Mona Zarghamipour

Mona Zarghamipour

Ph.D. in Meteorology

Research Background

Ph.D.

Relevant Courses: Air Pollution; Boundary-Layer Meteorology; Physical Climatology; Atmospheric Radiation; General Atmospheric Circulation; Climate Change

Ph.D. Research Overview

Socio-economic growth and increasing global energy demand have promoted the exploitation and use of fossil fuels in many West Asian countries, leading to increased emissions of short-lived (NO2 and SO2) and long-lived (CO2) pollutants. The emission of these pollutants is a major concern for air quality, climate change, and human and environmental health. Natural ecosystems play an important role in absorbing atmospheric pollutants.

Anthropogenic CO2 greenhouse gas emissions in the West Asian region have increased dramatically since the 1980s and have become the most dominant greenhouse gas in the atmosphere. Oceans and terrestrial ecosystems act as significant sinks of atmospheric CO2. Anthropogenic greenhouse gas emissions are reshaping oceanic CO2 uptake patterns. My study focused on the crucial regions of the Arabian Sea, Red Sea, and Mediterranean Sea which are highly affected by human-caused climate change, aiming to unravel the complexities of air-sea CO2 exchange dynamics. Understanding these processes is essential for predicting climate changes and assessing the health of marine ecosystems. In this context, a combination of observation-based data (Oc_v2020), and a multi-model ensemble of climate model simulations, were employed to explore the spatial and temporal variations in air-sea CO2 flux (FCO2) over these areas from 1982 to 2019. We implemented the Bayesian Model Averaging approach on the model outputs, resulting in a better representation of simulated CO2 flux. Overall, climate models seem to underestimate the FCO2 over the western Arabian Sea. We speculate that this model failure is attributed to the negative bias in vertical water velocity and the unrealistic representation of carbon release during coastal upwelling processes in the model. Our findings suggest that CO2 source across the Red Sea, the Arabian Sea, and the central region of the Mediterranean Sea has been reduced with a trend of −0.494 ± 0.009, −1.350 ± 0.001, and −0.329 ± 0.074 gCm-2 year-1 decade-1 respectively. In contrast, the CO2 sink across the Western Mediterranean has been enhanced with a trend of −0.793 ± 0.086 gCm-2 year-1 decade-1. In general, change in the water temperature was recognized as the major contributor to the sea surface partial pressure of CO2 (pCO2). The exception was found in the Arabian Sea, where non-thermal effects play a major role. Our results show that the CO2 flux variation is accompanied by regional changes in the sea surface pCO2. Across the North Arabian Sea, FCO2 is also correlated to the surface wind variability, which is likely due to the changes in wind-driven upwelling. In conclusion, our study advances the understanding of regional air-sea CO2 exchange dynamics, emphasizing the need for improved model representation in areas with intense seasonal upwelling. The prominent changes in the Arabian Sea, underscore the immediate necessity for science-based management in this region to mitigate the impacts of human-induced global warming. Link

The terrestrial ecosystem also plays an important role in the carbon cycle and each year absorbs more than a quarter of human carbon emissions, which is called terrestrial carbon sinks. In the last few decades, carbon sources and sinks in West Asia and around the Mediterranean Sea have changed due to drastic changes in land cover due to economic development and urbanization growth. In my Ph.D. study, using the observations-based CO2 flux data of Jena CarboScope Institute, temperature and precipitation data, the seasonal and annual pattern of CO2 exchanges during the period 1982-2019, were investigated, as well as the role of teleconnection patterns on the CO2 flux fluctuations was analyzed. The results showed that on a long-term average, the land areas of the northern Mediterranean Sea were CO2 sinks with absorption up to -114 g C m-2 year-1) and the amount of CO2 absorption in these areas decreased with a trend of up to 5 g C m-2 year-1 decade-1) during the study period. While the CO2 sinks in the western parts of India (up to -70 g C m-2 year-1) increased with the trend of up to -8 g C m-2 year-1 decade-1. Also, the central regions (including Iran, Saudi Arabia, and the northern parts of Africa), the northeast (including Afghanistan, Turkmenistan, and Tajikistan), and the southwest (including the central regions of Africa) of the study area, which were the CO2 sources on average (between 0 to 50 g C m-2 year-1), the intensity of CO2 emissions has been reduced with a trend of up to -10 g C m-2 year-1 decade-1). Based on the results, in the land areas of the northern Mediterranean Sea, Turkmenistan, Tajikistan, and the coastal areas of the Caspian Sea in Iran (western parts of India, western Iran, and central Africa) in the study area, seasonal temperature changes (precipitation) played a more important role in the seasonal cycle of CO2 exchanges between the atmosphere and the terrestrial ecosystem. The positive correlation between the MEI.v2 index related to El Niño/Southern Oscillation (ENSO) and the variability of the atmosphere-land CO2 flux showed that in El Niño conditions (positive and warm phase of ENSO) the amount of CO2 absorption and sink in the land areas of the northern Mediterranean Sea and West India, Southeast Iran and Pakistan decreased, which can be due to the decrease in rainfall in El Niño conditions in these areas. In La Niño conditions (negative and cold phase of ENSO) in these areas, the amount of CO2 absorption increased and the sinks became stronger. The negative correlation of atmospheric-land CO2 flux variability with both El Niño/Southern Oscillation and Indian Ocean Dipole Oscillation showed that in El Niño and positive IOD conditions, CO2 emission decreased in the western and central parts of Africa in the study area, while in La Niño and negative IOD conditions, CO2 emission increased in these regions. Also, in the positive phase of IOD, the CO2 sink in the eastern part of Iran, Afghanistan, Turkmenistan, Tajikistan, the southeastern regions of Iran, southern Pakistan, and western parts of India became weaker, and in the negative phase of IOD, the amount of CO2 absorption in these areas increased. Link

In addition to CO2, which has seen significant growth in this region, short-lived gases such as NO2 and SO2 have the highest human emissions in West Asia. In this area, natural resources are a minor part of these pollutants and the majority of emissions come from fossil fuel combustion. Nitrogen and sulfur oxides released from fossil fuels and other combustion processes affect air quality and climate. Dry deposition is a natural process that plays an important role in controlling the concentration of these pollutants. Nitrogen and sulfur deposition can damage the ecosystem. We examined the dry deposition of NO2 and SO2 in the West Asia region in January and July from 2020 to 2022 using the Weather Research and Forecasting with Chemistry (WRF-Chem) model. “This part of my research has not yet been published in a peer-reviewed journal. I am currently awaiting acceptance from a journal, and once the results are officially published, they will be updated and detailed here ”

Tehran, the capital of Iran, experiences high levels of pollution, particularly during the cold seasons. Recent studies have shown an increase in the concentration of nitrogen compounds in Tehran. However, the role of advection, deposition, vertical diffusion processes and chemical conversion of NOx in this region requires further investigation. In my study, The Weather Research and Forecasting model with Chemistry (WRF-Chem) was employed to numerically simulate each of these processes during a severe pollution episode in winter from November 28, 2021, to December 8, 2021. During this high pollution episode, the weather conditions were calm, and based on the Air Quality Index (AQI), the air quality was unhealthy for sensitive groups. The presence of a ridge at the 500 hPa level, the placement of a low-level high-pressure cell over the region, and consequently, atmospheric subsidence and low wind speed create favorable conditions for severe pollution events in Tehran. Additionally, temperature inversion during the night and a decrease in the boundary layer height contribute to increased surface NOx concentration during this period. When comparing different processes influencing NOx concentrations, it has been observed that advection has the most significant impact, while dry deposition and chemical conversion have the least effect. On stable days advection increases NOx concentration in the central and northeast of Tehran urban area during the daytime. The maximum vertical diffusion is observed in the southern and western regions, corresponding to the emission pattern of NO and NO2. The examination of the vertical profile of advection and vertical diffusion shows that vertical diffusion dominates near the surface layer, while advection dominates at higher altitudes in terms of NOx concentration changes. Under unstable conditions (Dec-02), with the arrival of the cold front and the influence of convective clouds, the impact of convective transport becomes more pronounced in reducing NOx concentrations in the southern and central regions of Tehran’s urban area. The highest NOx deposition is observed in the early morning in the southern and southwestern suburban areas of Tehran, correlating with wind direction variations, NOx concentration, and vegetation coverage. The results indicate that nearly 98% of the total NOy deposition (dry and wet deposition of NO, NO2, HNO3, and NO3) in Tehran’s urban and suburban areas is attributed to dry deposition of NO2. Link

Master

Relevant Courses: Programming and Numerical Methods; Advanced Atmospheric Dynamics; Advanced Synoptic Meteorology; Atmospheric Physics; Microphysical Meteorology; Numerical Modeling of Atmosphere and Ocean; Remote Sensing in Meteorology; Time Series and Spectral Analysis; Physical Oceanography; Atmospheric and Oceanic Modeling Laboratory

Master thesis overview

Since the importance of wind patterns on various activities in islands as well as its effect on other meteorological parameters, long–term temporal and spatial variations of the wind field are studied. Then, the warmest month (July) and the coldest month (January) 2015, are selected for sensitivity conduction of low-level wind simulations of the Weather Research and Forecasting (WRF) model to the parameterization of the boundary layer (PBL), the surface layer (SL) and the land surface (LSM) over Qeshm Island. Since this work was focused on the simulation of near-surface and vertical wind profiles, the physical options related to the parameterizations of boundary layer processes (SL, PBL, and LSM) that have significant influence for this purpose are validated. Although more physical options are available in the model (for cumulus convection, short and long wave radiation, microphysics, etc.), it is not feasible or necessary to include all the model configuration options in the sensitivity analysis to obtain an efficient model configuration optimization. The model grid comprised four nested domains at horizontal resolutions of 45, 15, 5, and 1 km respectively. The innermost domain (D4) with 1 km spatial resolution covered the chosen area to simulate the PBL wind field over the Qeshm island region. The results of the simulations under five different configurations are validated with the observational wind speed of Qeshm Airport and Marine Qeshm Stations. The results demonstrate that in both episodes, the ACM2 boundary layer scheme has presented the best performance in combination with the Pleim - Xio surface layer and the Noah land surface because it considers vertical mixing both local and non-local in the simulation of planetary boundary layer wind structure. The simulations of WRF are sensitive to warm and cold seasons as well as selected parameterizations. After selecting the appropriate configuration, the simulation of the wind field for one year was carried out to investigate the low-level wind field, the vertical structure of the boundary layer wind, and the impact of the land mask distribution on and around Qeshm Island. These simulations indicate higher wind speed in spring and summer and the roughness of the island causes a low-level wind convergence, then turn to the left on the Strait of Hormuz and decreasing wind speed. The monthly average of the wind direction during the daytime of the reference month of each season is generally simulated southwest (January, April, July, October), and during the nights of January and July is south to southeast and in April and October is simulated southwesterly. The direction of the wind has significant variations at sunrise and sunset due to changes in regional scale forcing and baroclinicity behavior between the sea and the coast. Surface roughness in coastal areas, strait narrowing, and sea breeze enhance the low-level jet during summer and spring middays at altitudes of about 180 to 200 meters. In other words, we can say these low-level jet (Shamal winds) during summer and spring occur as a result of the interaction of two low-pressure systems; the heat low-pressure cell (low-level cyclone) over Iran and a semi-permanent high over northwestern Saudi Arabia and it gets some convergence because of the above reasons. A weighted overlay analysis in ArcGIS 10.2 was used to produce a map of the suitable areas for wind farms using land use data, power grid lines, road networks, and slopes. Link