- freely available
Computers 2019, 8(3), 53; https://doi.org/10.3390/computers8030053
- Will the raising air generate a cloud?
- If the answer is yes, what is the forecasted cloud base?
- It is fully configurable, allowing to explore the nomogram at different levels of complexity.
- It provides clear connection with the sounding procedure.
- It presents a high degree of interactivity, allowing to explore data details and test different hypotheses to quickly forecast weather.
2. Visualisation of Aerological Soundings
3. The Herlofson’s Nomogram
- increasing the angle between isotherms and adiabats cooling gradients; and
- increasing the temperature resolution with the clear advantage of getting a better precision in manually finding a crossing point between these lines (see Figure 3), generated using our interactive environment.
3.1. Getting a Situational Awareness about the Weather Conditions
3.2. Forecasting Clouds Base and Cloud Evolution
4. The IVAN System
- Step 1: State curve, sounding points, and P, T lines are represented in this step (see Figure 7a). The system is configured to show only the state curve and the T and P axes. Moreover, sounding points are plotted on the curve, making clear that the curve is an interpolation of finite data points, whose numerical values are visible in the upper center part of Figure 6. Mouse overing a sounding point triggers the drawing of two dashed black lines that correspond to the P and the T values on the axes, helping the user in reading these values.
- Step 2: In this step, dry adiabats are added with respect to information present in Step 1, as visible in Figure 7b. The user is presented with the concept of dry adiabats and understands how to evaluate the state curve bending with respect to the dry adiabats gradient, getting the idea that, when a dry adiabat crosses the status curve, the air rising stops.
- Step 3: In this step, wet adiabats are added with respect to information presented in Step 1 (see Figure 7c). The user is presented with the concept of wet adiabats and understands how to evaluate the state curve bending with respect to the dry adiabats gradient, getting the idea that, when a wet adiabat crosses the status curve, the raising cloud stops growing.
- Step 4: State curve, dew-point curve, and P, T lines are represented in this step (see Figure 8a). The system is configured to show both the state and dew-point curves together with sounding points, making evident that both curves represent temperatures (even the “humidity” curve) and that they refer to two temperature values of the same sounding point. Moreover, in this way, even the distance between the curves is highlighted, explaining the risk of fog or veiling of the sky that can reduce the solar radiation.
- Step 5: In this step, the dew-point curve, mix legend and iso-humidity lines are represented (see Figure 8b). The user is presented with the definition of iso-humidity and with an additional second legend on the x-axis, and learns how to read the effective humidity values of a sounding point on the dew-point curve, using a third projection parallel to iso-humidity lines. To simplify the understanding of this operation, we remove all other lines (isotherms, red line, iso-metric, and yellow bands), reducing the overplotting and making it easier to read and use the iso-humidity lines.
- Step 6: In this step, the state curve and iso-humidity lines are represented (see Figure 8c). The confusing concept of iso-humidity is further clarified showing, through interaction, that two points on the same iso-humidity line, P1 and P2, have different humidity but share the same maximum humidity they can bear before condensing.
- Step 7: In this step, state curve, dew-point curve, iso-humidity lines, and P, T lines are represented (see Figure 9a). The system is configured to show both the state and dew-point curves together with sounding points and iso-humidity lines, and allows practicing calculating the humidity on the state curve that will be useful to forecast condensation altitudes. Selecting a sounding point on the state curve triggers selecting its corresponding point on the dew-point curve and identifying on the humidity legend the actual humidity value. That further clarifies that the two points correspond to the same sounding point and that they share P, T, humidity and dew-point temperature.
- Step 8: In this step, state curve, dry and wet adiabats and P, T lines are represented (see Figure 9b). Mouse-clicking the nomogram on the right of the state curve allows for making hypotheses on future evolution of air raising from a specific altitude at a given temperature. In the figure, the user is forecasting that the air temperature at 0.9 km altitude (e.g., the top of a little mountain) will be of 31 °C. IVAN shows that such warm air will dry climb (solid green line parallel to dry adiabats) until about 3.4 km and generate a cloud (thus, the cloud base will be 3.4 km). After that, the climbing will go on as a purple wet adiabat (parallel to wet-adiabat), generating a high cloud (thunderstorm risk) and stopping against the red state curve around 11.5 km. The user can interactively test different hypotheses, discovering situations in which the air stops before generating a cloud (blue thermals) and compare different thermals starting from different altitudes (e.g., mountain, hill, and flat land).
- Step 9: In this step, iso-humidity lines are added with respect to information present in Step 8, as visible in Figure 9c. The goal of this step is to explain how the condensation altitude can be computed on the nomogram. The user moves from the point she clicked on to the blue curve at the same altitude (0.9 km) and discovers the humidity (6.8) and the dew-point temperature (6 °C) of the rising air. Under the assumption that the composition of the air does not depend on the location but only on the altitude, he concludes that the dew-point temperature of the raising air is 6 °C: intersecting the actual dry adiabat with the 6 °C isotherm, he forecasts the condensation (and the cloud base) at about 3.4 km.
5.1. Pilot Study
5.2. E-Learning Content
- The introduction (Slides 1, 2, 3, 4, and three questions) explained the history and the purpose of the Herlofson’s diagram, the structure of the x- and y-axes, the two main curves depicting sounded data, the visual indication of absolute humidity, the standard air temperature gradient, and the correct way of reading the curves. Questions asked to locate an altitude satisfying a simple criteria (e.g., the highest relative humidity) or air temperature at a given altitude.
- Cloud genesis (Slides 8, 9, and three questions) explained the temperature gradient of (wet and dry) rising air, how to compute graphically the equilibrium point, and how (and where) condensing vapor generates a cloud. Questions asked to inspect the evolution of raising till their equilibrium point (disregarding the humidity).
- Humidity (Slide 13 and two questions) showed how to use the dew-point curve to compute graphically the specific humidity. The questions asked to compute the specific humidity at a given altitude and the maximum in an interval.
- Clouds height (Slide 16 and one question) showed how to compute a cloud height generated by rising airs and considering humidity. The question asked to follow the evolution of rising air along a dry adiabat, discover its dew-point and follow the clod generation until its equilibrium, along a wet adiabat.
5.3. Formal User Study
- “At which altitude does the air have maximum relative humidity?”
- “At what altitude the air stops being colder with increasing altitude?”
- “What is the air temperature at 9 km?”
- “Starting from the point indicated in the diagram and ignoring the humidity, what is the maximum altitude at which the air could rise following a dry adiabatic?”
- “Starting from the point indicated in the diagram and ignoring the humidity, what is the maximum altitude at which the air could rise following a saturated adiabatic?”
- “Starting from the point indicated in the diagram and ignoring the humidity, what is the maximum altitude at which the air could rise following a dry adiabatic up to 3000 m and then a saturated adiabatic?”
- “At what altitude is the specific humidity equal to 0.8 g/kg?”
- “Between 500 and 2000 m what is the maximum specific humidity?”
- “ °C, altitude = 4000 m: at which altitude the rising air will generate a cloud?”
- Overall I am satisfied with how easy it is to use this diagram.
- It was simple to use this diagram.
- I was able to complete the tasks and scenarios quickly using this diagram.
- I felt comfortable using this diagram.
- It was easy to learn to use this diagram.
- I believe I could become productive quickly using this diagram.
- It was easy for me to find the information I needed.
- The information was effective in helping me complete the tasks and scenarios.
- The organization of information on the diagram was clear.
- I liked using the interface of this diagram.
- Overall, I am satisfied with this diagram.
Conflicts of Interest
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