Search

In this study, a global variable‐resolution modeling framework of atmospheric dust and its radiative feedback is established and evaluated. In this model, atmospheric dust is simulated simultaneously with meteorological fields, and dust‐radiation interactions are included. Five configurations of global mesh with refinement at different resolutions and over different regions are used to explore the impacts of regional refinement on modeling dust lifecycle at regional and global scales. The model reasonably produces the overall magnitudes and spatial variabilities of global dust metrics such as surface mass concentration, deposition, aerosol optical depth, and radiative forcing compared to observations and previous modeling results. Two global variable‐resolution simulations with mesh refinement over major deserts of North Africa (V16 km‐NA) and East Asia (V16 km‐EA) simulate less dust emissions and smaller dry deposition rates inside the refined regions due to the weakened near‐surface wind speed caused by better resolved topographic complexity at higher resolution. The dust mass loadings over North Africa are close to each other between V16 km‐NA and the quasi‐uniform resolution (∼120 km) (U120 km), while over East Asia, V16 km‐EA simulates higher dust mass loading. Over the non‐refined areas with the same resolution, the difference between global variable‐resolution and uniform‐resolution experiments also exists, which is partly related to their difference in dynamic time‐step and the coefficient for horizontal diffusion. Refinement at convection‐permitting resolution around the Tibetan Plateau (TP) simulates less dust due to its more efficient wet scavenging from resolved convective precipitation around the TP against coarse resolution. Plain Language Summary: Mineral dust plays an important role in Earth's climate system. Numerical simulation of dust and its impacts on a regional scale still has large uncertainties, partly due to the relatively coarse horizontal resolution. Limited‐area simulation at relatively high resolution can generally better characterize dust and its impacts on a regional scale; however, lateral boundary conditions may introduce some numerical issues and constrain regional feedback, such as dust‐cloud and dust‐radiation interactions, to large‐scale circulation. In this study, a novel modeling framework of atmospheric dust and its climatic feedbacks with the capability of global variable‐resolution simulation is established and evaluated. The model produces reasonable global spatial distributions of dust compared to observations and previous studies. The difference between the simulations at global quasi‐uniform resolution and global variable resolution with regional refinement over East Asia and North Africa is significant, particularly with refinement at convection‐permitting resolution. This model may be used in the future to provide new insights into the impacts of dust on regional and global climate systems. Key Points: A modeling framework of atmospheric dust with the capability of global variable‐resolution simulation is introduced and evaluatedExperiments with regional refinement produce less dust emissions and mass loading and smaller dry deposition due to weaker surface windRefinement at convection‐permitting resolution simulates stronger wet scavenging and less dust mass compared to coarse resolution [ABSTRACT FROM AUTHOR]

The unprecedented and long-lasting abnormal monsoon rainfall attacked Pakistan in the summer of 2022, causing severe flooding. This study investigated the sub-seasonal characteristics and mechanisms of this distinctively extreme precipitation event. The historical rainfall in July and August and extreme precipitation mainly occurred in northern Pakistan. Both the monthly rainfall in July and August 2022 and the extreme precipitation during the summer were far exceeding the historical record and involved unique spatial distribution. The rainfall in July 2022 is nationwide and mainly located in northern Pakistan, while the rainfall in August and extreme precipitation occurred in southern Pakistan. Different physical processes are responsible for the precipitation in July and August 2022. In July, the South Asian high (SAH) and Iranian high extended eastward. Meanwhile, the anticyclonic circulation anomalies occurred in northwestern Pakistan and the easterly winds enhanced in the south side of the Tibetan Plateau (TP), which strengthened water vapor transporting from the Bay of Bengal and cooperated with the cyclonic system over the Arabian Sea to enhance the precipitation over Pakistan. In August, the SAH further extended eastward and the Western Pacific Subtropical High extended westward to the TP. Meanwhile, the European blocking (EB) developed, and a deep trough appeared over northwestern Pakistan. This weakened the easterly flow along southern TP but enhanced the southerly flow accompanying the cyclone over the Bay of Bengal and the Arabian Sea, and thus guided the water vapor transporting to southern Pakistan and enhanced the precipitation. The extreme precipitation in July was mainly attributed to the unusually strong Indian monsoon, while the extreme precipitation in August was the result of a combination of the Indian monsoon and EB. The study provided important information about extreme precipitation in Pakistan, which will help policymakers take measures to deal with the effects of flooding. [ABSTRACT FROM AUTHOR]

Record-breaking extreme precipitation occurred in July and August 2022 in Pakistan, causing flooding and landslides. In this study, the characteristics and mechanisms of these extreme precipitation events are investigated. The consecutive extreme precipitation events emerged in July and mid to late August. Precipitation above 500 mm occurred in the northern and southern regions of Pakistan, and the maximum precipitation was concentrated in the same regions. The diagnosis indicated that the precipitation extremes were closely tied to anomalous late spring snow cover in the western Tibetan Plateau. In July, owing to the reduction of late spring snow cover, the strengthened diabatic heating promoted the South Asian High (SAH) and its pumping effect, which contributed to abundant water vapor and strong southeasterly jet along the southwest Tibetan Plateau. Cooperating with the cyclone over Arabian Sea, extreme precipitation with a return period of 50 years occurred in Pakistan. In August, the SAH was an anomalously strong and eastward extension at 200 hPa. In the middle troposphere, the blocking high-pressure over western Russia was extremely active, and the West Pacific Subtropical High shifted anomalously westward, extending to the Tibetan Plateau. Cyclone anomalies occurred over the Arabian Sea and Bay of Bengal. With the atmospheric circulation anomaly, the southeasterly jet shifted southward, and water vapor was transported from the Arabian Sea and Bay of Bengal to south Pakistan, causing extreme precipitation with a return period of 30 years in August. • Late spring snow anomalies decreased over the western Tibetan Plateau contributes to Pakistan extreme precipitation in 2022. • The reduced snow intensifies the South Asian High and southeasterly jet which strengthen July Pakistan extreme precipitation. • The reduced snow promotes August Pakistan extreme precipitation by western Russia blocking and West Pacific Subtropical High. [ABSTRACT FROM AUTHOR]