Modeling hourly air temperature based on internationally agreed times and the daily minimum temperature

ABSTRACT There are several fields that require knowledge of air temperature variation throughout the day, such as disease prediction or calculation of chill-hours. However, automatic meteorological stations are not always located in the vicinity to accurately monitor this variable. In this sense, models that describe the daily temporal variation of air temperature can be used to meet this demand, and transform the climatic data series of conventional meteorological stations into an estimated hourly series. The aim of this study was to adjust and validate models for the hourly air temperature variation through data obtained at internationally agreed times (0, 12 and 18 h Universal Time Coordinated: UTC) and the daily minimum air temperature. The hourly database of the automatic station was used for model adjustment and validation. Functions were adjusted based on values measured at internationally agreed times and the daily minimum air temperature for certain daily variation patterns. The air temperature estimation was performed on an hourly basis using sinusoidal and linear models. The model that presented the lowest root mean square error (RMSE) was used for the estimation. The accuracy of the air temperature estimates varied according to the time, presenting RMSE from 0.7 to 1.6 °C, with maximum mean deviation of 0.4 °C. The results of this study showcase the necessity of knowledge of the daily air temperature variation, as well as a series of data from conventional meteorological stations, which can be estimated using hourly models. RESUMO Existem áreas que exigem conhecimento da variação da temperatura do ar ao longo do dia, como previsão de doenças ou cálculo de horas de frio. Porém, nem sempre há estações meteorológicas automáticas próximas para observar esta variável. Nesse sentido, modelos que descrevem a variação temporal diária da temperatura do ar podem ser utilizados para suprir essa demanda. Também, series climáticas de dados de estações meteorológicas convencionais podem ser transformadas em séries horárias estimadas. O objetivo do trabalho foi ajustar e validar modelos para a variação horária da temperatura do ar, através de dados obtidos nos horários de medida das estações convencionais. O banco de dados horários da estação automática foi utilizado para ajuste e validação dos modelos. Funções foram ajustadas com base nos valores medidos nos horários convencionados internacionalmente (0, 12 e 18 h UTC) e na temperatura diária do ar mínima pa