Empirical orthogonal function analysis of lightning flashes over India

IF 1.8 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Journal of Atmospheric and Solar-Terrestrial Physics Pub Date : 2024-07-20 DOI:10.1016/j.jastp.2024.106311

Konatham Prasanna, V. Gopalakrishnan, Rupraj Biswasharma Ph. D, S.D. Pawar

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Abstract

Lightning studies are highly focused on spatial and temporal variability in various scales but very limited studies are focused on dominant spatial modes of variability. This study intends to identify the possible spatial modes of climate variability of lightning over India during different seasons and relate them to regional and large-scale climate modes. Empirical orthogonal function analysis of lightning has been carried out and the first three orthogonally independent modes are considered in order to retrieve the maximum variance explained by each mode. To understand the role of remote and local teleconnections on the lightning flash rate (LFR) variability, we have analyzed two Pacific Ocean modes (El Niño Southern Oscillation; ENSO, Pacific Decadal Oscillation; PDO) and two Indian Ocean modes (Indian Ocean Dipole; IOD and Bay of Bengal (BOB) meridional Sea Surface Temperature (SST) gradient). First mode is positively correlated with the warm phase of ENSO and PDO whereas second and third modes are negatively correlated with the warm phase of ENSO and PDO during pre-monsoon, post-monsoon and winter. Reverse is true for the monsoon season due to the shift in walker cell caused by the changes in the location of the heat sources and sinks. A strong positive correlation of IOD and BOB meridional SST gradient with first mode, suggests the vital role of nearby Indian Ocean in explaining the typical lightning flashes over India due to the enhanced zonal and meridional circulation, thereby moisture supply to the Indian subcontinent. The impact of Nino-3.4, IOD and BOB meridional SST gradient on lightning over India further suggest the role of SST in local and remote influence on lightning variability through the distribution and transport of heat and moisture.

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印度上空闪电的经验正交函数分析

闪电研究高度集中于各种尺度的空间和时间变异性，但对主要空间变异模式的研究却非常有限。本研究旨在确定印度不同季节闪电气候变异的可能空间模式，并将其与区域和大尺度气候模式联系起来。对闪电进行了经验正交函数分析，并考虑了前三个正交独立模式，以检索每个模式所解释的最大方差。为了了解远程和本地远缘联系对闪电闪烁率变化的作用，我们分析了两种太平洋模式（厄尔尼诺南方涛动、太平洋十年涛动）和两种印度洋模式（印度洋偶极子和孟加拉湾经向海面温度梯度）。在季风前、季风后和冬季，第一模式与厄尔尼诺/南方涛动和 PDO 的暖相呈正相关，而第二和第三模式与厄尔尼诺/南方涛动和 PDO 的暖相呈负相关。季风季节的情况正好相反，这是因为热源和热汇位置的变化导致了沃克单元的移动。IOD和BOB经向海温梯度与第一模式的强正相关性表明，由于带状和经向环流增强，印度次大陆的水汽供应增加，附近的印度洋在解释印度上空典型的闪电现象方面发挥了重要作用。尼诺-3.4、IOD 和 BOB 经向海温梯度对印度上空闪电的影响进一步表明，海温通过热量和水汽的分布和输送对闪电变异产生局部和远程影响。

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来源期刊

Journal of Atmospheric and Solar-Terrestrial Physics 地学-地球化学与地球物理

CiteScore

4.10

自引率

5.30%

发文量

审稿时长

6 months

期刊介绍： The Journal of Atmospheric and Solar-Terrestrial Physics (JASTP) is an international journal concerned with the inter-disciplinary science of the Earth''s atmospheric and space environment, especially the highly varied and highly variable physical phenomena that occur in this natural laboratory and the processes that couple them. The journal covers the physical processes operating in the troposphere, stratosphere, mesosphere, thermosphere, ionosphere, magnetosphere, the Sun, interplanetary medium, and heliosphere. Phenomena occurring in other "spheres", solar influences on climate, and supporting laboratory measurements are also considered. The journal deals especially with the coupling between the different regions. Solar flares, coronal mass ejections, and other energetic events on the Sun create interesting and important perturbations in the near-Earth space environment. The physics of such "space weather" is central to the Journal of Atmospheric and Solar-Terrestrial Physics and the journal welcomes papers that lead in the direction of a predictive understanding of the coupled system. Regarding the upper atmosphere, the subjects of aeronomy, geomagnetism and geoelectricity, auroral phenomena, radio wave propagation, and plasma instabilities, are examples within the broad field of solar-terrestrial physics which emphasise the energy exchange between the solar wind, the magnetospheric and ionospheric plasmas, and the neutral gas. In the lower atmosphere, topics covered range from mesoscale to global scale dynamics, to atmospheric electricity, lightning and its effects, and to anthropogenic changes.