Welcome to the Weather Tool Help documentation. This is the on-line help file that accompanies the Weather Tool software. You can use the menu below or displayed on the left of this page to navigate.
The Weather Tool allows you to visualise, analyse and edit hourly weather data. It recognises a wide range of international weather file formats as well as user-specified custom data import formats for ASCII files. It also provides a wide range of display options, including both 2D and 3D graphs as well as wind roses and sun-path diagrams.
Add full psychrometric processing to its feature list and you have a unique mechanism for assessing the relative potential of different passive design systems. Add solar radiation analysis and you can then accurately determine optimum orientations for specific building design criteria. The result is a pre-design analysis tool that is a must for all architects, designers and urban planners interested in climate-responsive design.
The key features of the Weather Tool are the way it allows you to visualise weather data, the flexibility it allows in the import, export and editing of ASCII data files and its many different analysis functions. The following is a summary of some of the analysis features.
Passive Design Analysis
Given detailed hourly data for a site, psychrometric analysis can be used to determine the potential effects of a range of passive design techniques (as per Szokolay, 1987). You can also assess multiple passive systems in combination.
The effect of each system is shown as an increase in the number of hours spent within the comfort zone each month, which is defined using the monthly thermal neutrality range. This lets designers quickly see the most effective passive systems to suit any specific location.
A major part of any climate is the Sun. Its radiation is a major source of passive heating energy available on any site. Making best use of this is therefore very important when heating is required, but adequate protection is just as important when it is not.
Sun-path diagrams are a 2D representation of the annual movement of the Sun through the sky. Both stereographic and orthographic diagrams are available. In the one diagram, the designer can quickly determine both the direction and time of any solar event throughout the year.
Solar Radiation Analysis
Based on a 1mÃ‚Â² vertical surface, the total daily incident solar radiation can be calculated at any orientation. The underheated and overheated periods within the year are shown as coloured blocks, so you can compare total solar collection values. This graph can also be animated, clearly showing the full effects of different orientations.
If the above calculation is done for the full 360 degrees, a table of underheated/overheated values can be generated. This is used to determine the most favourable range of orientations for passive solar heating, whilst still considering the effects of unwanted solar gains in summer.
Psychrometry is the study of moist air. The Psychrometric Chart provides a graphic representation of the full state of the air under any condition. This includes all the major climatic indicators, dry-bulb and wet-bulb temperatures, relative and absolute humidity, vapour pressure, air volume and even enthalpy.
If hourly weather data for a location is known, it is possible to plot this on the chart as frequency data. This results in a set of colours ranging from dark blue (occurring quite infrequently) to very light blue (occurring very often). With a range of overlays, a simple visual analysis of such information can actually tell you a lot about the characteristics of a climate.
Point Data and Overlays
When hourly data is plotted as points on the graph, and the relative effects of various passive design techniques on the comfort zone are overlayed, it becomes very obvious which systems are most appropriate for any climate. This information forms the basis of the passive design analysis system described above.
Wind Data Analysis
The direction and speed of winds is a significant design consideration in virtually all climates. In a hot country capturing every cooling breeze is important, even more so if it is also very humid. In a cold climate, wind protection is the main objective.
WeaTool includes a proprietary wind analysis graph which displays wind frequency, direction and speed, all in the one diagram. This can be analysed over any range of dates and times, so it is possible to determine the predominant wind direction on a summer afternoon or a winters morning, or even between 2pm and 3pm in April.
In addition to frequency and direction, it is also possible to visually compare other conditions such as dry-bulb temperature, relative humidity and hourly rainfall, side by side with frequency. This makes discerning the difference between hot-dry winds and cooling breezes at different times of the year a trivial task.
This display shows values for an average day each month. The range of average maximum and minimum temperatures are shown as a graded red scale along with direct and diffuse solar radiation. It is also possible to overlay the thermal neutrality temperature and its associated comfort band (shown here in green). The graph at the bottom of the screen shows all hourly values for the selected day of the year.
This graph shows hourly dry-bulb temperature with rolling mean monthly maximum and minimum values overlaid. Also shown is a rolling monthly comfort band. Other values that can be graphed include wet-bulb, relative humidity, direct radiation, diffuse radiation and hourly rainfall. More dynamic data such as wind speed, direction and cloud cover are shown only in the 3D weekly grid.
Establishing trends within data is fundamental to any accurate analysis. Many types of weather data are very dynamic, varying not just seasonally but daily and hourly. Such data is best viewed as a three dimensional grid, with weeks of the year along the X axis and hours of the day along the Y.
Interactive 3D Graphs
Average weekly data is displayed on a 3D graph. Simply click and drag in the drawing area to rotate your view. The graph below shows average weekly wind speeds. A trend towards stronger winds during the middle of the day is clearly evident. So too are higher velocities at night in summer compared to winter (its a southern hemisphere location).
Such graphs can be displayed for temperature, humidity, solar radiation, wind speed, cloud cover and rainfall - all at the same time if required. If we take the previous graph as an example, simply comparing night-time summer wind speeds with average temperature will quickly determine if this location is suitable for a night-purge ventilation system. If so, a quick wind analysis would then show on what side to put the vents.
A monthly climate summary is also generated whenever you load weather data. Some of the data required for this may not be present in all file formats, so an area has been provided for you to enter or edit this data manually. Only the total monthly rainfall data is really important as it is used when determining the climate type (using the Kppen classification system).