Currently, there is a lack of investigating moisture sources for precipitation over the upstream catchment of the Three Gorges Dam (UCTGD), the world’s largest dam. Using the dynamical recycling model (DRM), trajectory frequency method (TFM), and the Climate Forecast System Reanalysis (CFSR), this study quantifies moisture sources and transport paths for UCTGD summer precipitation from 1980 to 2009 based on two categories of sources: region-specific and source-direction. Overall, the land and oceanic sources contribute roughly 63% and 37%, respectively, of the moisture to UCTGD summer precipitation. UCTGD and the Indian Ocean are the most important land and oceanic sources, respectively, in which the southern Indian Ocean with over 10% of moisture contribution was overlooked previously. Under the influence of the Asian monsoon and prevailing westerlies, the land contribution decreases to 57.3% in June, then gradually increases to 68.8%. It is found that for drought years with enhanced southwest monsoon, there is a weakening of the moisture contribution from the C-shaped belt along the Arabian Sea, South Asia, and UCTGD, and vice versa. TFM results show three main moisture transport paths and highlight the importance of moisture from the southwest. Comparison analysis indicates that, generally, sink regions are more affected by land evaporation with their locations more interior to the center of the mainland. Furthermore, correlations between moisture contributions and indices of general circulation and sea surface temperature are investigated, suggesting that these indices affect precipitation by influencing moisture contributions of the subregions. All of these are useful for comprehending the causes of summer UCTGD precipitation. Significance Statement: Quantitative research on the moisture sources of summer precipitation has been implemented for the upstream catchment of the Three Gorges Dam (UCTGD), which is of particular hydrological significance but has not been investigated previously. The dynamical recycling model (DRM)–trajectory frequency method (TFM) approach is used to quantify and interpret the results of the moisture sources both in different specific subregions and directions, which produce more meaningful results than a single method for the areal division of moisture sources. Furthermore, antecedent indices that significantly influence the following moisture contributions of the subregions and then summer UCTGD precipitation are studied in terms of large-scale general circulation indices, which would help our understanding of precipitation forecast for UCTGD.

Previously, the types of impacts of land–atmosphere interactions have scarcely been clarified systematically. In this article, we present a classification of these impacts based on modeling boundary layer variables/parameters, which is grouped into local, regional, and remote impacts. In the narrow sense, land surface processes (LSPs) influence the atmospheric state via vertical land–atmosphere coupling at local scales, which is referred to as local LSP impacts. However, local LSP impacts can lead to the advection effect due to the horizontal heterogeneity in the parameters over a region, which can be defined as regional LSP impacts. Furthermore, remote LSP impacts on the regional atmospheric state are induced by some land/sea surface variables/parameters over remote key areas of the Earth’s surface, which are conventionally taken as strong signals of climate variation. Of the three impacts, local impacts are the most important essential, as the other two types of impacts are derived from these impacts. We describe the quantification of local impacts based on our previous studies from the perspective of modeling approaches, and we discuss some issues related to these impacts. Previous investigations showed that local LSP impacts are mostly stronger than regional LSP impacts, e.g., the diabatic process is dominant in the physical processes responsible for daily maximum temperatures, and two first-order physical processes including vertical diffusion largely induce changes in surface wind speed in China. Finally, some aspects for future research are noted. This study provides insights into the research on land–atmosphre interactions at different scales.

In this paper, we utilize the Advanced Research version of the Weather Research and Forecasting model (ARWv4) to explore how the fog is affected by the basin’s topography during a radiation fog event in the Sichuan Basin in December 2016 by setting up three sets of terrain tests. The simulation results demonstrate that the fog area in the expanded basin terrain emerges 40 min earlier than in the original topography control test (CTL), with the fog area extent marginally reduced. Conversely, the fog area in the reduced basin terrain emerges one hour earlier than in the CTL, with the fog area extent increased by 133.5%. Basin topography is an essential factor influencing the humidity, temperature, and dynamical fields. The expansion of basin topography was shown to be unfavorable for water vapor convergence. Moreover, the area exhibiting relative humidity levels exceeding 95% at the peak of the fog intensity was smaller than that observed in CTL. The impact of radiative cooling was diminished, and the thickness and intensity of the inversion layer were reduced compared to CTL. In addition, the wind speed in the marginal area exceeded 5 m s⁻¹, and the fog formation was observed only in the central portion of the basin, where wind speeds ranged from 0 to 3 m s⁻¹. In contrast, the change in the topography of the narrowed basin resulted in the opposite phenomenon overall. This work emphasizes the importance of basin topography in forming and developing the fog in the Sichuan Basin.

Matched-field processing localizes underwater acoustic targets by measuring the degree of correlation between the acoustic field and replica fields. The intrusion of mesoscale eddies can induce sound speed mismatch in the matched-field process. Therefore, it is essential to investigate the impact of mesoscale eddies on matched-field localization errors. In this study, the typical vertical structure of mesoscale eddies in a certain region of the Northwestern Pacific was synthesized using the mesoscale eddy dataset META 2.0 and Argo float data. Furthermore, by employing both an idealized eddy model and composite-analysis structure of eddy, the performance of the localization algorithm was evaluated under the influence of mesoscale eddies with different structures and in different regions. The results show that under specific conditions, the distribution of localization errors exhibits certain patterns, which is beneficial for inverting eddy parameters via matched-field processing. Finally, the mechanism behind the systematic distribution of localization errors is discussed and analyzed. In the simulations, the source frequency was swept from 50 to 75 Hz with a 1 Hz step, and a circular array was employed as the receiving aperture. These findings indicate that, in the absence of small-scale interference and within a certain range of sound speed mismatch, the localization error of underwater acoustic targets increases with the strengthening of mesoscale eddy disturbances.

This study investigates the moisture sources for a heavy rainfall event in southern China from July 7 to 9, 2019, using the DRM model combined with ERA5 reanalysis data. The results indicate that the moisture for this precipitation process primarily originates from the southwest direction. The area with high moisture contribution forms a narrow elongated band, starting from the southern Indian Ocean, passing through the Arabian Sea, Bay of Bengal, Indochina Peninsula, and southwestern China, and ultimately reaching southern China. Oceanic evaporation serves as the primary moisture source for this heavy rainfall event, contributing 68.43% of the precipitation, with the southern Indian Ocean as the most important source region, followed by the Arabian Sea and Bay of Bengal. Terrestrial evaporation contributes less, with the Indochina Peninsula as the main land source. The moisture transport during this heavy rainfall process is influenced by the Indian monsoon and the anomalous westward extension and southward shift of the western Pacific subtropical high, which guides the southwest airflow from the Indian Ocean along the western side of the subtropical high to southern China.

This study analyzed the convergence zone distance under the critical depth conditions of the sound source and the occurrence probability of the convergence zone at different sound source depths in the northern South China Sea by using the Bellhop model and GLORYS12V1 data. The results show that with the increase of water depth, the critical depth of the sound source decreases, and the corresponding convergence zone distance increases. Under the same water depth conditions, the convergence zone distance is closer in winter and farther in summer. When the water depth is less than 3000 meters, the seasonal variation of the convergence zone distance is relatively large, while when the water depth exceeds 3000 meters, the variation is relatively small. Except for the marginal areas, the occurrence probability of the convergence zone is above 99% in most sea areas throughout the year. The probability distribution in the marginal areas shows seasonal differences. With the increase of the sound source depth, the high-probability area expands from the deep water in the east to the northwest, and the low-probability area is concentrated in the marginal areas or the closed ring in the southwest corner. The range of the high-probability area is usually larger in winter and spring than in summer and autumn.