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20 pages, 4049 KiB  
Article
Anthropogenic Aerosol Dominates the Decadal Change in Evapotranspiration over Southeastern China in the Past Four Decades
by Zhiyong Kong, Jian Cao and Boyang Wang
Remote Sens. 2025, 17(3), 561; https://doi.org/10.3390/rs17030561 - 6 Feb 2025
Abstract
Evapotranspiration (ET) is vital for global water balance, energy cycle, and biological processes, representing a key component of Earth systems interactions. However, how human activities affect regional ET is still unknown. This study identified a decadal decrease in ET before 2000, followed by [...] Read more.
Evapotranspiration (ET) is vital for global water balance, energy cycle, and biological processes, representing a key component of Earth systems interactions. However, how human activities affect regional ET is still unknown. This study identified a decadal decrease in ET before 2000, followed by an increase over southeastern China in observations. Simulations from the coupled model intercomparison project phase 6 (CMIP6) models well reproduced the observed decadal ET change, with a lag of 10 years, which may be due to the spatial and temporal simplification of aerosol forcing data in CMIP6. Attribution analysis reveals that the change in anthropogenic aerosol emissions was the primary driver of the ET change, while the contribution of greenhouse gas was negligible. The Penman–Monteith framework identified that the net surface radiation contributed 77% of the ET trend change in the anthropogenic aerosol-only experiment. The increase and reduction in anthropogenic aerosol emissions reduce and increase the shortwave radiation reaching the Earth’s surface, respectively, resulting in the different trends of energy sources for ET. Our findings underscore the critical role of aerosols in shaping surface energy balance and influencing regional hydrological cycles. Full article
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21 pages, 9069 KiB  
Article
Optimal Methods for Estimating Shortwave and Longwave Radiation to Accurately Calculate Reference Crop Evapotranspiration in the High-Altitude of Central Tibet
by Jiandong Liu, Jun Du, Fei Wang, De Li Liu, Jiahui Tang, Dawei Lin, Yahui Tang, Lijie Shi and Qiang Yu
Agronomy 2024, 14(10), 2401; https://doi.org/10.3390/agronomy14102401 - 17 Oct 2024
Cited by 1 | Viewed by 730
Abstract
The FAO56 Penman–Monteith model (FAO56-PM) is widely used for estimating reference crop evapotranspiration (ET0). However, key variables such as shortwave radiation (Rs) and net longwave radiation (Rln) are often unavailable at most weather stations. [...] Read more.
The FAO56 Penman–Monteith model (FAO56-PM) is widely used for estimating reference crop evapotranspiration (ET0). However, key variables such as shortwave radiation (Rs) and net longwave radiation (Rln) are often unavailable at most weather stations. While previous studies have focused on calibrating Rs, the influence of large Rln, particularly in high-altitude regions with thin air, remains unexplored. This study investigates this issue by using observed data from Bange in central Tibet to identify the optimal methods for estimating Rs and Rln to accurately calculate ET0. The findings reveal that the average daily Rln was 8.172 MJ m−2 d−1 at Bange, much larger than that at the same latitude. The original FAO56-PM model may produce seemingly accurate ET0 estimates due to compensating errors: underestimated Rln offsetting underestimated net shortwave radiation (Rsn). Merely calibrating Rs does not improve ET0 accuracy but may exacerbate errors. The Liu-S was the empirical model for Rs estimation calibrated by parameterization over the Tibetan Plateau and the Allen-LC was the empirical model for Rln estimation calibrated by local measurements in central Tibet. The combination of the Liu-S and Allen-LC methods showed much-improved performance in ET0 estimation, yielding a high Nash–Sutcliffe Efficiency (NSE) of 0.889 and a low relative error of −5.7%. This strategy is indicated as optimal for ET0 estimation in central Tibet. Trend analysis based on this optimal strategy indicates significant increases in ET0 in central Tibet from 2000 to 2020, with projections suggesting a continued rise through 2100 under climate change scenarios, though with increasing uncertainty over time. However, the rapidly increasing trends in precipitation will lead to decreasing trends in agricultural water use for highland parley production in central Tibet under climate change scenarios. The findings in this study provide critical information for irrigation planning to achieve sustainable agricultural production over the Tibetan Plateau. Full article
(This article belongs to the Section Agricultural Biosystem and Biological Engineering)
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22 pages, 9842 KiB  
Article
Urbanization Effect on Regional Thermal Environment and Its Mechanisms in Arid Zone Cities: A Case Study of Urumqi
by Aerzuna Abulimiti, Yongqiang Liu, Jianping Tang, Ali Mamtimin, Junqiang Yao, Yong Zeng and Abuduwaili Abulikemu
Remote Sens. 2024, 16(16), 2939; https://doi.org/10.3390/rs16162939 - 10 Aug 2024
Cited by 1 | Viewed by 1428
Abstract
Urumqi is located in the arid region of northwestern China, known for being one of the most delicate ecological environments and an area susceptible to climate change. The urbanization of Urumqi has progressed rapidly, yet there is a lack of research on the [...] Read more.
Urumqi is located in the arid region of northwestern China, known for being one of the most delicate ecological environments and an area susceptible to climate change. The urbanization of Urumqi has progressed rapidly, yet there is a lack of research on the urbanization effect (UE) in Urumqi in terms of the regional climate. This study investigates the UE of Urumqi (urban built-up area) on the regional thermal environment and its mechanisms for the first time, based on the WRF (Weather Research and Forecasting) model (combined with the Urban Canopy Model, UCM) simulation data of 10 consecutive years (2012–2021). The results show that the UE on surface temperature (Ts) and air temperature at 2 m (T2m) is strong (weak) during the night (daytime) in all seasons, and the UE on these is largest (smallest) in spring (winter). In addition, the maximum UE on both Ts and T2m is present over southern Urumqi in winter, whereas the maximum UE is identified over the northern Urumqi in other seasons. The maximum UE on Ts occurred in northwestern Urumqi at 18 LST (Local Standard Time, i.e., UTC+6) in autumn (reaching 5.2 °C), and the maximum UE on T2m occurred in northern Urumqi at 4 LST in summer (reaching 2.6 °C). Urbanization showed a weak cooling effect during daytime in summer and winter, reflecting the unique characteristics of the UE in arid regions, which are different from those in humid regions. The maximum cooling of Ts occurred in northern Urumqi at 11 LST in summer (reaching −0.4 °C), while that of T2m occurred at 10 LST in northern and northwestern Urumqi in winter (reaching −0.25 °C), and the cooling effect lasted for a longer period of time in summer than in winter. The UE of Urumqi causes the increase of Ts mainly through the influence of net short-wave radiation and geothermal flux and causes the increase of T2m through the influence of sensible heat flux and net long-wave radiation. The UE on the land surface energy balance in Urumqi can be used to explain the seasonal variation and spatial differences of the UEs on the regional thermal environment and the underlying mechanism. Full article
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21 pages, 3594 KiB  
Article
Different Responses of Terrestrial Carbon Fluxes to Environmental Changes in Cold Temperate Forest Ecosystems
by Mihang Jiang, Xinjie Liu and Liangyun Liu
Forests 2024, 15(8), 1340; https://doi.org/10.3390/f15081340 - 1 Aug 2024
Cited by 1 | Viewed by 1552
Abstract
As the largest carbon reservoir within terrestrial ecosystems, forest ecosystems play a major role as carbon sinks in the global carbon cycle. There are still some uncertainties regarding the responses of different carbon fluxes to environmental changes in cold temperate climate forest ecosystems. [...] Read more.
As the largest carbon reservoir within terrestrial ecosystems, forest ecosystems play a major role as carbon sinks in the global carbon cycle. There are still some uncertainties regarding the responses of different carbon fluxes to environmental changes in cold temperate climate forest ecosystems. Here, 14 cold temperate forest flux sites for at least ten years were investigated, including carbon fluxes and environmental variables such as temperature, precipitation, shortwave radiation, and vapor pressure deficit. By calculating the Spearman correlation coefficient, there was a congruence between photosynthetic productivity (i.e., gross primary productivity, GPP) and carbon sequestration (i.e., net ecosystem productivity, NEP) at thirteen forest sites, and at one forest site, GPP and NEP were decoupled. Annual GPP and NEP displayed a consistent trend when temperature and precipitation had significantly opposite trends and when temperature had a significantly positive correlation with VPD. But when VPD was significantly negatively correlated with both temperature and SW in spring and when temperature was negatively correlated with both SW and VPD in summer, a decoupling of GPP and NEP occurred. The impacts of various environmental factors on the annual carbon fluxes were calculated for each year and season using the path analysis method. At forest sites with consistent trends in GPP and NEP, annual, spring, and summer temperatures had significant positive correlations with GPP and ecosystem respiration (RE). While at the decoupled forest site, environmental factors had a stronger effect on RE, which then contributed to the observed decoupling of GPP and NEP. Finally, the Partial Least Squares method was used to analyze the relative contribution of each environmental factor to annual carbon fluxes. The results revealed that temperature and summer precipitation were the key environmental factors affecting forest ecosystems. This study provides important insights into the different responses of carbon fluxes in forest ecosystems undergoing environmental changes. Full article
(This article belongs to the Topic Forest Carbon Sequestration and Climate Change Mitigation)
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34 pages, 4425 KiB  
Article
Atmospheric Processes over the Broader Mediterranean Region: Effect of the El Niño–Southern Oscillation?
by Harry D. Kambezidis
Atmosphere 2024, 15(3), 268; https://doi.org/10.3390/atmos15030268 - 23 Feb 2024
Viewed by 1587
Abstract
The Mediterranean area is considered a hot spot on our planet because it represents the crossroads of various aerosols. Several studies have shown that the weather in the region is affected by the North-Atlantic Oscillation, which, in turn, is well connected with the [...] Read more.
The Mediterranean area is considered a hot spot on our planet because it represents the crossroads of various aerosols. Several studies have shown that the weather in the region is affected by the North-Atlantic Oscillation, which, in turn, is well connected with the El Niño–Southern Oscillation (ENSO) phenomenon. Nevertheless, no study has investigated the ENSO effect on the solar radiation and atmospheric aerosols in this region. The present study considers a greater area around the Mediterranean Sea over the period 1980–2022. The results show that there exists a loose but significant dependence, in some cases, of the optical properties of aerosols (aerosol optical depth, Ångström exponent, cloud optical depth) and solar radiation (net short-wave and net long-wave radiation, direct aerosol radiative forcing) on ENSO events. The results of this study provide motivation for further investigations, since such results can increase the accuracy of general circulation models that deal with climate change. Besides the ENSO effect, the enrichment of the Mediterranean atmosphere in suspended particles from great volcanic eruptions is shown. The inter-annual variation of the examined parameters is presented. A classification of the existing aerosols over the area is also provided. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Impact on Air Quality and the Climate)
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19 pages, 5956 KiB  
Article
Radiative Regime According to the New RAD-MSU(BSRN) Complex in Moscow: The Roles of Aerosol, Surface Albedo, and Sunshine Duration
by Daria Piskunova, Natalia Chubarova, Aleksei Poliukhov and Ekaterina Zhdanova
Atmosphere 2024, 15(2), 144; https://doi.org/10.3390/atmos15020144 - 23 Jan 2024
Cited by 2 | Viewed by 1194
Abstract
The radiative budget is one of the key factors that influences climate change. The aim of this study was to analyze the radiative regime in Moscow using the RAD-MSU(BSRN) complex and to estimate the radiative effects of the main geophysical factors during the [...] Read more.
The radiative budget is one of the key factors that influences climate change. The aim of this study was to analyze the radiative regime in Moscow using the RAD-MSU(BSRN) complex and to estimate the radiative effects of the main geophysical factors during the 2021–2023 period. This complex is equipped and maintained according to the recommendations of the Baseline Surface Radiation Network; however, it is not a part of this network. In cloudless conditions, the decrease in global shortwave irradiance (Q) is about 18–22% due to the aerosol content with a pronounced change in the direct to diffuse ratio. In winter, the increase in Q is about 45 W/m2 (or 9%) at h = 30° due to a high surface albedo and reduced aerosol and water vapor contents, while the net shortwave irradiance (Bsh) demonstrates a significant decrease due to the prevailing effects of snow albedo. In cloudy conditions, a nonlinear dependence of Q and Bsh cloud transmittance on the relative sunshine duration is observed. The mean changes in Q for the 2021–2023 against the 1955–2020 period are characterized by negative anomalies (−22%) in winter and positive anomalies in summer (+3%) due to the changes in cloudiness. This is in line with the global tendencies in the long-term changes in shortwave irradiance in moderate climates in Europe in recent years. Full article
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16 pages, 5868 KiB  
Article
Diagnosis of Warm-Sector Heavy Rainfall with Warm Shear in the Yangtze–Huaihe Coastal Areas from the Perspective of Moist Static Energy
by Yiping Yu and Ling Zhang
Atmosphere 2023, 14(12), 1730; https://doi.org/10.3390/atmos14121730 - 24 Nov 2023
Viewed by 1459
Abstract
Based on the Climate Precipitation Center Morphing (CMORPH) precipitation data and the fifth-generation ECMWF reanalysis (ERA5) data, moist static energy (MSE) diagnosis for 14 cases of southerly warm-sector heavy rainfall with warm shear (WSWR) along the Yangtze-Huaihe coastal area (YHCA) was conducted. The [...] Read more.
Based on the Climate Precipitation Center Morphing (CMORPH) precipitation data and the fifth-generation ECMWF reanalysis (ERA5) data, moist static energy (MSE) diagnosis for 14 cases of southerly warm-sector heavy rainfall with warm shear (WSWR) along the Yangtze-Huaihe coastal area (YHCA) was conducted. The results indicate that the vertically integrated MSE tendency peaks before the precipitation reaches its maximum. This suggests a rapid MSE accumulation leading up to precipitation onset, with moist enthalpy advection dominantly influencing this increase. The vertical advection of MSE is negative, suggesting that upward motions and rainfall play a crucial role in consuming MSE. Vertical integrated MSE budget analysis for the nine cases of nocturnal rain shows that moist enthalpy advection was the primary contributor, driven mainly by meridional latent energy advection. Scale analysis shows that the combination of meridional disturbance wind and the mean specific humidity field results in pronounced meridional latent energy advection. For the five cases of non-nocturnal rain, the net energy flux was dominant before the onset of precipitation, primarily driven by clear-sky net shortwave radiation (SWCS). The meridional internal energy advection also makes a substantial contribution. The scale analysis indicates that the combined effects of the meridional disturbance wind and the average temperature field lead to significant meridional internal energy advection. Full article
(This article belongs to the Section Meteorology)
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16 pages, 12447 KiB  
Article
Validation and Spatiotemporal Analysis of Surface Net Radiation from CRA/Land and ERA5-Land over the Tibetan Plateau
by Limimg Gao, Yaonan Zhang and Lele Zhang
Atmosphere 2023, 14(10), 1542; https://doi.org/10.3390/atmos14101542 - 9 Oct 2023
Cited by 3 | Viewed by 1546
Abstract
High spatial–temporal resolution surface net radiation (RN) data are of great significance to the study of climate, ecology, hydrology and cryosphere changes on the Tibetan Plateau (TP), but the verification of the surface net radiation products on the plateau is not sufficient. In [...] Read more.
High spatial–temporal resolution surface net radiation (RN) data are of great significance to the study of climate, ecology, hydrology and cryosphere changes on the Tibetan Plateau (TP), but the verification of the surface net radiation products on the plateau is not sufficient. In this study, the China Meteorological Administration Global Land Surface Reanalysis Products (CRA/Land) and ECMWF Land Surface Reanalysis version 5 (ERA5-Land) RN data were validated using ground measurements at daily and monthly time scales, and the spatiotemporal patterns were also analyzed. The results indicate the following: (1) CRA/Land overestimated while ERA5-Land underestimated RN, but CRA/Land RN outperformed ERA5-Land in observations at the daily and monthly scale. (2) The CRA/Land RN data had a larger error in the central part and a smaller error in the northeast of the TP, while ERA5-Land showed the opposite. (3) The spatial patterns of RN revealed by CRA/Land and ERA5-Land data showed differences in most regions. The CRA/Land data showed that the RN of the TP had a downward trend during 2000 and 2020 with a slope of −0.112 W·m−2/a, while the ERA5-Land data indicated an upward trend with a change rate of 0.016 W·m−2/a. (4) Downwelling shortwave radiation (DSR), upwelling shortwave radiation (USR), downwelling longwave radiation (DLR) and upwelling longwave radiation (ULR) are the four components of RN, and the evaluation results indicate that the DSR, DLR and ULR recorded via CRA/Land and ERA5-Land are consistent with the observed data, but the consistency between the USR recorded via CRA/Land and ERA5-Land and the observed data is poor. (5) The inconsistency of the USR data is the main reason for the large differences in the spatiotemporal distribution of CRA/Land and ERA5-Land RN data across the TP. Full article
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
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21 pages, 5728 KiB  
Article
Effects of Spring Dust Aerosols on Direct Radiative Forcing in China from 2000 to 2020
by Feng Wang, Minghui Qi, Shuxin Ren, Mengjie Zhu, Qianlong Xing, Mengqiang Wang, Hongquan Song, Qianfeng Wang and Pengfei Liu
Remote Sens. 2023, 15(18), 4564; https://doi.org/10.3390/rs15184564 - 16 Sep 2023
Cited by 2 | Viewed by 1695
Abstract
In order to understand the mechanism of dust aerosol influence on regional climate change, it is crucial to quantify the radiative forcing effect of dust aerosols. However, studies on the direct radiative forcing of dust aerosols over long time series in China are [...] Read more.
In order to understand the mechanism of dust aerosol influence on regional climate change, it is crucial to quantify the radiative forcing effect of dust aerosols. However, studies on the direct radiative forcing of dust aerosols over long time series in China are still lacking. The direct radiative forcing effect of dust aerosols in China over the past 20 years was simulated and evaluated based on the WRF-Chem (Weather Research and Forecasting model coupled to Chemistry) model in conjunction with remote sensing satellites and ground-based observations. The results showed that dust aerosols exhibited an obvious inter-annual positive radiative forcing effect (about 0.38 W m−2) on net radiation at the top of the atmosphere, mainly in northwest China and the North China Plain, while at the atmosphere dust aerosols presented negative radiative forcing effects on shortwave radiation and positive effects on longwave radiation, with a value of 1.54 W m−2 of net radiative forcing, showing a warming effect. Dust aerosols have a net radiative forcing value of −1.16 W m−2 at the surface, indicating a cooling effect, with a positive forcing effect on longwave radiation and a negative forcing effect on shortwave radiation, both of which coincide with the geographical distribution of dust aerosol concentrations. In terms of inter-monthly variations, at both the atmosphere and top of the atmosphere, the dust aerosols net radiative forcing values showed an increasing trend, with March (−0.20 W m−2 and 0.68 W m−2) < April (0.48 W m−2 and 1.44 W m−2) < May (0.94 W m−2 and 2.42 W m−2). Meanwhile, at the surface, the dust aerosols net radiative forcing values displayed a decreasing trend, with March (−0.88 W m−2) > April (−0.96 W m−2) > May (−1.48 W m−2). Full article
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21 pages, 5486 KiB  
Article
Characteristics of Marine Heatwaves in the Indonesian Waters during the PDO, ENSO, and IOD Phases and Their Relationships to Net Surface Heat Flux
by Erlin Beliyana, Nining Sari Ningsih, Sekar Ramdanira Gunawan and Ayi Tarya
Atmosphere 2023, 14(6), 1035; https://doi.org/10.3390/atmos14061035 - 16 Jun 2023
Cited by 5 | Viewed by 3014
Abstract
We conducted an investigation into the characteristics of marine heatwaves (MHWs) in Indonesian waters, aiming to understand the underlying mechanisms responsible for their formation, particularly the ones generated by net surface heat flux. To accomplish this, we utilized remote sensing data from the [...] Read more.
We conducted an investigation into the characteristics of marine heatwaves (MHWs) in Indonesian waters, aiming to understand the underlying mechanisms responsible for their formation, particularly the ones generated by net surface heat flux. To accomplish this, we utilized remote sensing data from the National Oceanic and Atmospheric Administration and the European Centre for Medium-Range Weather Forecasts. The dataset covered a 40-year period (1982–2021) encompassing both warm (1982–2007) and cold (2008–2021) phases of the Pacific Decadal Oscillation (PDO). Statistical analysis methods were employed to process the data. Our study reveals significant findings regarding MHWs in Indonesian waters. We observed the highest average frequency and maximum intensity of MHWs, occurring approximately 2–3 times a year and exceeding 1.5 °C, respectively, during the warm phase of PDO (with El Niño events occurring more frequently than La Niña). Conversely, the longest durations of MHWs in Indonesian waters were recorded during the cold phase of PDO (with La Niña events occurring more frequently than El Niño), spanning approximately 7–15 days. We identified local forcing in the form of net surface heat flux as the primary driver of MHW frequency and maximum intensity. During the warm phase of PDO, the net surface heat flux was notably higher, primarily due to increased shortwave radiation (heat gain) and reduced latent heat flux (heat loss) through the evaporation process. These factors collectively contributed to maintaining warmer ocean temperatures. Moreover, our study provides valuable insights into the interannual variability of MHWs through the application of composite calculations. We discovered a strong correlation between the occurrence of El Niño and positive Indian Ocean Dipole (IOD) events during the warm PDO phase and the highest frequency and maximum intensity of MHWs, with approximately 2.52 events and 1.54 °C, respectively. In contrast, we found that MHWs with the longest durations were closely linked to La Niña and negative IOD events during the cold PDO phase, lasting approximately 10.90 days. These findings highlight the complex interplay between climate phenomena and MHW characteristics, further deepening our understanding of their dynamics. Full article
(This article belongs to the Section Biosphere/Hydrosphere/Land–Atmosphere Interactions)
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9 pages, 2189 KiB  
Communication
The Application of a Convolutional Neural Network for the Detection of Contrails in Satellite Imagery
by Jay P. Hoffman, Timothy F. Rahmes, Anthony J. Wimmers and Wayne F. Feltz
Remote Sens. 2023, 15(11), 2854; https://doi.org/10.3390/rs15112854 - 31 May 2023
Cited by 10 | Viewed by 3381
Abstract
This study presents a novel approach for the detection of contrails in satellite imagery using a convolutional neural network (CNN). Contrails are important to monitor because their contribution to climate change is uncertain and complex. Contrails are found to have a net warming [...] Read more.
This study presents a novel approach for the detection of contrails in satellite imagery using a convolutional neural network (CNN). Contrails are important to monitor because their contribution to climate change is uncertain and complex. Contrails are found to have a net warming effect because the clouds prevent terrestrial (longwave) radiation from escaping the atmosphere. Globally, this warming effect is greater than the cooling effect the clouds have in the reduction of solar (shortwave) radiation reaching the surface during the daytime. The detection of contrails in satellite imagery is challenging due to their similarity to natural clouds. In this study, a certain type of CNN, U-Net, is used to perform image segmentation in satellite imagery to detect contrails. U-Net can accurately detect contrails with an overall probability of detection of 0.51, a false alarm ratio of 0.46 and a F1 score of 0.52. These results demonstrate the effectiveness of using a U-Net for the detection of contrails in satellite imagery and could be applied to large-scale monitoring of contrail formation to measure their impact on climate change. Full article
(This article belongs to the Special Issue Deep Learning for Satellite Image Segmentation)
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11 pages, 3367 KiB  
Article
Spatial Variability of Albedo and Net Radiation at Local Scale Using UAV Equipped with Radiation Sensors
by Anders Lindroth
Drones 2023, 7(4), 276; https://doi.org/10.3390/drones7040276 - 18 Apr 2023
Viewed by 1644
Abstract
Energy balance closure is an important feature in studies of ecosystem exchanges of energy and greenhouse gases using the eddy covariance method. Previous analyses show that this is still a problem with imbalances in the order of 0.6–0.7 to full closure (for only [...] Read more.
Energy balance closure is an important feature in studies of ecosystem exchanges of energy and greenhouse gases using the eddy covariance method. Previous analyses show that this is still a problem with imbalances in the order of 0.6–0.7 to full closure (for only a few sites). It has been suggested that mesoscale transport processes that are not captured by the eddy covariance measurements are the main reason behind the closure problem. So far, very little action has been taken to investigate another potential cause of the problem, namely, the role of spatial variation in net radiation at the scale of typical flux footprints. The reason for this knowledge gap is mainly due to the lack of suitable methods to perform such investigations. Here, we show that such measurements can be performed with an unmanned aerial vehicle equipped with radiation sensors. A comparison using a reference radiometer on a fixed mast with a hovering UAV equipped with pyranometers for incoming and outgoing shortwave radiation and an infrared thermometer for surface temperature measurements shows that incoming and outgoing shortwave radiation can be measured with a standard error of 7.4 Wm−2 and 1.8 Wm−2, respectively. An application of the system was made over a five-year-old forest flux site in Sweden. Here, the net longwave radiation was estimated from the measured surface temperature and the calculated incoming longwave radiation. The results show that during the mission around noon on a clear day, distinct ‘hotspots’ existed over the plantation with the albedo varying between 15.5 and 17.9%, the surface temperature varying between 22.2 and 25.5 °C and the net radiation varying between 330 and 380 Wm−2. These variations are large enough to have a significant impact on the energy balance closure problem. Our conclusion is that we now have the tools to investigate the spatial variability of the radiation regime over flux sites and that this should be given more attention in the future. Full article
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12 pages, 4077 KiB  
Article
Radiation and Temperature of a Tropical Grassland in Summer Times: Experimental Observations
by Yunan Lu, Tianyu Wang, Chan Huang and Yinghong Qin
Atmosphere 2023, 14(4), 649; https://doi.org/10.3390/atmos14040649 - 30 Mar 2023
Viewed by 2026
Abstract
The surface texture of urbanized regions is altered by the replacement of natural vegetated surfaces with hardened pavement surfaces, which have been described as a heat source for the formation of urban heat islands. Grasslands may store rainfall in their roots and leaves [...] Read more.
The surface texture of urbanized regions is altered by the replacement of natural vegetated surfaces with hardened pavement surfaces, which have been described as a heat source for the formation of urban heat islands. Grasslands may store rainfall in their roots and leaves for later cooling, but this has received little attention. This study investigated the radiant flux and temperature of a tropical grassland throughout the summer in order to understand the albedo, long-wave radiation, short-wave radiation, and surface temperature of the grassland over 10 days. The grassland had an albedo of 0.13, which did not fluctuate during the day compared to the albedo of other surfaces in metropolitan areas. Even if the local weather changes considerably, this albedo does not alter significantly. The surface temperature and the air temperature above the grassland increase linearly with the upwelling reflectance, incident solar radiation, and upwelling long-wave radiation. These two temperatures do not correspond with downwelling long-wave radiation, which is influenced by cloud cover in the sky. However, the peaks of these temperatures lag behind the incident shortwave radiation and net radiation that reaches the grassland surface. The finding that the thermal properties of grasslands could be harnessed to reduce the heat absorbed by urban surfaces provides valuable insights into the grasslands’ potential to mitigate the impacts of urbanization on temperature. Full article
(This article belongs to the Special Issue Passive Techniques for Sustainable Buildings and Cities)
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16 pages, 4070 KiB  
Article
Cloud-MobiNet: An Abridged Mobile-Net Convolutional Neural Network Model for Ground-Based Cloud Classification
by Emmanuel Kwabena Gyasi and Purushotham Swarnalatha
Atmosphere 2023, 14(2), 280; https://doi.org/10.3390/atmos14020280 - 31 Jan 2023
Cited by 9 | Viewed by 3027
Abstract
More than 60 percent of the global surface is covered by clouds, and they play a vital role in the hydrological circle, climate change, and radiation budgets by modifying shortwaves and longwave. Weather forecast reports are critical to areas such as air and [...] Read more.
More than 60 percent of the global surface is covered by clouds, and they play a vital role in the hydrological circle, climate change, and radiation budgets by modifying shortwaves and longwave. Weather forecast reports are critical to areas such as air and sea transport, energy, agriculture, and the environment. The time has come for artificial intelligence-powered devices to take the place of the current method by which decision-making experts determine cloud types. Convolutional neural network models (CNNs) are starting to be utilized for identifying the types of clouds that are caused by meteorological occurrences. This study uses the publicly available Cirrus Cumulus Stratus Nimbus (CCSN) dataset, which consists of 2543 ground-based cloud images altogether. We propose a model called Cloud-MobiNet for the classification of ground-based clouds. The model is an abridged convolutional neural network based on MobileNet. The architecture of Cloud-MobiNet is divided into two blocks, namely the MobileNet building block and the support MobileNet block (SM block). The MobileNet building block consists of the weights of the depthwise separable convolutions and pointwise separable convolutions of the MobileNet model. The SM block is made up of three dense network layers for feature extraction. This makes the Cloud-MobiNet model very lightweight to be implemented on a smartphone. An overall accuracy success of 97.45% was obtained for the CCSN dataset used for cloud-type classification. Cloud-MobiNet promises to be a significant model in the short term, since automated ground-based cloud classification is anticipated to be a preferred means of cloud observation, not only in meteorological analysis and forecasting but also in the aeronautical and aviation industries. Full article
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
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31 pages, 23306 KiB  
Article
On the Interplay between Desert Dust and Meteorology Based on WRF-Chem Simulations and Remote Sensing Observations in the Mediterranean Basin
by Umberto Rizza, Elenio Avolio, Mauro Morichetti, Luca Di Liberto, Annachiara Bellini, Francesca Barnaba, Simone Virgili, Giorgio Passerini and Enrico Mancinelli
Remote Sens. 2023, 15(2), 435; https://doi.org/10.3390/rs15020435 - 11 Jan 2023
Cited by 11 | Viewed by 3016
Abstract
In this study, we investigate a series of Saharan dust outbreaks toward the Mediterranean basin that occurred in late June 2021. In particular, we analyze the effect of mineral dust aerosols on radiation and cloud properties (direct, semi-direct and indirect effects), and in [...] Read more.
In this study, we investigate a series of Saharan dust outbreaks toward the Mediterranean basin that occurred in late June 2021. In particular, we analyze the effect of mineral dust aerosols on radiation and cloud properties (direct, semi-direct and indirect effects), and in turn, on meteorological parameters. This is achieved by running the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) over a domain covering North Africa and the Central Mediterranean Basin. The simulations were configured using a gradual coupling strategy between the GOCART aerosol model and the Goddard radiation and microphysics schemes available in the WRF-Chem package. A preliminary evaluation of the model performances was conducted in order to verify its capability to correctly reproduce the amount of mineral dust loaded into the atmosphere within the spatial domain considered. To this purpose, we used a suite of experimental data from ground- and space-based remote sensing measurements. This comparison highlighted a model over-estimation of aerosol optical properties to the order of 20%. The evaluation of the desert dust impact on the radiation budget, achieved by comparing the uncoupled and the fully coupled (aerosol–radiation–clouds) simulation, shows that mineral dust induces a net (shortwave–longwave) cooling effect to the order of −10 W m−2. If we consider the net dust radiative forcing, the presence of dust particles induces a small cooling effect at the top of the atmosphere (−1.2 W m−2) and a stronger cooling at the surface (−14.2 W m−2). At the same time, analysis of the perturbation on the surface energy budget yields a reduction of −7 W m−2 when considering the FULL-coupled simulation, a positive perturbation of +3 W m−2 when only considering microphysics coupling and −10.4 W m−2 when only considering radiation coupling. This last result indicates a sort of “superposition” of direct, indirect and semi-direct effects of dust on the radiation budget. This study shows that the presence of dust aerosols significantly influences radiative and cloud properties and specifically the surface energy budget. This suggests (i) that dust effects should be considered in climate models in order to increase the accuracy of climate predictions over the Mediterranean region and (ii) the necessity of performing fully coupled simulations including aerosols and their effects on meteorology at a regional scale. Full article
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