{"eligibility":{"baseline_site_cohort":"At the primary-period start, baseline eligible physical sites are those marked active in the station registry and with at least one valid PM2.5 observation during the preceding 7 Delhi-local calendar days. The resulting baseline cohort is frozen before primary analysis.","geography":"Primary analysis includes Delhi and NCR sites in the frozen baseline cohort; Delhi-only is a prespecified sensitivity analysis.","missingness":"Missing observations remain missing. No temporal interpolation, carry-forward, or substitution from neighboring monitors is permitted.","network_hour":"A primary network hour is included when at least 50% of baseline eligible physical sites have a valid PM2.5 value in that hour.","site_level":"A physical site is included in the primary site-level heterogeneity summary when it has a valid value in at least 70% of included primary network hours."},"ethics":{"human_participants":false,"note":"This protocol uses publicly available area-level environmental measurements and contains no individual-level patient or participant data. No claim of ethics exemption is made; any institutional determination required for submission will be sought. Any future linkage to individual or non-public health data requires separate ethics, privacy, and data-governance review."},"external_registration":{"note":"The internal protocol is frozen before the primary study window. External registration should occur before 2026-10-01 and the resulting public DOI should be linked without modifying this frozen protocol document.","status":"prepared_not_submitted","target_registry":"OSF Registries","template":"OSF Preregistration"},"multiplicity_and_interpretation":{"causality":"The protocol does not infer causal local emission sources, personal exposure, or health effects from ambient spatial differences.","primary":"The primary estimand is descriptive and interval-based; no binary null-hypothesis significance claim is designated as the study's primary conclusion.","secondary":"Secondary analyses are explicitly exploratory/descriptive unless separately amended and registered before analysis."},"pilot_period":{"end":"2026-09-30T23:59:59+05:30","role":"Method-development and pipeline-validation period. Excluded from the primary prospective analysis.","start":"2026-09-06T00:00:00+05:30"},"primary_estimand":{"overall_heterogeneity":"Primary network heterogeneity is summarized by the interquartile range and the 90th–10th percentile range of site-level effects across eligible physical sites.","site_effect":"For each eligible physical site i, the primary site-level effect is the median R_it across all included primary-period hours for that site.","site_hour_residual":"R_it = PM2.5_it - median_j(PM2.5_jt), where j indexes eligible physical monitoring sites reporting at hour t.","uncertainty":"95% percentile confidence intervals from a local-calendar-day block bootstrap with 1,000 resamples and deterministic random seed 20261001. Confidence intervals are not reported until at least 30 represented primary-period days are available."},"primary_outcome":{"aggregation":"If more than one source feed maps to the same physical_site_key in an hour, the physical-site value is the median of non-missing feed values for that hour.","name":"Hourly PM2.5 concentration","observational_unit":"physical monitoring site × Delhi-local hour","source":"CPCB-linked ambient monitoring feeds captured by Delhi Air Health","unit":"µg/m³"},"primary_period":{"end":"2027-03-31T23:59:59+05:30","start":"2026-10-01T00:00:00+05:30","stopping_rule":"The primary analysis window ends at the prespecified timestamp regardless of observed effect sizes. Operational collection may continue."},"protocol_id":"DAH-PM25-2026-27-v1","quality_control":{"critical_flags":"Observations carrying a critical, observation-specific QC flag are excluded from the primary analysis and retained in the raw/provenance archive.","outliers":"No discretionary concentration outlier deletion is permitted. High but valid source values remain unless excluded by a prespecified QC rule.","review_flags":"Review-flagged observations remain in the primary analysis unless the flag itself indicates an invalid normalized value. A sensitivity analysis excludes review-flagged observations.","source_metadata_changes":"Station renames, operator changes, and coordinate shifts are retained as audit events. A material identity change may require a protocol amendment before combining pre- and post-change observations as one site."},"reporting":{"guideline":"STROBE will be used as the reporting checklist for the eventual observational-study manuscript.","minimum_results_reporting":["station/site flow and inclusion counts","hour and day coverage","missingness and QC summaries","primary site-effect distribution with uncertainty","all prespecified sensitivity analyses","deviations from protocol"]},"research_question":"How much persistent spatial heterogeneity in hourly ambient PM2.5 exists across Delhi-NCR after removing the concurrent network-wide temporal signal?","secondary_analyses":["PM10 analyzed analogously as a secondary pollutant outcome.","Delhi-local diurnal PM2.5 summaries using network-hour medians grouped by local clock hour.","Station-to-station Pearson correlation on shared hourly PM2.5 observations, with same-physical-site pairs excluded from independence-sensitive summaries.","Paired campus-reference monitor differences restricted to shared observed hours; campus analyses are secondary applications, not the primary scientific estimand.","Delhi-only versus wider Delhi-NCR descriptive comparisons."],"sensitivity_analyses":["Exclude all review-flagged observations.","Repeat site inclusion using 60% and 80% completeness thresholds instead of 70%.","Restrict geography to Delhi only.","Use a deterministic single-feed-per-physical-site representation instead of within-site hourly median aggregation.","Repeat heterogeneity summaries using mean site-hour residuals in place of medians."],"short_title":"Delhi Air Health prospective PM2.5 study 2026-27","software_and_reproducibility":{"analysis_seed":20261001,"canonical_site":"https://delhiair.shashwattiwary.com","frozen_release_policy":"Analysis-ready datasets used for manuscripts must be exported as named immutable research releases with checksums and versioned analysis code.","software_release_prepared_with_protocol":"2.12.0"},"status":"finalized","study_design":"Prospective longitudinal observational environmental-exposure study using publicly available ambient monitoring data; no individual-level human participant data are collected in this protocol.","timezone":"Asia/Kolkata","title":"Spatiotemporal heterogeneity of ambient PM2.5 across Delhi-NCR: a prospective longitudinal observational study","version":"1.0.0","weather_adjustment":{"covariates":["temperature_2m_c","relative_humidity_2m_pct","precipitation_mm","surface_pressure_hpa","wind_speed_10m_kmh","wind_direction_10m_deg","boundary_layer_height_m"],"gate":"No weather-adjusted model will be fitted until at least 30 represented air-data days and 21 days of protocol-eligible locked-model meteorology exist.","rule":"The exact model formula, transformations, diagnostics, and inferential procedure must be frozen in a dated protocol amendment before the first weather-adjusted model is fitted. Weather-adjusted results are not part of the v1.0.0 primary estimand.","status":"planned_exploratory_extension"}}