scholarly journals Estimating Zonal Ekman Transport along Coastal Senegal during Passage of Hurricane Fred (2015) from August 30 to 31, 2015

2019 ◽  
Author(s):  
Abdou Lahat Dieng ◽  
Siny Ndoye ◽  
Gregory S. Jenkins ◽  
Saïdou Moustapha Sall ◽  
Amadou Thierno Gaye
Keyword(s):  
Forecast Model ◽  
Ocean Model ◽  
Coastal Communities ◽  
Ekman Transport ◽  
Southerly Wind ◽  
Wind Speeds ◽  
Meridional Winds ◽  
Observed Damage ◽  
Coastal Damage

We examine the role of zonal Ekman transport along the coast of Senegal on 30 August, 2015 when the tropical disturbance associated with Tropical Cyclone Fred was located to the west of Senegal causing considerable coastal damage to coastal areas south of Dakar, Senegal. Ten-meter winds from three Weather Research and Forecast model simulations were used to estimate zonal Ekman transport, with the largest values found during the 30 August. The simulations are in agreement with limited coastal observations showing increasing southerly wind speeds during 30 August but are overestimated relative to the 3 coastal stations. The strong meridional winds translate into increased zonal Ekman transport to the coast of Senegal on 30 August. The use of a coupled ocean model will improve the estimates of Ekman transport along the Guinea-Senegalese coast. The observed damage suggests that artificial and natural barriers (mangroves) should be strengthened to protect coastal communities in Senegal.

scholarly journals Estimating zonal Ekman transport along coastal Senegal during passage of Hurricane Fred, 30–31 August 2015

2021 ◽  
Vol 3 (5) ◽  
Author(s):  
Abdou Lahat Dieng ◽  
Siny Ndoye ◽  
Gregory S. Jenkins ◽  
Saïdou M. Sall ◽  
Amadou T. Gaye
Keyword(s):  
Forecast Model ◽  
Ocean Model ◽  
Ekman Transport ◽  
Southerly Wind ◽  
Wind Speeds ◽  
Meridional Winds ◽  
Water Level Variations ◽  
Observed Damage ◽  
Coastal Damage

AbstractWe examine the role of zonal Ekman transport along the coast of Senegal on 30 August 2015 when the tropical disturbance associated with Tropical Cyclone Fred was located to the west of Senegal, causing considerable coastal damage in the southern Senegal–Gambia domain (south of Dakar, Senegal). Ten-meter winds from three Weather Research and Forecast model simulations were used to estimate zonal Ekman transport, when the maximum values were found on 30 August. These simulations are in agreement with limited coastal observations showing increasing southerly wind speeds during 30 August but overestimated relative to the three coastal stations. The strong meridional winds translate into increased zonal Ekman transport to the coast of Senegal on 30 August and are likely responsible for some coastal flooding. Ekman transport along the coast contributes significantly to the water-level variations during swell events. The use of a coupled ocean model will improve the estimates of Ekman transport along the Guinea-Senegalese coast. The observed damage suggests that artificial and natural barriers (mangroves) should be strengthened to protect coastal communities in Senegal.

Why Are There Tropical Warm Pools?

2005 ◽  
Vol 18 (24) ◽  
pp. 5294-5311 ◽  
Author(s):  
Amy C. Clement ◽  
Richard Seager ◽  
Raghu Murtugudde
Keyword(s):  
Surface Wind ◽  
Warm Pool ◽  
Ocean Dynamics ◽  
Ekman Transport ◽  
The West ◽  
Surface Solar Radiation ◽  
Easterly Wind ◽  
Atmospheric Processes ◽  
Wind Speeds

Abstract Tropical warm pools appear as the primary mode in the distribution of tropical sea surface temperature (SST). Most previous studies have focused on the role of atmospheric processes in homogenizing temperatures in the warm pool and establishing the observed statistical SST distribution. In this paper, a hierarchy of models is used to illustrate both oceanic and atmospheric mechanisms that contribute to the establishment of tropical warm pools. It is found that individual atmospheric processes have competing effects on the SST distribution: atmospheric heat transport tends to homogenize SST, while the spatial structure of atmospheric humidity and surface wind speeds tends to remove homogeneity. The latter effects dominate, and under atmosphere-only processes there is no warm pool. Ocean dynamics counter this effect by homogenizing SST, and it is argued that ocean dynamics is fundamental to the existence of the warm pool. Under easterly wind stress, the thermocline is deep in the west and shallow in the east. Because of this, poleward Ekman transport of water at the surface, compensated by equatorward geostrophic flow below and linked by equatorial upwelling, creates a cold tongue in the east but homogenizes SST in the west, creating a warm pool. High clouds may also homogenize the SST by reducing the surface solar radiation over the warmest water, but the strength of this feedback is quite uncertain. Implications for the role of these processes in climate change are discussed.

scholarly journals The use of regression for assessing a seasonal forecast model experiment

2016 ◽  
Vol 7 (4) ◽  
pp. 851-861 ◽  
Author(s):  
Rasmus E. Benestad ◽  
Retish Senan ◽  
Yvan Orsolini
Keyword(s):  
Sea Ice ◽  
Forecast Model ◽  
Ocean Model ◽  
Seasonal Forecasts ◽  
Air Temperatures ◽  
Model Set ◽  
Set Up ◽  
Numerical Model Experiments ◽  
The Tropics

Abstract. We show how factorial regression can be used to analyse numerical model experiments, testing the effect of different model settings. We analysed results from a coupled atmosphere–ocean model to explore how the different choices in the experimental set-up influence the seasonal predictions. These choices included a representation of the sea ice and the height of top of the atmosphere, and the results suggested that the simulated monthly mean air temperatures poleward of the mid-latitudes were highly sensitivity to the specification of the top of the atmosphere, interpreted as the presence or absence of a stratosphere. The seasonal forecasts for the mid-latitudes to high latitudes were also sensitive to whether the model set-up included a dynamic or non-dynamic sea-ice representation, although this effect was somewhat less important than the role of the stratosphere. The air temperature in the tropics was insensitive to these choices.

scholarly journals The use of regression for assessing a seasonal forecast model experiment

2016 ◽  
Author(s):  
Rasmus E. Benestad ◽  
Retish Senan ◽  
Yvan Orsolini
Keyword(s):  
Sea Ice ◽  
Forecast Model ◽  
Seasonal Forecast ◽  
Ocean Model ◽  
Seasonal Forecasts ◽  
Model Set ◽  
Set Up ◽  
Numerical Model Experiments ◽  
The Tropics

Abstract. We demonstrate how factorial regression can be used to analyse numerical model experiments, testing the effect of different model settings. We analysed results from a coupled atmosphere-ocean model to explore how the different choices in the experimental set-up influence the seasonal predictions. These choices included a representation of the sea-ice and the choice of top of the atmosphere, and the results suggested that the simulated monthly mean temperatures poleward of the mid-latitudes are highly sensitivity to the specification of the top of the atmosphere, interpreted as the presence or absence of a stratosphere. The seasonal forecasts for the mid-to-high latitudes were also sensitive to whether the model set-up included a dynamic or non-dynamics sea-ice representation, although this effect was less important than the role of the stratosphere. The temperature in the tropics was insensitive to these choices.

scholarly journals Evaluation of a Distributed Streamflow Forecast Model at Multiple Watershed Scales

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1279
Author(s):  
Tyler Madsen ◽  
Kristie Franz ◽  
Terri Hogue
Keyword(s):  
Local Population ◽  
Model Performance ◽  
Forecast Model ◽  
Hydrologic Model ◽  
Laboratory Research ◽  
Discharge Data ◽  
Distributed Hydrologic Model ◽  
Verification Period ◽  
Silver Spring

Demand for reliable estimates of streamflow has increased as society becomes more susceptible to climatic extremes such as droughts and flooding, especially at small scales where local population centers and infrastructure can be affected by rapidly occurring events. In the current study, the Hydrology Laboratory-Research Distributed Hydrologic Model (HL-RDHM) (NOAA/NWS, Silver Spring, MD, USA) was used to explore the accuracy of a distributed hydrologic model to simulate discharge at watershed scales ranging from 20 to 2500 km2. The model was calibrated and validated using observed discharge data at the basin outlets, and discharge at uncalibrated subbasin locations was evaluated. Two precipitation products with nominal spatial resolutions of 12.5 km and 4 km were tested to characterize the role of input resolution on the discharge simulations. In general, model performance decreased as basin size decreased. When sub-basin area was less than 250 km2 or 20–40% of the total watershed area, model performance dropped below the defined acceptable levels. Simulations forced with the lower resolution precipitation product had better model evaluation statistics; for example, the Nash–Sutcliffe efficiency (NSE) scores ranged from 0.50 to 0.67 for the verification period for basin outlets, compared to scores that ranged from 0.33 to 0.52 for the higher spatial resolution forcing.

scholarly journals Topographic Speed-Up Effects and Observed Roof Damage on Bermuda following Hurricane Fabian (2003)

2013 ◽  
Vol 28 (1) ◽  
pp. 159-174 ◽  
Author(s):  
Craig Miller ◽  
Michael Gibbons ◽  
Kyle Beatty ◽  
Auguste Boissonnade
Keyword(s):  
Surface Roughness ◽  
Wind Speed ◽  
Surface Wind ◽  
Open Water ◽  
Clear Trend ◽  
Wind Speeds ◽  
Research Division ◽  
Hurricane Wind ◽  
Layer Flow ◽  
Observed Damage

Abstract In this study the impacts of the topography of Bermuda on the damage patterns observed following the passage of Hurricane Fabian over the island on 5 September 2003 are considered. Using a linearized model of atmospheric boundary layer flow over low-slope topography that also incorporates a model for changes of surface roughness, sets of directionally dependent wind speed adjustment factors were calculated for the island of Bermuda. These factors were then used in combination with a time-stepping model for the open water wind field of Hurricane Fabian derived from the Hurricane Research Division Real-Time Hurricane Wind Analysis System (H*Wind) surface wind analyses to calculate the maximum 1-min mean wind speed at locations across the island for the following conditions: open water, roughness changes only, and topography and roughness changes combined. Comparison of the modeled 1-min mean wind speeds and directions with observations from a site on the southeast coast of Bermuda showed good agreement between the two sets of values. Maximum open water wind speeds across the entire island showed very little variation and were of category 2 strength on the Saffir–Simpson scale. While the effects of surface roughness changes on the modeled wind speeds showed very little correlation with the observed damage, the effect of the underlying topography led to maximum modeled wind speeds of category 4 strength being reached in highly localized areas on the island. Furthermore, the observed damage was found to be very well correlated with these regions of topographically enhanced wind speeds, with a very clear trend of increasing damage with increasing wind speeds.

scholarly journals New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa

2017 ◽  
Vol 35 (2) ◽  
pp. 333-344 ◽  
Author(s):  
Fasil Tesema ◽  
Rafael Mesquita ◽  
John Meriwether ◽  
Baylie Damtie ◽  
Melessew Nigussie ◽  
...  
Keyword(s):  
Local Time ◽  
Zonal Wind ◽  
Meridional Wind ◽  
Local Times ◽  
Maximum Speed ◽  
Wind Speeds ◽  
Early Evening ◽  
Meridional Winds ◽  
Thermospheric Winds ◽  
Wind Surge

Abstract. Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry–Perot interferometer (FPI), which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic). The results obtained in this study cover 6 months (53 nights of useable data) between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms−1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms−1 poleward during the winter months and 10 to 25 ms−1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM) to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was  ∼  110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT). Climatological models, HWM14 and MSIS-00, were compared to the observations and the HWM14 model generally predicted the zonal wind observations well with the exception of higher model values by 25 ms−1 in the winter months. The HWM14 model meridional wind showed generally good agreement with the observations. Finally, the MSIS-00 model overestimated the temperature by 50 to 75 K during the early evening hours of local winter months. Otherwise, the agreement was generally good, although, in line with prior studies, the model failed to reproduce the MTM peak for any of the 6 months compared with the FPI data.

scholarly journals Local Wisdom Values of Maritime Community in Preserving Marine Resources in Indonesia

2020 ◽  
Vol 4 (2) ◽  
pp. 84-94
Author(s):  
Sem Touwe
Keyword(s):  
Cultural Practices ◽  
Modern Technology ◽  
Coastal Communities ◽  
Marine Resources ◽  
Role Of Government ◽  
The People ◽  
Traditional Institutions ◽  
Customary Laws ◽  
Living Objects

This study identifies and describes the local wisdom carried out by the coastal communities, especially the people of North Seram, Maluku in preserving the island and marine environment as well as the customary institutions in determining and guarding local wisdom of coastal communities to manage marine resources. The marine resource is started to weaken along with the development of modern technology. This paper provides contemporary phenomena regarding the weakness of customary laws and traditional institutions that regulate marine resources, including social values in the form of rituals, representing the relationship between humans and their environment. The protection of marine resources around them will be an important discussion to see the role of government and society in preserving marine and coastal resources. This study used a qualitative approach to produce descriptive explanations from reports, book reviews, and documents that describe theories and information of both past and present. The result is that the local wisdom maintained as superior cultural practices that are beneficial to human survival, especially in maintaining the sustainability and balance between humans and living objects.

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