SST) during ~332.5–331.5 Ma in the late Visean. This cooling event coincides with fast decline of metazoan reef abundance, followed by decrease of benthic faunal diversity. The δ18Ocalcite data, in combination with calibrated sedimentological and biodiversity data, demonstrate the coupling between late Visean (~332 Ma) onset of the main glaciation phase of the LPIA and initiation of the M-LMBC.

Numerical Study of Topographic Effects on Wind-Driven Coastal Upwelling on the Scotian Shelf

Wind-driven coastal upwelling can cause a sudden drop in sea surface temperatures (SSTs) of up to more than 8 °C on the inner Scotian Shelf (ScS) in the summer months. Three major coastal upwelling events on the ScS in the summer of 2012 are analyzed using in-situ SST observations and satellite remote sensing SST data. A spatial correlation analysis of satellite SST data shows an asymmetric distribution in the along-shore direction with smaller correlation coefficients in the downstream area than in the upstream area over the inner ScS during upwelling events. A regression analysis indicates that the wind impulse plays a major role in generating the SST cooling during the initial response stage of upwelling events. A nested-grid ocean circulation model (DalCoast-CSS) is used to examine the effect of irregular coastline and rugged bathymetry on the spatial and temporal variability of wind-driven upwelling over the inner ScS. The model has four submodels downscaling from the eastern Canadian Shelf to the central ScS. The model external forcing includes tides, winds, river discharges, and net heat flux at the sea surface. A comparison of model results with the satellite SST data reveals a satisfactory performance of the model in reproducing the development of coastal upwelling on the ScS. Model results demonstrate that the irregular coastline and rugged bathymetry play important roles in influencing the temporal and spatial evolution of the upwelling plume over the inner ScS. The irregular coastline (e.g., cape) is responsible for the relatively warm SSTs in two downstream inlets (i.e., St. Margarets Bay and Mahone Bay) and adjacent coastal waters. The rugged bathymetry (e.g., submerged bank) influences the spatial extent of filaments through the advection process.

Tropical Cyclone Heat Potential (TCHP) from the NCMRWF NEMO based global ocean analysis and forecast system

In this study, the Nucleus European Modelling of Ocean (NEMO) based global ocean analysis and forecast system configured at National Centre for Medium Range Weather Forecasting (NCMWRF) is used to compute the upper ocean heat content up to 26° isotherm depth called as Tropical Cyclone Heat Potential (TCHP). NCMRWF has the real-time TCHP monitoring capability on daily basis. It is produced in real time using the global ocean forecast system up to 10 days using the ocean only model and up to 15 days using the coupled atmosphere-ocean model for monitoring the upper ocean and also for research purpose mainly for Tropical Cyclone (TC) study. Four pre-monsoon TCs with category above cyclonic storms in which two from Arabian Sea and two from Bay of Bengal are also examined. The Sea Surface Temperature drop is much more over the regions where the surface wind stress anomaly is strong. In both regions, various small scale warm and cold eddies are observed during TCs. TCHP anomaly is positive/negative over the region where Sea Surface Height (SSH) anomaly is positive/negative. From TCHP, it is manifest that the magnitude of TCHP anomaly is higher in BoB than AS region during TCs.

Impact of global cooling on Early Cretaceous high pCO2 world during the Weissert Event

The Weissert Event ~133 million years ago marked a profound global cooling that punctuated the Early Cretaceous greenhouse. We present modelling, high-resolution bulk organic carbon isotopes and chronostratigraphically calibrated sea surface temperature (SSTs) based on an organic paleothermometer (the TEX86 proxy), which capture the Weissert Event in the semi-enclosed Weddell Sea basin, offshore Antarctica (paleolatitude ~54 °S; paleowater depth ~500 meters). We document a ~3–4 °C drop in SST coinciding with the Weissert cold end, and converge the Weddell Sea data, climate simulations and available worldwide multi-proxy based temperature data towards one unifying solution providing a best-fit between all lines of evidence. The outcome confirms a 3.0 °C ( ±1.7 °C) global mean surface cooling across the Weissert Event, which translates into a ~40% drop in atmospheric pCO2 over a period of ~700 thousand years. Consistent with geologic evidence, this pCO2 drop favoured the potential build-up of local polar ice.

Bio-Physical Changes in the Gulf of Mexico During the 2018 Hurricane Michael

We investigate the impacts of one of the strongest recorded hurricanes to have hit the Florida Panhandle, Hurricane Michael (2018), on the upper ocean using a suite of satellite data, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> profiles, and outputs from the HYbrid Coordinate Ocean Model (HYCOM). Strong, low-level cyclonic winds associated with the hurricane generated strong Ekman suction that propagated ahead of the hurricane and caused changes in the surface and subsurface ocean. Following the passage of Hurricane Michael, a 3 °C drop in sea surface temperature (SST) was accompanied with a 4–5 mg <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}^{-3}$ </tex-math></inline-formula> increase in chlorophyll-a concentration. In the subsurface, a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 15$ </tex-math></inline-formula> m mixed layer deepening preceded upward displacements of the isotherms and cooling of the mixed layer. The impact of hurricane conditions on sea surface salinity (SSS) was localized and influenced by competing processes, with upwelling of salty subsurface water increasing SSS and enhanced precipitation decreasing SSS. During the peak of the hurricane, the impact of upwelling was greater than that of enhanced precipitation and, thus, SSS increased. Further away from the upwelling centers, hurricane-influenced precipitation, and river runoff freshened SSS.

Effects of the Covid-19 pandemic on the oceans

ABSTRACT A lockdown due to the novel coronavirus (COVID-19) resulting in the closure of largest industries in the world for a period of 2 months was enough to cause a drop of 7% of the anthropogonic carbon dioxide (CO2) in the atmosphere. Besides, the atmosphere oceans play a key role to buffer the greenhouse effect. Herein, the resultant reduction in CO2 emissions on the productivity of the global oceans are studied. Often chlorophyll-a (chl-a), particulate inorganic and organic carbon (PIC:POC), and sea surface temperature (SST), are used to indicate the productivity of oceans. Based on the satellite estimates, a drop in chl-a is observed in North Europe, South China and Southeast USA during the pandemic. The observed reduction in mean chl-a by around 5% in China may have occurred due to a drop of 123 tonnes of CO2 emissions. A cooling response of 0.5°C in mean SST is observed over most of the coastal areas. A considerable drop in CO2 emissions in the North Indian Ocean translates into a drop of mean SST in the region by 5%. All these suggest that maintaining global activities as sustainable as the pandemic period, can help to recover the oceans.

A limited effect of sub-tropical typhoons on phytoplankton dynamics

Abstract. Typhoons are assumed to stimulate primary ocean production through the upward mixing of nutrients into the ocean surface. This assumption is based largely on observations of increased surface chlorophyll concentrations following the passage of typhoons. This surface chlorophyll enhancement, occasionally detected by satellites, is often undetected due to intense cloud coverage. Daily data from a BGC-Argo profiling float revealed the upper-ocean response to Typhoon Trami in the northwest Pacific Ocean. Temperature and chlorophyll changed rapidly, with a significant drop in sea surface temperature and a surge in surface chlorophyll associated with strong vertical mixing, which was only partially captured by satellite observations. However, no net increase in vertically integrated chlorophyll was observed during Typhoon Trami or in its wake. In contrast to the prevailing dogma, the result shows that typhoons likely have a limited effect on net primary ocean production. Observed surface chlorophyll enhancements during and immediately following typhoons in tropical and subtropical waters are more likely to be associated with surface entrainment of deep chlorophyll maxima. Moreover, the findings demonstrate that remote sensing data alone can overestimate the impact of storms on primary production in all oceans. Full understanding of the impact of storms on upper-ocean productivity can only be achieved with ocean-observing robots dedicated to high-resolution temporal sampling in the path of storms.

Observational and modeling studies of oceanic responses and feedbacks to typhoons Hato and Mangkhut over the northern shelf of the South China Sea

Meteorological and oceanic responses to Typhoons Hato and Mangkhut were captured by storm-monitoring network buoys over the northern shelf of the South China Sea. With similar shelf-traversing trajectories, these two typhoons exhibited distinctly different features in storm-induced oceanic mixing and oceanic heat transfer through the air-sea interface. A well-defined cold wake was detected underneath the storm due to a rapid drop in sea surface temperature during the Hato crossing, but not during the Mangkhut crossing. Impacts of oceanic mixing on forming a storm-produced cold wake were associated with the pre-storm condition of water stratification. In addition to oceanic mixing produced through the diffusion process by shear and buoyancy turbulence productions, the short-time scale of mixing suggested convection/overturning may play a critical role in the rapid cooling at the sea surface. The importance of convection/overturning to mixing depended on the duration of atmospheric cooling above the sea surface-the longer the atmospheric cooling, the more significant effect on mixing. Including the oceanic mixed layer (OML) in the WRF model was capable of reproducing the observed storm-induced variations of wind and air pressure, but not the air and sea surface temperatures. Process-oriented numerical experiments with the OML models supported both observational and modeling findings. To simulate the storm-induced mixing in a coupled atmospheric and oceanic model, we need to improve the physics of vertical mixing with non-hydrostatic convection/overturning. Warming over the shelf is projected to have a more energetic influence on future typhoon intensities and trajectories.

Cyclone Ockhi Induced Upwelling and Associated Changes in Biological Productivity in Arabian Sea

In this study, the effect of severe tropical cyclone Ockhi on the physical and biological changes in ocean properties has been investigated. Winds from SCATSAT-1 was used for estimating the cyclone induced Ekman pumping. The role of ocean stratification, cyclonic wind stress, eddies and cyclone translation speed on the post cyclone oceanic response has been investigated. 8-day composite data of winds, sea surface temperature (SST), chlorophyll and sea level anomaly (SLA) have been analyzed for pre-cyclone, during cyclone and after cyclone period to understand the effect of wind forcing on the ocean variables. It was observed that there was a significant phytoplankton bloom like concentration along with 2-3 °C drop in SST after the passage of Ockhi. Thermocline displacements of up to 56 m were observed along the cyclone track. SLA data analyzed for the period shows formation of a cyclonic cold core eddy and weakening of anticyclonic warm core eddies. The entire cyclone track was divided into 12 track points based on the 12 hourly position and the change in SST and chlorophyll analyzed. The maximum change in chlorophyll and SST was observed where the cyclone was slowest and mixed layer shallow.

Satellite Data Analysis of the Upper Ocean Response to Hurricane Dorian (2019) in the North Atlantic Ocean

A suite of satellite-derived data and high-resolution ocean model outputs were used to study the response of the upper ocean to Hurricane Dorian (2019), which impacted the Bahamas and the eastern coast of the United States in August and September of 2019. We observe enhanced upwelling that in conjunction with surface cooling from precipitation led to an approximate 4 °C drop in sea surface temperature (SST) along and slightly ahead of Dorian’s path. The upwelling also increased the local coastal chlorophyll-a levels. Soil Moisture Active Passive (SMAP) sea surface salinity (SSS) shows a clear eye and eye wall structure on September 4 (the day of peak intensity), which has never been seen due to the recency of the SMAP satellite’s launch and the strength of Hurricane Dorian (2019). The initial forecast path of Hurricane Dorian was set to travel northward through central Florida; however, we can see from satellite observations that a high-pressure system in the north Atlantic redirects the path of the hurricane offshore. We show a clear upper ocean response to Hurricane Dorian using satellite observations and hope that this multiparameter approach can improve the current quantification of air–sea interactions during Category 5 conditions.