Refine Risk Assessment Terms: Vulnerability and Impact Functions (Upd…

…ate Guide_Introduction.ipynb) (#802)

* Update Guide_Introduction.ipynb

The choice of terminology in risk assessment models such as CLIMADA is crucial, as it shapes the framework and perspective of the analysis. The distinction between "vulnerability function" and "impact function" is particularly significant. I made some changes along the lines of making this terminology more visible. I also made changes in the documentation where vulnerability function or damage function was still referenced in order to unify the communication of CLIMADA terminology. 

I considered adding a few lines to explain that the concepts of damage function, vulnerability function, and impact function, though interrelated, each serve a distinct purpose. Damage functions quantify specific damages, focusing on concrete impacts. Vulnerability functions, in contrast, articulate the susceptibility of different exposures to hazards. This susceptibility encompasses more than just the potential for damage; it includes a variety of preconditions that define an exposure's overall vulnerability. Meanwhile, impact functions assess the likelihood of a hazard's effects, both negative and positive, by parameterizing the degree to which an exposure will be impacted by a particular hazard.Something along those lines..... but maybe it's too much... we can discuss it sometime ......

* Update Guide_Introduction.ipynb

* Implementations of comments

doc/guide/Guide_Introduction.ipynb

@@ -12,13 +12,15 @@
     "According to the IPCC [[1]](#1), natural risks emerge through the\n",
     "interplay of climate and weather-related hazards, the exposure of goods\n",
     "or people to this hazard, and the specific vulnerability of exposed\n",
-    "people, infrastructure and environment. The unit chosen to measure risk\n",
-    "has to be the most relevant one in a specific decision problem, not\n",
-    "necessarily monetary units. Wildfire hazard might be measured by burned\n",
-    "area, exposure by population or replacement value of homes and hence\n",
-    "risk might be expressed as number of affected people in the context of\n",
-    "evacuation, or repair cost of buildings in the context of property\n",
-    "insurance.\n",
+    "people, infrastructure and environment. \n",
+    "\n",
+    "The unit of measurement for risk in CLIMADA is selected based on its relevance\n",
+    "to the specific decision-making context and is not limited to monetary units\n",
+    "alone. For instance, wildfire risk may be quantified by the burned area\n",
+    "(hazard) and the exposure could be measured by the population density or the\n",
+    "replacement value of homes. Consequently, risk could be expressed in terms of\n",
+    "the number of people affected for evacuation planning, or the cost of repairs\n",
+    "for property insurance purposes.\n",
     "\n",
     "Risk has been defined by the International Organization for\n",
     "Standardization as the \"effect of uncertainty on objectives\" as the\n",
@@ -36,13 +38,16 @@
     "$$\\text{severity} = F(\\text{hazard intensity}, \\text{exposure}, \\text{vulnerability}) = \\text{exposure} * f_{\\text{imp}}(\\text{hazard intensity})$$\n",
     "\n",
     "where $f_{\\text{imp}}$ is the impact function which parametrizes to what extent\n",
-    "an exposure will be affected by a specific hazard. While 'vulnerability\n",
-    "function' is broadly used in the modelers community, we refer to it as\n",
-    "'impact function' to explicitly include the option of opportunities\n",
-    "(i.e. negative damages). Using this approach, CLIMADA constitutes a\n",
-    "platform to analyse risks of different hazard types in a globally\n",
-    "consistent fashion at different resolution levels, at scales from\n",
-    "multiple kilometres down to meters, depending on the purpose.\n",
+    "an exposure will be affected by a specific hazard. **While the term 'vulnerability\n",
+    "function' is broadly used in the modelers community, we adopt the broader term \n",
+    "'impact function'. Impact functions can be vulnerability functions or structural \n",
+    "damage functions, but could also be productivity functions or warning levels. This \n",
+    "definition also explicitly includes the option of opportunities (i.e. negative damages).**\n",
+    "\n",
+    "Using this approach, CLIMADA constitutes a platform to analyse risks of different\n",
+    "hazard types in a globally consistent fashion at different resolution levels, \n",
+    "at scales from multiple kilometres down to meters, tailored to the specific \n",
+    "requirements of the analysis.\n",
     "\n",
     "\n",
     "<br/><br/>\n",