Some characteristics of fog over Guwahati airport

The statistical characteristics like frequencies of occurrence, time of onset, duration, time of dispersal and intensity of fog over Guwahati airport are found out and analysed using 10 years data during 1994-95 to 2003-04 for the months of November to February. Also the interannual and intraseasonal variations of occurrence of fog are analysed by calculating the coefficient of variation of monthly frequency of fog and by calculating the significant periodicities in the daily probability of occurrence of fog respectively. The meteorological parameters at 1200 UTC leading to fog in the following night or morning over Guwahati airport are analysed to find out the precursors for occurrence of fog. Statistical characteristics are given in tables and their significance discussed. It is observed that monitoring of Dew Point Depression (DPD) and surface wind can help prediction of occurrence of fog and its intensity over Guwahati airport.

An exploratory analysis of seasonal and intraseasonal variations of the main airborne pollen types in Sunchales city, Argentina

Background and aims: The study of the seasonal and intra-seasonal variability of the airborne pollen concentration is of paramount importance to understand the relationships with the emitting vegetation and the atmospheric parameters that modulate pollen transport. This research aims to study these variabilities in Sunchales, a city located in the center-east of Argentina. M&M: Atmospheric monitoring was carried out with a Burkard trap during two seasons in 2012 and 2013 on the outskirts of the city. Results & Conclusions: The pollination periods of the studied pollen types show a delay in 2013 compared to the previous year, presumably related to a greater amount of cumulative heat units in 2012. However, the integral pollen for the period 2013 was 1.4 times higher than 2012, a fact that is not explained by accumulated precipitation but by the time of day when the hydrometeors occur. Binned pollen concentrations show that the highest concentrations coincide with the urban location of the tree sources while the herbaceous ones show an association with a rural origin. Regarding the intra-seasonal variability, the highest proportion of the airborne pollen variance accumulates on the synoptic-scale (80 - 60%) with periods between 3 and 10 days. During 2012 long waves predominated (> 5.5 days) while in 2013 medium waves prevailed (3.9 - 5.5 days).

Incidence and Risk Factors in Concussion Events: A 5-Season Study in the French Top 14 Rugby Union Championship

Background: Concussions are a source of major concern in rugby, and a limited number of studies have attempted to identify risk factors for these injuries. Purpose: To investigate the incidence of match concussion and associated risk factors, including individual workload, anthropometric variables, playing position, and season phase, in elite rugby union players. Study Design: Case-control study; Level of evidence 3. Methods: All concussions and explanatory variables were collected for every match over 5 consecutive seasons (2014-2018) in 1334 professional players participating in the French Top 14 championship. Concussion risk was estimated using mixed effects Poisson regression. Results: Mean match concussion incidence equated to 10.4 (95% CI, 9.3-11.5) concussions for 1000 hours of game exposure. A peak was reached in the 2016-2017 season (13.7; 95% CI, 11.0-16.5). A greater risk was observed in the playoffs as compared with the first phase of the season (incidence rate ratio, 3.96; 95% CI, 2.10-7.35). In comparison with other positions, half-backs incurred the highest rate of concussion events (incidence, 16.1; 95% CI, 11.8-20.3). Irrespective of playing position, those with greater height and lower body mass reported a higher risk of concussions ( P = .02), especially during tackling actions for lighter players ( P = .01) and during other match events for taller players ( P = .03). When adjusted for season phase, players who had accumulated a higher amount of playing time since the beginning of the season demonstrated a lower risk of concussion ( P = .005). Conclusion: Inter- and intraseasonal variations in concussion rates were observed. Within positional groups, lighter and taller players were more at risk, with the highest incidence generally observed in half-backs. Workload was measured by the number of matches played before a concussion event, and it appeared to have a protective rather than deleterious effect on concussion risk.

Warm core mesoscale eddies along the boundary current and in the Sofia Deep north of Svalbard

<p>The Atlantic water boundary current north of Svalbard is a major heat and salt source to the Arctic Ocean. Yet, the mechanisms controlling the lateral transport of Atlantic water properties are not well understood. Model simulations suggest mesoscale eddies may be important for transporting heat away from the boundary current, but supporting observations are sparse.</p><p>Between September and November in 2018, a Seaglider was deployed north of Svalbard as part of the Nansen Legacy project to investigate intraseasonal variations in the boundary current and the transformation of Atlantic water. It made several transects across the boundary current and a transect across the Sofia deep. Warm core eddies originating from the boundary current were detected in the Sofia deep. Combining the Seaglider data with two year-long mooring arrays north of Svalbard, deployed in 2018 within the Nansen Legacy framework, we investigate mesoscale eddies using eddy recognition algorithms applied to glider transects and timeseries from moorings. Initial results indicate that mesoscale eddies frequently occur in the boundary current, with radius less than 10 km and velocity maxima as high as 0.35 m/s.</p>

Modelling seasonal and intraseasonal variations of circulation,temperature, salinity and sea level in the Bellingshausen Seaand on the Antarctic Peninsula shelf

The objective of the study is to simulate using numerical methods the seasonal and intraseasonal variations of circula-tion, sea level, temperature and salinity in the Bellingshausen Sea and on the shelf of the western part of the Antarctic Penin-sula (WAP). The Semi-implicit Cross-scale Hydroscience Integrated System Model with an unstructured triangular horizontal grid and a vertical local sigma coordinate system and ice dynamic-thermodynamic Finite-Element Sea Ice Model were applied. Heat, momentum and salt fluxes were set on the ocean surface using the ERA5 reanalysis data. At the open boundaries, the vertical distribution of temperature and salinity was determined according to the COPERNICUS reanalysis. At the western open boundary of the computational domain, the vertical distribution of velocity of currents from COPERNICUS was also specified, whereas at the open eastern boundary the level deviations were specified. Time variability analysis of sea level wasperformed using wavelet analysis. The results of modelling of the sea level, temperature, and salinity fields for 2014–2015 were compared with the available observational data on the shelf of the WAP, including data from the Ukrainian Antarctic Expedition. The simulated horizontal and vertical distributions of the subsurface layer with minimum of potential temperature Tmin (Winter Water) are given. The depth of the Tmin varies in the range of 10–100 m increasing to the north. The values of minimum of po-tential temperature Tmin also increase to the north from –1.8 to 1.2 °C. The intraseasonal oscillations of sea level computed by the model for 2014—2015 were analysed together with data of observations at the tidal stations Faraday/Akademik Vernadsky and Rothera located at the coast of WAP. In the range 1–150 days the largest amplitudes of the level scalegrams were found for a period of approximately 100 days in 2014 and 120 days in 2015 at both stations. The largest amplitudes of modelled level scale-grams were observed with a period of approximately 88 days in 2014 and 80 days in 2015 at both stations. The largest amplitudesof scalegrams for Antarctic Oscillation (AAO) were found for a period of 105 days in 2014 and 123 days in 2015. The corresponding correlation coefficients between observed sea level scalegrams and AAO for 2014 were 0.84 and 0.86, respectively, whereas for 2015 they were 0.87 and 0.90, respectively. It was concluded that the relationship between intraseasonal processes in the ocean in West Antarctica and AAO existed at a time scale of about 100 days.

Remote influences on the Indian monsoon Low-Level Jet intraseasonal variations

<p>A strong Low-Level Jet (LLJ), also known as the Findlater jet, develops over the Arabian Sea during the Indian summer monsoon. This jet is an essential source of moisture for monsoonal rainfall over the densely-populated Indian subcontinent and is a key contributor to the Indian Ocean oceanic productivity by sustaining the western Arabian Sea upwelling systems. The LLJ intensity fluctuates intraseasonally within the ~20- to 90-day band, in relation with the northward-propagating active and break phases of the Indian summer monsoon. Our observational analyses reveal that these large-scale regional convective perturbations  only explain about half of the intraseasonal LLJ variance, the other half being unrelated to large-scale convective perturbations over the Indian Ocean. We show that convective fluctuations in two regions outside the Indian Ocean can remotely force a LLJ intensification, four days later. Enhanced atmosphericdeep convection over the northwestern tropical Pacific yields westerly wind anomalies that propagate westward to the Arabian Sea as baroclinic atmospheric Rossby Waves. Suppressed convection over the eastern Pacific / North American monsoon region yields westerly wind anomalies that propagate eastward to the Indian Ocean as dry baroclinic equatorial Kelvin waves. Those largely independent remote influences jointly explain ~40% of the intraseasonal LLJ variance that is not related to convective perturbations over the Indian Ocean (i.e. ~20% of the total), with the northwestern Pacific contributing twice as much as the eastern Pacific. Taking into account these two remote influences should thus enhance the ability to predict the LLJ.</p><p> </p><p>Related reference: Swathi M.S, Takeshi Izumo, Matthieu Lengaigne, Jérôme Vialard and M.R. Ramesh Kumar:Remote influences on the Indian monsoon Low-Level Jet intraseasonal variations, accepted in Climate Dynamics.</p>

Intraseasonal Variations of the British–Baikal Corridor Pattern

The British–Baikal Corridor (BBC) pattern is the dominant waveguide mode trapped along the summertime polar front jet over northern Eurasia. It consists of four geographically fixed centers over the west of the British Isles, the Baltic Sea, western Siberia, and Lake Baikal, respectively. Its intraseasonal variations and dynamics are investigated based on reanalysis datasets. The BBC pattern has a life cycle of about two weeks. Its precursor could be traced back to an upstream wave packet propagating along the Atlantic jet 10 days before its peak, and its life cycle resembles the evolution of a quasi-stationary Rossby wave train. Diagnosis of the streamfunction tendency equation suggests that the growth and decay of the BBC pattern are primarily driven by the nonlinear processes, whereas the quasi-stationary feature of the BBC pattern arises from the cancellation among the linear processes. Energetics analysis indicates that the energy cycle with the transient eddies (TEs) plays an essential role in the growth and decay of the BBC pattern. The BBC pattern first feeds on the barotropic energy provided by the TEs and then returns the energy to TEs in the form of baroclinic energy. It is this nonlinear interaction with the TEs that poses a tough challenge to the current state-of-the-art models to capture the BBC pattern reasonably.