Cold Spell Duration Index CSDI

Calculate cold CSDI minimum-temperature spells against caller independently calibrated day-of-year percentiles with strict exceedance and minimum run; threshold ties excluded, gap-free coverage required.

Description

Cold spell duration counts days belonging to sustained unusually cold periods.

Cold spell duration counts days belonging to sustained unusually cold periods. Independently supplied daily thresholds allow the reference level to follow the seasonal cycle.^{[1, 2]}

When to use Cold Spell Duration Index CSDI

Use this tool to calculate cold CSDI minimum-temperature spells against caller independently calibrated day-of-year percentiles with strict exceedance and minimum run; threshold ties excluded, gap-free coverage required.

Prepare the climate observations and independently chosen model parameters. Confirm units, daily coverage, chronological order and the intended seasonal window.

How to use Cold Spell Duration Index CSDI and understand its results

Prepare the climate observations and independently chosen model parameters. Confirm units, daily coverage, chronological order and the intended seasonal window.
Enter dailyExtremesC, callerDayOfYearPercentileThresholdsC, callerMinimumSpellDays using the field table and calculation rules, then run the tool.
Read qualifyingSpellStartIndices, qualifyingSpellLengthsDays, spellDurationIndexDays. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
dailyExtremesC	Daily extremes c	list of number	Required
callerDayOfYearPercentileThresholdsC	Caller day of year percentile thresholds c	list of number	Required
callerMinimumSpellDays	Caller minimum spell days	integer	Required

Enter aligned nonempty daily minimum temperatures and daily percentile thresholds in °C, with a positive integer minimum run length. Only temperatures strictly below their matching threshold qualify; ties are excluded. The tool finds maximal qualifying runs and returns their zero-based starts, lengths and total retained days.

Paired lists must be nonempty and have equal lengths.

cold_i = (Tmin_i < threshold_i); duration = Σ lengths of runs meeting minimum length

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
qualifyingSpellStartIndices	Qualifying spell start indices	list of number
qualifyingSpellLengthsDays	Qualifying spell lengths days	list of number
spellDurationIndexDays	Spell duration index days	number

json

{
  "input": {
    "dailyExtremesC": [
      20,
      20,
      5,
      20
    ],
    "callerDayOfYearPercentileThresholdsC": [
      10,
      10,
      10,
      10
    ],
    "callerMinimumSpellDays": 2
  },
  "output": {
    "qualifyingSpellStartIndices": [],
    "qualifyingSpellLengthsDays": [],
    "spellDurationIndexDays": 0
  }
}

Limitations and assumptions

The tool does not fit percentile thresholds or infer missing observations. Supply a gap-free daily sequence and a separately established baseline. Window-edge runs may continue outside the supplied period.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Numeric lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Consecutive Dry Days Counter: Find complete dry runs in a caller gap-free observed daily sequence using strict precipitation below supplied threshold; endpoints may be truncated by observation coverage, not proven climate-season boundaries. For a complementary task, use Warm Spell Duration Index WSDI: Calculate warm WSDI maximum-temperature spells against caller independently calibrated day-of-year percentiles with strict exceedance and minimum run; threshold ties excluded, gap-free coverage required.

Further background: Climate extreme index definitions.

References

Cold Spell Duration Index CSDI — tool.io
Climate extreme index definitions — Climdex

Similar or alternative tools

Consecutive Dry Days Counter
Find complete dry runs in a caller gap-free observed daily sequence using strict precipitation below supplied threshold; endpoints may be truncated by observation coverage, not proven climate-season boundaries.
Warm Spell Duration Index WSDI
Calculate warm WSDI maximum-temperature spells against caller independently calibrated day-of-year percentiles with strict exceedance and minimum run; threshold ties excluded, gap-free coverage required.