rainfall variability index

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The Soaring Index

Lapse rate

Total Totals Index (TT)

Delta-T Index (DTI)/700-500 mb Lapse Rate

K Index

Lifted Index (LI)

Showalter Index (SI)

Deep Convective Index (DCI)

Severe Weather Threat Index (SWEAT)

Convective Available Potential Energy (CAPE)

Convective Inhibition (CIN)

Cap/Lid Strength Index (LSI)

Bulk Richardson's Number (BRN)

BRN Shear

Storm-Relative 500 mb Winds

Storm-Relative Helicity

Storm-relative (S-R) helicity (Hs-r)

Energy-Helicity Index (EHI)

Height of the Wet-Bulb Zero (WBZ)

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http://www.weather.gov/lmk/indices

Thermal comfort  (apparent temperature to indicate wind chill & heat index.  Heat stress index using Wet Bulb Globe Temperature (WBGT). See for details at Australian Bureau of Meteorology.

http://www.bom.gov.au/info/thermal_stress/

There are many many indices out there with regard to atmospheric science and its integration with other disciplines as well as for specific purposes. You may wish to classify the types of indices to better separate them from one another in terms of application and meaning based upon their derivation. Some are more empirical based upon limited data/evidence, others more based upon correlation and regression analysis.

For example, some are simple surrogates that combine several variables known to be important to the occurrence of some phenomenon (e.g., stability indices with regard to thunderstorms or severe) whereas others are derived empirically. In the first case it can be to capture the essence of the mechanisms and/or causative factors rather than using differential equations to simulate or calculate the complex process directly (particularly if they are unknown). In the latter case empiricism points to processes and likely causative factors that have not been fully vetted or proven mathematically or physically.

Still other indices are devised according to the need or impact with regard to the target-impact/audience (e.g., wind chill). The importance of categorization is so that you may consider various indices according to how they were developed, for what purpose, and thus how reliable or useful they may or may not be...and thus how successful they may or may not be in application. A different approach would be if you are looking solely at one phenomenon or only those which relate directly to a target/audience. Also be careful to consider time and spatial domains/intents of the indices you choose...and whether for weather or climate or other purposes. Try the WMO, NOAA/NWS, AMS, NWA, The Weather Channel, and a few other sources for listings of indices.

Hope these thoughts help you move forward...

 Besides the wind chill factor (index), a humidity index for winter only (soon to be implemented in N. America?)