Sensible, latent heat and store energy fluxes in the suburban São Paulo Megacity: seasonal and interannual variations and empirical modeling

Abstract

Half-hourly values of turbulent sensible (H) and latent (LE) heat fluxes, net radiation (𝑄∗) at the surface, and heat store in the canopy (𝛥𝑄𝑆) are used to characterize seasonal and interannual changes during three not-consecutive years (2009–12) in a suburban area (LCZ 6) of the megacity of São Paulo. Turbulent fluxes are estimated applying eddy covariance method to turbulence measurements performed with sampling rate of 10 Hz, between 25 and 26 m above the surface, and enforcing quality control procedures. The diurnal evolution of monthly average hourly values of 𝐻, 𝐿𝐸, 𝑄∗ and 𝛥𝑄𝑆 observed in 2012 indicate a seasonal variation with a daytime maximum with 𝐻 varying from a maximum of 180 ± 12 W m-2 in October to a minimum of 80.1 ± 9 W m2 in June, 𝐿𝐸 varying from a maximum of 152.0 ± 7.6 W m-2 in February to a minimum of 66.4 ± 7.6 W m-2 in September, -𝑄∗ varying from a maximum of 554 ± 14 W m-2 in February to a minimum of 369±13 W m-2 in July, and -𝛥𝑄𝑆 varying from a maximum of 249± 47 W m-2 in April to a minimum of 181 ± 58 W m-2 in July. Monthly average daily values of H, LE and 𝑄∗ corroborate seasonal pattern displayed by monthly average hourly values, with maximum of 5 ± 0.5 MJ m-2 day-1 for H and 5.3 ± 0.6 MJ m-2 day-1 for LE in November (summer), and minimum of 1.3 ± 0.2 MJ m-2 day-1 for H in June and 1.9 ± 0.2 MJ m-2 day-1 for LE in August. −𝑄∗ shows a maximum of 11.6 ± 1.1 MJ m2 day-1 in March and a minimum of 4.5±0.9 MJ m-2 day-1 in June. Similar patterns was observed during 2009 and 2010. An empirical model based on Modified Priestly-Taylor Method coupled to Objective Hysteresis Method was validated with observations carried out during May and June (2009–2010, 2012) and applied successfully to estimate monthly average hourly values of 𝐻, LE and 𝛥𝑄𝑆 during February–April and August–Novemb 2012.