Oceanic and terrestrial origin of precipitation over 50 major world river basins: Implications for the occurrence of drought.

The terrestrial and oceanic origins of precipitation over 50 major river basins worldwide were investigated for the period 1980-2018. For this purpose, we used a Lagrangian approximation that calculates the humidity that results in precipitation from the entire ocean area (ocean component of the precipitation, PLO) and the entire land area (land component, PLT) as well as the sum of both components (Lagrangian precipitation, PL). PL and its components were highly correlated with precipitation over the basins, where PLT accounted for >50 % of the PL in most of them. This confirmed the importance assigned by previous studies to terrestrial recycling of precipitation and moisture transport within the continents. However, the amount of PLO in almost all North American river basins was highlighted. The assessment of drought conditions through the Standardized Precipitation Index (SPI) at a temporal scale of 1- and 3-months revealed the number of drought episodes that affected each river basin, especially the Amazon, Congo, and Nile, because of the lower number of episodes but higher average severity and duration. A direct relationship between the severity of drought episodes and the respective severity computed on the oceanic and terrestrial SPI series was also found for the majority of basins. This highlights the influence of the severity of the SPI of oceanic origin for most basins in North America. However, for certain basins, we found an inverse relationship between the severity of drought and the associated severity according to the SPI of oceanic or terrestrial origin, thus highlighting the principal drought attribution. Additionally, a copula analysis provided new information that illustrates the estimated conditional probability of drought for each river basin in relation to the occurrence of drought conditions of oceanic or terrestrial origin, which revealed the possible main driver of drought severity in each river basin.

Dataset of outer tropical cyclone size from a radial wind profile.

Pérez-Alarcón et al. [1] developed a comparative climatology of the outer radius of tropical cyclones (TCs) from several radial wind profiles. They showed that the Willoughby et al. (2006) (W06) profile can be used to reproduce the TC tangential wind speed; thus, this profile is skilful for estimating the TC outer radius. Here, we present a database of TC sizes estimated from the W06 radial wind profile in each cyclogenetic basin worldwide. The database incorporates the critical wind radii, where the tangential wind speed is approximately 17.5 ms-1 (R34), 26 ms-1 (R50), 33 ms-1 (R64), and 51 ms-1 (R100), estimated by the W06 profile. The database has a comma-delimited text format with six-hour information on the location, maximum wind speed, central pressure, and the different TC metrics mentioned above. This database has a similar structure to that of the Atlantic Hurricane Database (HURDAT2) of the National Hurricane Center. The database presented here is applicable to studies on TC storm surge risks as well as to the determination of the sources and sinks of atmospheric moisture related to tropical cyclogenesis processes.

Oceanic versus terrestrial origin of El Niño Southern Oscillation-associated continental precipitation anomalies.

Precipitation is significantly influenced by the El Niño Southern Oscillation (ENSO), which is considered to be the most important factor that brings about climate variability. In this study, the asymmetry of the origin of continental precipitation anomalies during El Niño and La Niña events was investigated. An already validated Lagrangian approach was used to determine the proportion of the total Lagrangian precipitation that is of oceanic and terrestrial origin. Further, the role of these components of the Lagrangian precipitation in regions with significant precipitation anomalies during the ENSO was investigated. A two-phase asymmetric behavior of precipitation, particularly in tropical regions, was obtained. For some of these regions, precipitation anomalies based on other datasets were also calculated to confirm the observed changes, and for these regions, it was observed that in all cases, the calculated anomaly of Lagrangian precipitation agreed with the precipitation change. The percentage of precipitation of oceanic origin was higher in most of these regions. However, it was observed that an increase in the percentage of precipitation of oceanic origin did not bring about a general increase in precipitation for all the regions, revealing the importance of precipitation of terrestrial origin during both phases of the ENSO.