Evaluation of Atmospheric Downward Longwave Radiation in the Brazilian Pampa Region
| Autor: | Tiago Bremm, Dirceu Luis Herdies, Daniele Morgenstern Aimi, Tamíres Zimmer, Leugim Corteze Romio, Roilan Hernandez, Silvana Maldaner, Gisele Cristina Rubert, Gustavo Pujol Veeck, Lidiane Buligon, Vanessa de Arruda Souza, Marcelo Bortoluzzi Diaz, Débora Regina Roberti |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Atmospheric Science
Correlation coefficient media_common.quotation_subject Astrophysics::High Energy Astrophysical Phenomena Biome Flux Environmental Science (miscellaneous) lcsh:QC851-999 Atmospheric sciences Physics::Geophysics Pampa biome Emissivity statistical analyses Astrophysics::Solar and Stellar Astrophysics Relative humidity Precipitation Astrophysics::Galaxy Astrophysics Physics::Atmospheric and Oceanic Physics media_common Astrophysics::Instrumentation and Methods for Astrophysics modeling Vegetation Sky atmospheric downward longwave radiation Environmental science lcsh:Meteorology. Climatology Astrophysics::Earth and Planetary Astrophysics |
| Zdroj: | Atmosphere, Vol 12, Iss 28, p 28 (2021) Atmosphere Volume 12 Issue 1 |
| ISSN: | 2073-4433 |
| Popis: | Atmospheric downward longwave radiation flux (L&darr ) is a variable that directly influences the surface net radiation and consequently, weather and climatic conditions. Measurements of L&darr are scarce, and the use of classical models depending on some atmospheric variables may be an alternative. In this paper, we analyzed L&darr measured over the Brazilian Pampa biome. This region is located in a humid subtropical climate zone and characterized by well defined seasons and well distributed precipitation. Furthermore, we evaluated the performance of the eleven classical L&darr models for clear sky with one-year experimental data collected in the Santa Maria experimental site (SMA) over native vegetation and high relative humidity throughout the year. Most of the L&darr estimations, using the original coefficients, underestimated the experimental data. We performed the local calibration of the L&darr equations coefficients over an annual period and separated them into different sky cover classifications: clear sky, partly cloudy sky, and cloudy sky. The calibrations decreased the errors, especially in cloudy sky classification. We also proposed the joint calibration between the clear sky emissivity equations and cloud sky correction function to reduce errors and evaluate different sky classifications. The results found after these calibrations presented better statistical indexes. Additionally, we presented a new empirical model to estimate L&darr based on multiple regression analysis using water vapor pressure and air temperature. The new equation well represents partial and cloudy sky, even without including the cloud cover parameterization, and was validated with the following five years in SMA and two years in the Cachoeira do Sul experimental site (CAS). The new equation proposed herein presents a root mean square error ranging from 13 to 21 Wm&minus 2 and correlation coefficient from 0.68 to 0.83 for different sky cover classifications. Therefore, we recommend using the novel equation to calculate L&darr over the Pampa biome under these specific climatic conditions. |
| Databáze: | OpenAIRE |
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