Development of an Objective Scheme to Estimate Tropical Cyclone Intensity from Digital Geostationary Satellite Infrared Imagery

Abstract

The standard method for estimating the intensity of tropical cyclones is based on satellite observations (Dvorak technique) and is utilized operationally by tropical analysis centers around the world. The technique relies on image pattern recognition along with analyst interpretation of empirically based rules regarding the vigor and organization of convection surrounding the storm center. While this method performs well enough in most cases to be employed operationally, there are situations when analyst judgment can lead to discrepancies between different analysis centers estimating the same storm.In an attempt to eliminate this subjectivity, a computer-based algorithm that operates objectively on digital infrared information has been developed. An original version of this algorithm (engineered primarily by the third author) has been significantly modified and advanced to include selected ''Dvorak rules,'' additional constraints, and a time-averaging scheme. This modified version, the Objective Dvorak Technique (ODT), is applicable to tropical cyclones that have attained tropical storm or hurricane strength.The performance of the ODT is evaluated on cases from the 1995 and 1996 Atlantic hurricane seasons. Reconnaissance aircraft measurements of minimum surface pressure are used to validate the satellite-based estimates. Statistical analysis indicates the technique to be competitive with, and in some cases superior to, the Dvorak-based intensity estimates produced operationally by satellite analysts from tropical analysis centers. Further analysis reveals situations where the algorithm needs improvement, and directions for future research and modifications are suggested.

A Pronounced Bias in Tropical Cyclone Minimum Sea Level Pressure Estimation Based on the Dvorak Technique

“…The latitude-dependent bias is a product of the relationship between tropopause temperature and latitude, and since this relationship is fairly consistent in all other ocean basins (except the northern Indian Ocean), it is likely that a very similar bias exists in TC MSLP estimates from the east, west, and South Pacific Ocean, and the southern Indian Ocean. In addition, methods such as the Objective Dvorak Technique (ODT; Velden et al 1998) that imitate the IRmeasured temperature relationships of the Dvorak technique should also benefit from a similar bias correction.…”

Southern hemisphere tropical cyclone intensity forecast methods used at the Joint Typhoon Warning Center, Part II: statistical-dynamical forecasts

“…Because routine aircraft reconnaissance has never been available in this region, one caveat concerning the best track intensities is that they are determined solely from satellite-based methods (e.g., Dvorak 1984;Demuth et al 2006Demuth et al , 2004Olander et al 2007;Velden et al 1998) the majority of the time. The actual errors associated with the use of satellite intensity estimation methods have been quantified in Olander et al (2007), Velden et al (1998) and Demuth et al (2006). Those results, which show all of the satellite techniques are capable of capturing intensification trends, give some confidence in the operational and best track intensity estimates.…”

A Multiple Linear Regression Model for Tropical Cyclone Intensity Estimation from Satellite Infrared Images

“…Several revisions of the DT technique were developed during the later decades. The Objective Dvorak Technique (ODT) [15] The region of interest in this paper covers the NWP basin from 5˝to 45˝N and from 100˝to 165˝E (Figure 1). The inputs include digital brightness temperatures (BTs) of the IR (10.3-11.3 um) and water vapor (WV, 6.5-7.0 um) channel images with spatial and temporal resolution of 8 km and 3 h, respectively.…”