A Numerical Experiment on Sea Surface Temperature Anomalies and Warm Winter in Japan

Abstract

Impact of the sea surface temperature anomalies (SSTAs) on atmospheric circulations are studied with emphasis on the winter climate in Japan with the use of an atmospheric general circulation model.The empirical orthogonal function analyses are performed for precipitation, geopotential height at 500mb and surface air temperature. It is shown that leading eigenvectors of precipitation are zonally elongated in the tropics and that the distribution of positive and negative precipitation anomalies is dependent on the SST and precipitation field in the control run. Surface air temperature in East Asia is mostly governed by the temperature contrast between Japan-East China region and the Sea of Okhotsk. This is associated with high pressure anomalies in the North Pacific Ocean, which weakens the cold surge from Siberia. This circulation is found in the first eigenvector in the present experiment El(Z500) and is dominant in the run which uses the composited January SSTA observed during warm winter in Japan. The simulated anomalies in mid-latitude circulation correspond well with the observations.An additional run with the SSTA over the equator east of the dateline gives the largest anticyclonic circulation response over the North Pacific Ocean and the warmest surface air temperature anomalies in East Asia. The pattern relevant to warm winter in Japan is not a simple atmospheric response to tropical heating. It is conceivable that inherently there is a dominant circulation mode like El(Z500) and that this mode can be activated either by a direct and/or an indirect orographic effect or by anomalous heating induced by the SSTA.This pattern can be understood as a response to subtropical mass source/sink distribution under the framework of a linear theory.

Consideration of the Origin of the Different Midlatitude Atmospheric Responses among El Niño Events

“…2d). So it may be possible that higher SSTs over the central equatorial Pacific region can produce more WP-type circulations in the extratropics (Kitoh, 1988a). However, when compared with Fig.…”

Correlation between the Surface Air Temperature over Japan and the Global Sea Surface Temperature

“…Orography as well as SST anomalies must play an important role in such a zonal/eddy relationship. Kitoh (1988) performed ten 180-day runs with the MRI•GCM under perpetual January conditions and obtained a circulation pattern relevant to a warm winter in Japan for run AW (the composited SST when Japan experienced warm winters) or for run A7 (positive SSTA over the equator east of the dateline), but not for run AS (very close to A7, but positive SSTA south of the equator on the dateline).…”

“…The winter climate in Japan tends to be mild during El Nino years, but there have been exceptions, such as the 1976/77 winter. Kitoh (1988) performed a GCM experiment to study the impact of SST anomalies on the resulting atmospheric circulation with emphasis on the winter climate in Japan. His results produced a northern mid-latitude circulation pattern which was closely related to the winter temperature in Japan and showed a possible role of the equatorial SST anomaly east of the dateline in inducing such a circulation pattern.…”

Relationship between Sea-Water Temperature in the Tropics and Winter Weather over Japan

“…(2) Sea-surface temperature (SST) Monthly-mean SST, which is digitized on 2°*2° latitude-longitude grids over the whole globe, was obtained from the Climate Analysis Center (CAC) during 1970-1984and the Oceanographical Division in JMA during 1985-1988 (3) Sea-water temperature along 137°E…”

“…In East Asia, there exist three types of temperature anomaly distributions according to the fluctuation of a blocking ridge in the northeastern Pacific. Kitoh (1988) indicated that a positive SST anomaly over the equator east of the dateline gives the largest anticyclonic circulation response over the North Pacific Ocean and the warmest surface-air temperature anomalies in East Asia in winter. Iwasaka et al (1988) divided the North Pacific Ocean into four subdomains on the basis of similarity in temporal variations of the SST anomaly and showed the simultaneous relationship between winter monsoon strength and the SST of the subdomain around Japan.…”