Air archive maturity
Short-term archive
15 represented calendar days
Methods register · analysis methods v1.2.0
Prospective methods and analysis protocol.
Delhi Air Health separates measurement, normalization, comparison and interpretation. These methods sit alongside a separately frozen prospective study protocol that defines the primary 2026–27 analysis window, estimand and eligibility rules.
Meteorology nodes
5/5
Latest hourly capture complete
Meteorology hours
1,111
Collector 1.1.0 · meteo-1.1.0
Weather-adjusted model
Locked
Requires ≥30 archive days + sufficient meteorology coverage
Primary research question
How large are persistent site-level departures from the concurrent Delhi-NCR network median of hourly ambient PM2.5 during the prespecified primary period?
The raw archive is organized at station-feed × hour level. The primary study aggregates colocated feeds to physical-site × Delhi-local-hour observations before calculating each site's departure from the concurrent network median. PM10 and campus-linked comparisons are secondary.
Open the prospective study protocol →Internal protocol frozenRegistered under embargoMeteorology collectingPilot gate active
Observation model
What counts as one datum?
Air pollution
One CPCB-linked station feed in one hourly bucket. When multiple source snapshots land in the same feed-hour, the latest source timestamp is selected deterministically.
Missingness
Missing hours remain missing. No temporal interpolation and no substitution from a neighbouring monitor.
Physical sites
Multiple feeds at identical coordinates are preserved as separate source feeds but flagged as the same physical site for independence-sensitive analyses.
Campus interpretation
A campus inherits a nearby monitor reference with explicit distance. It is never treated as an on-campus dosimeter or a personal exposure measurement.
Comparison rules
Use matched observation times for location comparisons.
Paired campus differences
Compare only hours observed at both linked monitors. For hour t: Dₜ = PM2.5(comparator,t) − PM2.5(reference,t).
Primary network-relative comparison
For each eligible primary network hour, compare every reporting physical site with the concurrent median across reporting eligible physical sites. The full-period site effect is the median of those hourly residuals.
Diurnal summaries
For the separate descriptive diurnal view, first calculate the median across reporting Delhi feeds in each Delhi-local hour, then group those network-hour medians by local clock hour across days.
Station correlation
Pearson r uses shared hourly PM2.5 observations. Same-physical-site pairs are excluded from the independent-pair distribution.
No causal language
Correlation and raw paired differences are descriptive. They do not establish a local pollution source or causal campus effect.
Prospective meteorology archive
Meteorological covariates
Beginning with v2.10.0, five fixed Delhi meteorology reference nodes are captured hourly through Open-Meteo using a locked ECMWF IFS HRES 9 km model selection. They are model-derived gridded values, not weather-station measurements. The full provider response and SHA-256 digest are preserved for every collector run; pre-lock Best Match rows are retained but excluded from the protocol-eligible weather series.
Latest model-derived hour
24 Oct 2026, 10:30 am
0 review flags · 5565 stored node-hours
| Covariate | Unit | Research role |
|---|---|---|
| Temperature at 2 m | °C | Thermal state and mixing context |
| Relative humidity at 2 m | % | Particle hygroscopic growth and weather context |
| Precipitation | mm/h | Wet scavenging context |
| Surface pressure | hPa | Synoptic context |
| Wind speed at 10 m | km/h | Dispersion / stagnation context |
| Wind direction at 10 m | degrees | Directional transport context |
| Boundary-layer height | m | Vertical dilution / mixing depth |
Spatial design
The five nodes were frozen from a deterministic five-cluster partition of the 43 unique active Delhi monitor coordinates present at v2.10.0. Future station-level models will use the nearest fixed node rather than moving weather reference points after seeing results.
Provider boundary
Open-Meteo's “best match” model selection may change as upstream models evolve. Delhi Air Health therefore stores provider coordinates, collection time, exact requested URL, raw response and digest. Weather values are never described as instrument observations.
Evidence gates
Evidence maturity
<7 days
Pilot
Pipeline validation and descriptive inspection only. No typical-cycle or persistent spatial claim.
7–29 days
Preliminary
Short-term patterns may be described, but remain highly sensitive to the represented days.
30–89 days
Early longitudinal
Weather-adjusted exploratory models may begin if completeness criteria are also met.
90–364 days
Stronger longitudinal
More stable temporal and spatial summaries become possible; seasonal coverage is still incomplete.
≥365 days
Annual archive
A complete annual cycle can be analysed, with season-specific sensitivity analyses.
Pre-specified weather-adjusted analysis
Weather-adjusted analysis plan
Weather-adjusted modelling will begin only after the prespecified data-availability thresholds are met. The final model specification must be frozen before the first fit.
PM2.5ₜ = β₀ + hour-of-day + day-of-week
+ temperature + humidity + precipitation
+ wind speed + wind direction terms
+ boundary-layer height + station effect + εₜ
+ temperature + humidity + precipitation
+ wind speed + wind direction terms
+ boundary-layer height + station effect + εₜ
Exact encoding, diagnostics, missing-covariate rule and sensitivity analyses must be frozen in a new analysis-spec version before the first model result is published. This equation is a protocol commitment, not a current result.
Current gate
Weather-adjusted modelling remains locked
Current archive: 15 air-data days and 1111 protocol-eligible meteorology hours. Until that threshold is met, meteorology is collected prospectively but is not used for adjusted modelling.
Missing data
No single imputation. Complete-case/shared-hour denominators are stated with every analysis. A future model's missing-covariate rule must be frozen before use.
Exclusions
QC flags do not automatically delete observations. Any exclusion rule requires a versioned protocol amendment plus sensitivity analysis with flagged data retained.
Multiple testing
Early analyses are descriptive. If formal hypothesis testing is introduced, primary contrasts and multiplicity handling must be specified before results are inspected.
Reproducibility boundary
Reproducible analysis requires a fixed data release.
Formal results should identify the software and analysis-spec versions, exact study window, station roster, completeness denominator and the frozen data release used. Corrections are issued as new releases rather than changes to an existing release.