Changes in Extreme Events

This project will examine hourly dew point data at first order weather stations across the conterminous US. The objectives are as follows: 1) Is humidity, as measured by dew point temperatures, increasing across the conterminous U.S.? 2) What are the monthly ranges of dew point temperatures? 3) How much geographical variability is there in dew point averages and extremes across the conterminous US. Results have implications with both climate change issues, as well as having impacts on human health.

Coastal communities have always been at risk of natural hazards such as floods, tropical cyclones, and other severe weather; however, climate change has and will continue to exacerbate this risk. As global sea levels rise at unprecedented rates and coastal populations continue to grow, more people will be exposed to coastal hazards. Coastal communities, such as those in Louisiana, are among the first in the United States to experience displacement due to modern-day climate change. This type of displacement, caused by the changing effects of the environment, such as coastal erosion, land loss, and flooding, can be defined as climate migration. Certain populations will decide to move inland, relocating themselves to more climate-resilient communities; however, little is known about what makes a desirable climate-resilient community. What characteristics make a community appealing to climate migrants in Louisiana? This study measures the following five socioeconomic characteristics of resilient receiving communities: affordable housing availability, public transportation, quality education, access to health care, and economic opportunities. Based on these characteristics and hazard risk, Louisiana’s most favorable receiving communities were ranked. Future research may seek to apply this methodology to diverse geographies.

To better understand the spatiotemporal pattern of extreme precipitation events, SCIPP will continue its collaboration with Applied Weather Associates (AWA) (e.g., Keim et al. 2018; Brown et al. 2020b) to create a database of extreme precipitation events across the U.S. (SPAS). AWA has supplied SCIPP with ~800 unique depth-area-duration (DAD) tables for > 500 extreme precipitation events across the U.S from 1810–2019. The storms analyzed by SPAS are generally the largest precipitation events that have occurred in the U.S. in the observational record and control probable maximum precipitation estimates in the country. DAD tables from each storm will be compiled into one database and metadata, such as location (lat./lon.), date, duration, storm type (synoptic characteristics), and magnitude, will be included. This will enable SCIPP to query the database and investigate the spatiotemporal patterns of extreme precipitation analyzed by SPAS.

A product of this project can be found here: US Storm Database

SCIPP will build on existing partnerships with Gulf Coast water utilities, the USGS National Wetland and Aquatic Research Center, and Louisiana Sea Grant to quantify how extreme low temperatures and freeze days have changed since the early 1950s. A manuscript titled “Tropicalization of the Temperate Zone: Warming Winter Temperatures and Fewer Freeze Days across the Conterminous United States” has been submitted for review to Environmental Research: Climate with the following abstract:

“Here, we investigated changes in cool season and winter temperatures, along with the occurrence of freeze days, between 1952–2024 across the conterminous United States (CONUS). Many of our analyses span the CONUS, with emphasis placed on the tropical-temperate transition zone (TTTz) in the southeastern U.S. Since 1952, daily Tmin has increased at a higher rate and over a larger portion of the CONUS than daily maximum temperature (Tmax), particularly during winter. Annual (winter) Tmax significantly increased across 79% (53%) of the land area of the CONUS, while Tmin increased over 99% (70%). During winter, ~70% of the land area of CONUS observed Tmin warming rates that exceeded Tmax. The countywide average coldest Tmin during the cool season became milder across 57% of the CONUS, while the coldest Tmax showed little change and even cooled east of the Rocky Mountains in the central U.S. The timing of occurrence in the coldest Tmin and coldest Tmax, assessed from the single date of each year’s event, displayed no substantial change. Roughly 85% of the CONUS experienced a significant decline in cool-season freeze days, with the largest relative declines in regions where winter average Tmins are above freezing. An analysis of unique freeze day isopleths (30, 45, 60, and 75 days) across twenty-year periods shows that the average latitude of freeze days has migrated poleward substantially. Between 101°W and 79°W in the TTTz, the 30 freeze-day isopleth for the late period (2005–2024) was, on average, 122 km farther north than in the early period (1952–1971). Generally, the largest latitudinal shifts in freeze-day isopleths between early and late periods occurred in regions near the freezing threshold with low topographic relief, where freeze days are both climatologically marginal and often physiographically unprotected (e.g., the Mississippi River Basin).”

Following the manuscript, we created a tool (accessible at https://cmintemp.scipp.lsu.edu/) to make the results, data, and time series available to our stakeholders.

Engagement with coastal stakeholders will be conducted based on a recently updated sea-level rise manuscript to communicate the latest science and its implications for stakeholders. This will extend work that was produced through a previously completed NOAA Coastal and Oceans Climate Applications (COCA) grant. Interested coastal stakeholder groups include floodplain managers, water utilities, and city, county, and parish planning officials. SCIPP will leverage current partners (e.g., Louisiana Sea Grant, Mississippi- Alabama Sea Grant, Texas Sea Grant) and groups (e.g., Gulf of Mexico Alliance, Gulf of Mexico Community of Practice) to disseminate updated estimates, data, information, and resources outlined in the manuscript.

This study will examine the redistribution of South Louisiana population over the past 20 years. While Katrina’s impacts were in southeastern Louisiana, Mississippi, and Alabama, the other three hurricanes affected southwestern Louisiana, and some of Ike’s majorly impacted area included eastern Texas. The surge magnitudes of both Katrina and Rita led to a large number of individuals leaving New Orleans and the surrounding area for various periods, including permanently (Fussell et. al. 2014; Plyer 2011). We will examine population census statistics at the county and parish level for the coastal zone from Galveston County, Texas to Mobile County, Alabama to assess changes over time from 2000 to present. We will also conduct a survey assessing the decision making processes of inhabitants that both returned to the coast and those that did not. We will examine demographic data to assess ethnicity/race, socioeconomic status, levels of education, etc., and how these parameters have changed since Hurricane Katrina.