Search Results (65)

In the Atlantic Ocean, the Intertropical Convergence Zone (ITCZ) sustains the climate of northeastern Brazil and northwestern Africa by modulating their rainy and dry seasons. Using observational data, radiosondes and Expendable Bathythermographs (XBTs), we investigated short-term ocean–atmosphere coupling across the ITCZ region along the 38° W meridian. The data represents synchronous measurements of the marine atmospheric boundary layer (MABL) and the ocean’s mixed layer (OML) for the period between 17 October and 8 November 2018. The ITCZ demonstrated pronounced variability in position, intensity, and width, driven by the changes in the predominance of northeast and southeast trade winds. These atmospheric changes directly impacted the Equatorial Divergence (ED), which transitioned from an asymmetric structure with shallower isothermal layer depths (ILDs) (~−14 m) around 11° N to a more homogenous region between 5° N and 10° N, with an average ILD of −21.83 ± 5.23 m. A comparison with ORAS5 and WOA23 indicates that the products reproduce the vertical thermal structure of the WTAO well (r² > 0.9) but systematically overestimate the temperature at the bottom of the ILD by 3–4 °C. The difference between the ILD and the mixed layer depth (MLD) is more pronounced south of the ED due to the Amazon River salinity front, advected by the NECC, but the ILD estimated from XBT data closely matches the MLD estimated for ORAS5 and WOA23 in the ED region. These unprecedented observations showcase, for the first time, short-term ocean–atmosphere coupled variability across the WTAO ITCZ region, highlighting the importance of atmospheric synoptic-scale processes in modulating the OML and the ED. Full article

Southwestern China serves as a critical region for carbon sources and sinks, influenced by both natural ecosystems and anthropogenic activities. The Shangri-La atmospheric background station (28.01° N, 99.73° E), the only regional station in southwestern China, provides essential data for understanding CO₂ dynamics. This study analyzes hourly CO₂ mole fractions from 2019 to 2022. Background signals were extracted using the Robust Extraction of Baseline Signal (REBS) algorithm, and air-mass trajectories were analyzed using HYSPLIT model and Potential Source Contribution Function (PSCF) and Concentration Weighted Trajectory (CWT) methods. The REBS-derived background CO₂ concentration increased from ~409 ppm in 2019 to ~417 ppm in 2022, yielding a growth rate of 1.9 ± 0.1 ppm yr⁻¹, slightly lower than the 2010–2014 rate reported previously and consistent with the recent global slowdown associated with ENSO-driven carbon–climate variability. A coherent seasonal cycle, with spring maxima and late-summer minima, reflects the combined influence of biospheric uptake and monsoonal inflow. Comparison with the global marine boundary layer and Waliguan records shows similar phase and amplitude, confirming the representativeness of Shangri-La as a regional background site, albeit with a one-month phase lag to Waliguan station due to regional climatic and phenological differences. Trajectory and wind analyses identify southern Indo-Myanmar and Sichuan–Yunnan regions as major transport corridors influencing high-CO₂ events. Overall, the results highlight that regional transport rather than local emissions dominates CO₂ variability at Shangri-La. The derived background and transport signals thus provide an updated and internally consistent characterization of carbon-cycle variability over the southeastern Tibetan Plateau, offering critical observational support for future regional carbon budget assessments. Full article

Oceanic mesoscale activity influences the atmosphere in the southwestern and southern sectors of the Atlantic Ocean. However, the influence of high latitudes, specifically sea ice, on mid-latitudes and a better understanding of mesoscale ocean–atmosphere thermodynamic interactions still require further study. To quantify the effects of oceanic mesoscale activity during the periods of maximum and minimum Antarctic sea ice extent (September 2019 and February 2020), numerical experiments were conducted using a coupled regional model and an online two-dimensional spatial filter to remove high-frequency sea surface temperature (SST) oscillations. The largest SST anomalies were observed in the Brazil–Malvinas Confluence and along oceanic fronts in September, with maximum SST anomalies reaching 4.23 °C and −3.71 °C. In February, the anomalies were 2.18 °C and −3.06 °C. The influence of oceanic mesoscale activity was evident in surface atmospheric variables, with larger anomalies also observed in September. This influence led to changes in the vertical structure of the atmosphere, affecting the development of the marine atmospheric boundary layer (MABL) and influencing the free atmosphere above the MABL. Modulations in precipitation patterns were observed, not only in oceanic regions, but also in adjacent continental areas. This research provides a novel perspective on ocean–atmosphere thermodynamic coupling, highlighting the mesoscale role and importance of its representation in the study region. Full article

The Marine Atmospheric Boundary Layer (MABL), as a critical component of Earth’s climate system, governs the exchange of matter and energy between the ocean surface and the lower atmosphere. This study presents shipborne Doppler lidar observations conducted during 12 January to 3 February 2024, along the southeastern Chinese coast. Employing a Coherent Doppler Wind Lidar (CDWL) system onboard the R/V “Yuezhanyu” research vessel, we investigated the spatiotemporal variability of MABL characteristics through integration with ERA5 reanalysis data. The key findings reveal a significant positive correlation between MABL height and surface sensible heat flux in winter, underscoring the dominant role of sensible heat flux in boundary layer development. Through the Empirical Orthogonal Function (EOF) analysis of the ERA5 regional boundary layer height, sensible heat flux, and sea level pressure, we demonstrate MABL height over the coastal seas typically exceeds the corresponding terrestrial atmospheric boundary layer height and exhibits weak diurnal variation. The CDWL observations highlight complex wind field dynamics influenced by synoptic conditions and maritime zones. Compared to onshore regions, the MABL over offshore areas further away from land has lower wind shear changes and a more uniform wind field. Notably, the terrain of Taiwan, China, induces significant low-level jet formations within the MABL. Low-level jets and low boundary layer height promote the pollution episode observed by CDWL. This research provides new insights into MABL dynamics over East Asian marginal seas, with implications for improving boundary layer parameterization in regional climate models and advancing our understanding of coastal meteorological processes. Full article

Marine atmospheric boundary-layer height (MABLH) is crucial for ocean heat, momentum, and substance transfer, affecting ocean circulation, climate, and ecosystems. Due to the unique geographical location of the South China Sea (SCS), coupled with its complex atmospheric environment and sparse ground-based observation stations, accurately determining the MABLH remains challenging. Coherent Doppler wind lidar (CDWL), as a laser-based active remote sensing technology, provides high-resolution wind profiling by transmitting pulsed laser beams and analyzing backscattered signals from atmospheric aerosols. In this study, we developed a stacking optimal ensemble model (SOEM) to estimate MABLH in the vicinity of the site by integrating CDWL measurements from a representative SCS site with ERA5 (fifth-generation reanalysis dataset from the European Centre for Medium-Range Weather Forecasts) data from December 2019 to May 2021. Based on the categorization of the total cloud cover data into weather conditions such as clear/slightly cloudy, cloudy/transitional, and overcast/rainy, the SOEM demonstrates enhanced performance with an average mean absolute percentage error of 3.7%, significantly lower than the planetary boundary-layer-height products of ERA5. The SOEM outperformed random forest, extreme gradient boosting, and histogram-based gradient boosting models, achieving a robustness coefficient ($R^2$) of 0.95 and the lowest mean absolute error of 32 m under the clear/slightly cloudy condition. The validation conducted in the coastal city of Qingdao further confirmed the superiority of the SOEM in resolving meteorological heterogeneity. The predictions of the SOEM aligned well with CDWL observations during Typhoon Sinlaku (2020), capturing dynamic disturbances in MABLH. Overall, the SOEM provides a precise approach for estimating convective boundary-layer height, supporting marine meteorology, onshore wind power, and coastal protection applications. Full article

Amidst the rapid global urbanization and economic integration, coastal cities have undergone significant changes in urban spatial patterns. These changes have further worsened the complex urban thermal environment, making it crucial to study the interaction between human-driven development and natural climate systems. To address the insufficient quantification of marine elements in the urban planning of subtropical coastal zones, this study takes Xiamen, a typical deep-water port city, as an example to construct a spatial analysis framework integrating marine boundary layer parameters. This research employs interpolation simulation, atmospheric correction, and other techniques to simulate the inversion of land use and Landsat 8 data, deriving urban morphological elements and Land Surface Temperature (LST) data. These data were then assigned to 500 m grids for analysis. A bivariate spatial auto-correlation model was applied to examine the relationship between urban carbon emission and LST. The study area was categorized based on the influence of marine factors, and the spatial relationships between urban morphological elements and LST were analyzed using a multiscale geographically weighted regression model. Three Xiamen-specific discoveries emerged: (1) the marine exerts a significant thermal mitigation effect on the city, with an average influence range of 7.94 km; (2) the relationship between urban morphology and the thermal environment exhibits notable spatial heterogeneity across different regions; and (3) to mitigate urban thermal environments, connected green corridors should be established in the southern coastal areas of outer districts in regions significantly influenced by the ocean. In areas with less marine influence, spatial complexity should be introduced by disrupting relatively intact blue–green spaces, while regions unaffected by the ocean should focus on increasing green spaces and reducing impervious surfaces and water bodies. These findings directly inform Xiamen’s 2035 Master Plan for combating heat island effects in coastal special economic zones, providing transferable metrics for similar maritime cities. Full article

In contemporary times, wastewater treatment plants (WWTPs) were recognized as substantial sources of odorous emissions, potentially impacting nearby communities’ sensory experience. This study investigates the half-lives (T½) of odorous compounds emitted from WWTPs and their degradation due to atmospheric hydroxyl radicals (•OH) in different environmental settings. The calculated half-lives of specific odorants in rural areas ranged from 31.36 min to 517.33 days, in urban areas from 42.50 min to 1550 days, and in the marine boundary layer from 42.50 min to 129,861 days. These results show that compounds with high reactivity and short T½, such as methanethiol and ethanethiol, degrade rapidly and are less likely to contribute to long-term odor nuisances. In contrast, compounds with longer half-lives, such as carbonyl sulfide and ammonia, persist longer in the atmosphere, with higher potential for sustained odor issues. The findings suggest that •OH plays a significant role in degrading odorous compounds. These insights into odorant–oxidant kinetics may aid in predicting atmospheric half-lives and their contribution to secondary aerosol formation, thus informing regulatory and mitigation strategies to improve air quality. Full article

Wind power plays an increasingly vital role in sustainable energy development. However, accurately simulating wind turbine aerodynamics, particularly in offshore wind farms, remains challenging due to complex environmental factors such as the marine atmospheric boundary layer. This study investigates the integration and assessment of the Actuator Line Model (ALM) within the high-order spectral/hp element framework, Nektar++, for wind turbine aerodynamic simulations. The primary objective is to evaluate the implementation and effectiveness of the ALM by analyzing aerodynamic loads, wake behavior, and computational demands. A three-bladed NREL-5MW turbine is modeled using the ALM in Nektar++, with results compared against established computational fluid dynamics (CFD) tools, including SOWFA and AMR-Wind. The findings demonstrate that Nektar++ effectively captures velocity and vorticity fields in the turbine wake while providing aerodynamic load predictions that closely align with finite-volume CFD models. Furthermore, the spectral/hp element framework exhibits favorable scalability and computational efficiency, indicating that Nektar++ is a promising tool for high-fidelity wind turbine and wind farm aerodynamic research. Full article

Marine aerosol particles can act as cloud condensation nuclei and influence the atmospheric boundary layer by scattering solar radiation. The interaction of ocean waves and coral reefs may affect the distribution and size of marine aerosol particles. Measuring this effect has proven challenging. Here, we tested the hypothesis that the distribution and size of marine aerosol particles would vary over three distinct zones (i.e., coral lagoon, surf break, and open water) near One Tree Island in the Great Barrier Reef, which is approximately 85 km off the east coast of Australia. We used a modified DJI Agras T30 drone fitted with a miniaturised scanning electrical mobility sizer and advanced mixing condensation particle counter to collect data on aerosol size distribution between 30 and 300 nm at 20 m above the water surface. We conducted 30 flights over ten days during the Austral summer/autumn of 2023. The fitted bimodal lognormal curves indicate that the number concentrations for aerosols below 85 nm diameter are more than 16% higher over the lagoon than over open water. The average mean mode diameters remained constant across the different zones, indicating no significant influence of breaking waves on the detected aerosol size modes. The most influential explanatory variable for aerosol size distribution was the difference between air temperature and the underlying sea surface, explaining around 40% of the variability. Salinity also exhibited a significant influence, explaining around 12% of the measured variability in the number concentration of aerosols throughout the campaign. A calculated wind stress magnitude did not reveal significant variation in the measured marine aerosol concentrations. Overall, our drone-based aerosol measurements near the water surface effectively characterise the dynamics of background marine aerosols around One Tree Island Reef, illustrating the value of drone-based systems for providing size-dependent aerosol information in difficult-to-access and environmentally sensitive areas. Full article

Oceanic biogenic emissions exert a significant impact on the atmospheric environment within the marine boundary layer (MBL). This study employs the extreme gradient boosting (XGBoost) machine learning method and clustering method combined with satellite observations and model simulations to discuss the effects of marine biogenic emissions on MBL formaldehyde (HCHO). The study reveals that HCHO columnar concentrations peaked in summer with 8.25 × 10¹⁵ molec/cm², but the sea–air exchange processes controlled under the wind and sea surface temperature (SST) made marine biogenic emissions represented by isoprene reach their highest levels in winter with 95.93 nmol/m²/day. Analysis was conducted separately for factors influencing marine biogenic emissions and affecting MBL HCHO. It was found that phytoplankton functional types (PFTs) and biological degradation had a significant impact on marine biogenic emissions, with ratio range of 0.07~15.87 and 1.02~5.42 respectively. Machine learning methods were employed to simulate the conversion process of marine biogenic emissions to HCHO in MBL. Based on the SHAP values of the learning model, the importance results indicate that the factors influencing MBL HCHO mainly included NO₂, as well as temperature (T) and relative humidity (RH). Specifically, the influence of NO₂ on atmospheric HCHO was 1.3 times that of T and 1.6 times that of RH. Wind speed affected HCHO by influencing both marine biogenic emission and the atmospheric physical conditions. Increased marine biogenic emissions in air masses heavily influenced by human activities can reduce HCHO levels to some extent. However, in areas less affected by human activities, marine biogenic emissions can lead to higher levels of HCHO pollution. This research explores the impact of marine biogenic emissions on the HCHO status of the MBL under different atmospheric chemical conditions, offering significant insights into understanding chemical processes in marine atmospheres. Full article

The Sahara Desert is the largest contributor of global atmospheric dust aerosols impacting regional climate, health, and ecosystems. The climate effects of these dust aerosols remain uncertain due, in part, to climate model uncertainty of Saharan source region contributions and aerosol microphysical properties. This study distinguishes source region elemental signatures of Saharan dust aerosols sampled during the 2015 Aerosols Ocean Sciences Expedition (AEROSE) in the tropical Atlantic. During the 4-week campaign, cascade impactors size-dependently collected airborne Saharan dust particulate upon glass microfiber filters. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis differentiated metal isotope concentrations within filter samples from various AEROSE dust sampling periods. Back-trajectory analysis and NOAA satellite aerosol optical depth retrievals confirmed source regions of AEROSE ’15 dust samples. Pearson correlational statistics of source region activity and dust isotope concentrations distinguished the elemental signatures of North African potential source areas (PSAs). This study confirmed that elemental indicators of these PSAs remain detectable within dust samples collected far into the marine boundary layer of the tropical Atlantic. Changes detected in dust elemental indicators occurred on sub-weekly timescales across relatively small sampling distances along the 23W parallel of the tropical Atlantic. PSA-2 emissions, covering the western coast of the Sahara, were very strongly correlated (R² > 0.79) with Ca-44 isotope ratios in AEROSE dust samples; PSA-2.5 emissions, covering eastern Mauritania and western Mali, were very strongly correlated with K-39 ratios; PSA-3 emissions, spanning southwestern Algeria and eastern Mali, were very strongly correlated with Fe-57 and Ti-48 ratios. The abundance of Ca isotopes from PSA-2 was attributed to calcite minerals from dry lakebeds and phosphorous mining activities in Western Sahara, based on source region analysis. The correlation between K isotope ratios and PSA-2.5 was a likely indicator of illite minerals near the El Djouf Desert region, according to corroboration with mineral mapping studies. Fe and Ti ratio correlations with PSA-3 observed in this study were likely indicators of iron and titanium oxides from Sahelian sources still detectable in Atlantic Ocean observations. The rapid changes in isotope chemistry found in AEROSE dust samples provide a unique marker of Saharan source regions and their relative contributions to desert outflows in the Atlantic. These elemental indicators provide source region apportionments of Sahara Desert aerosol flux and deposition into the Atlantic Ocean, as well as a basis for model and satellite validation of Saharan dust emissions for regional climate assessments. Full article

Fast atmospheric processes such as deep convection and severe storms are challenging to observe and understand without adequate spatiotemporal sampling. Geostationary (GEO) imaging has the advantage of tracking these fast processes continuously at a cadence of the 10 min global and 1 min mesoscale from thermal infrared (TIR) channels. More importantly, the newly-available GEO-GEO stereo observations from our 3D-Wind algorithm provide more accurate height assignment for atmospheric motion vectors (AMVs) than those from conventional TIR methods. Unlike the radiometric methods, the stereo height is insensitive to radiometric TIR calibration of satellite sensors and can assign the feature height correctly under complex situation (e.g., multi-layer clouds and atmospheric inversion). This paper shows a case study from continuous GEO-GEO stereo observations over the Eastern Pacific during 1–5 February 2023, to highlight diurnal variations of clouds and dynamics in the planetary boundary layer (PBL), altocumulus/congestus, convective outflow and tropical tropopause layer (TTL). Because of their good vertical resolution, the stereo observations often show a wind shear in these cloud layers. As an example, the stereo winds reveal the classic Ekman spiral in marine PBL dynamics with a clockwise (counterclockwise) wind direction change with height in the Northern (Southern) Hemisphere subtropics. Over the Southeastern Pacific, the stereo cloud observations show a clear diurnal variation in the closed-to-open cell transition in the PBL and evidence of precipitation at a lower level from broken stratocumulus clouds. Full article

In this work, we utilize space-based radar products from CloudSat mission and provide statistics on the properties of the clouds observed above the PANGEA (PANhellenic GEophysical observatory of Antikythera) observatory, located in the Eastern Mediterranean. We found that the variable atmospheric conditions that prevailed above the region in 2007–2017 resulted in complex cloud structures. From the clouds observed, 39.8% were low-level clouds formed at the top of the marine boundary layer (≤2 km), 34.2% were mid-level clouds (between 2–7 km), and 25.9% were high-level or deep convective clouds (between 7–15 km). Thin clouds (<1 km depth) are observed in 33% of the cases, while thick clouds (>6 km) in 15% of the cases. The results of this study can be used from regional and climate models to evaluate their cloud predictions and investigate the performance of different cloud microphysics schemes. Full article

Atmospheric near-surface stress and boundary layer wind responses to surface currents are examined with high resolution coupled atmosphere–ocean models over the Gulf Stream during winter. Because the ocean and atmosphere are linked through surface stress, the two fluids can cause dramatic changes through feedback processes. When the current feedback is included, we find that the current gradient in the cross-wind direction drives the stress curl pattern and wind curl pattern to have minima and maxima at locations matching those of the ocean surface vorticity pattern. Furthermore, we find the large- (>30 km) and small-scale, or submesoscale (<30 km), stress curl and wind curl responses to ocean surface vorticity are complimentary; however, the large- and small-scale wind divergence responses are counteractive. These responses (commonly called coupling coefficients) are found to depend on the relative position to the Gulf Stream maximum current. Throughout the atmospheric boundary layer, we find including the current feedback also leads to changes in the atmospheric secondary circulation on either side of the Gulf Stream extension. The winter seasonal means suggest the current feedback will impact climate, and investigating individual events, such as an atmospheric front passing over the Gulf Stream, suggests the current feedback will also impact the intensity of weather. Full article

We present reactive VOC observations over the North Pacific and the Arctic Ocean from airborne and shipborne measurements, investigating, in particular, distributions of biogenic volatile organic compounds that may be emitted from phytoplankton. In contrast to terrestrial observations, isoprene (C₅H₈), the most dominant BVOC emission from the terrestrial ecosystem, was mostly present under the lower detection limit along with monoterpenes (C₁₀H₁₆), the second largest emission from the terrestrial ecosystem. However, we consistently detected sesquiterpenes (C₁₅H₂₄) over the Arctic Ocean for the two Arctic cruises. The results of the analysis of sorbent cartridge samplings conducted over the Arctic Ocean on Korean icebreaker R/V Araon in 2016 and 2017 illustrate that few tens ppt levels of sesquiterpenes were present over the Arctic Ocean. Moreover, the concentration variation was positively correlated with the quantitative indicators of ocean biological activities, such as chlorophyll-a, dissolved DMS, and the ratio of dissolved O₂ and Ar. This suggests that further investigations on sesquiterpene’s emission and atmospheric transformation processes over the marine boundary layer are required. Full article