Assessment of Gridded CRU TS Data for Long-Term Climatic Water Balance Monitoring over the São Francisco Watershed, Brazil

Pedro R Mutti,Vincent Dubreuil,Bergson G Bezerra,Cláudio M Santos E Silva,Cristiano P De Oliveira,Damien Arvor

doi:10.3390/atmos11111207

Abstract

Understanding the long-term behavior of rainfall and potential evapotranspiration (PET) over watersheds is crucial for the monitoring of hydrometeorological processes and climate change at the regional scale. The São Francisco watershed (SFW) in Brazil is an important hydrological system that transports water from humid regions throughout the Brazilian semiarid region. However, long-term, gapless meteorological data with good spatial coverage in the region are not available. Thus, gridded datasets, such as the Climate Research Unit TimeSeries (CRU TS), can be used as alternative sources of information, if carefully validated beforehand. The objective of this study was to assess CRU TS (v4.02) rainfall and PET data over the SFW, and to evaluate their long-term (1942–2016) climatological aspects. Point-based measurements retrieved from rain gauges and meteorological stations of national agencies were used for validation. Overall, rainfall and PET gridded data correlated well with point-based observations (r = 0.87 and r = 0.89), with a poorer performance in the lower (semiarid) portion of the SFW (r ranging from 0.50 to 0.70 in individual stations). Increasing PET trends throughout the entire SFW and decreasing rainfall trends in areas surrounding the semiarid SFW were detected in both gridded (smoother slopes) and observational (steeper slopes) datasets. This study provides users with prior information on the accuracy of long-term CRU TS rainfall and PET estimates over the SFW.

Highlights

Precipitation and potential evapotranspiration (PET) are among the most important meteorological variables related to the water and energy cycles that regulate climate worldwide
This study provides users with prior information on the accuracy of long-term Climate Research Unit TimeSeries (CRU TS) rainfall and PET estimates over the São Francisco watershed (SFW)
In a global climate change context, evidence indicates that long-term changes in these variables are leading to important impacts in agriculture, water resources management, and ecosystems dynamics in general [1,2,3,4]. Their consistent and reliable monitoring is crucial to understand past, present, and future climate behavior. This is important in regions that are more vulnerable to climate change, such as arid and semiarid regions, which are sensitive to small shifts in precipitation and PET patterns [5]

Summary

Introduction

Precipitation and potential evapotranspiration (PET) are among the most important meteorological variables related to the water and energy cycles that regulate climate worldwide. In a global climate change context, evidence indicates that long-term changes in these variables are leading to important impacts in agriculture, water resources management, and ecosystems dynamics in general [1,2,3,4] Their consistent and reliable monitoring is crucial to understand past, present, and future climate behavior. Given the high spatial variability of rainfall, long-term point-based measurements should be carried out with a good spatial coverage in order to account for as many physical factors as possible, such as elevation and the influence of nearby geographical elements [6,7,8] This is usually less important for PET, since it is generally more spatially homogeneous, but having consistent, long-term, gapless

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