热带印度洋赤道辐合带的季节和年际变化特征

Seasonal and Interannual Variation Characteristics of the Tropical Indian Ocean’s Intertropical Convergence Zone

摘要: 赤道辐合带(ITCZ)是一个靠近赤道的行星尺度强降水带，同时也是哈德莱(Hadley)环流圈的上升中心。为了研究长期不同时间尺度上热带印度洋赤道辐合带的位置、强度和宽度的长期变化特征，本文利用了1979年至2017年的逐月降水观测资料定义并计算出赤道辐合带及其位置、强度和宽度，分析了其季节和年际变化特征。结果表明：1) 赤道辐合带是南北半球之间气流辐合、气压最低的地区，是热带气候系统的重要组成部分。它的位置和强度的变化会影响热带印度洋降水区域、强度和大气环流状况。2) 印度洋赤道辐合带中心位置的移动具有明显的季节和年际变化特征，夏季位于赤道以北，冬季位于赤道以南，春秋季则位于赤道附近地区；而夏季ITCZ的中心位置常年位于北纬13˚，东经73˚附近。3) 赤道辐合带的宽度常年南北跨越大约20个纬度，但南北界波动幅度不大，近年来宽度都有较弱的变窄。4) 降水量的中心强度可表示赤道辐合带的强弱，它的最大中心强度值随时间变化波动明显，2000年前后的最大中心强度存在明显地由平均高值向平均低值的转变，而近年来强度逐渐变强。5) 印度洋和太平洋、大西洋上的赤道辐合带存在一定的区别和联系，在印度洋和大西洋上赤道辐合带都是呈散点式分布，而在太平洋上却呈东西带状分布。

Abstract: The Intertropical Convergence Zone (ITCZ) is a belt of planetary-scale heavy rainfall near the equator and the ascending center of the Hadley Circulation. In order to study the longterm variation characteristics of the position, intensity and width of the tropical Indian Ocean Equatorial Convergence Zone on different time scales over a long period of time, this paper uses monthly precipitation observations from 1979 to 2017 to calculate the ITCZ and its position, intensity and width, and analyzes its seasonal and interannual variation characteristics. The results showed that: 1) The equatorial convergence zone is the region with the lowest air pressure between the northern and southern hemispheres, and it is an important part of the tropical climate system. Changes in its location and intensity will affect rainfall area, intensity and atmospheric circulation in the tropical Indian Ocean. 2) The central location of the Indian Ocean Equatorial Convergence Zone has obvious seasonal and interannual characteristics, with summer located north of the equator, winter located south of the equator, and spring and autumn located near the equator. In summer; the center of ITCZ is located at 13˚N and 73˚E throughout the year. 3) The width of the equatorial convergence zone spans about 20 latitudes from north to south throughout the year, but the fluctuation range between the north and south is not large, and in recent years, the width of the equatorial convergence zone has narrowed slightly. 4) The central intensity of precipitation can indicate the strength of the equatorial convergence zone. The value of the maximum central intensity fluctuates obviously with time. The maximum central intensity of precipitation around 2000 has an obvious change from the average high value to the average low value, but in recent years, the intensity has gradually become stronger. 5) Equatorial convergence zones in the Indian Ocean, the Pacific Ocean and the Atlantic Ocean have certain differences and connections; the equatorial convergence zones in the Indian Ocean and the Atlantic Ocean have scattered distribution, but in the Pacific Ocean it is an eastwest belt distribution.