Meteorological impacts of sea-surface temperature associated with the humid airflow from Tropical Cyclone Talas (2011)

M Yamamoto

doi:10.5194/angeo-32-841-2014

Abstract

Abstract. This paper examines meteorological impacts of sea-surface temperature (SST) in the presence of the humid airflow from Tropical Cyclone Talas (2011). To investigate the influence of the SST on the severe weather in and around Japan, sensitivity simulations were conducted using six SST data products covering a period of 7 days. The upward sea-surface latent heat flux that accumulated over the 7-day period was high around the Kuroshio during the slow passage of the tropical cyclone. Large differences were found among the individual SST products around the southern coast of Japan. The coastal warm SST anomaly of ~ 1.5 °C enhanced the surface upward latent heat fluxes (by 60 to 80%), surface southeasterly winds (by 6 to 8%), and surface water mixing ratios (by 4%) over the coastal sea area. The enhanced latent heat flux resulting from the coastal SST anomaly contributed to the further enhancement of the latent heat flux itself via a positive feedback with the amplified surface horizontal wind. The SST anomalies produced an anomaly in 7-day precipitation (ca. 40 mm) along the mountainsides and over a coastal area where the surface wind anomaly was locally large. Thus, coastal SST error is important in the atmospheric simulation of accumulated evaporation and precipitation associated with tropical cyclones making landfall.

Highlights

Tropical Cyclone Talas brought heavy rain and severe winds to Japan in September 2011, and caused many deaths and severe damage
The concentric circles of the 500 hPa height contours were broken at 00:00 UTC, 4 September, before the tropical cyclone was downgraded to an extratropical cyclone
This paper investigated the influences of the weekly sea-surface temperature (SST) anomaly on 7-day accumulated coastal meteorological elements in the presence of the humid airflow from the Tropical Cyclone Talas (2011)

Summary

Introduction

Tropical Cyclone Talas brought heavy rain and severe winds to Japan in September 2011, and caused many deaths and severe damage. More than 1000 mm of precipitation accumulated between 30 August and 6 September on the Kii Peninsula (around 34◦ N, 136◦ E), with 2000 mm being recorded in some areas This extremely large accumulation of rainfall caused landslides and floods. Because low-frequency microwave observations produce low-resolution data, such observations cannot provide SST information along the coasts of marginal seas. Interpolated SST (OISST) data are widely applied to lowerboundary conditions in weather simulations. This interpolation smoothes out the high-resolution SST structures resulting from oceanic mesoscale eddies. 3. Because accumulation of precipitation amounts is an important factor in hazard risk management for tropical cyclones, the meteorological impacts of the SST anomalies on the 7-day accumulated precipitation and seasurface fluxes are investigated in Sect.

Data and model

Results

Seven-day mean and accumulated structures

Meteorological impacts of the weekly SST anomaly

Time evolutions of meteorological influences of the coastal SST anomaly

Concluding remarks