Balanço hídrico climatológico via reanálise ERA5-Land no estado de Pernambuco

Abstract

The observed data from surface weather stations are an important option for research, hydrological and climatological studies worldwide. However, due to the failures in the final data resulting from errors of human reading (conventional stations) and failures in equipment and sensors (automatic stations), it generated a search for alternatives that can replace or complete the data of meteorological stations, such as the estimated climatological data from global atmospheric models. The climatological water balance was consolidated as an extremely important tool to obtain answers about the intrinsic variables of agricultural planning. The use of estimated reanalysis data in the calculation of climatological water balance is already a global reality due to the consistency and availability of these data. Therefore, this research aimed to estimate the climatological water balance (BHC) and water deficiency from the monthly data of average air temperature and Rainfall estimated by the ERA5-Land reanalysis data from the European Center for Medium-Range Weather Forecasts (ECMWF), validated based on surface weather data, in the state of Pernambuco in the period of 31 years (01/01/1990 – 31/12/2020). The air temperature and precipitation data were stratified by state mesoregions (forest zone, agrest and semiarid), and the validation of ERA5-Land reanalysis data was performed by calculating statistical indices that evaluated accuracy and accuracy at the model estimating. The BHC calculation was obtained according to Thorthwaite and Mather (1955) methodology through the BHnorm program and adopted the value of 100 mm for storage soil available water capacity (CAD). The reanalysis of ERA5-Land obtained accuracy greater than 52% for the variable total precipitation and higher than 90% for air temperature in almost all over the state. In general, the total precipitation and air temperature data generated by ERA5-Land and compared with surface data through systematic MBE error were underestimated. Water deficiency of the semiarid mesoregion was higher than rainfall in all months, with the highest values observed in Cabrobó in November (-170 mm) and in Forest in December (-172 mm) throughout the dry season. In the Agreste mesoregion, the highest values of water deficit in December were recorded in the municipalities of Surubim (-96 mm) and Caruaru (-84 mm), on the other hand, the municipality of Garanhuns presented a maximum value of -76 mm in December and 0 mm in June and July, where there was a slight storage of water in the soil without the presence of water surplus. In the Zona da Mata/Litoral there was a water deficit from January to April and from September to December, with the highest values observed in December in Recife (-87 mm) and Palmares (-72 mm). The water surplus totaled 71 mm, distributed in June and July (44.13 mm and 0.37 mm, respectively) in Recife and Palmares (14.5 mm and 12 mm, respectively). Therefore, with the results obtained in the validation of era5-land reanalysis data, it can be ensured that the reanalysis safely estimated the total precipitation and the average air temperature for the state of Pernambuco, requiring major improvements in the variable precipitation and small in the variable air temperature. Based on the climatological water balance, it is recommendable to use supplementary irrigation for crops that require water supplementation above five months a long of year in the Sertão mesoregion, since this mesoregion presented a dry period by seven months resulting higher water deficiency. The results of this study provide support for the planning of agricultural activities and climate classification for the state of Pernambuco.