The tool “Using an Aerological Diagram” should be understood. The on-line tool or equivalent tools can be used to simplify analysis of the Diagrams.
Derived products include:
- Ventilation Index, a combination of mixing layer depth and surface wind speed, which estimates the likely dispersal of smoke. Detailed guidance is also available from BoM models of smoke dispersion available on the registered user pages.
- Lifted Index, an index derived from the temperature (T) difference between ambient and lifted air at the 500 hPa level, is a measure of thunderstorm potential. 500 hPa is a higher level than is used for fire indices, but is relevant to violent pyro-convection. Intermediate values suggest that storms will form if there is a lifting mechanism present – such as a mountain range or an approaching cold front.
- Dry storm potential can be estimated from T and dew point (DP) data from 850 hPa and 700 hPa levels. While general guidance only is possible, the guidance should also reflect the storm potential derived from the lifted index.
- The mid-level Haines Index is a measure of the potential for the atmosphere above a fire to couple with the fire and cause it to escalate. HI is also derived from T and DP data from 850 hPA and 700 hPa levels. Also known as the Lower Atmosphere Stability Index (LASI), it can also be derived from higher layers over mountainous regions. HI is restricted to between 2 and 6, with 6 indicating a high fire growth potential generally equivalent to a FDI over 40.
- The Continuous Haines Index bypasses the range restriction of HI. CH is open ended, but should not exceed 13. It is best interpreted in terms of percentiles of the site’s climatology, which often means a value of 10 corresponds to a dangerous 95% value.
- Fuel moisture content can be estimated, but does need a value for Drought Factor. FDI can then also be estimated.