If, when (a future date or frequency) and how (intensity or magnitude and/or duration) of an external shock, for example an epidemic (viral in origin, i.e. COVID-19 SARS-CoV-2 coronavirus, Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF) caused by ebolaviruses, etc.) or non-epidemic disaster (natural, anthropic or technological, or a combination of, in origin, i.e. hurricane, flood, earthquake, etc.) strikes a particular region depends on statistical representations of historical event characteristics (probability or distribution), (climate model) as well as spatial and temporal factors. The most important factor associated with exposure are the numbers of people and assets (in terms of wealth) exposed to (spatial and temporal or time and place) the hazard, and their vulnerability to be damaged or loss of life. In the case of flooding, storm surge, tsunami’s and torrential downpours exposure means that human and animal population as well as accumulated wealth in close proximity of the coast, rivers (delta’s) or basins and low lying regions.
Both short- and long-term drought events can affect human as well as livestock populations, food security, assets, production or goods, i.e. agriculture or crop yield and production, water consumption for industrial production and other sectors of activity. There is also environment damage, i.e. ecological units or natural habitats. Drought exposure is a matter of seasonality and geographic distribution (spatial and temporal). Worldwide more and more arable land is being encroached on by expanding deserts. Southern US, Australia, Southern Europe, arid Latin American countries, many African and Asian countries are affected by drought hazard, which can be a result of accelerating desertification that is a consequence of global warming attributed to climate change. Other threats of the exposure to drought are wildfires and water stress. Faced with increasing drought and limited access to fresh water, many government are/will be forced to facilitate mitigation, adaptation and resilience strategies into public plans and development policies.
This reoccurrence of flooding, hurricanes, tornadoes, earthquakes, wildfires, and all natural events and their associated specific return periods that lead to disasters can be captured in event catalogues and stored in databases. With the help of these catalogues with statistical representations of event characteristics (i.e. for a cyclone, storm frequency, intensity, and radius to maximum wind) are parameterized, along with an associated probability distribution for each parameter. Armed with probabilistic or stochastic distribution of events scientists, engineers, researchers, decision and policy makers as well as government are able to model and plan for future events, rationalise decision making for preparedness, adaptation, mitigation as well as used them as a base for vulnerability assessment and disaster management.
If, when (a future date) and how (the intensity or magnitude), for example a hurricane, can impact a particular region depends on statistical representations of historical event characteristics (i.e. for a cyclone, storm wind speed, intensity, and radius to maximum wind, position: latitude and longitude, central pressure, translation velocity, etc. ) that are parameterized, along with an associated probability distribution for each parameter and associated climate models and general circulation models (GCMs), which are mathematical equations to characterize how energy and matter interact in different parts of the ocean, atmosphere, land. The result of such as complicated modelling techniques will yield future projections or distributions of, i.e. hurricane impact counts for various regions. National, regional and local resources, measures and assets will dictate how the modelled event will affect communities.
Changing climate patterns as a result of climate change leads to extreme fluctuating prevailing weather conditions. For example, increase in atmospheric moisture content as a result of anthropogenic (or human induced) warming leads to increased tropical cyclone rainfall rates. This in combination with another result of global warming that contributes to deglaciation of the continental ice volume and in turn rising sea levels. Increase cyclone activity together with sea level rise leads to greater storm surge flooding. This implies that an even larger percentage increase in the destructive potential per flood event resulting from storms. These are just some examples of extreme inundation that account for the billions of dollars in flood damage world-wide. The losses encompasses every aspect of a nation, region or community. From the economy, society, livelihoods, healthcare, etc.
The North Atlantic Oscillation (NAO) describes the fluctuations in the difference of atmospheric pressure at sea level between (1) Greenland and Iceland that generally experience lower air pressure than surrounding regions, called the sub-polar low, or sometimes the Icelandic Low, and (2) farther to the south, air pressure over the central North Atlantic Ocean is generally higher than surrounding regions. This atmospheric feature is called the subtropical high, or the Azores High. The increased difference in pressure between the two regions results in a stronger Atlantic jet stream and a northward shift of the hurricane and storm tracks. During a negative phase of NAO, eastern North America and the Caribbean experience lower air pressure which is associated with stronger cold-air outbreaks and an increase hurricane season.