Abstract

In this study, we investigated the effects of the Tibetan High near the tropopause and the North Pacific High in the troposphere on occurrences of hot or cool summers in Japan. We first classified Japan into six regions and identified hot and cool summer years in these regions from a 38-year sample (1980–2017) based on the monthly air temperature. To investigate the features of circulation fields over Asia during hot and cool summers in Japan, we calculated the composite differences (hot summer years minus cool summer years) of several variables such as geopotential height, which indicated significant high-pressure anomalies in the troposphere and lower stratosphere. These results suggest that both the North Pacific and the Tibetan Highs tend to extend to Japan during hot summer years, while cool summers seem to be associated with the weakening of these highs. We found that extension of the Tibetan High to the Japanese mainland can lead to hot summers in Northern, Eastern, and Western Japan. On the other hand, hot summers in the Southwestern Islands may be due to extension of the Tibetan High to the south. Similarly, the latitudinal direction of extension of the North Pacific High is profoundly connected with the summer climate in respective regions.

Highlights

  • Meteorological disasters, including drought, a cool summer, or heavy rain, have a serious effect on crop yields in Japan

  • 10 hottest years were defined as hot summer years, and 10 coolest years were defined as cool summer years based on the surface temperature data during the studied period

  • At 150 hPa in the tropopause, we find the center of the Tibetan

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Summary

Introduction

Meteorological disasters, including drought, a cool summer, or heavy rain, have a serious effect on crop yields in Japan. This high is a warm, gigantic, anti-cyclonic circulation and covers East Asia from the upper troposphere to the lower stratosphere [12,13,14], and greatly influences the summer climate in East Asia [15]. This is characterized by a high-pressure system over the Tibetan Plateau, which is called the South Asian. We clarify the influences of the Tibetan High and North Pacific High on the occurrence of drought and cool summers in Japan by statistical analyses of the atmospheric circulation fields during a.

Surface air Temperature data and Definitions of Hot and Cool Summer Years
Reanalysis Data for Composite Maps and Analysis Procedure
North Pacific Subtropical High and Tibetan High
Extension of the Tibetan High in Hot or Cool Summer Years
Extension
Relationships between the Extension of Two Highs and Occurrences of Hot o
Summary
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