A Comparative Analysis of CAN-SAT Flight Data and the International Standard Atmosphere in Urban Sub Tropical Environments : Characterizing Boundary Layer Deviations

Abstract

Laksh Pandey

A low-cost Can-Sat flight was conducted over Bengaluru (lat 13.0748°N, long 77.3670°E) to record temperature (T), relative humidity (RH), and pressure (P) profiles in the lowest few hundred meters of the troposphere. The key finding is that the observed profiles strongly deviate from the International Standard Atmosphere (ISA) model: near-surface temperatures were ≈25–26 °C higher than ISA predicts (observed ~35 °C vs. ISA ~9–10 °C), while pressure closely matched ISA (within ≈0.1%). This indicates an anomalously warm boundary layer (a thermal inversion/cap) likely caused by daytime heating and urban effects. I computed the lapse rate (≈– 1.6 °C/km) and humidity gradient (≈– 9.3%RH/km) from the cleaned data. Temperature and RH were strongly anticorrelated (r≈–0.86, p<10−19), consistent with Clausius– Clapeyron expectations for moist air. I quantify these deviations versus ISA (absolute ΔT ≈+26 °C, ΔP≈0.0– 0.3 hPa) and analyze their causes. Possible physical causes include intense surface heating (urban heat island effect) and radiative inversion; instrumental factors include sensor heating/radiation lag and calibration. I have detailed all metadata (sensors, rates, location) and describe data-cleaning steps. This Can-Sat-based study is novel: it exposes micro-scale atmospheric anomalies that standard models miss, using inexpensive COTS sensors[1]. The results suggest that ISA is not valid at such local scales, implying a need for microclimate corrections in models.

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