scholarly journals Wind Stress Curl and Coastal Upwelling in the Area of Monterey Bay Observed during AOSN-II

2011 ◽  
Vol 41 (5) ◽  
pp. 857-877 ◽  
Author(s):  
Q. Wang ◽  
J. A. Kalogiros ◽  
S. R. Ramp ◽  
J. D. Paduan ◽  
G. Buzorius ◽  
...  
Keyword(s):  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Coastal Upwelling ◽  
Surface Wind ◽  
Sea Surface ◽  
Monterey Bay ◽  
Surface Currents ◽  
Surface Wind Stress

Abstract Aircraft measurements obtained during the 2003–04 Autonomous Ocean Sampling Network (AOSN-II) project were used to study the effect of small-scale variations of near-surface wind stress on coastal upwelling in the area of Monterey Bay. Using 5-km-long measurement segments at 35 m above the sea surface, wind stress and its curl were calculated with estimated accuracy of 0.02–0.03 N m−2 and 0.1–0.2 N m−2 per 100 kilometers, respectively. The spatial distribution of wind speed, wind stress, stress curl, and sea surface temperature were analyzed for four general wind conditions: northerly or southerly wind along the coastline, onshore flow, and offshore flow. Wind stress and speed maxima frequently were found to be noncollocated as bulk parameterizations imply owing to significant stability and nonhomogeneity effects at cold SST pools. The analyses revealed that complicated processes with different time scales (wind stress field variation, ocean response and upwelling, sea surface currents, and heating by solar radiation) affect the coastal sea surface temperature. It was found that the stress-curl-induced coastal upwelling only dominates in events during which positive curl extended systematically over a significant area (scales larger than 20 km). These events included cases with a northerly wind, which resulted in an expansion fan downstream from Point Año Nuevo (wind speed peaks greater than about 8–10 m s−1), and cases with an offshore/onshore flow, which are characterized by weak background upwelling due to Ekman transport. However, in general, observations show that cold pools of sea surface temperature in the central area of Monterey Bay were advected by ocean surface currents from strong upwelling regions. Aircraft vertical soundings taken in the bay area showed that dominant effects of the lee wave sheltering of coastal mountains resulted in weak atmospheric turbulence and affected the development of the atmospheric boundary layer. This effect causes low wind stress that limits upwelling, especially at the northern part of Monterey Bay. The sea surface temperature is generally warm in this part of the bay because of the shallow oceanic surface layer and solar heating of the upper ocean.

scholarly journals Observations of Coupling between Surface Wind Stress and Sea Surface Temperature in the Eastern Tropical Pacific

2001 ◽  
Vol 14 (7) ◽  
pp. 1479-1498 ◽  
Author(s):  
Dudley B. Chelton ◽  
Steven K. Esbensen ◽  
Michael G. Schlax ◽  
Nicolai Thum ◽  
Michael H. Freilich ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Surface Wind ◽  
Tropical Pacific ◽  
Sea Surface ◽  
Eastern Tropical Pacific ◽  
Surface Wind Stress

scholarly journals Sea surface wind perturbations over the Kashevarov Bank of the Okhotsk Sea: a satellite study

2011 ◽  
Vol 29 (2) ◽  
pp. 393-399
Author(s):  
T. I. Tarkhova ◽  
M. S. Permyakov ◽  
E. Yu. Potalova ◽  
V. I. Semykin
Keyword(s):  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Surface Wind ◽  
Sea Surface ◽  
Cold Spot ◽  
Okhotsk Sea ◽  
Autumn Period ◽  
Sea Surface Wind ◽  
Spot Center

Abstract. Sea surface wind perturbations over sea surface temperature (SST) cold anomalies over the Kashevarov Bank (KB) of the Okhotsk Sea are analyzed using satellite (AMSR-E and QuikSCAT) data during the summer-autumn period of 2006–2009. It is shown, that frequency of cases of wind speed decreasing over a cold spot in August–September reaches up to 67%. In the cold spot center SST cold anomalies reached 10.5 °C and wind speed lowered down to ~7 m s−1 relative its value on the periphery. The wind difference between a periphery and a centre of the cold spot is proportional to SST difference with the correlations 0.5 for daily satellite passes data, 0.66 for 3-day mean data and 0.9 for monthly ones. For all types of data the coefficient of proportionality consists of ~0.3 m s−1 on 1 °C.

scholarly journals A Comparative Assessment of Surface Wind Speed and Sea Surface Temperature over the Indian Ocean by TMI, MSMR, and ERA-40

2007 ◽  
Vol 24 (6) ◽  
pp. 1131-1142 ◽  
Author(s):  
Anant Parekh ◽  
Rashmi Sharma ◽  
Abhijit Sarkar
Keyword(s):  
Wind Speed ◽  
Indian Ocean ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Microwave Radiometer ◽  
Surface Wind ◽  
Surface Wind Speed ◽  
Sea Surface ◽  
Wind Speeds ◽  
Low Wind Speeds

A 2-yr (June 1999–June 2001) observation of ocean surface wind speed (SWS) and sea surface temperature (SST) derived from microwave radiometer measurements made by a multifrequency scanning microwave radiometer (MSMR) and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) is compared with direct measurements by Indian Ocean buoys. Also, for the first time SWS and SST values of the same period obtained from 40-yr ECMWF Re-Analysis (ERA-40) have been evaluated with these buoy observations. The SWS and SST are shown to have standard deviations of 1.77 m s−1 and 0.60 K for TMI, 2.30 m s−1 and 2.0 K for MSMR, and 2.59 m s−1 and 0.68 K for ERA-40, respectively. Despite the fact that MSMR has a lower-frequency channel, larger values of bias and standard deviation (STD) are found compared to those of TMI. The performance of SST retrieval during the daytime is found to be better than that at nighttime. The analysis carried out for different seasons has raised an important question as to why one spaceborne instrument (TMI) yields retrievals with similar biases during both pre- and postmonsoon periods and the other (MSMR) yields drastically different results. The large bias at low wind speeds is believed to be due to the poorer sensitivity of microwave emissivity variations at low wind speeds. The extreme SWS case study (cyclonic condition) showed that satellite-retrieved SWS captured the trend and absolute magnitudes as reflected by in situ observations, while the model (ERA-40) failed to do so. This result has direct implications on the real-time application of satellite winds in monitoring extreme weather events.

scholarly journals Interannual correlations between sea surface temperature and concentration of chlorophyll pigment off Punta Eugenia, Baja California during different remote forcing conditions

2013 ◽  
Vol 10 (3) ◽  
pp. 853-882 ◽  
Author(s):  
H. Herrera-Cervantes ◽  
S. E. Lluch-Cota ◽  
D. B. Lluch-Cota ◽  
G. Gutiérrez-de-Velasco
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Baja California ◽  
Coastal Upwelling ◽  
Empirical Orthogonal Functions ◽  
Sea Surface ◽  
Tropical Ocean ◽  
Chl A ◽  
Remote Forcing

Abstract. Interannual correlation between satellite-derived sea surface temperature (SST) and surface chlorophyll a (Chl a) are examined in the coastal upwelling zone off Punta Eugenia on the west coast of the Baja California Peninsula, area identified as intense biological productivity and oceanographic transition between mid-latitude and tropical ocean conditions. We used empirical orthogonal functions (EOF) analysis separately and jointly on the two fields from 1997 through 2007, a time period dominated by different remote forcing; ENSO conditions (weak, moderate and strong) and the largest intrusion of subarctic water reported in the last 50 yr. Coastal Upwelling Index anomalies (CUI) and the Multivariate ENSO Index (MEI) were used to identify the influence of local (wind stress) and remote (ENSO) forcing over the interannual variability of both variables. The individual EOF1 analysis showed the greater variability of SST and Chla offshore, their corresponding amplitude time series presented the highest peaks during the intrusion of subartic water (2002–2004) and were significantly correlated with the MEI (RSST &amp;approx; 0.68, RChl a &amp;approx; −0.30, P < 0.001) and moderately correlated with the CUI (RSST &amp;approx; −0.4, RChl a &amp;approx; 0.25, P < 0.001), showing similar trends. The joint EOF1 and the SST–Chl a correlations pattern show the area where both variables covary tightly; a band near to the coast with the largest correlations (R > |0.4|) mainly regulated by ENSO cycles. This was revealed when we calculate the homogeneous correlations for the periods El Niño–La Niña and the intrusion of subartic water. Both, SST and Chl a showed higher coupling and two distinct physical-biological responses; on average ENSO influence were clearly along the coast mostly in SST while the subarctic water influence, were observed offshore mostly in Chl a. We found a coastal chlorophyll bloom correlated strongly with high wind stress anomalies that reach the coast off Punta Eugenia during spring and summer 2002 and continued its presence during 2003 which showed an enrichment pattern similar to that observed at high latitudes (∼40° N). This observation may provide an explanation of why Punta Eugenia is one of the most important biological action centers.

scholarly journals Wind increase above warm Agulhas Current eddies

2014 ◽  
Vol 11 (5) ◽  
pp. 2367-2389
Author(s):  
M. Rouault ◽  
P. Verley ◽  
B. Backeberg
Keyword(s):  
Wind Speed ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Sea Level ◽  
Surface Wind ◽  
Sea Surface ◽  
Temperature Perturbation ◽  
Surrounding Water ◽  
Agulhas Current ◽  
Speed Increase

Abstract. Sea surface temperature estimated from the Advanced Microwave Scanning Radiometer E onboard the Aqua satellite and altimetry derived sea level anomalies are used south of the Agulhas Current to identify warm mesoscale eddies presenting a distinct SST perturbation superior to 1 °C to the surrounding ocean. The analysis of 2500 instantaneous charts of equivalent stability neutral wind speed estimates from the SeaWinds scatterometer onboard the QuikScat satellite collocated with sea surface temperature and sea level anomaly show stronger wind speed above warm eddies than surrounding water at all wind directions in about 800 of the 2500 cases. For those cases where the wind is stronger above warm eddies, we do not find any relationship between the increase in surface wind speed and the sea surface temperature perturbation. Sea surface temperature perturbations that we consider range from 1 to 5.5 °C. Sizes of eddies range from 100 to 250 km diameter. Mean background wind speed is about 11 m s−1 with a mean increase above the eddy of 2 m s−1. Wind speed increase of 4 to 7 m s−1 above warm eddies is not uncommon.

scholarly journals Influences of Sea Surface Temperature Gradients and Surface Roughness Changes on the Motion of Surface Oil: A Simple Idealized Study

2013 ◽  
Vol 52 (7) ◽  
pp. 1561-1575 ◽  
Author(s):  
Yangxing Zheng ◽  
Mark A. Bourassa ◽  
Paul Hughes
Keyword(s):  
Surface Roughness ◽  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Surface Wind ◽  
Free Water ◽  
Sea Surface ◽  
Ekman Transport ◽  
Wind Stress Curl ◽  
Transition Zones

AbstractThe authors' modeling shows that changes in sea surface temperature (SST) gradients and surface roughness between oil-free water and oil slicks influence the motion of the slick. Physically significant changes occur in surface wind speed, surface wind divergence, wind stress curl, and Ekman transport mostly because of SST gradients and changes in surface roughness between the water and the slick. These remarkable changes might affect the speed and direction of surface oil. For example, the strongest surface wind divergence (convergence) occurring in the transition zones owing to the presence of an oil slick will induce an atmospheric secondary circulation over the oil region, which in turn might affect the surface oil movement. SST-related changes to wind stress curl and Ekman transport in the transition zones appear to increase approximately linearly with the magnitude of SST gradients. Both surface roughness difference and SST gradients give rise to a net convergence of Ekman transport for oil cover. The SST gradient could play a more important role than surface roughness in changes of Ekman transport when SST gradients are large enough (e.g., several degrees per 10 km). The resulting changes in Ekman transport also induce the changes of surface oil movement. Sensitivity experiments show that appropriate selections of modeled parameters and geostrophic winds do not change the conclusions. The results from this idealized study indicate that the feedbacks from the surface oil presence to the oil motion itself are not trivial and should be further investigated for consideration in future oil-tracking modeling systems.

scholarly journals Distinct Influence of Air–Sea Interactions Mediated by Mesoscale Sea Surface Temperature and Surface Current in the Arabian Sea

2017 ◽  
Vol 30 (20) ◽  
pp. 8061-8080 ◽  
Author(s):  
Hyodae Seo
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Wind Stress ◽  
Arabian Sea ◽  
Spatial Scales ◽  
Surface Current ◽  
Sea Surface ◽  
Surface Currents ◽  
Ekman Pumping ◽  
Wind Stress Curl

Abstract During the southwest monsoons, the Arabian Sea (AS) develops highly energetic mesoscale variability associated with the Somali Current (SC), Great Whirl (GW), and cold filaments (CF). The resultant high-amplitude anomalies and gradients of sea surface temperature (SST) and surface currents modify the wind stress, triggering the so-called mesoscale coupled feedbacks. This study uses a high-resolution regional coupled model with a novel coupling procedure that separates spatial scales of the air–sea coupling to show that SST and surface currents are coupled to the atmosphere at distinct spatial scales, exerting distinct dynamic influences. The effect of mesoscale SST–wind interaction is manifested most strongly in wind work and Ekman pumping over the GW, primarily affecting the position of GW and the separation latitude of the SC. If this effect is suppressed, enhanced wind work and a weakened Ekman pumping dipole cause the GW to extend northeastward, delaying the SC separation by 1°. Current–wind interaction, in contrast, is related to the amount of wind energy input. When it is suppressed, especially as a result of background-scale currents, depth-integrated kinetic energy, both the mean and eddy, is significantly enhanced. Ekman pumping velocity over the GW is overly negative because of a lack of vorticity that offsets the wind stress curl, further invigorating the GW. Moreover, significant changes in time-mean SST and evaporation are generated in response to the current–wind interaction, accompanied by a noticeable southward shift in the Findlater Jet. The significant increase in moisture transport in the central AS implies that air–sea interaction mediated by the surface current is a potentially important process for simulation and prediction of the monsoon rainfall.

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