Search Results (7)

This study examines the evolution, structure, and dynamic and thermodynamic mechanisms of a Mediterranean tropical-like cyclone (TLC), or medicane (from Mediterranean–Hurricane), that occurred in the central Mediterranean region from 15 to 19 September 2020. This event is considered an extreme meteorological phenomenon, particularly impacting the Greek area and affecting the country’s economic and social structures. It is one of the most significant recorded Mediterranean cyclone phenomena in the broader Mediterranean region. The synoptic and dynamic environment, as well as the thermodynamic structure of this atmospheric disturbance, were analyzed using thermodynamic parameters. The system’s development can be described through three distinct phases, characterized by its symmetrical structure and warm core, as illustrated in the phase space diagrams and further supported by dynamical analysis. During the first phase, on 15 September, the structure of the upper tropospheric layers began to strengthen the parent barometric low, which had been in the Sirte Bay region since 13 September. The influence of upper-level dynamical processes was responsible for the reconstruction of the weakened barometric low. In the second phase, during the formation of the Mediterranean cyclone, low-level diabatic processes determined the evolution of the surface cyclone without significant support from upper-tropospheric baroclinic processes. Therefore, in this phase, the system is characterized as barotropic. In the third phase, the system remained barotropic but showed a continuous weakening tendency as the sea surface pressure steadily increased. This comprehensive analysis highlights the intricate processes involved in the development and evolution of Mediterranean cyclones with tropical characteristics. Full article

Our work presents a reliable procedure to obtain real-time assessment of the sea water elevation at the Kaštela Bay site to ensure the a priori warning in the case of expected coastal flooding along the site area. In its origin, the presented procedure relies on relevant data sets which are site-specific and locally observed. Observed data sets are used within the procedure to assess sea water surface elevation when induced by barometric pressure changes and wind-generated waves. Tidal-induced changes are introduced into the assessment procedure by a pre-learned algorithm which relies on long-term sea level oscillations from the relevant tidal gauge. Wind-generated wave heights are determined in the near shore area, following the features of the depth and reflection of the shoreline subsections. By coupling three mechanisms, this paper offers a unique real-time procedure to determine the sea water elevation and assess the possibility for coastline structure to be flooded by the sea. Given information is visualized in a form of mobile application that implements the algorithm and allows end users to set the notifications based on the given ruleset. Full article

Sea surface barometric pressure contributes to calculating the surface transmissivity so that the observations of Microwave Temperature Sounder-II channels with non-zero surface transmissivity contain the sea surface barometric pressure information. Meanwhile, all channels of Microwave Temperature Sounder-II are sensitive to sea surface barometric pressure due to the correlation between channels. However, the traditional sensitivity test method based on the radiative transfer model cannot characterize the sensitivity of Microwave Temperature Sounder-II to sea surface barometric pressure due to the correlations between channels. In this study, the relationship between atmospheric parameters and Microwave Temperature Sounder-II observations is studied by a deep neural network, and the deep neural network-based model for Microwave Temperature Sounder-II simulations is established. Then, the deep neural network-based test method for the sensitivity of Microwave Temperature Sounder-II to sea surface barometric pressure is developed, and the sensitivity test experiments are carried out. The experimental results show that the sensitivity of all channels of Microwave Temperature Sounder-II to sea surface barometric pressure is captured by the deep neural network-based test method. In addition, the retrieval experiments of sea surface barometric pressure using Microwave Temperature Sounder-II observations are carried out, and the retrieval results further validate the feasibility of the deep neural network-based test method. Full article

The 60 GHz and 118 GHz oxygen absorption bands are prominent in the passive microwave remote sensing of atmospheric temperature, and also can be used for sounding sea surface barometric pressure (SSP). Microwave Temperature Sounder II (MWTS-II) has 13 channels in the 60 GHz band, and Microwave Humidity and Temperature Sounder (MWHTS) has 8 channels in the 118 GHz band. They are both carried on Fengyun-3C Satellite (FY-3C) and Fengyun-3D Satellite (FY-3D), which provide measurements for comparing the retrieval accuracies of SSP using 60 GHz and 118 GHz bands. In this study, based on the weighting functions for MWHTS and MWTS-II, the 60 GHz and 118 GHz channel combinations representing 60 GHz and 118 GHz are established, respectively, and the retrieval accuracies of SSP from these two channel combinations are compared in different weather conditions. The experimental results show that the retrieval accuracy of SSP at 60 GHz is higher than that of 118 GHz in clear, cloudy, and rainy sky conditions. In addition, the retrieval experiments of SSP from MWTS-II and MWHTS are also carried out, and the experimental results show that the retrieval accuracy of SSP from MWTS-II is higher. The comparative study of the 60 GHz and 118 GHz for sounding SSP can provide support for the theoretical study of microwave remote sensing of SSP with practical measurements, and further contribute to understand the performance of 60 GHz and 118 GHz in atmospheric sounding. Full article

Both the Microwave Humidity and Temperature Sounder (MWHTS) and the Microwave Temperature Sounder-II (MWTS-II) operate on the Fengyun-3 (FY-3) satellite platform, which provides an opportunity to retrieve the sea surface barometric pressure (SSP) with high accuracy by fusing the observations from the 60 GHz, 118.75 GHz, and 183.31 GHz channels. The theory of retrieving SSP using passive microwave observations is analyzed, and the sensitivity test experiments of MWHTS and MWTS-II to SSP as well as the test experiments of the contributions of MWHTS and MWTS-II to SSP retrieval are carried out. The theoretical channel combination is established based on the theoretical analysis, and the SSP retrieval experiment is carried out based on the Deep Neural Network (DNN) for the theoretical channel combination. The experimental results show that the retrieval accuracy of SSP using the theoretical channel combination is higher than that of MWHTS or MWTS-II. In addition, based on the test results of the contributions of MWHTS and MWTS-II to the retrieval SSP, the optimal theoretical channel combination can be built, and can further improve the retrieval accuracy of SSP from the theoretical channel combination. Full article

An extratropical cyclone reported to have the largest wind speed in Newfoundland in more
than a decade landed on the island of Newfoundland on 11 March 2017. The oceanic responses in
Placentia Bay on the southeast coast of Newfoundland to the winter storm were examined using
observed data and the Finite-Volume Community Ocean Model (FVCOM). The peak non-tidal water
level increase, i.e., storm surge, reached 0.85mat St. Lawrence and 0.77mat Argentia on Placentia Bay.
Sea surface temperature slightly decreased after the storm passage according to buoy and satellite
measurements. Root mean square dierences (RMSD) of the magnitude of storm surge between model
results and observations are 0.15 m. The model sea surface temperature showed a small decrease,
consistent with observations, with RMSDs from 0.19 to 0.64 C at buoy stations. The simulated
surface current changes agree with buoy observations, with model-observation velocity dierence
ratios (VDR) of 0.75–0.88. It was found that, at Argentia (St. Lawrence), the peak storm surge in
Placentia Bay was dominantly (moderately) associated with the inverse barometric eect, and the
subsequent negative surge was mainly due to the wind eect at both stations. The sea surface cooling
was associated with oceanic heat loss. In the momentum balance, the Coriolis, pressure gradient,
and advection terms were all important during the storm, while the first two terms were predominant
before and after the storm. Full article

Originally designed for applications over the ocean, satellite altimetry has been proven to be a useful tool for hydrologic studies. Altimeter products, mainly conceived for oceanographic studies, often fail to provide atmospheric corrections suitable for inland water studies. The focus of this paper is the analysis of the main issues related with the atmospheric corrections that need to be applied to the altimeter range to get precise water level heights. Using the corrections provided on the Radar Altimeter Database System, the main errors present in the dry and wet tropospheric corrections and in the ionospheric correction of the various satellites are reported. It has been shown that the model-based tropospheric corrections are not modeled properly and in a consistent way in the various altimetric products. While over the ocean, the dry tropospheric correction (DTC) is one of the most precise range corrections, in some of the present altimeter products, it is the correction with the largest errors over continental water regions, causing large biases of several decimeters, and along-track interpolation errors up to several centimeters, both with small temporal variations. The wet tropospheric correction (WTC) from the on-board microwave radiometers is hampered by the contamination on the radiometer measurements of the surrounding lands, making it usable only in the central parts of large lakes. In addition, the WTC from atmospheric models may also have large errors when it is provided at sea level instead of surface height. These errors cannot be corrected by the user, since no accurate expression exists for the height variation of the WTC. Alternative and accurate corrections can be computed from in situ data, e.g., DTC from surface pressure at barometric stations and WTC from Global Navigation Satellite System permanent stations. The latter approach is particularly favorable for small lakes and reservoirs, where GNSS-derived WTC at a single location can be representative of the whole lake. For non-timely critical studies, for consistency and stability, model-derived tropospheric corrections from European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis ERA Interim, properly computed at surface height, are recommended. The instrument-based dual-frequency ionospheric correction may have errors related with the land contamination in the Ku and C/S bands, making it more suitable to use a model-based correction. The most suitable model-based ionospheric correction is the Jet Propulsion Laboratory (JPL) global ionosphere map (GIM) model, available after 1998, properly scaled to the altimeter height. Most altimeter products provide the GIM correction unreduced for the total electron content extending above the altitude of these satellites, thus overestimating the ionospheric correction by about 8%. Prior to 1998, the NIC09 (NOAA Ionosphere Climatology 2009) climatology provides the best accuracy. Full article