Search Results

You are looking at 21 - 24 of 24 items for

  • Author or Editor: Gregory R. Foltz x
  • Refine by Access: All Content x
Clear All Modify Search
Samson Hagos
,
Gregory R. Foltz
,
Chidong Zhang
,
Elizabeth Thompson
,
Hyodae Seo
,
Sue Chen
,
Antonietta Capotondi
,
Kevin A. Reed
,
Charlotte DeMott
, and
Alain Protat
Free access
Effy B. John
,
Karthik Balaguru
,
L. Ruby Leung
,
Gregory R. Foltz
,
Robert D. Hetland
, and
Samson M. Hagos

Abstract

Tropical Cyclone (TC) Sally formed on 11 September 2020, traveled through the Gulf of Mexico (GMX), and intensified rapidly before making landfall on the Alabama coast as a devastating category-2 TC with extensive coastal and inland flooding. In this study, using a combination of observations and idealized numerical model experiments, we demonstrate that the Mississippi River plume played a key role in the intensification of Sally near the northern Gulf Coast. As the storm intensified and its translation slowed before landfall, sea surface cooling was reduced along its track, coincident with a pronounced increase in SSS. Further analysis reveals that TC Sally encountered a warm Loop Current eddy in the northern GMX close to the Mississippi River plume. Besides deepening the thermocline, the eddy advected low-salinity Mississippi River plume water into the storm’s path. This resulted in the development of strong upper-ocean salinity stratification, with a shallow layer of freshwater lying above a deep, warm “barrier layer.” Consequently, TC-induced mixing and the associated sea surface cooling were reduced, aiding Sally’s intensification. These results suggest that the Mississippi River plume and freshwater advection by the Loop Current eddies can play an important role in TC intensification near the U.S. Gulf Coast.

Restricted access
Sang-Ki Lee
,
Hosmay Lopez
,
Gregory R. Foltz
,
Eun-Pa Lim
,
Dongmin Kim
,
Sarah M. Larson
,
Kandaga Pujiana
,
Denis L. Volkov
,
Soumi Chakravorty
, and
Fabian A. Gomez

Abstract

A phenomenon referred to here as Java–Sumatra Niño/Niña (JSN or JS Niño/Niña) is characterized by the appearance of warm/cold sea surface temperature anomalies (SSTAs) in the coastal upwelling region off Java–Sumatra in the southeastern equatorial Indian Ocean. JSN develops in July–September and sometimes as a precursor to the Indian Ocean dipole, but often without corresponding SSTAs in the western equatorial Indian Ocean. Although its spatiotemporal evolution varies considerably between individual events, JSN is essentially an intrinsic mode of variability driven by local atmosphere–ocean positive feedback, and thus does not rely on remote forcing from the Pacific for its emergence. JSN is an important driver of climate variability over the tropical Indian Ocean and the surrounding continents. Notably, JS Niña events developing in July–September project onto the South and Southeast Asian summer monsoons, increasing the probability of heavy rainfall and flooding across the most heavily populated regions of the world.

Full access
Chidong Zhang
,
Gregory R. Foltz
,
Andy M. Chiodi
,
Calvin W. Mordy
,
Catherine R. Edwards
,
Christian Meinig
,
Dongxiao Zhang
,
Edoardo Mazza
,
Edward D. Cokelet
,
Eugene F. Burger
,
Francis Bringas
,
Gustavo J. Goni
,
Hristina G. Hristova
,
Hyun-Sook Kim
,
Joaquin A. Trinanes
,
Jun A. Zhang
,
Kathleen E. Bailey
,
Kevin M. O’Brien
,
Maria Morales-Caez
,
Noah Lawrence-Slavas
,
Richard Jenkins
,
Shuyi S. Chen
, and
Xingchao Chen

Abstract

On 30 September 2021, a saildrone uncrewed surface vehicle (USV) was steered into category 4 Hurricane Sam, the most intense storm of the 2021 Atlantic hurricane season. It measured significant wave heights up to 14 m (maximum wave height = 27 m) and near-surface winds exceeding 55 m s−1. This was the first time in more than seven decades of hurricane observations that in real time a USV transmitted scientific data, images, and videos of the dynamic ocean surface near a hurricane’s eyewall. The saildrone was part of a five-saildrone deployment of the NOAA 2021 Atlantic Hurricane Observations Mission. These saildrones observed the atmospheric and oceanic near-surface conditions of five other tropical storms, of which two became hurricanes. Such observations inside tropical cyclones help to advance the understanding and prediction of hurricanes, with the ultimate goal of saving lives and protecting property. The 2021 deployment pioneered a new practice of coordinating measurements by saildrones, underwater gliders, and airborne dropsondes to make simultaneous and near-collocated observations of the air–sea interface, the ocean immediately below, and the atmosphere immediately above. This experimental deployment opened the door to a new era of using remotely piloted uncrewed systems to observe one of the most extreme phenomena on Earth in a way previously impossible. This article provides an overview of this saildrone hurricane observations mission, describes how the saildrones were coordinated with other observing platforms, presents preliminary scientific results from these observations to demonstrate their potential utility and motivate further data analysis, and offers a vision of future hurricane observations using combined uncrewed platforms.

Open access