# Designing an Interactive Visual Analytics System for
## 5 Interactive Precipitation Data Analysis System
### Station-Specific Analysis Interface
#### 5.1.3 Analysis of Precipitation Duration and Intensity Patterns  
The interface also provides visualizations to support the analysis of annual precipitation volume and duration. Evaluating the changes in annual precipitation volumes is critical because it helps understand significant deviations from typical probability distributions. Analyzing precipitation durations is also important because it provides valuable insights into how long major precipitation events last. Precipitation duration analysis is often considered a significant method in flood forecasting and water resource management because longer-duration precipitation events can have substantial impacts on hydrological systems [54].  
Figure 5 presents visualization results of precipitation data at the Reagan National Airport. In all visualizations (Figure 5A-D), precipitation intensity amount and event duration are used to build each display. Figure 5A,B show the top ten longest (duration) and largest (intensity volume) precipitation events, respectively. The height and width of each bar denote the amount and duration of precipitation. Thus, a wider bar indicates that the precipitation event lasted longer, and a narrow bar represents a high-intensity rainfall event. Figure 5A shows that rain continued for 82 h in 1952, with a total precipitation of 3.24 inches. Figure 5B indicates that an intense rainfall occurred in 2022 with a total precipitation of 17.70 inches in six hours. Figure 5C shows the annual maximum precipitation events in chronological order for the user-selected time period. Each bar graph represents the highest recorded precipitation amount for its respective year. Figure 5D shows the hydrology analysis results by evaluating precipitation amounts. It primarily focuses on measuring, analyzing, and managing the volume of water, emphasizing how much water might move through drainage systems over time [55]. The volume-based hydrology analysis categorizes the IETD precipitation events by classifying them into nine precipitation intensity ranges: \(\leq\)0.25 inches, 0.25\(\sim\)0.5 inches, 0.5\(\sim\)1.0 inches, 1.0\(\sim\)2.0 inches, 2.0\(\sim\)5.0 inches, 5.0\(\sim\)10.0 inches, 10.0\(\sim\)15.0 inches, 15.0\(\sim\)20.0 inches, and \(>\)20.0 inches. Each bar represents the total number of events observed within the corresponding intensity range.  
To show detailed information, including average, maximum, and minimum precipitation intensities and event durations, mouse hovering user interaction is supported on individual bars. When a bar graph is highlighted, its corresponding precipitation event is highlighted in other graphs if matched precipitation events are available. For instance,  
Figure 5: Visualizations of (**A**) ten longest (duration), (**B**) ten largest (volume), (**C**) annual maximum, and (**D**) volume-based hydrology precipitation events. (**A–C**) show the identified precipitation events in chronological order. (**D**) represents results sorted by intensity ranges.  
the two red-colored arrows in Figure 5C indicate the longest-duration event (left) and the largest-intensity-volume event (right) in the years 1952 and 1922, respectively. This interactive analysis feature allows users to track and analyze precipitation events across different visualizations.