Impact of Assimilating Underwater Glider Data on Hurricane Gonzalo (2014) Forecasts

Abstract

The initialization of ocean conditions is essential to coupled tropical cyclone (TC) forecasts. This study investigates the impact of ocean observation assimilation, particularly underwater glider data, on high-resolution coupled TC forecasts. Using the coupled Hurricane Weather Research and Forecasting (HWRF) Model–Hybrid Coordinate Ocean Model (HYCOM) system, numerical experiments are performed by assimilating underwater glider observations alone and with other standard ocean observations for the forecast of Hurricane Gonzalo (2014). The glider observations are able to provide valuable information on subsurface ocean thermal and saline structure, even with their limited spatial coverage along the storm track and the relatively small amount of data assimilated. Through the assimilation of underwater glider observations, the prestorm thermal and saline structures of initial upper-ocean conditions are significantly improved near the location of glider observations, though the impact is localized because of the limited coverage of glider data. The ocean initial conditions are best represented when both the standard ocean observations and the underwater glider data are assimilated together. The barrier layer and the associated sharp density gradient in the upper ocean are successfully represented in the ocean initial conditions only with the use of underwater glider observations. The upper-ocean temperature and salinity forecasts in the first 48 h are improved by assimilating both underwater glider and standard ocean observations. The assimilation of glider observations alone does not make a large impact on the intensity forecast due to their limited coverage along the storm track. The 126-h intensity forecast of Hurricane Gonzalo is improved moderately through assimilating both underwater glider data and standard ocean observations.

Autonomous and Lagrangian Ocean Observations for Atlantic Tropical Cyclone Studies and Forecasts

“…Assimilation of ALPS measurements reduces the upper-ocean thermal bias and corrects errors in the representation of mesoscale features in the initial oceanic fields. Dong et al (2017) demonstrate the positive impact of assimilating oceanic observations on ocean model initialization and TC intensity forecasts. ALPS are also important for evaluating ocean model performance, devising strategies to improve their performance, ABSTRACT.…”

“…The presence of this barrier layer may have favored the storm's intensification, as Gonzalo continued intensifying into a Category-4 hurricane . Observations collected by the glider before (July 15 to October 13, 2015), during, and after the passage of Gonzalo were assimilated into the high-resolution Hurricane Weather Research and Forecasting (HWRF)-Hybrid Coordinate Ocean Model (HYCOM) coupled forecast system (Dong et al, 2017). Results indicated that assimilation of the underwater glider observations significantly improved the pre-storm thermal and saline model initializations, in particular, the barrier layer (Figure 6b).…”

“…A recent study by Dong et al (2017) assessed the impact of underwater glider data and other in situ and satellite observations on the forecast of Hurricane Gonzalo (2014). This hurricane developed in the tropical North Atlantic on October 12, 2014, and then traveled ~85 km northeast of one glider deployed north of Puerto Rico by AOML and CARICOOS.…”

Ocean Observations in Support of Studies and Forecasts of Tropical and Extratropical Cyclones

“…Clearly, ocean observations are vital in ECs and TCs research and forecasts, since they enable examining the details of air-sea interaction processes that can lead to the formation and intensification of these systems (e.g., Leipper and Volgenau, 1972;Sanders and Gyakum, 1980;Mainelli et al, 2008;Kuwano-Yoshida and Minobe, 2017). In addition, ocean observations have been increasingly acknowledged by the forecast community as a critical piece to improve extreme weather forecasts (e.g., Dong et al, 2017). Their important role will likely continue to increase in light of improvements in coupled model capabilities (see below), and future extreme weather projections, which expects intense weather systems to become more frequent (e.g., Colle et al, 2015;Bacmeister et al, 2018).…”

Improved Tropical Cyclone Intensity Forecasts by Assimilating Coastal Surface Currents in an Idealized Study

“…The upper ocean is influenced by TCs (e.g., Price, 1981Price, , 1983Price et al, 1994), and the feedback affects the TC development (e.g., Bruneau et al, 2018;D'Asaro et al, 2007;Halliwell et al, 2015;Schade & Emanuel, 1999). Thus, oceanic observations have been assimilated in the TC forecast systems, including both in situ (e.g., Dong et al, 2017;Goni et al, 2017) and satellite (e.g., Halliwell, Mehari, Shay et al, 2017) observations. However, the spatial coverage of in situ observations is quite limited, especially in the coastal regions, and the satellite observations can be infrequent, impacted by clouds, and are of coarse resolution.…”