Hossein Mousavi

Large lakes face considerable challenges due to human activities and climate change, impacting local weather conditions and ecosystem sustainability. Lake Urmia, Iran’s largest lake and the world’s second-largest saltwater lake, has undergone a substantial reduction in water levels, primarily due to drought, climate change, and excessive irrigation. This study focuses on the potential repercussions on local climate conditions, particularly investigating the impact of moisture sources, evaporation from lake surfaces, and evapotranspiration from agricultural activities, on local convection rainfall. The prevailing westerly winds in the basin suggest a hypothesis that this moisture is transported eastward within the basin, potentially leading to local precipitation as it ascends to higher altitudes near the eastern basin border. To validate this hypothesis, climate data from 1986 to 2017 from the Sarab meteorological station (east of the lake basin, influenced by local precipitation) and Saqez meteorological station (south of the basin, unaffected by local precipitation) were analyzed. The impact of lake water level reduction was assessed by categorizing data into periods of normal lake conditions (1986–1995) and water level reduction (1996–2017). Additionally, the MSWEP global precipitation product was used to examine the precipitation distribution in the entire basin over the entire period and sub-periods. The findings indicate Lake Urmia’s significant influence on convective rainfall in the eastern basin, especially during the summer. Despite decreasing lake levels from 1996 to 2017, convective rainfall in the eastern basin increased during the summer, suggesting intensified agricultural irrigation, particularly in hot seasons.

In the Middle East (ME), varying degrees of dust events occur due to its expansive arid regions. Lately, the increasing dust events in this area have become a major environmental concern. Dust particles naturally separate from the soil because of climate drivers, a regular process. However, human destructive activities as non-climate factor disrupts the environment can amplify the transport of dust on both regional and extra-regional scales. The ME comprises parts of Western Asia and Egypt, encompassing 17 countries with a combined population of around 463 million and a total area of approximately 7.9 million km2. Characterized by an arid to semi-arid climate, the region often experiences scorching summer temperatures, commonly exceeding 40oC and occasionally reaching 50oC. Precipitation is scarce in the ME, with the majority of areas receiving less than 250 mm/y. The Arabian Desert, covering an extensive area of 2.33 million km2, stands as the largest desert in the Middle East. Within its vast expanse lie distinct sub-regions, including the Rub' al Khali (Empty Quarter), Al-Dahna Desert, and An-Nafud Desert. This study has assessed the evolution of dust trends over a span of four decades (1980 to 2020) alongside alterations in climatic variables. Initially, remote sensing data for dust from the MERRA-2 dataset spanning the period between 1980 and 2020 was collected and processed. The AOD (Aerosol Optical Depth) product of MERRA-2 dataset was extracted for assessing dust concentrations. To explore the influential factors contributing to the increase in dust within the study area, three hydroclimate variables (actual evapotranspiration (AET), potential evapotranspiration (PET) and precipitation(P)) were extracted from the GLEAM (AET & PET) and MSWEP (P) datasets, respectively. Subsequently, trend of dust and the climate variables were investigated by using Mann-Kendall on their associated time series, then the homogeneity tests (Pettitt test) were applied on them to detect the significant change time of each variable. This allowed for the division of the time interval for each parameter into two segments: before- and after- change time spans. This division facilitated a comparative analysis of climatic and non-climatic drivers contributing to the increase in dust, with a particular focus on the potential impact of hydroclimate variables in this context. Results reveal an upward trend in dust levels across significant regions, including Saudi Arabia, Iraq, western and southern Iran, Egypt, and Yemen (Approximately 45.86% of the study area). The observed increase is particularly prominent in areas associated with the deserts of the Rub' al Khali, Al-Dahna, and Al-Nafud, as well as countries around the Persian Gulf. Notably, surrounding the Tigris and Euphrates in Iraq, as well as the western and southwestern parts of Iran, a substantial increase in dust levels has been recorded. The findings indicate a rise in precipitation in the Tigris and Euphrates region. However, there is also an observed increase in dust. It appears that these dust events are influenced not only by climate drivers but also by non-climatic drivers. A parallel pattern is evident for AET and PET in this region.

Lake Urmia in northwestern Iran is the largest lake in Iran and the second largest saltwater lake in the world. The water level in Lake Urmia has decreased dramatically in recent years, due to drought, climate change, and the overuse of water resources for irrigation. This shrinking of the lake may affect local climate conditions, assuming that the lake itself affects the local climate. In this study, we quantified the lake’s impact on the local climate by analyzing hourly time series of data on climate variables (temperature, vapor pressure, relative humidity, evaporation, and dewpoint temperature for all seasons, and local lake/land breezes in summer) for the period 1961–2016. For this, we compared high quality, long-term climate data obtained from Urmia and Saqez meteorological stations, located 30 km and 185 km from the lake center, respectively. We then investigated the effect of lake level decrease on the climate variables by dividing the data into periods 1961–1995 (normal lake level) and 1996–2016 (low lake level). The results showed that at Urmia station (close to the lake), climate parameters displayed fewer fluctuations and were evidently affected by Lake Urmia compared with those at Saqez station. The effects of the lake on the local climate increased with increasing temperature, with the most significant impact in summer and the least in winter. The results also indicated that, despite decreasing lake level, local climate conditions are still influenced by Lake Urmia, but to a lesser extent.

Lake Urmia in northwestern Iran is the largest lake in Iran and the second largest saltwater lake in the world. The water level in Lake Urmia has decreased dramatically in recent years, due to drought, climate change, and overuse of water resources for irrigation. This shrinking of the lake may affect local climate conditions, assuming that the lake itself affects the local climate. In this study, we quantified the lake’s impact on the local climate by analyzing hourly time series of data on climate variables (temperature, vapor pressure, relative humidity, evaporation, and dewpoint temperature for all seasons, and local lake/land breezes in summer) for the period 1961-2016. For this, we compared high quality, long-term climate data obtained from Urmia and Saqez meteorological stations, located 30 km and 185 km from the lake center, respectively. We then investigated the effect of lake level decrease on the climate variables by dividing the data into 1961-1995 (normal lake level) and 1996-2016 (low lake level). The results showed that at Urmia station (close to the lake), climate parameters displayed fewer fluctuations and were evidently affected by Lake Urmia compared with those at Saqez station. The effects of the lake on the local climate increased with increasing temperature, with the most significant impact in summer and the least in winter. The results also indicated that, despite decreasing lake level, local climate conditions are still influenced by Lake Urmia, but to a lesser extent.