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Climate data

TESSA uses climate data at two points in a study: to drive the heat and cooling demand model for the district's buildings, and to generate future scenarios when you apply the future climate and retrofit tool.

Present-day climate data

TESSA uses Typical Meteorological Year (TMY) data sourced from climate.onebuilding.org.

A TMY represents a "typical" year for a given location — not the hottest or coldest year on record, but one that reflects median conditions month by month. TMYx datasets are created using the ISO 15927-4:2005 method: for each calendar month, hourly data is selected from a multi-year archive of real observations to best represent the median climate for that month. The result is an 8760-hour dataset of temperature, solar radiation, humidity, and wind.

What climate data feeds into

Once a climate file is loaded for a district:

  • The heat demand model uses dry-bulb temperature to compute degree-days and daily average temperatures, which drive the building archetype heating demand calculation.
  • The load curve model uses temperature data to distribute annual demand into hourly profiles, using the mean daily temperature regression method.
  • The cooling demand model uses temperature and solar data to estimate peak cooling loads.

Climate data is loaded at the district level. Multiple districts in the same scenario can use different climate files if the study area spans a large geographic range.

Future climate projections

Future climate data is derived from CMIP6 ensemble projections for Switzerland. TESSA covers climate scenarios from 2030 to 2050 and constructs future Typical Meteorological Years for each target decade and SSP (Shared Socioeconomic Pathway).

How future TMY files are built

TESSA uses a monthly climate anomaly method:

  1. CMIP6 ensemble gridded data is processed for different SSP scenarios to generate mean monthly temperature anomalies over a 20-year time window centred on the target decade.
  2. These anomalies are applied to the baseline TMY hourly values by offsetting each month's temperatures.
  3. An 8-hour interpolation window is applied at month boundaries to smooth the transition and avoid step discontinuities in the resulting time series — following the TMY ISO method.

The resulting future TMY has the same 8760-hour structure as the baseline, but with higher temperatures in the months where warming is projected.

Applying future climate in TESSA

The Apply future climate and retrofit tool takes a future climate scenario and optionally a building retrofit scenario, then re-calculates demand for the district under those assumptions. This produces a new load curve that reflects the combined effect of warmer climate (reduced heating demand, increased cooling demand) and improved building envelopes. See Future demand.

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