{"eligibility":{"baseline_site_cohort":"At the start of the primary period, baseline eligible physical sites are those marked active in the station registry with at least one valid PM2.5 observation during the preceding 7 Delhi-local calendar days. This baseline cohort is then frozen for the primary analysis.","geography":"The primary analysis includes Delhi and NCR sites in the frozen baseline cohort. A Delhi-only analysis is prespecified as a sensitivity analysis.","missingness":"Missing observations remain missing. No interpolation, carry-forward, or substitution from a neighboring monitor is used.","network_hour":"A 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 summary when it has valid PM2.5 values for at least 70% of included primary network hours."},"ethics":{"human_participants":false,"note":"The study uses publicly available area-level environmental measurements and contains no individual-level patient or participant data. No formal ethics exemption is claimed in advance. Any determination required by an institution or journal will be sought. Any future linkage to individual-level or non-public health data would require separate ethics, privacy, and data-governance review."},"external_registration":{"note":"Version 1.1.1 is the external-registration copy. It is scientifically identical to v1.1.0 and corrects one stale version label in the weather-adjustment text. The v1.1.0 literature-positioning amendment and its two descriptive secondary persistence analyses remain unchanged. External registration should occur before 1 October 2026.","status":"prepared_not_submitted","target_registry":"OSF Registries","template":"OSF Preregistration"},"multiplicity_and_interpretation":{"causality":"Differences between monitoring sites are not interpreted as evidence of a causal local emission source, personal exposure, a campus-specific exposure effect, or a health effect.","primary":"The primary analysis is descriptive and interval-based. No single binary null-hypothesis test is designated as the primary conclusion.","secondary":"Secondary analyses are treated as exploratory unless they are separately specified and registered before confirmatory use."},"pilot_period":{"end":"2026-09-30T23:59:59+05:30","role":"Method-development and pipeline-validation period. These data are excluded from the primary prospective analysis.","start":"2026-09-06T00:00:00+05:30"},"primary_estimand":{"overall_heterogeneity":"Spatial heterogeneity across the monitoring network is summarized by the interquartile range and the 90th–10th percentile range of the site-level effects.","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 denotes eligible physical monitoring sites reporting at hour t.","uncertainty":"After at least 30 represented primary-period days are available, 95% percentile confidence intervals will be calculated by block-bootstrap resampling Delhi-local calendar days 1,000 times using deterministic seed 20261001."},"primary_outcome":{"aggregation":"If more than one source feed maps to the same physical site in a given hour, the physical-site value is the median of the available non-missing feed values.","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 period ends at the prespecified timestamp regardless of the results observed. Routine data collection may continue afterward."},"protocol_id":"DAH-PM25-2026-27-v1-1-1","quality_control":{"critical_flags":"An observation with an observation-specific critical QC flag is excluded from the primary analysis. The underlying raw and provenance records remain retained.","outliers":"No discretionary concentration outlier deletion is allowed. High source values remain unless they meet a prespecified QC exclusion rule.","review_flags":"Review-flagged observations remain in the primary analysis unless the flag identifies the normalized value as invalid. A prespecified sensitivity analysis excludes all review-flagged observations.","source_metadata_changes":"Station renames, operator changes, and coordinate shifts are retained as audit events. If a metadata change suggests that observations before and after the change may not represent the same physical site, a protocol amendment is required before they are combined in the primary analysis."},"reporting":{"guideline":"The eventual observational-study manuscript will be reported using the STROBE checklist.","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","monthly site-effect persistence summaries","literature-positioning statement distinguishing the primary estimand from prior Delhi spatial-heterogeneity work"]},"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?","secondary_analyses":["PM10 analyzed using the same descriptive framework as a secondary pollutant outcome.","Delhi-local diurnal PM2.5 summaries based on network-hour medians grouped by local clock hour.","Station-to-station Pearson correlations using shared hourly PM2.5 observations, with same-physical-site pairs excluded from independence-sensitive summaries.","Paired campus-reference monitor differences using only hours observed at both monitors. Campus comparisons are a secondary application and are not the primary scientific estimand.","Descriptive comparison of Delhi-only and wider Delhi-NCR results.","Monthly site-level median residuals using the primary R_it definition, requiring at least 70% site completeness within included network hours for that Delhi-local calendar month.","Temporal persistence of network-relative site contrasts: for sites with at least 3 eligible months, report sign concordance of monthly versus full-period site effects; for month pairs with at least 10 shared eligible sites, report Spearman rank correlation of monthly site-effect rankings. These are descriptive secondary measures."],"secondary_research_question":"Are the direction and relative ordering of site-level network-relative PM2.5 contrasts stable across Delhi-local calendar months?","sensitivity_analyses":["Exclude all review-flagged observations.","Repeat site inclusion using 60% and 80% completeness thresholds instead of 70%.","Restrict the analysis to Delhi only.","Use one deterministic source feed per physical site instead of the within-site hourly median.","Use mean site-hour residuals instead of median site-hour residuals."],"short_title":"Delhi Air Health network-relative 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":"2.13.0"},"status":"finalized","study_design":"Prospective longitudinal observational study of ambient particulate pollution using publicly available monitoring data. No individual-level human participant data are collected under this protocol.","study_positioning":{"claims_not_made":["first study of spatial PM2.5 variation in Delhi or Delhi-NCR","first Delhi study to use meteorological covariates","first quality-control analysis of CPCB or CAAQMS data","first hyperlocal air-pollution study in Delhi","evidence that a network-relative residual identifies a causal local emission source"],"literature_context":"Prior Delhi and Delhi-NCR studies have already documented spatial heterogeneity, long-term temporal trends, meteorological associations, and fine-scale pollution variation. This study does not claim that spatial variation itself is new.","manuscript_gap_statement":"Although spatial differences in Delhi PM2.5 are well documented, it remains unclear how large and stable site-level contrasts are when locations are compared against the concurrent monitoring-network level using only eligible shared hours and explicit completeness rules.","primary_contribution":"The primary analysis estimates each physical monitoring site's repeated same-hour departure from the concurrent Delhi-NCR network median, using a frozen physical-site cohort and explicit shared-hour completeness rules. The network median is used as a contemporaneous reference, not as an official city average or an estimate of regional background."},"temporal_persistence_secondary":{"monthly_site_effect":"For each physical site and Delhi-local calendar month, calculate the median R_it within that month when the site has valid PM2.5 for at least 70% of the included primary network hours in that month.","rank_stability":"For each pair of calendar months with at least 10 shared eligible physical sites, report Spearman rank correlation between monthly site effects. These correlations are descriptive; no binary significance threshold is used as a study conclusion.","role":"Secondary descriptive analysis. It does not alter the primary estimand or primary eligibility rules.","sign_persistence":"For sites with at least 3 eligible calendar months, report the proportion of eligible months in which the monthly median residual has the same sign as the full-period primary site effect. A zero monthly median is counted as neither positive nor negative and therefore as not sign-concordant."},"timezone":"Asia/Kolkata","title":"Persistent site-level contrasts in hourly PM2.5 across Delhi-NCR relative to the concurrent network median: a prospective observational study","version":"1.1.1","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 are available.","rule":"The exact model formula, transformations, diagnostics, and inferential procedure must be specified in a dated protocol amendment before the first weather-adjusted model is fitted. Weather-adjusted analyses are not part of the primary estimand in this protocol.","status":"planned_exploratory_extension"}}