Dinâmica da Chuva na Região Metropolitana de Maceió via Produtos de Precipitação (CHELSA e CHIRPS)

Abstract

Rainfall is a climatic variable that completely modifies the geographical landscape. Its spatial-temporal distribution is of extreme relevance in the planning of water resources in metropolitan areas (MA), especially in northeastern Brazil (NEB). The Metropolitan Region of Maceió (MRM) has 13 municipalities and, therefore, the rainfall brings risk to the life and health of this population, since part of it presents social vulnerability. In MRM there are few studies on the dynamics of rain and existing ones do not relate in an integrated way the performance of multi-scale meteorological systems and socio-environmental factors. Observed data from automatic weather stations (AWS) and conventional weather stations (CWS) of INMET and precipitation products (CHIRPS - Climate Hazards Group InfraRed Precipitation with Station and CHELSA - Climatologies at High Resolution for the Earth's Land Surface Areas) were used and the corresponding period was 1979- 2013. Statistical indicators (R2, r, EPE and RMSE, mm) were used to validate the precipitation products. After validation of CHIRPS and CHELSA, annual and seasonal maps were made using the spatial interpolation method IDQ (inverse of the square of the distance) from QGIS version. And data from CHIRPS and CHELSA products were compared with MRM population data from data from the latest IBGE censuses (1980, 1991, 2000 and 2010). The greatest dispersion in the rainy season, in relation to the 1:1 line occurred from the value of 50 mm in CHELSA, while in the CHIRPS it was less than 50 mm. in contrast, in the dry and transition seasons, where there was the greatest dispersion in relation to the 1:1 line from 0 mm. In the rainy season, the coefficients R2 were 49% (CHELSA) and 48% (CHIRPS), both being close. In the dry season there was a difference between CHELSA products (47%) and CHIRPS (52%) due to the spatial resolution being different between precipitation products. The r coefficients of both products (CHELSA, r = 0.7 and CHIRPS, r = 0.69) were moderate and satisfactory. CHELSA and CHIRPS products can be used in the spatio-temporal assessment of MRM rainfall. In both CHIRPS and CHELSA products showed the formation of a rainfall gradient between the coast and the upper part of the MRM. It is worth highlighting the spatial and temporal resolution of each precipitation product and clearly distinguished the intensity classes in the study region, where the CHELSA product indicated higher rain classes in the northern portion and in the central region, while the CHIRPS product the largest rain classes are on the coast of the RMM. Individually, the municipalities of Atalaia and Murici, Pilar and Maceió presented the smallest errors (EPE and RMSE) and, therefore, the products can be used in the assessment of rain. In both CHELSA and CHIRPS products, the annual accumulated rainfall indicated a decrease, from the 2000s and a growth in the population of the MRM; this is worrying for the future of water supply and the maintenance of existing ecosystems in the RMM. The main Meteorological systems that affect the dynamics of the in MRM rainfall are: circulations of lagoon breezes, sea-land, Wave Disturbance of Trade Winds (WDTW), Easterly Wave Disturbances (EWDs), Upper Tropospheric Cyclone Vortex (UTCV) and convective rains caused by the urbanization process.