Assessing the Monthly Trends in Precipitable Water Vapor over the Indian Subcontinent

Abstract

This study estimates the trends in precipitable water vapor (PWV), atmospheric moisture budget (AMB), and the factors influencing them: air temperature, evapotranspiration (ET), convective available potential energy (CAPE), and vertical velocity (Omega) over the Indian subcontinent using ERA5 reanalysis data sets between 1980 and 2020. PWV is examined across three atmospheric layers (1000–850 hPa: lower layer; 850–500 hPa: middle layer; 500–300 hPa: upper layer), and the entire atmospheric column (EAC; 1000–300 hPa). The observed PWV trends exhibit variability within the EAC, ranging from −0.53 to 1.25 mm/decade across the study area, with the middle layer showing the most pronounced variation (–0.44 to 0.83 mm/decade), followed by the lower layer (0.10 to 0.45 mm/decade), and the upper layer (–0.02 to 0.23 mm/decade). These fluctuations in PWV are attributed to changes in air temperature, ET, CAPE, and Omega. This investigation, however, underscores the necessity of delving into the impacts of these influencing factors on PWV using finer resolution data, to enhance our comprehension of its spatial and temporal dynamics in the region. Furthermore, the annual AMB analysis reveals a declining trend in the study region. These findings collectively contribute to the understanding of regional water-energy cycles and the recent shifts in atmospheric dynamics.

本研究利用1980年至2020年的ERA5再分析数据集, 估算了印度次大陆可降水量(PWV)和大气水分平衡(AMB)的趋势, 并估算了它们的影响因子: 气温、蒸散量(ET)、对流有效位能(CAPE)和垂直速度(Omega)。PWV研究涉及三个大气层(1000–850 hPa: 下层, 850–500 hPa: 中层, 500–300 hPa: 上层)和整个大气柱(EAC, 1000–300 hPa)。PWV的趋势在EAC内具有可变性, 变化范围为每10年-0.53至1.25毫米, 中间层的变化最为明显(每10年-0.44至0.83毫米), 其次是下层(每10年0.10至0.45毫米)和上层(每10年-0.02至0.23毫米)。PWV的波动是由于空气温度、ET、CAPE和Omega的变化。本研究强调了采用更高分辨率数据深入研究这些PWV影响因子的必要性, 从而加强对该地区PWV时空动态的理解。此外, 年际AMB分析显示, 研究区内的AMB呈下降趋势。这些发现有助于理解区域水和能量循环、大气动力学的近期变化。

Este estudio calcula las tendencias del vapor de agua precipitable (PWV), el balance de la humedad atmosférica (AMB) y los factores que influyen sobre ellos: temperatura del aire, evapotranspiración (ET), energía potencial convectiva disponible (CAPE) y velocidad vertical (Omega), sobre el subcontinente indio, usando un conjunto de datos de reanálisis ERA5, entre 1980 y 2020. El PWV fue examinado en tres capas atmosféricas (1000–850 hPa: capa inferior; 850–500 hPa: capa intermedia; 500–300 hPa: capa superior) y toda la columna atmosférica (EAC; 1000–300 hPa). Las tendencias observadas en el PWV exhiben variabilidad dentro de EAC, que van desde –0,53 a 1,25 mm/década a través del área de estudio, con la capa intermedia mostrando la variación más pronunciada (–0,44 a 0,83 mm/década), seguida por la capa inferior (0,10 a 0,45, y la capa superior (–0,02 a 0,23 mm/década). Estas fluctuaciones del PWV se atribuyen a cambios en la temperatura del aire, de ET, CAPE y Omega. Sin embargo, esta investigación subraya la necesidad de ahondar en los impactos de estos factores influyentes sobre el PWV usando datos de resolución más fina para mejorar nuestra comprensión de su dinámica espacial y temporal en la región. Además, el análisis anual del AMB pone de manifiesto su tendencia decreciente en la región estudiada. Estos descubrimientos contribuyen colectivamente a la comprensión de los ciclos hidro-energéticos regionales y de los cambios recientes en la dinámica atmosférica.

Key Words:

• climate change
• Indian subcontinent
• precipitable water vapor
• sustainability

关键词:

• 气候变化
• 印度次大陆
• 可降水量
• 可持续性

Palabras clave:

• cambio climático
• subcontinente indio
• sustentabilidad
• vapor de agua precipitable

Acknowledgments

The authors are grateful to the Copernicus Climate Change Service (C3S) team for making ERA5 reanalysis data accessible to the researchers. The authors are thankful to the anonymous reviewers for their invaluable comments and suggestions that have greatly enhanced the quality of this work. The data for this study are available from the European Center for Medium-Range Weather Forecasts (https://www.ecmwf.int and http://climate.copernicus.eu/climate-reanalysis).

Disclosure Statement

No potential conflict of interest was reported by the authors.

Funding

Seema Rani is grateful to the Banaras Hindu University, Varanasi, Uttar Pradesh, India, for providing a seed grant (No.R/Dev/D/IoE/Equipment/Seed Grant-II/2022-23/62810) for this work under the Institute of Eminence (IoE).

Supplemental Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/24694452.2023.2294899

Additional information

Notes on contributors

Seema Rani

SEEMA RANI is an Assistant Professor in the Department of Geography, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India. E-mail: [email protected]. Her research interests include climate change impacts on river hydrology and land surface dynamics.

Pyarimohan Maharana

PYARIMOHAN MAHARANA is an Assistant Professor in the Department of Environmental Studies, Delhi College of Arts and Commerce, University of Delhi, New Delhi, India. E-mail: [email protected]. He held the position of Teaching Fellow at the School of Ecology and Environment Studies, Nalanda University, Rajgir, Bihar, India during the development of this research. His research interests include monsoon variability, climate change, and climate extremes using various observation and climate models.

Suraj Mal

SURAJ MAL is an Associate Professor in the Center for the Study of Regional Development, Jawaharlal Nehru University, New Delhi, Delhi, India. E-mail: [email protected]. He held the position of Professor in the Department of Geography, Shaheed Bhagat Singh College, University of Delhi, New Delhi, India during the development of this research. His research interests include linkages between climate change, cryosphere, extreme events, and disaster risk reduction, particularly in the Himalayas.