A Lagrangian perspective of the hydrological cycle in the Congo River basin

Abstract

Abstract. The Lagrangian model FLEXPART is used to identify the moisture sources of the Congo River basin (CRB) and investigate their role in the hydrological cycle. This model allows us to track atmospheric parcels while calculating changes in the specific humidity through the budget of evaporation minus precipitation. This method permits the annual-scale identification of five continental and four oceanic principal regions that provide moisture to the CRB from both hemispheres over the course of the year. The most important is the CRB, which provides more than 50 % of the total atmospheric moisture contribution to precipitation over itself. Additionally, both the land that extends to the east of the CRB and the eastern equatorial South Atlantic Ocean are very important sources, while the Red Sea source is merely important in the (E − P ) budget over the CRB despite its high evaporation rate. The moisture-sink patterns over the CRB in air masses that were tracked forward in time from all the sources follow the latitudinal rainfall migration and are mostly highly correlated with the pattern of the precipitation rate, ensuring a link between them. In wet (dry) years, the contribution of moisture to precipitation from the CRB over itself increases (decreases). Despite the enhanced evaporative conditions over the basin during dry years, the vertically integrated moisture flux (VIMF) divergence inhibits precipitation and suggests the transport of moisture from the CRB to remote regions.

The Identification of Iran’s Moisture Sources Using a Lagrangian Particle Dispersion Model

“…As input data to run FLEXPART model we used ERA-Interim reanalysis datasets from the European Centre for Medium-Range Weather Forecast (ECMWF) [30] at a 1° horizontal resolution on 61 vertical levels from 0.1 to 1000 hPa. In a global experiment, FLEXPART v9.0 divides the atmosphere into approximately 2,000,000 uniformly distributed particles with the same mass, and then moving these particles with time through a 3-dimensional wind field (two horizontal dimensions and one vertical dimension) [31][32][33]. Along the trajectories, for each parcel the evaporation is e and the precipitation is p. The balance of evaporation (e) minus precipitation (p) is calculated considering the changes of specific humidity (q) in each air particle within time (t), keeping constant the mass of the parcels, which is described by Equation (1):…”

Variations in Moisture Supply from the Mediterranean Sea during Meteorological Drought Episodes over Central Europe

“…In addition, fluctuations in specific humidity (q) along trajectories may occur for nonphysical reasons, due to the interpolation of q or trajectory errors; however, this limitation can be compensated for by the large numbers of particles that are contained in an atmospheric column over a given area. A more detailed description of backward and forward analyses can be found in a number of studies that have applied this model to estimate humidity changes along trajectories and identify sources of moisture and sinks in many different regions worldwide, such as the Danube River Basin [74], the Congo River Basin [32], Central America [75], the Mediterranean region [48], Iceland [76], the Fertile Crescent region [24] and the Indus, Ganges, and the Brahmaputra River Basin [77]. Furthermore, Stojanovic et al [13] recently applied this method to investigate anomalies in the moisture supply during the 2003 drought episode in Europe.…”

<strong>Drought and </strong><strong>wet episodes in Amazonia: the role of atmospheric moisture transport</strong>

“…FLEXPART has been previously applied for investigating the hydrological cycle at different river basins, as the whole ARB [14], the Congo River basin [22], the Yangtze River basin [23], the Danube River basin [24] and several worldwide river basins [20]. FLEXPART utilizes data from ERA-interim reanalysis datasets [25].…”