Assessment of the IMERG Early-Run Precipitation Estimates over South American Country of Chile

Accurate rainfall measurement is a challenge, especially in regions with diverse climates and complex topography. Thus, knowledge of precipitation patterns requires observational networks with a very high spatial and temporal resolution, which is very difficult to construct in remote areas with complex geological features such as desert areas and mountains, particularly in countries with high topographical variability such as Chile. This study evaluated the performance of the near-real-time Integrated Multi-satellite Retrievals for GPM (IMERG) Early product throughout Chile, a country located in South America between 16°S–66°S latitude. The accuracy of the IMERG Early was assessed at different special and temporal scales from 2015 to 2020. Relative Bias (PBIAS), Mean Absolute Error (MAE), and Root-Mean-Squared Error (RMSE) were used to quantify the errors in the satellite estimates, while the Probability of Detection (POD), False Alarm Ratio (FAR), and Critical Success Index (CSI) were used to evaluate product detection accuracy. In addition, the consistency between the satellite estimates and the ground observations was assessed using the Correlation Coefficient (CC). The spatial results show that the IMERG Early had the best performance over the central zone, while the best temporal performance was detected for the yearly precipitation dataset. In addition, as latitude increases, so do errors. Also, the satellite product tends to slightly overestimate the precipitation throughout the country. The results of this study could contribute towards the improvement of the IMERG algorithms and open research opportunities in areas with high latitudes, such as Chile

A Study of UVER in Santiago, Chile Based on Long-Term In Situ Measurements (Five Years) and Empirical Modelling

Ultraviolet radiation is a highly energetic component of the solar spectrum that needs to be monitored because is harmful to life on Earth, especially in areas where the ozone layer has been depleted, like Chile. This work is the first to address the long-term (five-year) behaviour of ultraviolet erythemal radiation (UVER) in Santiago, Chile (33.5° S, 70.7° W, 500 m) using in situ measurements and empirical modelling. Observations indicate that to alert the people on the risks of UVER overexposure, it is necessary to use, in addition to the currently available UV index (UVI), three more erythema indices: standard erythemal doses (SEDs), minimum erythemal doses (MEDs), and sun exposure time (tery). The combination of UVI, SEDs, MEDs, and tery shows that in Santiago, individuals with skin types III and IV are exposed to harmfully high UVER doses for 46% of the time that UVI indicates is safe. Empirical models predicted hourly and daily values UVER in Santiago with great accuracy and can be applied to other Chilean urban areas with similar climate. This research inspires future advances in reconstructing large datasets to analyse the UVER in Central Chile, its trends, and its changes

Influence of solar and geomagnetic storms on terrestrial photosynthesis

It is reviewed the potential influence of solar and geomagnetic storms on terrestrial photosynthesis. Then it is presented a modification of a physical-mathematical model of photosynthesis published by some of us, which allows quantifying the influence of particulate ionizing radiation on this biological process. Some guidelines to obtain this new model from first principles are mentioned and it is applied to some case studies including atmospheric and geomagnetic perturbation due to solar storms

Influence of solar and geomagnetic storms on terrestrial photosynthesis

It is reviewed the potential influence of solar and geomagnetic storms on terrestrial photosynthesis. Then it is presented a modification of a physical-mathematical model of photosynthesis published by some of us, which allows quantifying the influence of particulate ionizing radiation on this biological process. Some guidelines to obtain this new model from first principles are mentioned and it is applied to some case studies including atmospheric and geomagnetic perturbation due to solar storms

Assessment of the Diffuse Attenuation Coefficient of Photosynthetically Active Radiation in a Chilean Lake

The diffuse attenuation coefficient of photosynthetically active radiation is an important inherent optical property of the subaquatic light field. This parameter, as a measure of the transparency of the medium, is a good indicator of water quality. Degradation of the optical properties of water due to anthropogenic disturbances is a common phenomenon in freshwater ecosystems. In this study, we used four algorithm-based Landsat 8 OLI and Sentinel-2A/B MSI images to estimate the diffuse attenuation coefficient of photosynthetically active radiation in Lake Villarrica located in south-central Chile. The algorithms’ estimated data from the ACOLITE module were validated with in situ measurements from six sampling stations. Seasonal and intralake variations of the light attenuation coefficient were studied. The relationship between the diffuse attenuation coefficient of photosynthetically active radiation, meteorological parameters, and an optical classification was also explored. The best results were obtained with QAA v6 KdPAR Nechad (R2 = 0.931, MBE = 0.023 m−1, RMSE = 0.088 m−1, and MAPE = 35.9%) for spring and QAA v5 Kd490 algorithms (R2 = 0.919, MBE = −0.064 m−1, RMSE = −0.09 m−1, and MAPE = 30.3%) for summer. High KdPAR values are associated with the strong wind and precipitation events suggest they are caused by sediment resuspension. Finally, an optical classification of freshwater ecosystems was proposed for this lake. The promising results of this study suggest that the combination of in situ data and observation satellites can be useful for assessing the bio-optical state of water and water quality dynamics in Chilean aquatic systems

Assessment of the Diffuse Attenuation Coefficient of Photosynthetically Active Radiation in a Chilean Lake

The diffuse attenuation coefficient of photosynthetically active radiation is an important inherent optical property of the subaquatic light field. This parameter, as a measure of the transparency of the medium, is a good indicator of water quality. Degradation of the optical properties of water due to anthropogenic disturbances is a common phenomenon in freshwater ecosystems. In this study, we used four algorithm-based Landsat 8 OLI and Sentinel-2A/B MSI images to estimate the diffuse attenuation coefficient of photosynthetically active radiation in Lake Villarrica located in south-central Chile. The algorithms’ estimated data from the ACOLITE module were validated with in situ measurements from six sampling stations. Seasonal and intralake variations of the light attenuation coefficient were studied. The relationship between the diffuse attenuation coefficient of photosynthetically active radiation, meteorological parameters, and an optical classification was also explored. The best results were obtained with QAA v6 KdPAR Nechad (R2 = 0.931, MBE = 0.023 m−1, RMSE = 0.088 m−1, and MAPE = 35.9%) for spring and QAA v5 Kd490 algorithms (R2 = 0.919, MBE = −0.064 m−1, RMSE = −0.09 m−1, and MAPE = 30.3%) for summer. High KdPAR values are associated with the strong wind and precipitation events suggest they are caused by sediment resuspension. Finally, an optical classification of freshwater ecosystems was proposed for this lake. The promising results of this study suggest that the combination of in situ data and observation satellites can be useful for assessing the bio-optical state of water and water quality dynamics in Chilean aquatic systems

A Study of UVER in Santiago, Chile Based on Long-Term In Situ Measurements (Five Years) and Empirical Modelling

Ultraviolet radiation is a highly energetic component of the solar spectrum that needs to be monitored because is harmful to life on Earth, especially in areas where the ozone layer has been depleted, like Chile. This work is the first to address the long-term (five-year) behaviour of ultraviolet erythemal radiation (UVER) in Santiago, Chile (33.5° S, 70.7° W, 500 m) using in situ measurements and empirical modelling. Observations indicate that to alert the people on the risks of UVER overexposure, it is necessary to use, in addition to the currently available UV index (UVI), three more erythema indices: standard erythemal doses (SEDs), minimum erythemal doses (MEDs), and sun exposure time (tery). The combination of UVI, SEDs, MEDs, and tery shows that in Santiago, individuals with skin types III and IV are exposed to harmfully high UVER doses for 46% of the time that UVI indicates is safe. Empirical models predicted hourly and daily values UVER in Santiago with great accuracy and can be applied to other Chilean urban areas with similar climate. This research inspires future advances in reconstructing large datasets to analyse the UVER in Central Chile, its trends, and its changes

Influence of (extreme) radiation and optical characteristics in physical and biological features of a regulated lake

Radiation plays an essential role in the establishment and proliferation of biota in natural environments. The photosynthetic process determines the existence of all life forms, since it supplies the energy that this photobiological process needs for the reaction, it is carried out by absorbing photons in the visible and infrared bands of the electromagnetic spectrum, while ultraviolet (UV) photons and ionizing radiation tends to inhibit it (decreasing, by various mechanisms, its quantum yield). The speed of photosynthesis, measured by the amount of O2 released in the unit of time (or CO2 absorbed) depends on the intensity of the incident light, in the last three decades this radiation has been increased by the decrease of stratospheric ozone in the South latitudes of our planet, for this reason the UV values in the aquatic ecosystems of Chile have been high as well as a considerable increase in the surface temperature of the bodies of water, having possible implications in the primary biological productivity of the ecosystems lakes, especially in Andean lakes. This increase in radiation could be related to the abundance of the different algal groups and the seasonal variability of them, creating favorable conditions for those dominant species considered invasive of these ecosystems. This paper shows the direct relationship between the concentration of ozone (O3) and ultraviolet radiation and how it influences the vertical distribution of the phytoplankton groups in the water column. For the first time it was found in this lake the appearance of a bloom of toxic cyanobacteria

Signals of Surface Deformation Areas in Central Chile, Related to Seismic Activity—Using the Persistent Scatterer Method and GIS

Interferometric synthetic aperture radar is an effective means of measuring changes in the altitude of the Earth’s surface. In this research, the areas of surface deformation associated with low- and medium-intensity seismic events in Central Chile were analyzed using SENTINEL 1 satellite radar interferograms and geographical information system (GIS) tools. The persistent scatterer method was used to reduce noise from conventional InSAR methods. The results revealed that the coastal zone of Central Chile has a high density of daily earthquakes with a prevalence (93.03%) of low- and medium-intensity earthquakes. Monthly deformation maps were developed for the coast of the Biobio region in Central Chile. A clear deformation pattern is defined along the coast, being greater in the Arauco, Lota and Lebu areas. It was also shown that there was a slight upward trend in the north and northeast zone (i.e., δup ~3 mm/year), while there was an obvious accentuated upward trend (i.e., δup ~24 mm/year) in the southern part. This movement increases as latitude increases. This pattern is related to the daily seismic activity, the product of the movement between plates, and the geological faults located in the area. The deformation and trend maps provide certainty in terms of where hotspots are located, e.g., the most hazardous areas in the study zone, which can be applied to urban planning and/or safety assessment