A Step towards Integrating CMORPH Precipitation Estimation with Rain Gauge Measurements

Abstract

Accurate daily rainfall estimation is required in several applications such as in hydrology, hydrometeorology, water resources management, geomorphology, civil protection, and agriculture, among others. CMORPH daily rainfall estimations were integrated with rain gauge measurements in Brazil between 2000 and 2015, in order to reduce daily rainfall estimation errors by means of the statistical objective analysis scheme (SOAS). Early comparisons indicated high discrepancies between daily rain gauge rainfall measurements and respective CMORPH areal rainfall accumulation estimates that tended to be reduced with accumulation time span (e.g., yearly accumulation). Current results show CMORPH systematically underestimates daily rainfall accumulation along the coastal areas. The normalized error variance (NEXERVA) is higher in sparsely gauged areas at Brazilian North and Central-West regions. Monthly areal rainfall averages and standard deviation were obtained for eleven Brazilian watersheds. While an overall negative tendency (3 mm·h−1) was estimated, the Amazon watershed presented a long-term positive tendency. Monthly areal mean precipitation and respective spatial standard deviation closely follow a power-law relationship for data-rich watersheds, i.e., with denser rain gauge networks. Daily SOAS rainfall accumulation was also used to calculate the spatial distribution of frequencies of 3-day rainfall episodes greater than 100 mm. Frequencies greater than 3% were identified downwind of the Peruvian Andes, the Bolivian Amazon Basin, and the La Plata Basin, as well as along the Brazilian coast, where landslides are recurrently triggered by precipitation.

Assessment of satellite products for filling rainfall data gaps in the Amazon region

“…The Amazon region is characterized by a humid atmosphere of great and intense convective activity that together with the action of synoptic systems and climate variability mode influence the climate of the region. The main climatic systems that occur in the Amazon are (1) the Intertropical Convergence Zone (ITCZ), whose latitudinal oscillations define the dry and rainy seasons (Pereira Filho et al, 2018); (2) the South Atlantic Convergence Zone (SACZ), operating mainly in the south and southwest regions of the Amazon region (Espinoza et al, 2014); and (3) El Niño-Southern Oscillation (ENSO) events, which are responsible for the interannual variability of rainfall (Yoon & Zeng, 2010).…”

TOPMODEL Hydrometeorological Modeling with Rain Gauge Data Integrated by High-Resolution Satellite Estimates. A Case Study in Muriaé River Basin, Brazil

“…Several studies have already used SOAS to integrate precipitation data and apply them to hydrological models with satisfactory results [17] [29] [30] [31] [32]. In Pereira Filho et al (2018) [33], a sixth-order polynomial equation of CMORPH 24-hour precipitation correlation between two pixels as a function of the distance between them was adjusted. The correlation function was adapted for the CMORPH precipitation time series from 2000 to 2015 over the entire Brazil territory.…”

Convective Rainfall in Lake Victoria Watershed and Adjacent Equatorial Africa

“…This method is based on PMW and IR measurements with an 8-km and half-hour time-spatial resolution. It has been successfully used in several studies in South America by [2]- [7]. In the present study, CMORPH datasets are used to analyze the diurnal cycle of convection and respective dynamic and thermodynamic footprints from the Rift Valley to the Congo Forest with an emphasis on the mesoscale system induced by the lake and mountain-valley circulations by Lake Victory and the Easterlies.…”