Wind Intensity Research Articles

Capturing complex star dune dynamics—repeated highly accurate surveys combining multitemporal 3D topographic measurements and local wind data

AbstractMorphologies of highly complex star dunes are the result of aeolian dynamics in past and present times. These dynamics reflect climatic conditions and associated forces like sediment availability and vegetation cover, as well as feedbacks with adjacent environments. However, an understanding of aeolian dynamics on star dune morphometries is still lacking sufficient detail, and their influence on formation and evolution remains unclear. We therefore investigate the dynamics of a complex star dune (Erg Chebbi, Morocco) by analysing wind measurements compared to morphometric changes derived from multitemporal high‐accuracy 3D observations during two surveys (October 2018 and February 2020). Using real‐time kinematic global navigation satellite system (RTK‐GNSS) measurements and terrestrial laser scanning (TLS), the reaction of a star dune surface to an observed constant unimodal sand‐moving wind is presented. TLS point clouds are used for morphometric analysis as well as direct surface change analysis, which relates to sand transport. RTK‐GNSS measurements enable the assessment of horizontal crest movement. Observed surface changes lead to the identification of an overall shielding effect, resulting in sand accumulation mainly on windward slopes. Our results point to a self‐sustained dune growth, which has not yet been described in such spatial detail. Steep slopes, often found on star dunes around the globe, seem to partly hinder upslope sand transport. Though a comparatively short observation period, we therefore hypothesize that, besides wind intensity alone, slope angles are more decisive for sand transport than previously assumed. Our methodological approach of combining meteorological data and high‐resolution multitemporal 3D elevation models can be used for monitoring all dune forms and contributes to a general understanding of dune dynamics and evolution.

Simulation of the effects of biomass burning in a mesoscale convective system in the central amazon

During the dry season of 2014, the formation of a mesoscale convective system (MCS) caused intense precipitation and strong winds in the central Amazon region. In this period, cases of MCS that occurred during the days when there were higher concentrations of CO were analyzed. Through this criterion, a case of MCS occurred on August 16th, 2014 was selected. We used the chemical-atmospheric model WRF-Chem to assess the influence of biomass burning aerosol on the intensity of precipitation, winds, vertical and horizontal transport associated with this convective system. We show that biomass burning aerosol reduces the strength of the mesoscale convective system, with less vertical and horizontal transport of carbon monoxide and ozone. In the absence of biomass burning aerosol downdrafts and precipitation rate are more intense, and cloud development up to 5 km is more developed, making the horizontal flow and vertical transport of ozone more intense, however, much more efficient in reducing the concentrations of other gases.

A Retrospective Satellite Analysis of the June 2012 North American Derecho

The North American Derecho of 29–30 June 2012 exhibits many classic progressive and serial derecho features. It remains one of the highest-impact derecho-producing convective systems (DCS) over CONUS since 2000. This research effort enhances the understanding of the science of operational forecasting of severe windstorms through examples of employing new satellite and ground-based microwave and vertical wind profile data. During the track of the derecho from the upper Midwestern U.S. through the Mid-Atlantic region on 29 June 2012, clear signatures associated with a severe MCS were apparent in polar-orbiting satellite imagery, especially from the EPS METOP-A Microwave Humidity Sounder (MHS), Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager Sounder (SSMIS), and NASA TERRA Moderate Resolution Imaging Spectroradiometer (MODIS). In addition, morning (descending node) and the evening (ascending node) METOP-A Infrared Atmospheric Sounding Interferometer (IASI) soundings are compared to soundings from surface-based Radiometrics Corporation MP-3000 series microwave radiometer profilers (MWRPs) along the track of the derecho system. The co-located IASI and MWRP soundings revealed a pre-convective environment that indicated a favorable volatile tropospheric profile for severe downburst wind generation. An important outcome of this study will be to formulate a functional relationship between satellite-derived parameters and signatures, and severe convective wind occurrence. Furthermore, a comprehensive approach to observational data analysis involves both surface- and satellite-based instrumentation. Because this approach utilizes operational products available to weather service forecasters, it can feasibly be used for monitoring and forecasting local-scale downburst occurrence within derecho systems, as well as larger-scale convective wind intensity associated with the entire DCS.

POLA DISTRIBUSI RUANG TERBUKA HIJAU TERHADAP TEMPERATUR WILAYAH KOTA SAMARINDA

The physical development of the city of Samarinda that is not in harmony between the existence of Built Space and the distribution of Green Open Space has an impact on changes in the urban microclimate. These changes occur in microclimate elements such as temperature, humidity, intensity of sunlight and wind. If the microclimate element changes, it is feared that a change will occur in a direction that is not in accordance with the comfort of the human body condition. Then it becomes a question in this study, namely how is the relationship between regional temperature and the distribution of green open space in Samarinda City. The targets carried out to achieve the research objectives are to analyze the temperature distribution of the Samarinda City area, analyze the distribution of Samarinda City Green open space, analyze the characteristics of Samarinda City Green open space, and analyze the relationship between regional temperature and the distribution of Samarinda City Green open space. To answer this goal, this research uses interpretation analysis of Landsat 8, Sentinel 2 imagery and statistical analysis in the form of regression analysis. In the sentinel image analysis, the data obtained are the distribution of temperature and the distribution of green open space. Where the minimum temperature is 29.8oC, maximum temperature is 38.8oC, and the distribution of green open space is obtained. The results of the ANN analysis show that there are 4 categories of green open space distribution data, namely clustered, spread out, uniform, and non-green open space. After the data obtained from the two analyzes, a quantitative analysis was carried out using SPSS programming to obtain the relationship between the Y variable and the X variable. In this analysis, the calculated F value was 1.930 with a significance level of 0.009 where the regression model can be used to predict the independent variables in this data. RTH with temperature showed a significant closeness. In the research area, it is stated that green open space has a significant relationship to the regional temperature distribution. In addition, the research findings also show that the ratio of green open space, the distribution of green open space, and the percentage of dense vegetation have an inverse relationship, which means that if green open space increases then the temperature decreases and vice versa.

Ionic Wind Intensity Enhancement and Ozone Reduction in a Solid-State Fan Via Electromagnetic Field Action

Ionic Wind Intensity Enhancement and Ozone Reduction in a Solid-State Fan Via Electromagnetic Field Action

Atmospheric Conditions for Uplift and Dust Transport in the Latitudinal 10° North–20° North Band in Africa

Desert aerosols suspended in the atmosphere are a very marked fact in West Africa with estimates of 400 to 1000 million tons produced annually and concentrations exceeding 50 µg·m³ in Burkina. In Bamako, the daily dust concentration can go up to reach 504 µg/m³. The Sahara and the Sahel are recognized as the primary desert aerosol producing regions. Source areas continue to be discovered as the desert advances. Previous studies have mainly focused on the spatial and temporal variability of aerosols. The current question is: What makes an area a source of dust emission? Our study brings together all the climatic parameters of the 10–20 band, as well as the soil types and their characteristics; it reveals 4 soils characteristic of fine sandy semi-arid soils in Chad. The Ouadaï plateau in Chad was identified as a source area for dust emissions. We noted for JFM (January, February, March) that the strongest wind intensities were located mainly towards Chad for average rmaximum temperatures around 34.7 °C. The statistical study reveals a correlation of 66.8% between direct and indirect links between the climatic factors of the 10–20 band and the source area. The presence of vortexes throughout the year and a vertical wind profile that is among the strongest in the 10–20 band, this gradient is strongly localized in the grid “10° North, 20° North and 20° East, 30° East” next to the Kapka massif. The study shows that the AEJ (African Easterly Jet) profile, which is a strong wind, associated with the harmattan circulation, allows the transport of aerosols from Ouadaï to the West African coast. In Senegal, a significant deposition was observed.

A Survey of Additives to Improve the Solubility, Capacity, and Cycle Life of Emerging Aqueous Redox Flow Battery Electrolytes

Low carbon intensity wind and solar renewable energies are gaining ground on the entrenched fossil fuel-based energy market; however, energy storage is still an unsolved problem to making renewable energy economically competitive for global-scale adoption. Aqueous redox flow batteries (ARFBs) offer the characteristics necessary to store renewable energy at large scales: customizable energy capacity and power delivery, inflammable/non-toxic components, diverse chemistry options with ultra-long calendar/cycle lifetimes, and rapidly dropping system costs. There is an ever-broadening array of inorganic, organic, and organometallic active species under study for ARFBs. Much research has focused on novel anolyte or catholyte development. Despite this progress, the stringent cost targets set by the DOE (<$150 kWh-1 by 2023) virtually necessitate that all battery electrolytes be earth-abundant, off-the-shelf chemicals. Few of the so-called “next generation” ARFB electrolytes based on organic or organometallic species meet this requirement. Here, we explore opportunities to improve widely available ARFB electrolytes with low-cost additives that improve their solubility, cycle lifetime, and/or energy density.In this work we survey the impact of several additives on the battery performance of two major catholytes, iron tris-bipyridine (Fe(bpy)3 2+/3+) and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO-OH). Fe(bpy)3 2+/3+ has been of interest for energy storage for decades but not yet realized in a practical device. It is a low-cost, non-toxic, easily synthesized complex that operates at neutral pH with one of the highest achievable redox potentials among ARFB catholytes. We introduce the shortcomings of Fe(bpy)3 2+/3+, i.e. low aqueous solubility and dimerization after charging, and present means of addressing these issues. Isopropyl alcohol as an cosolvent additive boosts the solubility of Fe(bpy)3 2+/3+ to permit achieved capacities double that of the additive-free solution. To mitigate dimerization, copper hexacyanoferrate (CuHCF) added to the catholyte reservoir improves Fe(bpy)3 2+/3+’s discharge voltage through an apparent catalytic effect. Furthermore, we have discovered that alternative supporting electrolytes, i.e. LiNO3 vs. KCl, improve discharge voltage as well as cycle lifetime in Fe(bpy)3 2+/3+ catholyte-limited ARFBs.TEMPO-OH is another widely studied, low-cost ARFB catholyte with a high redox potential. It has moderate aqueous solubility and is susceptible to side reactions in both acidic and basic chemical environments. The TEMPO core is often covalently derivatized via synthetic organic approaches in order to improve its properties (solubility, stability, redox potential) in ARFBs. Despite these enhancements, the synthetic approaches are likely not practical for global scale deployment of TEMPOs in ARFBs. Thus, here we seek to enhance the commercially available TEMPO-OH complex via electrolyte/additive engineering. Two recent studies demonstrate strategies to improve the solubility of TEMPO-OH using sodium xylenesulfonate and ionic liquid additives. We report on the full battery performance of these modified electrolytes against the control solutions. To improve energy density, we push the TEMPO-OH catholytes towards their solubility limits to quantify the degradation rates of catholyte-limited ARFBs as a function of TEMPO-OH and additive concentrations.The work presented here showcases several specific examples of novel additives, supporting electrolytes, and their combinations applied to the low-cost Fe(bpy)3 2+/3+ and TEMPO-OH ARFB catholytes. We quantify significant metrics, i.e. capacity retention, achievable energy density, and voltage/energy efficiency, in the modified electrolytes. We hope the work inspires further studies on engineering the support system of ARFB catholytes and anolytes using low-cost, off-the-shelf additives.

Effects of Weather Conditions on the Public Demand for Weather Information via Smartphone in Multiple Regions of China

Abstract Understanding when weather information is required by the public is essential for evaluating and improving user-oriented weather services. Because of the popularity of smartphones, most people can easily access weather information via smartphone applications. In this study, we analyzed usage data for the Moji Weather smartphone application in 2017 and 2018 and devised a demand index to determine how often the weather information was used by the public under different weather conditions. Using hourly observations of surface temperature, wind intensity, precipitation, and visibility, we quantified the relationship between the demand for weather information and weather conditions in different regions of China. In general, the demand index increased with increases in local hourly precipitation or surface wind intensity in all regions; however, there were notable regional differences in the increasing trends. Extreme hot weather was found to increase the demand index in Northern China, Xinjiang, and the Sichuan Basin while in Southern China it increased more in response to extreme cold weather. We quantified the relationships between the demand index and weather conditions by performing a polynomial regression analysis for each weather element and region. The high-demand thresholds were found to vary among regions, suggesting the need for customized weather services for users in different geographical regions. The study also revealed the contribution of weather warnings to weather information demand in two megacities and showed that warnings were effective for conveying information about weather-related risks.

Electrohydrodynamic and heat transfer characteristics of a planar ionic wind generator with flat electrodes

• Two corona discharges with different polarities are produced simultaneously. • The minimum discharge gap to maintain a stable corona discharge is determined. • The intensity and direction of the generated ionic wind is revealed. • The relationship between the heat transfer enhancement ratio and power consumption is established. In this study, a planar ionic wind generator with two flat electrodes was investigated numerically and experimentally to reveal its electrohydrodynamic and heat transfer characteristics. The multi-physical characteristics, including the discharge process, movement of electrons, positive ions, and negative ions, as well as the formation of ionic wind and its flow characteristics were simulated numerically. It was found that two corona discharges with different polarities were produced simultaneously when a high voltage was applied between the emitting and the ground electrodes. The intensity and direction of ionic wind produced by planar ionic wind generator was revealed. The effects of discharge gap, flat electrode thickness, and discharge polarity on the heat transfer characteristics and power consumption of the planar ionic wind generator were also investigated experimentally. The minimum discharge gap to maintain a stable corona discharge is determined. A better heat dissipation capacity of the planar ionic wind generator can be obtained with a larger electrode gap, and the optimized ionic wind generator can reduce the surface temperature of a 2.05 W powered heat source by more than 46 °C compared with natural cooling. The maximum heat transfer coefficient is 35 W∙m −2 ∙K −1 . This study can provide a theoretical guidance for the application of planar ionic wind generators to highly compact electronic devices.

On the Value of Early Marine Weather Observations: The Malaspina Expedition (1789–94)

Abstract Great advances in meteorological science were made in the late eighteenth century. In particular, meteorological instruments were carried on ships and the first systematic meteorological readings over the oceans were made. One of these collections of instrumental meteorological readings was carried out by the Malaspina expedition (1789–94), organized by the Spanish Crown to study its vast possessions around the world. We have recovered meteorological variables such as air temperature (maximum and minimum), atmospheric pressure (maximum and minimum), wind (intensity and direction), and appearance (state of the sky) from the documentation generated by the explorers during the journey. In total, nearly 13,000 instrumental data have been digitized and rescued from this maritime expedition. The comparison of daily temperature and pressure observations with reanalysis and weather stations data shows a good overall agreement. Moreover, apparent discrepancies during several anchored periods have allowed for testing the consistency and quality of these early instrumental marine weather readings.

Analysis of northern events on the Gulf of Tehuantepec and their effects on navigation

The maritime areas of greatest risk in the Gulf of Tehuantepec, are derived from the strong winds and waves presented during the northern events that occurred during the cold front seasons, these meteorological phenomena affect activities related to navigation and represent a danger to the civil population due to the strong intensities of the wind and the height of the waves. The objective of the present investigation was to identify the maritime zones of greatest risk to navigation on the Gulf of Tehuantepec, derived from the analysis of the events of the north during the period 2015-2019, with the purpose of warning and making the maritime community aware. regional and national, the areas where the effects of the northern events are more intense. Likewise, for the analysis, interpretation and identification of the northern events, wind data recorded at the Automatic Meteorological Station (EMA) of the Secretary of the Navy (SEMAR), located in the Port of Salina Cruz, Oaxaca, and reanalysis data of the set were used. of wind and wave data from ERA5, for its subsequent processing through the Python programming language for the generation of maps of the variables. This gave as a result that a radius of the first 80 Nautical Miles (NM) of the Port of Salina Cruz, Oaxaca has intense wind and wave conditions during the month of January and very intense conditions appearing in a radius of 120 NM around said zone. Of the 56 northern events associated with cold fronts, 40 were classified as strong and 16 were classified as very strong, being of great relevance to avoid navigation accidents.

Orographic‐Induced Strong Wind Associated With a Low‐Pressure System Under Clear‐Air Condition During ICE‐POP 2018

AbstractA strong wind event under clear‐air conditions during the 2018 Winter Olympic and Paralympic games in Pyeongchang, Korea, was examined using various datasets. High spatiotemporal resolution wind information was obtained by Doppler lidars, automatic weather stations, wind profiler, sounding observations, reanalysis datasets under the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games (ICE‐POP 2018). This study aimed to understand the possible mechanisms of localized strong winds across a high mountainous area and on the leeside associated with the underlying large‐scale pattern of a low‐pressure system (LPS). The evolution of surface winds shows quite different patterns, exhibiting intensification of strong winds in the leeside and periodically persistent strong winds in upstream mountainous areas with the approaching LPS. The surface wind speed was intensified from ∼3 to ∼12 m s−1 (gusts were stronger than 20 m s−1 above the ground) at a surface station in the leeside. A budget analysis of the horizontal momentum equation suggested that the pressure gradient force (PGF) contributed from adiabatic warming and the passage of LPS was the main factor in the acceleration of the surface wind in the leeward side of the mountains. The detailed 3D winds revealed that the PGF also modulated the background winds at the mountainous station, which caused persistent strong and periodic winds (range of ∼7 to ∼12 m s−1) related to the channeling effect. The evidence showed that under the same synoptic condition of a LPS, different mechanisms are important for strong winds in determining the strength and persistence of orographic‐induced strong winds under clear‐air conditions.

Influence of Weather Conditions on the Spread of Fires in the Forest Fund of Zhytomyr Polesia

Fires are one of the critical factors in the weakening of forests. Given the high share of pine forests in the Zhytomyr Oblast, the conditions for fires are very favourable. Especially intense fires occurred in 2020, when rapid warming occurred in the spring, which in the absence of snow cover and the presence of intense winds in the February-March 2020 increased the fire danger in forests. The purpose of this study is to identify the features of the dynamics of the spread of fires in the forest stands of the Zhytomyr Oblast Department of Forestry and Hunting and assess the meteorological indicators that may affect their spread. Research methods: statistical – when analysing data on meteorological indicators and materials for accounting for forest fires. The study identified the specific features of the dynamics of fire spread in forest stands of Zhytomyr Oblast in 2014-2021. According to the analysis, there was a considerable increase in the number and area of fires in 2020 compared to the average figures for 2014-2019 and 2021 combined. During 2014-2021, 951 fires occurred on a forested area of 43,807.65 hectares. It was revealed that only 448 fires occurred in 2014-2019 and 2021, and 503 fires were recorded in 2020 on an area of 43,229 hectares. Among others, crown fires were recorded on an area of 6,389 hectares in the same 2020 year and on an area of 35.7 hectares in 2019 alone. The largest areas of crown fires were recorded on the territory of the State Enterprise “Ovrutske SF”, State Enterprise “Luhynske forestry”, State Enterprise “Ovrutske forestry” and State Enterprise “Slovechanske forestry”. The indicators of temperature, precipitation, and hydrothermal coefficient for 2014-2021 are analysed. The values of air temperature and precipitation were determined during the growing season, and the hydrothermal coefficient was calculated according to G.T. Selyaninov. The study established that the sum of air temperatures during the growing season was 3,127.6°C on average for 2014-2021. The highest temperature values were recorded during the growing season of 2018. According to the analysis of the amount of precipitation for the growing season 2014-2021, the indicators were set at 323.8 mm. The lowest precipitation rates were recorded in 2015. According to the ratio of temperature and precipitation indicators, the value of G.T. Selyaninov’s hydrothermal coefficient for the growing seasons of 2014-2021 was obtained, the average value of which was 1.04 units

On the understanding of very severe cyclone storm Ockhi with the WRF-ARW model

Understanding the dynamics of tropical cyclones (TCs) in terms of intensity, and their trajectory is essential for an adequate early warning and mitigation. The present study attempts to understand the synoptic features of the recent TC Ockhi through a simulation-based approach with the Weather Research and Forecasting (WRF, version 3.8.1) model. Ockhi is considered as a unique TC that originated from depression in the Bay of Bengal on 29 November 2017, recurved towards the Arabian Sea, where it intensified into a very severe cyclone storm and weakened on 5 December 2017. WRF model forced with initial condition from (global forecasting system) GFS data and sea surface temperature (SST) from Group for High-Resolution SST (GHRSST) product for different lead times to test the potential sensitivity of the model. One with an extended period from 20 November to 20 December 2017 (WRF1) and another initiated from 27 November to 6 December 2017 (WRF2). Comparison of the simulated track with the best track estimates from the Indian Meteorological Department indicated an overall track deviation greater than 100 km for both the simulations. The analysis with the extended lead time simulation indicates that the WRF simulated sea level pressure and wind intensity are close to that observed by Arabian sea buoys; CB02, AD08, AD10, and AD07. Daily averaged wind estimate comparison of WRF1 with Scatsat-1 and ERA-5 indicates that the model is slightly overestimating, whereas comparison of peak wind intensity with the time instantaneous swath product of Scatsat-1 leads to underestimation. Analysis of various simulated synoptic features of the cyclone, as discussed in this paper, indicates that the model is skillful in capturing the various stages of cyclone Ockhi.

Lisbon urban heat island in future urban and climate scenarios

Urban heat Islands (UHIs) may constitute a hazard for urban populations, particularly under extreme events such as heatwaves. Lisbon is a medium-size city regularly affected by heatwaves with maximum temperatures >35 °C and is expected to grow and densify during this century.This study evaluates the UHI in the Municipality of Lisbon (ML) for the heatwave with the highest maximum average temperature identified in long-term (2081–2100) RCP8.5 scenario climate simulations, relative to present conditions, represented by a typical heatwave identified in historical (1986–2005) period climate simulations. The expected future consolidation of the city (up to 2100) is considered, as well as the anthropogenic heat and irrigation effects. Simulations are performed with the Weather Research and Forecasting model (WRF) coupled with the Single-layer Urban Canopy Model (SLUCM). The results reveal that urban irrigation effects compensate anthropogenic heat due to increased latent heat release. The expected city consolidation up to 2100 produces the largest increase in the UHI intensity (UHII) during nighttime due to the introduction of urban land use land cover (LULC) with reduced green fraction. No evidence of synergistic interactions between UHI and heatwave intensities were found, with the UHII mostly depending on wind direction and intensity.

Review of satellite resources to assess environmental threats in rammed earth fortifications

The nature of rammed earth fortifications and the environmental conditions where they are located determine the pathologies that these structures suffer in the presence of humidity sources and strong winds. The objective of this project is to revise the main mechanisms of deterioration of rammed earth fortifications and evaluate the use of remote detection as a tool to register environmental threats that affect their preservation. The selected images and satellite results offer information about precipitation, ground humidity, temperature, wind intensity and direction and the presence of particles in the wind. The use of statistical analysis methodologies for large volumes of satellite images makes it possible to acquire daily, monthly and yearly maximums, averages and minimums of these variables. The application of satellite resources GPM, SMAP, MODIS, Merra-2 and the statistical analysis of large volumes of images for preventive conservation in Andalusia has become useful to monitor the main threats that affect rammed earth fortifications on a global level: humidity, wind and temperature.

A multiyear radar-based climatology of supercell thunderstorms in central-eastern Argentina

Some of the strongest storms on Earth occur over central-eastern Argentina. These storms are associated with severe weather phenomena such as big hail, heavy rain, intense wind gusts, and, occasionally, tornadoes. The relatively recent expansion of the radar network in this area brings the chance to better characterize severe weather storms.This study presents a nine-year climatology of supercells (SCs) and their associated mesocyclones (MCs) based on radar data over central Argentina, together with a preliminary analysis of the thermodynamic environment in which they develop. We propose an MC detection algorithm based on the Non-Maximum Suppression (NMS) technique and a subjective classification.The MCs have shown a mean lifetime of 73 min, with their maximum intensity located at 4.7 km above ground level (AGL) on average. The monthly frequency of SCs in central-eastern Argentina is similar to that reported in previous studies near the Sierras de Córdoba, with two relative maxima, one in November and the other one in February, and with an absolute minimum in June. The diurnal cycle shows an absolute maximum at around 0100 UTC (2200 local time) and a minimum between 0900 and 1500 UTC (0600 and 1200 local time).Based on the results obtained here, the pre-convective environments associated with SCs in the Paraná region are very similar to its analogs in the Sierras de Córdoba. They are characterized by high values of convective instability and vertical wind shear. Storm relative helicity (in the low and middle layers) and wind shear in the first kilometer above the surface are lower than those found in the U.S. Great Plains. Although the analysis shows that there are environmental parameters that can discriminate well between SC and non-SC events, their values are shown to be far from the thresholds considered in the U.S. Results hence suggest the need to adapt the thresholds of some of the parameters studied here, particularly those based on storm-relative helicity, to central-eastern Argentina.

Seasonal and Long-Term Variability of the Mixed Layer Depth and its Influence on Ocean Productivity in the Spanish Gulf of Cádiz and Mediterranean Sea

The warming of the surface ocean is expected to increase the stratification of the upper water column. This would decrease the efficiency of the wind-induced mixing, reducing the nutrient supply to the euphotic layer and the productivity of the oceans. Climatic projections show that the Mediterranean Sea will experience a strong warming and salting along the twenty first century. Nevertheless, very few works have found and quantified changes in the water column stratification of the Western Mediterranean. In this work, we obtain time series of Mixed Layer Depth (MLD) along the Spanish Mediterranean waters and the Gulf of Cádiz, using periodic CTD profiles collected under the umbrella of the Ocean Observing system of the Instituto Español de Oceanografía (IEO-CSIC). The length of the time series analyzed is variable, depending on the geographical area, but in some cases these time series extend from the beginning of the 1990s decade. Our results show that at present, no statistically significant changes can be detected. These results are confirmed by the analysis of MLD time series obtained from Argo profilers. Some of the meteorological factors that could affect the water column stratification (wind intensity and precipitation rates) did not experience significant changes for the 1990-2021 period, neither were observed long-term changes in the chlorophyll concentration. The hypothesis proposed to explain this lack of trends, is that the salinity increase of the surface waters has compensated for the warming, and consequently, the density of the upper layer of the Western Mediterranean (WMED) has remained constant. As the wind intensity has not experienced significant trends, the stratification of the Spanish Mediterranean waters and those of the Gulf of Cádiz would have not been affected. Nevertheless, we do not discard that our results are a consequence of the short length of the available time series and the large variance of the variables analyzed, evidencing the importance of the maintenance of the ocean monitoring programs.

Generating reliable estimates of tropical-cyclone-induced coastal hazards along the Bay of Bengal for current and future climates using synthetic tracks

Abstract. Deriving reliable estimates of design water levels and wave conditions resulting from tropical cyclones is a challenging problem of high relevance for, among other things, coastal and offshore engineering projects and risk assessment studies. Tropical cyclone geometry and wind speeds have been recorded for the past few decades only, thus resulting in poorly reliable estimates of the extremes, especially in regions characterized by a low number of past tropical cyclone events. In this paper, this challenge is overcome by using synthetic tropical cyclone tracks and wind fields generated by the open-source tool TCWiSE (Tropical Cyclone Wind Statistical Estimation Tool) to create thousands of realizations representative of 1000 years of tropical cyclone activity for the Bay of Bengal. Each of these realizations is used to force coupled storm surge and wave simulations by means of the processed-based Delft3D Flexible Mesh Suite. It is shown that the use of synthetic tracks provides reliable estimates of the statistics of the first-order hazard (i.e., wind speed) compared to the statistics derived for historical tropical cyclones. Based on estimated wind fields, second-order hazards (i.e., storm surge and waves) are computed that are generated by the first-order hazard of wind. The estimates of the extreme values derived for wind speed, wave height and storm surge are shown to converge within the 1000 years of simulated cyclone tracks. Comparing second-order hazard estimates based on historical and synthetic tracks shows that, for this case study, the use of historical tracks (a deterministic approach) leads to an underestimation of the mean computed storm surge of up to −30 %. Differences between the use of synthetic versus historical tracks are characterized by a large spatial variability along the Bay of Bengal, where regions with a lower probability of occurrence of tropical cyclones show the largest difference in predicted storm surge and wave heights. In addition, the use of historical tracks leads to much larger uncertainty bands in the estimation of both storm surges and wave heights, with confidence intervals being +80 % larger compared to those estimated by using synthetic tracks (probabilistic approach). Based on the same tropical cyclone realizations, the effect that changes in tropical cyclone frequency and intensity, possibly resulting from climate change, may have on modeled storm surge and wave heights was computed. As a proof of concept, an increase in tropical cyclone frequency of +25.6 % and wind intensity of +1.6 %, based on literature values and without accounting for uncertainties in future climate projection, was estimated to possibly result in an increase in storm surge and wave heights of +11 % and +9 %, respectively. This suggests that climate change could increase tropical-cyclone-induced coastal hazards more than just the actual increase in maximum wind speeds.

Vulnerability to typhoons: A comparison of consequence and driving factors between Typhoon Hato (2017) and Typhoon Mangkhut (2018)

Typhoon disasters have caused casualties, property loss, and other negative impacts to social and economic development. Vulnerability is an important component of typhoon risk. However, little is known about the contributions of vulnerability factors and their interaction effects on typhoon-induced losses at a fine scale. Focusing on the vulnerability measures of Typhoon Hato in 2017 and Typhoon Mangkhut in 2018, this study aims to quantify the contribution and interactive effects of physical and socioeconomic factors on vulnerability based on the GeoDetector method and determine the factors that account for most of the change in vulnerability. The results show that from Typhoon Hato in 2017 to Typhoon Mangkhut in 2018, the vulnerability of the economy and houses decrease on average. Rain intensity and wind intensity are the dominant factors of disaster loss for Typhoon Hato and Typhoon Mangkhut, respectively. Vegetation cover and landform explain vulnerability better than average slope in most instances. For different loss types, the dominant socioeconomic vulnerability factor is different. For both typhoons, emergency transfer has a higher determining power (q) ranking for the population vulnerability, while the percentage of the GDP made up of primary industry have higher q ranking for economic vulnerability. The dominant interaction effects between two vulnerability factors differ depending on the typhoon and loss type but show a nonlinear enhancement effect in most cases. Moreover, changes in the maximum 4-hour accumulated rainfall account for most of the change in vulnerability between Hato and Mangkhut. Overall, the results can be conducive to understanding the complexity of vulnerability to typhoons and provide a reference for possible indicators for vulnerability assessment models, and determining the reasons for changes in vulnerability can be constructive to the formulation of specific policies for disaster prevention and mitigation.