Simulation of Wind Speed Effect on the Fall Velocity of Raindrops

Raindrop motion is affected by several factors; one of which is wind speed during the rain. This study is aimed to investigate that impact by using mathematical simulation with Fortran and Matlab. Raindrops arrive on the Earth\u27s surface at their terminal velocities which depend on their size. Raindrop falling motion could be analyzed with net force equation (Newton\u27s second law). In order to determine velocity and position equations as a function of time, coefficients in those equations were fitted and compared toraindrop model developed by Boxel in 1997. In this study, equations used are fitted to both large and small size raindrops. Values resulted by equation for large size drops agreed with experimental data. Wind speedcauses the terminal velocities of raindrops to get larger, and so does their kinetic energy. In that condition, raindrops fall with certain inclination angle. The stronger wind speed, the larger raindrops\u27 inclination angle and their kinetic energy are when hitting soil surface. Therefore it increases the risk of soil erosion at place where the soil is unstable. Through this study, speed and direction of raindrop when hitting soil surface could be investigated in order to decrease the risk of avalanche at high risk area

Impact-based forecasting in South East Asia – what underlies impact perceptions?

The move towards impact-based forecasting presents a challenge for forecasters, who must combine information not just on what the weather might be, but also on what the weather might do. Yet different hazards and impacts are qualitatively distinct, meaning such information cannot be easily or straightforwardly integrated. The present study aimed to provide a way of characterising seemingly disparate impacts. In a collaboration between UK psychologists and partners from three meteorological organisations in Indonesia, Malaysia and the Philippines, the psychometric paradigm was employed to investigate how forecasters and stakeholders perceive weather-related impacts. Participants provided ratings of nine categories of impacts on a total of 10 characteristics, as well as providing an overall impact severity rating. Principal components analysis revealed differing component solutions across countries, which explained around 75% of the variance in perceptions. There were some similarities across all countries, with the characteristics ‘worry’ and ‘destructiveness’ loading positively together, as well as ‘likelihood of harm’ and ‘seriousness of harm’. We did not find strong evidence to indicate that forecasters and stakeholders perceive impacts in different ways. Our results highlight the complex nature of impact perceptions, which are characterised not just by objective factors such as impact scope and duration, but also subjective factors, such as worry and perceived severity

Simulasi faktor kecepatan angin terhadap kecepatan jatuh butiran hujan

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Investigating the decision thresholds for impact-based warnings in South East Asia

The move towards impact-based forecasting presents a challenge for forecasters, who must combine information not just on what the weather might be, but also on what the weather might do. Such forecasts require an integration of both likelihood and impact severity information to issue a particular weather warning. The current pre-registered study focusses on forecasters' and stakeholders’ thresholds for determining the level of impact-based warnings, set in an area of the world particularly susceptible to extreme weather events. Set in the context of one hazard (heavy rainfall or river flooding), forecasters and stakeholders from Indonesia, Malaysia and the Philippines provided hypothetical impact-based warnings for impacts of varying likelihood. Results indicated generally good alignment with the warnings implied by previously developed impact tables. In the one country where a comparison was possible (the Philippines), we did not find evidence to suggest that forecasters and stakeholders use different thresholds for issuing warnings. We suggest that warning thresholds should be subject to regular monitoring wherever in the world an impact-based approach is used