Search for: All records

Abstract During summer and fall 2023, Louisiana experienced a historic local drought while dry conditions elsewhere in the central US withheld vital runoff from the Mississippi River, leading to below‐normal discharge into the Gulf of Mexico. Thus, by late October 2023, Louisiana was gripped by two super‐imposed water crises: a severe local drought and saltwater contamination in the Mississippi River channel. This study frames the development of the water emergency through the lens of flash drought using the Evaporative Demand Drought Index (EDDI). The EDDI shows south Louisiana experience a flash drought during June 2023, while the Mississippi River basin was subsequently characterized by large expanses of high‐percentile EDDI in August‐September 2023 shortly before the saltwater intrusion episode along the lower Mississippi River. Over the last 15 years, MRB‐wide EDDI percentile has oscillated between years‐long elevated and depressed states, accounting for 23.7% of the monthly discharge anomaly near New Orleans. 

Aerosols are important modulators of the precipitation-generating process, with their concentrations potentially affecting the precipitation process in extreme events. Existing literature suggests that, through microphysical processes, additional aerosols lead to a larger number of smaller cloud droplets, which eventually redistributes the latent heat and the precipitation process. This research addresses the question of how sensitive the spatial and temporal patterns of heavy precipitation events are to aerosol concentration. National Centers for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS) final (FNL) data were used as input to the Weather Research and Forecasting (WRF) model, to simulate the case study of the catastrophic 2016 flood in Louisiana, USA, for three aerosol loading scenarios: virtually clean, average, and very dirty, corresponding to 0.1×, 1×, and 10× the climatological aerosol concentration. Overall, for the extreme precipitation event in Baton Rouge, Louisiana, in August 2016, increasing aerosol concentrations were associated with 1) a shifted peak precipitation period; 2) a more intense and extreme precipitation event in a more confined area; 3) greater maximum precipitation. Results are important in improving forecast models of extreme precipitation events, thereby further protecting life and property, and more comprehensively understanding the role of aerosols in heavy precipitation events. 

The Saharan Air Layer (SAL) is a hot, dry, and dust‐laden feature that advects large concentrations of dust across the Atlantic annually to destination regions in the Americas and Caribbean. However, recent work has suggested the SAL may be a contributing factor to high‐impact drought in the Caribbean basin. While the SAL's characteristic dust loadings have been the focus of much previous research, fewer efforts have holistically engaged the co‐evolution of the dust plume, its associated convective environment, and resultant rainfall in Caribbean islands. This study employs a self‐organizing map (SOM) classification to identify the common trans‐Atlantic dust transport typologies associated with the SAL during June and July 1981–2020. Using the column‐integrated dust flux, termed integrated dust transport (IDT), from MERRA‐2 reanalysis as a SAL proxy, the SOM resolved two common patterns which resembled trans‐Atlantic SAL outbreaks. During these events, the convective environment associated with the SAL, as inferred by the Gálvez‐Davison Index, becomes less conducive to precipitation as the SAL migrates further away from the west African coast. Simultaneously, days with IDT patterns grouped to the SAL outbreak typologies demonstrate island‐wide negative precipitation anomalies in Puerto Rico. The SOM's most distinctive SAL outbreak pattern has experienced a statistically significant increase during the 40‐year study period, becoming roughly 10% more frequent over that time. These results are relevant for both climate scientists and water managers wishing to better anticipate Caribbean droughts on both the long and short terms. 

These data represent a self-organizing map (SOM) classification of all trans-Atlantic integrated dust fluxes (IDT) between June-July 1981-2020 as presented in: Miller, P. W., and C. Ramseyer, In press: The relationship between the Saharan Air Layer, convective environmental conditions, and precipitation in Puerto Rico. Journal of Geophysical Research: Atmospheres.  Each daily IDT field is paired to one of 12 discrete pathways in idt_bmus_junjul.csv. The mean composite IDT over the tropical North Atlantic for each of these 12 patterns, as well as the mean composite Galvez-Davison Index (ERS_idt_node_gdi_1981_2020_junjul.nc) and mean composite precipitation over Puerto Rico (ERS_idt_node_prcp_1981_2020_junjul.nc) for the same node-date pairings are also provided. See the above-referenced manuscript for more details.